1. Chapter 3: The Biological Bases of Behavior The nervous system is the body’s communication network Behavior depends on rapid information travel and processing…the nervous system is the body’s communication network, handling information just as the circulatory system handles blood.

2. Communication in the Nervous System
The basic components of the nervous system are living cells called neurons and glia.
Hardware
Glia – structural support and insulation
Neurons – cells that receive, integrate, and transmit information
Soma – cell body
Dendrites – which are feeler-like structures specialized to receive information
Axon – a long, thin fiber that transmits signals away from the soma to other neurons, or to muscles or glands
Behavior depends on rapid information travel and processing…the nervous system is the body’s communication network, handling information just as the circulatory system handles blood.
The basic components of the nervous system are living cells called neurons and glia.
Glia are cells that provide structure and insulation for neurons…neural “glue.”
Neurons are cells that receive, integrate, and transmit information …permitting communication in the nervous system.
A “typical” neuron consists of a soma, or cell body; dendrites, which are feeler-like structures specialized to receive information; and an axon, which is a long, thin fiber that transmits signals away from the soma to other neurons, or to muscles or glands…the basic flow of information is as follows…the dendrite receives a signal, the signal passes through the soma and down the axon to the dendrites of another neuron.

4. Neural Communication: Insulation and Information Transfer
Myelin sheath – an insulating material that speeds up transmission (MS)
Terminal Button – end of axon; secretes neurotransmitters
Neurotransmitters – chemical messengers
Synapse – point at which neurons interconnect
The chemicals flow across the synapse and stimulate the next cell.
For efficient neural transmission to take place, many axons are covered with an insulating material called myelin. Myelin sheaths speed up transmission of signals that move along axons. Multiple sclerosis is a myelin degeneration disease, causing loss of muscle control, etc. due to loss of transmission efficiency in the nervous system when the myelin sheaths deteriorate.
At the end of an axon, the terminal buttons are small knobs that secrete chemical messengers called neurotransmitters. When the signal gets to the end of the axon, it causes these chemical messengers to be released into the synapse…the junction of two neurons. The chemicals flow across the synapse and stimulate the next cell.

5. Figure 3.1 Structure of the neuron

6. Figure 3.3 The synapse

7. The Neural Impulse: Electrochemical Beginnings
Hodgkin & Huxley (1952) - Alan Hodgkin and Andrew Huxley in the 1950’s discovered the mechanics of neural transmission by studying giant squids
Electrically charged particles (ions)
Neuron at rest – negative charge on inside compared to outside
-70 millivolts – resting potential
Alan Hodgkin and Andrew Huxley in the 1950’s discovered the mechanics of neural transmission by studying giant squid…which have axons that are about 100 times larger than human axons.
Found that fluids inside and outside the neuron contain electrically charged particles, or ions.
Also found that when a neuron is “at rest” the inside has more negative ions than the outside. The stable negative charge of a neuron when it is inactive is its resting potential.

8. The Neural Impulse: The Action Potential
Stimulation causes cell membrane to open briefly
Positively charged sodium ions flow in
The Action Potential: Shift in electrical charge travels along neuron
All – or – none law: Either an action potential occurs, or it doesn’t. Once an action potential is initiated, it goes full force
When a neuron is stimulated, channels in the cell membrane open briefly, allowing the positive ions outside the cell to flow into the electronegative inside…this shift in the electrical charge travels along the axon and is referred to as an action potential.
Either an action potential occurs, or it doesn’t. Once an action potential is initiated, it goes full force.

9. The Synapse: Chemicals as Signal Couriers
Synaptic cleft: Neurons don’t actually touch at a synapse, instead they are separated by a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron
Presynaptic neuron: the neuron that is sending the message across the gap
Synaptic vesicles: storage sacs for the neurotransmitter
Neurotransmitters
Postsynaptic neuron
The neurotransmitters diffuse across the space where they find open receptor sites on the postsynaptic neuron. These sites recognize and respond to some neurotransmitters, but not to others
Neurons don’t actually touch at a synapse, instead they are separated by a microscopic gap between the terminal button of one neuron and the cell membrane of another neuron - the synaptic cleft.
Electrical signals can’t jump this gap. Instead, the neuron that is sending the message across the gap (the presynaptic neuron) releases neurotransmitters into the synaptic cleft. This occurs when the action potential gets to the terminal button and causes the synaptic vesicles (storage sacs for the neurotransmitter) to fuse with the membrane at the end of the axon and spill its contents into the synaptic cleft.
The neurotransmitters diffuse across the space where they find open receptor sites on the postsynaptic neuron. These sites recognize and respond to some neurotransmitters, but not to others.

