General Psychology An Introduction Chapter 3 Biological Psychology

Chapter Biological Psychology The Brain and Nervous System Robert The brain is the most complex part of the human body . It is the center of consciousness and also controls all voluntary and involuntary movement and bodily functions . It communicates with each part of the body through the nervous system , a network of channels that carry electrochemical signals . Learning Objectives Name the various parts ofthe nervous system and their respective functions Explain how neurons communicate with each other Identify the location and function ofthe limbic system Articulate how the motor strip is an example of brain region specialization Name at least three techniques and describe how they work In the a German scientist by the name of Ernst Weber conducted several experiments meant to investigate how people perceive the world via their own bodies . It is obvious that we use our sensory eyes , and ears , and take in and understand the world around us . Weber was particularly interested in the sense of touch . Using a drafting compass he placed the two points far apart and set them on the skin of a volunteer . When the points were far apart the research participants could easily distinguish between them . As Weber repeated the process with ever closer points , however , most people lost the ability to tell the difference between them . Weber discovered that the ability to recognize these just noticeable differences depended on where on the body the compass was positioned . Your

The Brain and System 40 back , for example , is far less sensitive to touch than is the skin on your face . Similarly , the tip ofyour tongue is extremely sensitive ! In this way , Weber began to shed light on the way that nerves , the nervous system , and the brain form the biological foundation of psychological processes . In this module we will explore the biological side of psychology by paying particular attention to the brain and to the nervous system . Understanding the nervous system is vital to understanding psychology in general . It is through the nervous system that we experience pleasure and pain , feel emotions , learn and use language , and plan goals , just to name a few examples . In the pages that follow we howthe human nervous system develops and then we will learn about the parts of the brain Measuring just noticeable differences . and how they function We will conclude with a section on how modern psychologists study the brain . It is worth mentioning here , at the start , that an introduction to the biological aspects of psychology can be both the most interesting and most frustrating ofall topics for new students of psychology . This is , in large part , due to the fact that there is so much new information to learn and associated with all the various parts ofthe brain and nervous system . In fact , there are 30 key vocabulary words presented in this module ! We encourage you not to get bogged down in difficult words . Instead , pay attention to the broader concepts , perhaps even skipping over the vocabulary on reading . It is helpful to pass back through with a second reading , once you are already familiar with the topic , with attention to learning the vocabulary . Nervous System development across the human lifespan As a species , humans have evolved a complex nervous system and brain over millions ofyears . Comparisons ofour nervous systems with those of other animals , such as chimpanzees , show some similarities . Researchers can also use fossils to study the relationship between brain

The Brain and Nervous System 41 volume and human behavior over the course of evolutionary history . Homo , for instance , a human ancestor living about million years ago shows a larger brain volume than its own ancestors but far less than modern homo sapiens . The main difference between humans and other in terms of brain is that humans have a much more developed frontal cortex ( the front part ofthe brain associated with planning ) Interestingly , a person unique nervous system develops over the course oftheir lifespan in a way that resembles the evolution of nervous systems in animals across vast stretches of time . For example , the human nervous system begins developing even before a person is born . It begins as a simple bundle that forms into a tube and extends along the plane becoming the spinal cord and brain . By day 40 of gestation ( 40 days after fertilization ofthe egg ) the spinal cord , hind brain , mid brain and forebrain are all visibly distinct . What , exactly , is this nervous system that is developing and what does it do ?

The nervous system can be thought of as the body communication network that consists of all nerve cells . There are many ways in which we can divide the nervous system to understand it more clearly . One common way to do so is by parsing it into the central nervous system and the peripheral nervous system . Each of these can be , in turn . take a closer , more look at each . And , do worry , the nervous system is complicated with many parts and many new vocabulary words . It might seem overwhelming at first but through the figures and a little study you can get it . The Central Nervous System ( The Neurons inside the Brain The Central Nervous System , or for short , is made up ofthe brain and spinal cord ( see Figure ) The is the portion ofthe nervous system that is encased in bone ( the brain is protected by the skull and the spinal cord is protected by the spinal column ) It is referred to as central because it is the brain and spinal cord that are primarily a hot stove or seeing a rainbow , for example sending signals to the peripheral nervous system for action . It communicates largely by sending electrical signals through individual nerve cells that make up the fundamental building blocks of the nervous system , called neurons . There are approximately 100 billion Figure The central system

The Brain and Nervous System 42 neurons in the human brain and each has many contacts with other neurons , called synapses . If we were able to magnify a view of individual neurons we would see that they are cells made from distinct parts ( see Figure ) The three main components ofa neuron are the dendrites , the soma , and the axon . Neurons communicate with one another by receiving information through the dendrites , which act as an antenna . When the dendrites channel this information to the soma , or cell body , it builds up as an signal . This electrical part of the signal , called an action potential shoots down the axon , a long tail that leads away from the soma and toward the next neuron . When people talk about nerves in the nervous system , it typically refers to bundles of axons that form long neural wires along which electrical signals can travel . communication is helped by the fact that the soma is covered by a myelin layer of fatty cells that allow the signal to travel very rapidly from neuron to neuron . synapse dendrites nucleus Figure The parts ofa neuron Ifwe were to zoom in still fu we could take a closer look at the synapse , the space between neurons ( see Figure ) Here , we would see that there is a space between neurons , called the synaptic gap . To give you a sense of scale we can compare the synaptic gap to the thickness ofa dime , the thinnest ofall American coins ( about ) You could stack approximately synaptic gaps in the thickness of a single coin ! As the action potential , the electrical signal reaches the end of the axon , tiny packets of chemicals , called neurotransmitters , are released . This is the chemical part of the chemical signal . These neurotransmitters are the chemical signals that travel from one neuron to another , enabling them to communicate with one another . There are many different types

The Brain and Nervous System 43 and each has a specialized function . For example , serotonin affects sleep , hunger and mood . Dopamine is associated with attention , learning and pleasure . It is amazing to realize that when you , when you reach out to grab a glass of water , terminal when you realize that your best friend IS bum happy , when you try to remember the name of the parts of a you are experiencing is actually impulses shooting between nerves ! The Central Nervous System Looking at the Brain as a Whole receptor Figure A view of the synapse between neurons Ifwe were to zoom back out and look at the central nervous system again we would see that the brain is the largest single part ofthe central nervous system . The brain is the headquarters of the entire nervous system and it is here that most of your sensing , perception , thinking , awareness , emotions , and planning take place . For many people the brain is so important that there is a sense that it is the a person sense of self is located ( as opposed to being primarily in your toes , by contrast ) The brain is so important , in fact , that it consumes 20 of the total oxygen and calories we consume even though it is only , on average , about of our overall weight . It is helpful to examine the various parts ofthe brain and to understand their unique functions to get a better sense of the role the brain plays . We will start by looking at very general areas of the brain and then we will zoom in and look at more specific parts . and neuroscientists often divide the brain into portions based on the location and function of various brain parts . Among the simplest ways to organize the brain is to describe it as having three basic portions the hindbrain , midbrain and forebrain . Another way to look at the brain is to consider the brain stem , the , and the Cerebrum . There is another part , called the Limbic System that is less well defined . It is made up ofa number that are ( existing in the hindbrain ) as well as regions ofthe Cerebrum ( see Figure ) The brain stem is the most basic structure of the brain and is located at the top of the spine and bottom ofthe brain . It is sometimes considered the oldest part ofthe brain because we can see similar structures in other , less evolved animals such as crocodiles . It is in charge of a wide range of very basic life support functions for the human body including breathing , digestion , and the beating of the heart . Amazingly , the brain stem sends the signals to keep

The Brain and Nervous System 44 these processes running smoothly without any conscious effort on our behalf . The limbic system is a collection of highly specialized neural structures that sit at the top of the brain stem , which are involved in regulating our emotions . Collectively , the limbic system is a term that does have clearly defined areas as it includes forebrain regions as well as hindbrain regions . These include the amygdala , the pituitary gland , the thalamus and the hypothalamus . These structures influence hunger , the cycle , sexual desire , fear and aggression , and even memory . The cerebellum is a structure at the very back ofthe brain . Aristotle referred to it as the small brain based on its appearance and it is principally involved with movement and posture although it is also associated with a variety of other thinking processes . The cerebellum , like the brain stem , coordinates actions without the need for any conscious awareness . This is why reflexes can sometimes seem so automatic . The cerebrum ( also called the cerebral cortex ) is the newest , most advanced portion of the ' brain . The cerebral hemispheres ( the left and right hemispheres that make up each side of the top of the brain ) are in charge of the types of processes that are associated with more awareness and voluntary control such as speaking and planning as well as contain our primary sensory areas ( such as seeing , hearing , feeling , and moving ) These two hemispheres are connected to one another by a thick bundle called the corpus callosum . There are instances in which because of a genetic abnormality or as the result of had their corpus callosum severed so that the two halves ofthe brain can not easily communicate with one another . The rare patients offer helpful insights into how the brain works . For example , we now understand that the brain is contralateral , or . This means that the left side of the brain is responsible for controlling a number of sensory and motor functions of the right side of the body , and vice versa . Figure General areas ofthe brain ( Image biology corner ) Consider this striking example A split brain patient is seated at a table and an object such as a car key can be placed where a patient can only see the field .

The Brain and Nervous System 45 Right visual field images will be processed on the left side of the brain and left visual field images will be processed on the right side ofthe brain . Because language is largely associated with the left side ofthe brain the patient who sees car key in the right visual field when asked What do you see ?

would answer , I see a car In contrast , a patient who only saw the car key in the left visual field , thus the information went to the right side of the brain , might have a difficult time speaking the word car key . In fact in this case , the patient is likely to respond I did see anything at all . However , to draw the item with their left process associated with the right side of the patient will be able to do so ! See the outside resources below for a video demonstration of this striking phenomenon . Besides looking at the brain as an organ that is made up of two halves we can also examine it by looking at its four various lobes of the cerebral cortex , the outer part of the brain ( see Figure ) Each of these is associated with a specific function . The occipital lobe , located at the back of the cerebral cortex , is the house of the visual area of the brain . You can see the road in front of you when you are driving , track the motion ofa ball in the air , and recognize faces thanks to the occipital lobe . The temporal lobe , located on the underside ofthe cerebral cortex , is where sounds and smells are processed . The parietal lobe , at the upper back ofthe cerebral cortex , is where touch and taste are processed . Finally , the frontal lobe , located at the forward part ofthe cerebral cortex is where behavioral motor plans are processed as well as a number of highly complicated processes occur including speech and language use , creative problem solving , and planning and organization . One area in lobe is called the motor strip ( okay , scientists call it the central sulcus but have you had enough new vocabulary for the time being ?

This strip running along the side of the brain is in charge of voluntary movements like waving goodbye , wiggling your eyebrows , and kissing . It is an excellent example of the way that the various regions ofthe brain are Figure ofthe cerebral cortex highly specialized . Interestingly , each ofour various body parts has a unique portion of the motor strip devoted to it ( see Figure ) Each individual finger has about as much dedicated brain space as your entire leg . Your lips , in turn , require about as parietal lobe frontal lobe I occipital lobe temporal lobe

The Brain and Nervous System 46 much dedicated brain processing as all of your fingers and your hand combined ! Central sulcus Mastication So Figure The motor strip Because the cerebral cortex in general , and the frontal lobe in particular , are associated with such sophisticated functions as planning and being they are often thought a higher , less primal portion of the brain . Indeed , other animals such as rats and kangaroos while they do have frontal regions of their brain do not have the same level of development in the cerebral cortices . The closer an animal is to humans on the evolutionary chimpanzees and gorillas , the more developed is this portion of their brain . The Peripheral Nervous System In addition to the central nervous system ( the brain and spinal cord ) there is also a complex network of nerves that travel to every part of the body . This is called the peripheral nervous system ( and it carries the signals necessary for the body to survive ( see Figure ) Some ofthe signals carried by the are related to voluntary actions . Ifyou want to type a message to a friend , for instance , you make conscious choices about which letters go in what order and your brain sends the appropriate signals to your fingers to do the work . Other processes , by contrast , are not voluntary . Without your awareness your brain is also sending signals to your organs , your digestive system , and the muscles that are holding you up right now with instructions about what they should be doing . All ofthis occurs through the pathways ofyour peripheral nervous system .

The Brain and System 47 Process sensory information controls the voluntary muscle movements Figure The peripheral system Controls the other muscles visceral organs How we study the brain The brain is difficult to study because it is housed inside the thick bone of the skull . more , it is difficult to access the brain without hurting or killing the owner of the brain . As a result , many ofthe earliest studies ofthe brain ( and indeed this is still true today ) focused on unfortunate people who happened to have damage to some particular area of their brain . For instance , in the a surgeon named Paul conducted an autopsy on a former patient who had lost his powers of speech . Examining his patient brain , identified a damaged called the Area the left side of the brain ( see Figure ) Over the years a number of researchers have been able to gain insights into the function of specific regions of the brain from these types of patients . Figure Braca Area ( Image An alternative to examining the brains or behaviors of humans with brain damage or surgical lesions can be found in the instance of animals . Some researchers examine the brains of other animals such as rats , dogs and monkeys . Although animals brains differ from human brains in both size and structure there are many similarities as well . The use for study can yield important insights into human brain function . In modern times , however , we do not have to exclusively rely on the study of people with brain lesions . Advances in technology have led

The Brain and System 48 to ever more sophisticated imaging techniques . Just as technology allows us to peer inside the body , techniques allow us glimpses of the working brain . Each type of imaging uses a different technique and each has its own advantages and disadvantages . Positron Emission Tomography ( PET ) records metabolic activity in the brain by detecting the amount of radioactive substances , which are injected into a person bloodstream , the brain is consuming . This usto see how much an individual uses a particular part of the brain while at rest , or not performing a task . Another technique , known as Functional Magnetic Resonance Imaging ( relies on blood flow . This method measures changes in the levels of naturally occurring oxygen in the blood . As a brain region becomes active , it requires more oxygen . This technique measures brain activity based on this increase oxygen level . This means does not require a foreign substance to be injected into the body . Both PET and fMRI scans have poor temporal resolution , meaning that they can not tell us exactly when brain activity occurred . This is because it takes several seconds for blood to arrive at a portion of the brain working on a task . One imaging technique that has better temporal resolution is Electroencephalography ( EEG ) which Above A PET scan Below An scan ( Image ) measures electrical brain activity instead of blood flow . Electrodes are place on the scalp of participants and theyare picking up electrical activity . Because this activity could be coming from any portion of the brain , however , EEG is known to have poor spatial resolution , meaning that it is not accurate with An EEG cap ( Image Chris Hope ) regards to specific location .