10. When a Neurotransmitter Binds: The Postsynaptic Potential
Voltage change at receptor site – postsynaptic potential (PSP)
Not all-or-none
Changes the probability of the postsynaptic neuron firing
Positive voltage shift – excitatory PSP makes the neuron more likely to fire…decreases the negativity of the inside of the neuron with respect to the outside
Negative voltage shift – inhibitory PSP increases the negativity of the inside of the neuron with respect to the outside, making it less likely to fire.
When a neurotransmitter from the presynaptic neuron crosses the synapse, finds an appropriate receptor site on the postsynaptic neuron, and binds, a voltage change occurs. This voltage change in the postsynaptic neuron is not an all-or-none, the neuron will fire or it won’t, kind of thing. Instead, it changes the probability or potential that the postsynaptic neuron will fire. This is, therefore, called a postsynaptic potential.
The postsynaptic potential can be excitatory or inhibitory. An excitatory potential makes the neuron more likely to fire…decreases the negativity of the inside of the neuron with respect to the outside.
An inhibitory postsynaptic potential increases the negativity of the inside of the neuron with respect to the outside, making it less likely to fire.

11. The Action Potential
The axon membrane is pierced by tiny molecular channels called ion channels
These channels are blocked when the neuron is at its resting potential.
During the action potential, the channels open, allowing sodium ions (Na+) to rush into the axon, beginning at the soma and moving toward the axon terminals, briefly creating a positive charge within the axon.
This is an all-or-nothing event – the impulse occurs completely, or not at all

12. Figure 3.4 Overview of synaptic transmission

13. Signals: From Postsynaptic Potentials to Neural Networks
Thought occurs through the firing of millions of neurons in unison.
Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially –
neural networks: Interconnected neurons that fire together or sequentially

14. Signals: From Postsynaptic Potentials to Neural Networks
Synaptic connections
Synaptic pruning: the elimination of old or unused synapses
plays a larger role than the creation of new synapses in the sculpting of neural networks
One neuron may receive signals from thousands of other neurons, across thousands of different synapses.
Each neuron must integrate the many signals arriving at the same time before it “decides” to fire.
EPSPs together add up…enough can cause the cell’s voltage to reach the threshold at which the action potential will begin.
EPSPs and IPSPs may balance out, as well, and the neuron would remain at rest.
Thus, the state of the neuron is a weighted balance.
Thought occurs through the firing of millions of neurons in unison. Our perceptions, thoughts, and actions depend on patterns of neural activity in interconnected neurons that fire together or sequentially – neural networks.
The links in these networks are constantly changing, with synaptic pruning or the elimination of old or unused synapses playing a larger role than the creation of new synapses in the sculpting of neural networks. For example, the number of synapses in the human visual cortex begins to decline after the age of 1 year.

15. Figure 3.5 Synaptic pruning

16. Specific neurotransmitters work at specific synapses
Lock and key mechanism
Agonist – mimics neurotransmitter action
Antagonist – opposes action of a neurotransmitter
15 – 20 neurotransmitters known at present
Interactions between neurotransmitter circuits
most aspects of behavior are probably regulated by many
NTs deliver their messages by binding to a receptor site…in a lock and key type manner. Not just any receptor site will do…there must be a perfect fit between the shape of the NT and the shape of the receptor site.
Some drugs mimic neurotransmitters, fitting into receptor sites so perfectly that the site is fooled and a PSP is set up…these chemicals are called agonists.
Other chemicals oppose the action of a NT…they bind to the receptor site but don’t really fit well enough to “fool” the site…they just block it.
Right now, we know of about substances that qualify as NTs…5 are commonly researched.
While research has outlined many interesting connections between neurotransmitters and behavior, most aspects of behavior are probably regulated by many neurotransmitters interacting.