The Brain and Nervous System 49 Another technique , known as Diffuse Optical Imaging ( DOI ) can offer high temporal and spatial resolution . DOI works by shining infrared light into the brain . It might seem strange that light can pass through the head and brain . Light properties change as they pass through oxygenated blood and through active neurons . As a result , researchers can make inferences regarding where and when brain activity is happening . Conclusion It has often been said that the brain studies itself . This means that humans are uniquely capable of using our most sophisticated organ to understand our most sophisticated organ . Breakthroughs in the study of the brain and nervous system are among the most exciting discoveries in all of psychology . In the future , research linking neural activity to complex , real world attitudes and behavior will help us to understand human psychology and better intervene in it to help people .

The Brain and Nervous System 50 Outside Resources Video Animation of Neurons ?

Video Split Brain Patient ?

Web Animation of the Magnetic Resonance Imaging ( MRI ) Web Animation of the Positron Emission Tomography ( PET ) Web Teaching resources and videos for teaching about the brain , from Colorado State University Web The Brain Museum Discussion Questions . In your opinion is learning about the functions of various parts of the brain by studying the abilities of brain damaged patients ethical . What , in your opinion , are the potential benefits and considerations ?

Are research results on the brain more compelling to you than are research results from survey studies on attitudes ?

Why or why not ?

How does biological research such as studies ofthe brain influence public opinion regarding the science of psychology ?

If humans continue to evolve what changes might you predict in our brains and cognitive abilities ?

Which brain scanning techniques , or combination of techniques , do you find to be the best ?

Why ?

Why do you think scientists may or may not employ recommended techniques ?

The Brain and Nervous System 51 Vocabulary Action Potential A transient electrical current that is conducted down the axon when the membrane potential reaches the threshold of excitation . Axon Part of the neuron that extends off the soma , splitting several times to connect with other neurons main output of the neuron . Brain Stem The trunk of the brain comprised of the medulla , pons , midbrain , and diencephalon . Area An area in the frontal lobe of the left hemisphere . implicated in language production . Central Nervous System The portion of the nervous system that includes the brain and spinal cord . Cerebellum The distinctive structure at the back ofthe brain , Latin for small Cerebrum Usually refers to the cerebral cortex and associated white matter , but in some texts includes the subcortical structures . Contralateral opposite side used to refer to the fact that the two hemispheres ofthe brain process sensory information and motor commands for the opposite side of the body ( the left hemisphere controls the right side of the body ) Corpus Callosum The thick bundle of nerve cells that connect the two hemispheres ofthe brain and allow them to communicate . Dendrites Part of a neuron that extends away from the cell body and is the main input to the neuron .

The Brain and Nervous System 52 Diffuse Optical Imaging ( DOI ) A technique that brain activity by measuring changes in light as it is passed through the skull and surface of the brain . Electroencephalography ( EEG ) A technique that measures electrical brain activity via multiple electrodes on the scalp . Frontal Lobe The front most ( anterior ) part ofthe cerebrum anterior to the central sulcus and responsible for motor output and planning , language , judgment , and . Functional Magnetic Resonance Imaging ( Functional magnetic resonance imaging ( fMRI ) A technique that brain activity by measuring changes in oxygen levels in the blood . Limbic System Includes the subcortical structures of the amygdala and hippocampal formation as well as some cortical structures responsible for aversion and gratification . Myelin Sheath , that insulates the axons ofthe neurons myelin is normal conduction of electrical impulses among neurons . Nervous System The body network for electrochemical communication . This system includes all the nerves cells in the body . Neurons Individual brain cells Neurotransmitters Chemical substance released bythe presynaptic terminal button that acts on the postsynaptic cell . Occipital Lobe The back most ( posterior ) part of the cerebrum involved in vision . Parietal Lobe

The Brain and Nervous System 53 The part ofthe cerebrum between the frontal and occipital lobes involved in bodily sensations , visual attention , and integrating the senses . Peripheral Nervous System All of the nerve cells that connect the central nervous system to all the other parts ofthe body . Positron Emission Tomography ( PET ) A technique that measures brain activity by detecting the presence of a bloodstream and then pulled in by active brain tissue . Soma Cell body ofa neuron that contains the nucleus and genetic information , and directs protein synthesis . Spatial Resolution A term that refers to how small the elements ofan image are high spatial resolution means the device or technique can resolve very small elements in neuroscience it describes how small ofa structure in the brain can be imaged . Patient A patient who has had most or all of his or her corpus callosum severed . Synapses junction between the presynaptic terminal button of one neuron and the dendrite , axon , or soma ofanother postsynaptic neuron . Synaptic Gap Also known as the synaptic cleft the small space between the presynaptic terminal button and the postsynaptic dendritic spine , axon , or soma . Temporal Lobe The part ofthe cerebrum in front of ( the occipital lobe and lateral fissure involved in vision , auditory processing , memory , and integrating vision and audition . Temporal Resolution A term that refers to how small a unit of time can be measured high temporal resolution means capable of resolving very small units oftime in neuroscience it describes how precisely in time a process can be measured in the brain .

Hormones Behavior Randy . Nelson The goal ofthis module is to introduce you to the topic of hormones and behavior . This field of study is also called behavioral endocrinology , which is the scientific study ofthe interaction between hormones and behavior . This interaction is bidirectional hormones can influence behavior , and behavior can sometimes influence hormone concentrations . Hormones are chemical messengers released from endocrine glands that travel through the blood system to influence the nervous system to regulate behaviors such as aggression , mating , and parenting . Learning Objectives Define the basic terminology and basic principles of interactions . Explain the role of hormones in behavioral sex differentiation . Explain the role of hormones in aggressive behavior . Explain the role of hormones in parental behavior . Provide examples of some common interactions . Introduction This module describes the relationship between hormones and behavior . Many readers are likely already familiar with the general idea that hormones can affect behavior . Students are generally familiar with the idea that concentrations increase in the blood during decrease as we age , especially after about 50 years of age . Sexual behavior shows

Hormones Behavior 55 a similar pattern . Most people also know about the relationship between aggression and anabolic steroid hormones , and they know that administration of artificial steroid hormones Box . Neural Transmission versus Communication Although neural and communication both rely on chemical signals , several prominent differences exist . in the nervous system is analogous to traveling on a train . You can use the train in your travel plans as long as tracks exist between your proposed origin and destination . Likewise , neural messages can travel only to destinations along existing nerve tracts . communication , on the other hand , is like traveling in a car . You can drive to many more destinations than train travel allows because there are many more roads than railroad tracks . Similarly , hormonal messages can travel anywhere in the body via the circulatory system any cell receiving blood is potentially able to receive a hormonal message . Neural and hormonal communication differ in other ways as well . lo illustrate them , consider the differences between digital and analog technologies . Neural messages are digital , events that have rapid onset and offset neural signals can take place in milliseconds Accordingly , the nervous system changes in the body that are relatively rapid . For example , the nervous system regulates immediate food intake and directs body movement . In contrast , hormonal messages are analog , graded events that may take seconds , minutes , or even hours to occur . Hormones can mediate processes , such as growth , development , reproduction , and metabolism . and neural messages are both chemical in nature , and they are released and received by cells in a similar manner however , there are important differences as well . Neurotransmitters , the chemical messengers used by neurons , travel a distance of only ( 30 ) the membrane of the postsynaptic neuron , where they bind with receptors . Hormones enter the circulatory system and may travel from millimeter to meters before arriving at a target cell , where they bind with receptors . Another distinction between neural and hormonal communication is the degree of voluntary control that can be exerted over their functioning . In general , there is more voluntary control of neural than of hormonal signals . It is virtually impossible to will a change in your thyroid levels , for example , whereas moving your limbs on command is easy . Although these are differences , the division between the nervous system and the endocrine system is becoming more blurred as we learn more about how the nervous system regulates hormonal communication . A better understanding of the interface between the system and the nervous system , called , is likely to yield important advances in the future study of the interaction between hormones and behavior .

Hormones Behavior 56 sometimes results in uncontrollable , violent behavior called roid rage . Many different hormones can influence several types of behavior , but for the purpose ofthis module , we will restrict our discussion a few examples of hormones and behaviors . For example , are behavioral sex differences the result of hormones , the environment , or some combination of factors ?

men much more women to commit aggressive acts ?

Are hormones involved in mediating the maternal instinct ?

Behavioral are interested in how the general physiological effects of hormones alter the development and expression of behavior and how behavior may influence the effects of hormones . This module describes , both phenomenologically and functionally , how hormones affect behavior . To understand the relationship , it is important briefly to describe hormones . Hormones are organic chemical messengers produced and released by specialized glands called endocrine glands . Hormones are released from these glands into the blood , where they to act on target structures at some distance from their origin . Hormones are similar in function to neurotransmitters , the chemicals used by the nervous system in coordinating animals activities . However , hormones can operate over a greater distance and over a much greater temporal range than neurotransmitters ( Box ) Examples of hormones that influence behavior include steroid hormones such as testosterone ( a common type of androgen ) estradiol ( a common type of estrogen ) progesterone ( a common type of progestin ) and cortisol ( a common type ) Table ) Several types of protein or peptide ( small protein ) hormones also influence behavior , including oxytocin , prolactin , and . Steroid Hormones Cortisol Increases carbohydrate metabolism stree responses Uterine and other female tissue development Regulates sexual motivation and performance in females and males Testosterone Promotes sperm production and male secondary characters Promotes sexual motivation and behavior , typically by being converted to estradiol Hormones coordinate the physiology and behavior of individuals by regulating , integrating , and controlling bodily functions . Over evolutionary time , hormones have often been by the nervous system to influence behavior to ensure reproductive success . For example , the same hormones , testosterone and estradiol , that cause gamete ( egg or sperm ) maturation also promote mating behavior . This dual hormonal function ensures that mating behavior

Hormones Behavior social bonding Prolactin with parental care Thyroxine Table Prominent Hormones That Influence Behavior 57 Peptides and Protein Hormones Oxytocin Stimulates milk letdown and uterine contractions during birth Promotes Many actions relating to reproduction , water balance , and behavior associated Increases oxidation rates in tissue and affects neural development Increases water reabsorption in the kidney and affects learning and memory occurs when animals have mature available for fertilization . Another example of endocrine regulation of physiological and behavioral function is provided by pregnancy . and progesterone concentrations are elevated during pregnancy , and these hormones are often involved in mediating maternal behavior in the mothers . This is an image of oxytocin with its protein . Oxytocin is often called the . To learn more about it , see module Biochemistry of Love . and every hormone . Rather , any given hormone can hormone receptors for that particular hormone . Cells that have these specific receptors are called target cells for the interaction ofa hormone with its receptor begins a series of cellular events that eventually lead to activation of enzymatic pathways or , alternatively , turns on or turns activation that regulates protein synthesis . The newly synthesized proteins may activate or deactivate other genes , causing yet another cascade of , sufficient numbers hormone receptors must be available for a specific hormone to cellular events . produce any effects . For example , testosterone is important for male sexual behavior . If men have too little testosterone , then sexual motivation may be low , and it can be restored by testosterone treatment . However , if men have normal or even elevated levels of testosterone yet display low sexual drive , then it might be possible for a lack of receptors to be the cause

Hormones Behavior 58 and treatment with additional hormones will not be effective . How might hormones affect behavior ?

In terms of their behavior , one can think of humans and other animals conceptually as comprised of three interacting components ( input systems ( sensory systems ) the central nervous system ) and ( output systems , or ( muscles ) Hormones do not cause behavioral changes . Rather , hormones influence these three systems so that specific stimuli are more likely to elicit certain responses in the appropriate behavioral or social context . In other words , hormones change the probability that a particular behavior will be emitted in the appropriate situation ( Nelson , relationships . We can apply this behavioral scheme to a simple behavior , singing in zebra finches . Only male zebra finches sing . If the testes of adult male finches are removed , then the birds reduce singing , but castrated finches resume singing if the testes are , or if the birds are treated with either testosterone or estradiol . Although we commonly consider to be male hormones and to be female hormones , it is common for testosterone to be converted to estradiol in nerve cells ( Figure ) Thus , many behaviors are associated with the actions of ! Indeed , all must first be converted from because of the typical biochemical synthesis process . If the converting enzyme is low or missing , then it is possible for females to produce excessive and subsequently develop associated male traits . It is also possible for in the environment to affect the nervous system , including people ( et , concentrations are high . Males sing to attract mates or ward off potential competitors from their territories . Although it is apparent from these observations that are somehow involved in singing , how might the framework just introduced help us to formulate hypotheses to explore estrogen role in this behavior ?