17. Types of Neurotransmitters
Acetylcholine: only NT b/w motor neurons and voluntary muscles (every move you make depends on ACh)
Nicotine is an agonist
Monoamines
Dopamine voluntary movements and pleasure emotions (Parkinson’s, Schiz.)
Norepinephrine: modulates mood and arousal (cocaine and amphet.)
Serotonin: reg. Of sleep and wakefulness,eating and aggression (depression/ OCD)

18. Types of Neurotransmitters
Gaba: strictly inhibitory PSPs
Regulation of anxiety and plays a key role in seizures and modulation of sleep
Endorphins: resemble opiate drugs and effects, contribute to pain relief and some perhaps pleasurable emotions

19. Organization of the Nervous System
Central nervous system (CNS)
The central nervous system consists of the brain and spinal cord
Afferent = nerve fibers toward the CNS
Efferent = nerve fibers away from the CNS
The nervous system has two main divisions, central and peripheral.
The central nervous system consists of the brain and spinal cord, while the peripheral nervous system consists of nerves that lie outside the brain and spinal cord.
In the peripheral nervous system, afferent nerve fibers send information toward the CNS, while efferent nerve fibers send information away from the CNS.

20. Figure 3.7 The central and peripheral nervous systems

21. Organization of the Nervous System
Peripheral nervous system: the peripheral nervous system consists of nerves that lie outside the brain and spinal cord.
Somatic nervous system: voluntary portion
Autonomic nervous system (ANS)
governs involuntary, visceral functions
Sympathetic: mobilizes the body’s resources for emergencies and creates the fight-or-flight response
Parasympathetic: activates processes that conserve bodily resources…slowing heart rate, reducing blood pressure, etc
There are two divisions of the peripheral nervous system, the somatic, or voluntary portion, and the autonomic, or involuntary portion.
The autonomic portion of the peripheral nervous system governs involuntary, visceral functions…such as heart and breathing rate, blood pressure, etc.
When a person is autonomically aroused, these speed up. This speeding up is controlled by the sympathetic division of the autonomic nervous system…the sympathetic nervous system mobilizes the body’s resources for emergencies and creates the fight-or-flight response.
The parasympathetic division, in contrast, activates processes that conserve bodily resources…slowing heart rate, reducing blood pressure, etc.

22. Figure 3.6 Organization of the human nervous system

23. Figure 3.8 The autonomic nervous system (ANS)

24. The Cerebrum: Two Hemispheres, Four Lobes
Occipital – vision
Parietal – somatosensory (senses)
Temporal - auditory
Frontal – movement, executive control systems
The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres.
Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills.
Each hemisphere has four lobes: occipital – where the primary visual cortex is located, parietal – where the primary somatosensory cortex is located, temporal – where the primary auditory cortex is located, and frontal – where the primary motor cortex and executive control system is located.

25. Brain Regions and Functions
Hindbrain – vital functions –
Medulla: attaches to the spinal cord; controls: circulation, breathing, muscle tone, and regulating reflexes
Pons: means “bridge”, connects brainstem and cerebellum; sleep and arousal
Cerebellum: means “little brain” coordination of movement and equilibrium
The hindbrain is located at the lower end of the brain, where the spinal cord joins the brainstem. The medulla is in charge of circulation, breathing, muscle tone, and regulating reflexes…the pons is important in sleep and arousal…the cerebellum is critical in the coordination of movement and equilibrium.

26. Brain Regions and Functions
Midbrain: lies between the hindbrain and the forebrain
– integrates sensory functions (sight,smell,etc.)
dopaminergic projections: performance in voluntary movements
reticular activating system: bundle of nerve fibers running through the brain stem; sleep and arousal as well as breathing and pain perception (hind and midbrain)
Parkinson’s disease is due to degeneration of the substantia nigra, a structure in the midbrain
The midbrain lies between the hindbrain and the forebrain…it is involved in sensory functions such as locating where things are in space. It also contains structures which are important for voluntary movement (Parkinson’s disease is due to degeneration of the substantia nigra, a structure in the midbrain).
The reticular activating system is found in both the hind and midbrain, and is important in sleep and arousal as well as breathing and pain perception.

27. Brain Regions and Functions
Forebrain – emotion, complex thought
Thalamus: the way station for all incoming sensory information before it is passed on to appropriate higher brain regions
Hypothalamus: regulator of basic biological needs such as hunger, thirst, sex drive, and temperature regulation
limbic system: emotion, motivation, memory, and other aspects of behavior
The forebrain is the largest and most complex region of the brain. It includes the thalamus – the way station for all incoming sensory information before it is passed on to appropriate higher brain regions…the hypothalamus – which is the regulator of basic biological needs such as hunger, thirst, sex drive, and temperature regulation…the limbic system – which is a loosely connected network of structures involved in emotion, motivation, memory, and other aspects of behavior…

28. Brain Regions and Functions
Forebrain (cont.)
Cerebrum: largest and most complex portion of the human brain, responsible for complex mental activities such as learning, remembering, thinking, and consciousness
cerebral cortex: convoluted outer layer of the cerebrum
and finally, the cerebrum, which is the largest and most complex portion of the human brain…the convoluted outer layer of the cerebrum is the cerebral cortex…the cerebrum is responsible for complex mental activities such as learning, remembering, thinking, and consciousness.