By examining input systems , we could determine whether alter the birds sensory capabilities , making the environmental cues that singing more salient . Ifthis were the case , then females or competitors might be more easily seen or heard . also could influence the central nervous system . Neuronal architecture or the speed of neural processing could change in the presence of . Higher neural processes ( motivation , attention , or perception ) also might be influenced . Finally , the effector organs , muscles in this case , could be affected by the presence . Blood estrogen concentrations might muscles ofa songbird syrinx ( the vocal organ ) therefore , could affect birdsong by sensory capabilities , central processing system , or effector organs of an individual bird . We

Hormones Behavior 59 enzyme enzyme Figure Biochemical Pathway for Steroid Hormone Synthesis It is important to note that testosterone ( an androgen ) can be converted to another androgen , or an estrogen , estradiol . Too much or too little of the converting enzymes can brain and behavior . do not understand completely how estrogen , derived from testosterone , influences birdsong , but in most cases , hormones can be considered to affect behavior by influencing one , two , or all three of these components , and this framework can aid in the design of hypotheses and experiments to explore these issues . How might behaviors affect hormones ?

The birdsong example demonstrates how hormones can affect behavior , but as noted , the reciprocal relation also occurs that is , behavior can affect hormone concentrations . For example , the sight of a territorial intruder may elevate blood testosterone concentrations in resident male birds and thereby stimulate singing or fighting behavior . Similarly , male mice or rhesus monkeys that lose a fight decrease circulating testosterone concentrations for several days or even weeks afterward . Comparable results have also been reported in humans . Testosterone concentrations are affected not only in humans involved in physical combat , but also in those involved in simulated battles . For example , testosterone concentrations were elevated in winners and reduced in losers of

Hormones Behavior 60 regional chess tournaments . People do not have to be directly involved in a contest to have their hormones affected by the outcome of the contest . Male fans of both the Brazilian and Italian teams were recruited to provide saliva samples to be for testosterone before and after the final game of the World Cup soccer match in 1994 . Brazil and Italy were tied going into the final game , but Brazil won on a penalty kick at the last possible moment . The Brazilian fans were elated and the Italian fans were crestfallen . When the samples were , 11 of Brazilian fans who were sampled had increased testosterone concentrations , and of Italian fans had decreased testosterone concentrations , compared with baseline values ( In some cases , hormones can be affected by anticipation of behavior . For example , testosterone concentrations also influence sexual motivation and behavior in women . In one study , the interaction between sexual intercourse and testosterone was compared with other activities ( cuddling or exercise ) in women ( van Anders , Hamilton , Schmidt , Watson , a , and saliva sample . After analysis , the women testosterone was determined to be elevated prior to intercourse as compared to other times . Thus , an anticipatory relationship exists between sexual behavior and testosterone . Testosterone values were higher intercourse compared to exercise , suggesting that engaging in sexual behavior may also influence hormone concentrations in women . null . i The expectation of events can influence one hormonal activity . How do you think yours is affected ifyou anticipate going on a date with a Sex Differences romantic interest soon ?

Hens and roosters are different . Cows and bulls are different . Men and women are different . Even girls and boys are different . Humans , like many animals , are sexually dimorphic ( di , two morph , type ) in the size and shape of their bodies , their physiology , and for our purposes , their behavior . The behavior of boys and girls differs in many ways . Girls generally excel in verbal abilities relative to boys boys are nearly twice as likely as girls to suffer from dyslexia ( reading difficulties ) and stuttering and nearly times more likely to suffer from autism . Boys

Hormones Behavior 61 are generally better than girls at tasks that require abilities . Girls engage in nurturing behaviors more frequently than boys . More than 90 ofall anorexia cases involve young women . Young men are twice as likely as young women to schizophrenia . Boys are much more aggressive and generally engage in more play than girls ( sex differences , such as the difference in in nonhuman animals than in humans . Male birds throughout adulthood particularly , for example roosters , tend to have physical For example there are many more men than features that differ from the females and also differ women serving prison sentences for violent Sex differences in appearance are often more pronounced significantly in size . John behavior . The hormonal differences between men and women may account for adult sex differences that develop during puberty , but what accounts for behavioral sex differences among children prior to puberty and activation of their gonads ?

Hormonal secretions from the developing gonads determine whether the individual develops in a male or female manner . The mammalian embryonic testes produce , as well as peptide hormones , that steer the development ofthe body , central nervous system , and subsequent behavior in a male embryonic ovaries of mammals are virtually do not secrete high concentrations of hormones . In the presence of ovaries , or in the complete absence of any gonads , morphological , neural , and , later , behavioral development follows a female pathway . Gonadal steroid hormones have organizational ( or programming ) effects upon brain and behavior ( The organizing effects of steroid hormones are relatively constrained to the early stages of development . An asymmetry exists in the effects and ovaries on the organization of behavior in mammals . Hormone exposure early in life has organizational effects on subsequent rodent behavior early steroid hormone treatment causes relatively irreversible and permanent masculinization of rodent behavior ( mating and aggressive ) These early hormone effects can be contrasted with the reversible behavioral influences hormones provided in adulthood , which are called effects . The effects of hormones on adult behavior are temporary and may wane soon after the hormone is metabolized . Thus , typical male behavior requires exposure to during gestation ( in humans ) or immediately after birth ( in rodents ) to somewhat masculinize the brain and also requires during or after puberty to activate these neural circuits . Typical female behavior requires a lack of exposure to early in life

Hormones Behavior 62 which leads to feminization ofthe brain and also requires to activate these neural circuits in adulthood . But this simple dichotomy , which works well with animals with very distinct sexual dimorphism in behavior , has many when applied to people . If you walk through any major toy store , then you will likely observe a couple of aisles filled with pink boxes and the complete absence of pink packaging of toys in adjacent aisles . Remarkably , you will also see a strong of boys and girls in these aisles . It is rare to see boys in the pink aisles and vice versa . The toy manufacturers are often accused of making toys that are gender biased , but it seems more likely that boys and girls enjoy playing with specific types and colors of toys . Indeed , toy manufacturers would immediately double their sales ifthey could sell toys to both sexes . Boys generally prefer toys such as trucks and balls and girls generally prefer toys such as dolls . Although it is doubtful that there are genes that encode preferences for toy cars and trucks on the chromosome , it is possible that hormones might shape the development ofa child brain to prefer certain types of toys or styles of play behavior . It is reasonable to believe that children learn which types of toys and which styles are appropriate to . How can we understand and separate the contribution of physiological mechanisms from learning to understand sex differences in human behaviors ?

To untangle these issues , animal models are often used . Unlike the situation in humans , where sex differences are usually only a matter of degree ( often slight ) in some animals , members of only one sex may display a particular behavior . As noted , often only male songbirds sing . Studies of such strongly behaviors are particularly valuable for understanding the interaction among behavior , hormones , and the nervous system . A study of vervet monkeys calls into question the primacy of learning in the establishment of toy preferences ( Alexander preferred toys , such as dolls or cooking pots , whereas male vervet monkeys preferred toys , such as cars or balls . There were no sex differences in preference for Ifyou think back to the toys and clothing you played with and wore neutral toys Such as picture books or , stuffed animals . Presumably , monkeys activity or the choices that society and your parents made foryou ?

have no prior concept of boy or girl Sam Hormones Behavior 63 toys . Young rhesus monkeys also show similar toy preferences . What then underlies the sex difference in toy preference ?

It is possible that certain attributes of toys ( or objects ) appeal to either boys or girls . Toys that appeal to boys or male vervet or rhesus monkeys , in this case , a ball or toy car , are objects that can be moved actively through space , toys that can be incorporated into active , rough and tumble play . The appeal of toys that girls or female vervet monkeys prefer appears to be based on color . Pink and red ( the colors of the doll and pot ) may provoke attention to infants . Society may reinforce such stereotypical responses to toys . The sex differences in toy preferences emerge by 12 or 24 months of age and seem fixed by 36 months of age , but are sex differences in toy preference present during the first year of life ?

It is difficult to ask infants what they prefer , but in studies where the investigators examined the amount of time that babies looked at different toys , data indicate that infants as young as months showed sex differences in toy preferences girls preferred dolls , whereas boys preferred trucks . Another result that suggests , but does not prove , that hormones are involved in toy preferences is the observation that girls diagnosed with congenital adrenal hyperplasia ( whose adrenal glands produce varying amounts early in life , played with masculine toys more often than girls without . Further , a relationship between the extent ofthe disorder ( degree of fetal androgen exposure ) and degree of masculinization of play behavior was observed . Are the sex differences in toy preferences or play activity , for example , the inevitable consequences of the differential endocrine environments of boys and girls , or are these differences imposed by cultural practices and beliefs ?

Are these differences the result of receiving toys from an early age , or are these differences some combination of endocrine and cultural factors ?

Again , these are difficult questions to unravel in people . Even when behavioral sex differences appear early in development , there seems to be some question regarding the influences of societal expectations . One example is the pattern of human play behavior during which males are more physical this pattern is seen in a number of other species including nonhuman primates , rats , and dogs . Is the difference in the frequency of play between boys and girls due to biological factors associated with being male or female , or is it due to cultural expectations and learning ?

If there is a combination of biological and cultural influences mediating the frequency of play , then what proportion ofthe variation between the sexes is due to biological factors and what proportion is due to social influences ?

Importantly , is it appropriate to talk about ' normal sex differences when these traits virtually always arrange themselves along a continuum rather than in discrete categories ?

Hormones Behavior 64 Sex differences are common in humans and in nonhuman animals . Because males and females differ in the ratio of androgenic and estrogenic steroid hormone concentrations , have been behavioral sex differences are mediated by hormones . The process of becoming female or male is called sexual differentiation . The primary step in sexual differentiation occurs at fertilization . In mammals , the ovum ( which always contains an chromosome ) can be fertilized by a sperm bearing either a or an chromosome this process is called sex determination . The chromosomal sex of homogametic mammals ( is female the chromosomal sex of heterogametic mammals ( XY ) is male . Chromosomal sex determines gonadal sex . Virtually all subsequent sexual differentiation is typically the result exposure to gonadal steroid hormones . Thus , gonadal sex determines hormonal sex , which regulates morphological sex . Morphological differences in the central nervous system , as well as in some effector organs , such as muscles , lead to behavioral sex differences . The process of sexual differentiation is complicated , and the potential for errors is present . cause among females . The source of androgen may be internal ( secreted by the adrenal glands ) or external ( exposure to environmental ) Turner syndrome results when the second chromosome is missing or damaged these individuals possess dysgenic ovaries and are not exposed to steroid hormones until puberty . Interestingly , women with Turner syndrome often have impaired spatial memory . Female mammals are considered the neutral sex additional physiological steps are required for male differentiation , and more steps bring more possibilities for errors in differentiation . Some examples of male anomalous sexual differentiation include deficiency ( in which XY individuals are born with ambiguous genitalia because of a lack of and are reared as females , but masculinization occurs during puberty ) and androgen insensitivity syndrome or ( in which XY individuals lack receptors for and develop as females ) By studying individuals who do not neatly fall into the dichotic boxes or male and for whom the process differentiation is atypical , behavioral glean hints about the process of typical sexual differentiation . We may ultimately want to know how hormones mediate sex differences in the human brain and behavior ( to the extent to which these differences occur ) To understand the mechanisms underlying sex differences in the brain and behavior , we return to the birdsong example . Birds provide the best evidence that behavioral sex differences are the result of hormonally induced structural changes in the brain ( In contrast to mammals , in which structural differences in neural tissues have not been directly linked to behavior , structural differences in avian brains have been directly linked to a sexually behavior birdsong .

Hormones Behavior 65 Several brain regions in songbirds display significant sex differences in size . Two major brain circuit pathways , the song production motor pathway and ( the auditory transmission pathway , have been implicated in the learning and production of birdsong . Some parts ofthe song production pathway of male zebra finches are to times larger than those of female . The larger size of these brain areas reflects that neurons in these nuclei are larger , more numerous , and farther apart . Although castration of adult male birds reduces singing , it does not reduce the size of the brain nuclei controlling song production . Similarly , androgen treatment of adult female zebra finches does not induce changes either in singing or in the size of the song control regions . Thus , effects of steroid hormones do not account for the sex differences in singing behavior or brain nucleus size in zebra finches . The sex differences in these structures are organized or programmed in the egg by estradiol ( or the lack of steroids ( Taken together , appear to be necessary to activate the neural machinery underlying the song system in birds . The testes of birds primarily produce , which enter the circulation . The enter neurons containing , which converts them to . Indeed , the brain is the primary source of , which activate masculine behaviors in many bird species . Figure The sexually dimorphic nuclei of the preoptic area ( Gonadal steroid hormones have organizing effects upon brain and behavior . The organizing effects of steroid hormones are relatively constrained to the early stages of development . Exposure to testosterone ( which is converted to estradiol ) or estradiol causes masculinization of the brain . These are the brains of rats a male ( left ) a female ( center ) and a female treated with testosterone as a newborn ( right ) Note that the ( the dark cell bodies ) ofthe male are substantially larger than those ofthe untreated female but are equal in size to those of the female . The extent that these sex differences in brain structure account for sex differences in behavior remain in mammals . optic chiasm nucleus third ventricle .

Hormones Behavior 66 Sex differences in human brain size have been reported for years . More recently , sex differences in specific brain structures have been discovered ( Figure ) Sex differences in a number of cognitive functions have also been reported . Females are generally more sensitive to auditory information , whereas males are more sensitive to visual information . Females are also typically more sensitive than males to taste and olfactory input . Women display less lateralization of cognitive functions than men . On average , females generally excel in verbal , perceptual , and fine motor skills , whereas males outperform females on quantitative and tasks , including map reading and direction finding . Although reliable sex differences can be documented , these differences in ability are slight . It is important to note that there is more variation within each sex than between the sexes for most cognitive abilities ( Figure ) Average Sex Difference Frequency Trait ( or score ) Figure The Average Sex Differences in Human Performance Often Reflect Significant Overlap Between the Sexes There are often greater differences in performance between individuals of the same sex ( for example , between Steve and Rick in the figure ) than between individuals of the opposite sex ( for example , between Steve in the figure ) Aggressive Behaviors

Hormones Behavior 67 The possibility for aggressive behavior exists whenever the interests of two or more individuals are in conflict ( Conflicts are most arise over limited resources such as territories , food , and mates . A social interaction decides which animal gains access to the contested resource . In many cases , a submissive posture or gesture on the part ofone animal avoids the necessity of actual combat over a resource . Animals may also participate in threat displays or ritualized combat in which dominance is determined but no physical damage is inflicted . There is overwhelming circumstantial evidence that androgenic steroid hormones mediate aggressive behavior across many species . First , seasonal variations in blood plasma concentrations of testosterone and seasonal variations in aggression coincide . For instance , the incidence of aggressive behavior peaks for male deer in autumn , when they are secreting high levels of testosterone . Second , aggressive behaviors increase at the time of puberty , when the testes become active and blood concentrations deer do not participate in the fighting during the mating season . Third , in any given species , males are generally more aggressive than females . This is certainly true relative to stags , female deer rarely display aggressive behavior , and their rare aggressive acts are qualitatively different from the aggressive behavior males . Finally , castration typically reduces aggression in males , and testosterone replacement therapy restores aggression to castration levels . There are some interesting exceptions to these general observations that are outside the scope of this module . As mentioned , males are generally more aggressive than females . Certainly , human males are much more aggressive than females . Many more men than women are convicted crimes in North America . The sex differences in human aggressiveness appear very early . At every age throughout the school years , many more boys than girls initiate physical assaults . Almost everyone will acknowledge the existence of this sex difference , but assigning a cause to behavioral sex differences in humans always elicits much debate . It is possible that boys are more aggressive than girls because promote aggressive behavior and boys have higher blood concentrations of than girls . It is possible that boys and girls differ in their aggressiveness because the brains of boys are exposed to prenatally and the wiring of their brains is thus organized in a way that facilitates the expression of aggression . It is also possible that boys are encouraged and girls are discouraged by family , peers , or others from acting in an aggressive manner . These three hypotheses are not mutually exclusive , butitis discriminate to sex differences in human aggressiveness . What kinds of studies would be necessary to assess these hypotheses ?

It is usually difficult to separate outthe influences and physiology on the development Hormones Behavior 68 in humans . For example , boys and girls differ in their play at a very young age , which suggests an early physiological influence on aggression . However , female play more roughly with male infants than with females , which suggests that the sex difference in aggressiveness is partially learned . This difference in parental interaction style is evident by the first week of life . Because of these complexities in the factors influencing human behavior , the study of hormonal effects on people brains , and these individuals have burst into behavior has been pursued in nonhuman aggressive , violent behavior , helping demonstrate that such animals for Which . can be held relatively Constant models for which sexual differentiation occurs are often used so that this process can be easily manipulated experimentally . Researchers have electrically stimulated particular regions in Again , with the appropriate animal model , we can address the questions posed above Is the sex difference in aggression due to higher adult blood concentrations in males than in females , males more aggressive than females because their brains are organized differently by hormones ?

Are males usually more aggressive than females because of an interaction of early and current blood androgen concentrations ?

If male mice are castrated prior to their sixth day of life , then treated with testosterone propionate in adulthood , they show low levels of aggression . Similarly , females prior to their sixth day but given in adulthood do not express levels of aggression . Treatment of males or females with testosterone prior to their sixth day life and also in adulthood results in a level of aggression similar to that observed in typical male mice . Thus , in mice , the proclivity for males to act more aggressively than females is organized by but also requires the presence of after puberty in order to be fully expressed . In other words , aggression in male mice is both organized and activated by . Testosterone exposure in adulthood without prior organization ofthe brain by steroid hormones does not evoke typical male levels . The hormonal control of aggressive behavior in house mice is thus similar to the hormonal mediation male mating behavior in other rodent species . Aggressive behavior is both organized and activated by in many species , including rats , hamsters , voles ,

Hormones Behavior 69 dogs , and possibly some primate species . Parental Behaviors Parental behavior can be considered to be any behavior that contributes directly to the survival of fertilized eggs or offspring that have left the body of the female . There are many patterns of mammalian parental care . The developmental status of the newborn is an important factor driving the type and quality of parental care in a species . Maternal care is much more common than paternal care . The vast majority of research on the hormonal correlates of mammalian parental behavior has been conducted on rats . Rats bear altricial young , and mothers perform a cluster of stereotyped maternal behaviors , including nest building , crouching over the pups to allow nursing and to provide warmth , pup retrieval , and increased aggression directed at intruders . Ifyou expose nonpregnant female rats ( or males ) to pups , their most common reaction is to huddle far away from them . Rats avoid new things ( neophobia ) However , ifyou expose adult rats to pups every day , they soon begin to behave maternally . This process is called or sensitization and it appears to serve to reduce the adult rats fear of pups . Of course a new mother needs to act maternal as soon as her offspring in a week . The onset of maternal behavior in rats is mediated by hormones . Several methods of study , such as hormone removal and replacement therapy , have been used to determine the hormonal correlates of rat maternal behavior . A fast decline of blood concentrations of progesterone in late pregnancy after sustained high concentrations of this hormone , in combination with high concentrations of estradiol and probably prolactin and oxytocin , induces female rats to behave maternally almost immediately in the presence of pups . This pattern of hormones at parturition overrides the usual fear response of adult rats toward pups , and it permits the onset of maternal behavior . Thus , the maternal instinct requires hormones to increase the approach tendency and lower the avoidance tendency . Laboratory strains of mice and rats are usually docile , but mothers can be quite aggressive toward animals that venture too close to their litter . Progesterone appears to be the primary hormone that induces this maternal aggression in rodents , but species differences exist . The role aggression in women behavior has not been adequately described or tested . A series experiments by Alison Fleming and her collaborators studied the endocrine correlates ofthe behavior of human mothers as well as the endocrine correlates of maternal attitudes as expressed in questionnaires . Responses such as patting , cuddling , or kissing the baby were called affectionate behaviors talking , singing , or cooing to the baby were considered vocal behaviors . Both affectionate and vocal behaviors were considered

Hormones Behavior 70 approach behaviors . Basic activities , such as changing diapers and burping the infants , were also recorded . In these studies , no relationship between hormone concentrations and maternal responsiveness , as measured by attitude questionnaires , was found . For example , most women showed an increasing positive during early pregnancy that dipped during the second half of pregnancy , but recovered after parturition . A related dip in feelings of maternal engagement occurred during late pregnancy , but rebounded substantially after birth in most women . However , when behavior , rather than questionnaire responses , was compared with hormone concentrations , a different story emerged . Blood plasma concentrations of cortisol were positively associated with approach behaviors . In other words , women who had high concentrations of blood cortisol , in samples obtained immediately before or after nursing , engaged in more physically affectionate behaviors and talked more often babies than concentrations . this study revealed thatthe correlation was even mothers that had reported positive maternal regard ( feelings and attitudes ) during gestation . Indeed , nearly half of the variation in maternal behavior among women could be accounted for by cortisol concentrations and positive maternal attitudes during pregnancy . Presumably , cortisol does not induce maternal behaviors directly , but it may on the quality care by evoking an increase in the mother general level of arousal , thus increasing her responsiveness to cues . New mothers with high cortisol concentrations were also more attracted to their odors , infants , and generally found cues from Although cortisol may not directly increase maternal behaviors , the infants highly appealing next time your mom does your laundry , you know one hormone to thank . Image Scott Elaine van der The medial preoptic area is critical for the expression of rat maternal behavior . The amygdala appears to tonically inhibit the expression of maternal behavior . Adult rats are fearful of pups , a response that is apparently mediated by information . Lesions of the amygdala or afferent sensory pathways from the vomeronasal organ to the amygdala the expression of maternal behavior . Hormones or sensitization likely act to the amygdala , thus permitting the occurrence of maternal behavior . Although correlations have been established , direct evidence of brain structural changes in human mothers remains unspecified ( Fleming

Hormones Behavior 71 , 2009 ) Considered together , there are many examples of hormones influencing behavior and of behavior interactions are discovered , including hormones in the mediation of food and fluid intake , social interactions , salt balance , learning and memory , stress coping , as well as psychopathology including depression , anxiety disorders , eating disorders , postpartum depression , and seasonal depression . Additional research should reveal behavior interactions are mediated .

Hormones Behavior 72 Outside Resources Book , 2005 ) Hormones and animal social behavior . Princeton , Princeton University Press . Book Beach , A . 1948 ) Hormones and behavior . New York Paul . Book Beach , A . 1975 ) Behavioral endocrinology An emerging discipline . American Scientist , 63 . Book Nelson , 201 ) An introduction to behavioral endocrinology ( MA Associates . Book , 2009 ) Hormones , brain , and behavior ( Academic Press . Book , Phillips , Rubin , 2005 ) Principles of relations . New York Academic Press . Discussion Questions . What are some of the problems associated with attempting to determine causation in a interaction ?

What are the best ways to address these problems ?

Hormones cause changes in the rates processes or in cellular morphology . What are some ways that these hormonally induced cellular changes might theoretically produce profound changes in behavior ?

List and describe some behavioral sex differences that you have noticed between boys and girls . What causes girls and boys to choose different toys ?

Do you think that the sex differences you have noted arise from biological causes or are learned ?

How would you go about establishing your opinions as fact ?

Why is it inappropriate to refer to and as male hormones and as female hormones ?

Imagine that you discovered that the brains were different from those of , that the nuclei of the right temporal lobe were enlarged in architects as compared with . Would you argue that architects were destined to be architects because of their brain organization or that experience as

Hormones Behavior an architect changed their brains ?

How would you resolve this issue ?

73 Hormones Behavior 74 Vocabulary An enzyme required to convert testosterone to . Aggression A form of social interaction that includes threat , attack , and fighting . An enzyme that converts into . Chromosomal sex The sex of an individual as determined by the sex chromosomes ( typically or XY ) received at the time of fertilization . The removal of the potential for female traits . The removal of the potential for male traits . A primary androgen that is an androgenic steroid product and binds strongly to androgen receptors . Endocrine gland A ductless gland from which hormones are released into the blood system in response to specific biological signals . Estrogen Any of the class of steroid hormones , so named because of the properties in females . Biologically important include estradiol and estriol . Feminization The induction of female traits . Gonadal sex The sex ofan individual as determined by the possession ovaries or testes . Females

Hormones Behavior 75 have ovaries , whereas males have testes . Hormone An organic chemical messenger released from endocrine cells that travels through the blood to interact with target cells at some distance to cause a biological response . Masculinization The induction of male traits . Maternal behavior Parental behavior performed by the mother or other female . Neurotransmitter A chemical messenger that travels between neurons to provide communication . Some neurotransmitters , such as norepinephrine , can leak into the blood system and act as hormones . Oxytocin A peptide hormone secreted bythe lactation , as well as social bonding . Parental behavior Behaviors performed in relation to ones offspring that contributes directly to the survival of those offspring Paternal behavior Parental behavior performed by the father or other male . Progesterone A primary progestin that is involved in pregnancy and mating behaviors . Progestin A class of steroid hormones named for their progestational ( effects . Progesterone is a common progestin . A molecule that can act as a hormone itself or be converted into another hormone with different properties . For example , testosterone can serve as a hormone or as a for either or estradiol .

Hormones Behavior 76 Prolactin A protein hormone that is highly conserved throughout the animal kingdom . It has many biological functions associated with reproduction and synergistic actions with steroid hormones . Receptor A chemical structure on the cell surface or inside of a cell that has an affinity for a specific chemical configuration of a hormone , neurotransmitter , or other compound . Sex determination The point at which an individual begins to develop as either a male or a female . In animals that have sex chromosomes , this occurs at fertilization . Females are and males are XY . All eggs bear chromosomes , whereas sperm can either bear or chromosomes . Thus , it is the males that determine the sex ofthe offspring . Sex differentiation The process by which individuals develop the characteristics associated with being male or female . Differential exposure to gonadal steroids during early development causes sexual differentiation of several structures including the brain . Target cell A cell that has receptors for a specific chemical messenger ( hormone or neurotransmitter ) Testosterone The primary androgen secreted by the testes of most vertebrate animals , including men .

Hormones Behavior 77 References Alexander , Hines , 2002 ) Sex differences in response to child ren toys in nonhuman primates ( Evolution and Human Behavior , 23 , Martin , Briggs , Fabes , A . 2008 ) Sex differences in children play . In . Becker , Herman , Young ( Sex differences in the brain From genes to behavior . New York Oxford University Press . 2000 ) Heroes , rogues , and lovers Testosterone and behavior . Columbus , OH Hill . Fleming , A . 2009 ) Neurobiology of human maternal care . In Ellison . Gray ( Endocrinology relationships ( Cambridge , MA Harvard University Press . Fleming , 997 ) Cortisol , hedonics , and maternal responsiveness in human mothers . Hormones and Behavior , 32 , Hahn , Soma , 2005 ) Recent advances in behavioral Insights from studies on birds . Hormones and Behavior , 48 , Mills , Palace , Evans , Flick , 2007 ) Collapse of a fish population following exposure to a synthetic estrogen . Proceedings ofthe National Academy of 04 , Nelson , Ed . 2006 ) Biology of aggression . New York Oxford University Press . Nelson , 2011 ) An introduction to behavioral endocrinology ( MA Associates . Phoenix , Goy , A . Young , 1959 ) Organizing action of prenatally administered testosterone propionate on the tissues mediating mating behavior in the female guinea pig . Endocrinology , 65 van Anders , Hamilton , Schmidt , Watson , 2007 ) Associations between testosterone secretion and sexual activity in women . Hormones and Behavior , 51 ,