29. Studying the Brain: Research Methods
Electroencephalography (EEG): monitoring electrical activity of the brain
Damage studies/lesioning: observing consequences of damage to certain areas
Electrical stimulation (ESB): stimulating a portion of the brain and observing effects
Electroencephalography (EEG) – monitoring electrical activity of the brain
Damage studies/lesioning – observing consequences of damage to certain areas
Electrical stimulation (ESB) – stimulating a portion of the brain and observing effects

30. Studying the Brain: Research Methods
Transcranial magnetic stimulation (TMS): enhance or suppress activity in a particular region of the brain
Brain imaging –
computerized tomography: computer enhanced X-ray
positron emission tomography: radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray
magnetic resonance imaging: uses magnetic fields, radio waves, and computer enhancement to image brain structure
Transcranial magnetic stimulation – enhance or suppress activity in a particular region of the brain
Brain imaging:
computerized tomography – computer enhanced X-ray
positron emission tomography – radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray
magnetic resonance imaging – uses magnetic fields, radio waves, and computer enhancement to image brain structure

31. Figure 3.16 Structures and areas in the human brain

32. The Cerebrum: Two Hemispheres, Four Lobes
Cerebral Hemispheres – two specialized halves connected by the
corpus callosum: thick band of fibers (axons) that transmits information between the hemispheres
Left hemisphere – verbal processing: language, speech, reading, writing
Right hemisphere – nonverbal processing: spatial, musical, visual recognition
The cerebrum is divided into two specialized hemispheres that are connected by the corpus collosum. The corpus collosum is a thick band of fibers (axons) that transmits information between the hemispheres.
Researchers using split brain methodology (severing of the corpus collosum) have learned that each hemisphere is specialized for different functions, with left usually dominant for language and right for spatial skills.
Each hemisphere has four lobes: occipital – where the primary visual cortex is located, parietal – where the primary somatosensory cortex is located, temporal – where the primary auditory cortex is located, and frontal – where the primary motor cortex and executive control system is located.

33. Hemispheric Specialization
Right Hemisphere: better at visual-spatial tasks, music, perception of emotions, neg. emotions exhibited
Left Hemisphere: better at verbal stimuli (lang., speech, reading, and writing), positive emotions exhibited

34. Right Brain/Left Brain
Broca’s Area: left frontal lobe; plays an important role in the production of speech
Wernicke’s Area: left temporal lobe; comprehension of speech

35. Figure 3.21 Language processing in the brain

36. Split-Brain Research
Severing of the corpus callosum (the part that shares information b/w the 2 hemispheres)

37. Figure 3.18 The cerebral hemispheres and the corpus callosum

38. Figure 3.19 The cerebral cortex in humans

39. Figure 3.20 The primary motor cortex

40. The Endocrine System: Glands and Hormones
Hormones – chemical messengers in the bloodstream
Pulsatile released by endocrine glands
Negative feedback system: The levels of many hormones increase to a certain level, then signals are sent to the hypothalamus or other endocrine glands to stop secretion of that hormone
Endocrine glands
Pituitary – “master gland,” growth hormone
Thyroid – metabolic rate
Adrenal – salt and carbohydrate metabolism
Pancreas – sugar metabolism
Gonads – sex hormones
Hormones are chemical messengers in the bloodstream that are secreted by the endocrine glands in a pulsatile manner – that is, several times per day in brief bursts or pulses. The levels of many hormones increase to a certain level, then signals are sent to the hypothalamus or other endocrine glands to stop secretion of that hormone – a negative feedback system.
These glands include: the pituitary – the master gland that secretes substances influencing the operation of all the other glands, as well as growth hormone; the thyroid gland – which controls metabolic rate; the adrenal glands – which control salt and carbohydrate metabolism; the pancreas – which secretes insulin to control sugar metabolism; and the gonads – which secrete sex hormones involved in the development of secondary sex characteristics and reproduction.

41. Genes and Behavior: The Field of Behavioral Genetics
Behavioral genetics = the study of the influence of genetic factors on behavioral traits
Chromosomes – strands of DNA carrying genetic information
Human cells contain 46 chromosomes in pairs (sex-cells – 23 single)
Each chromosome – thousands of genes, also in pairs
Dominant: sometimes a member of a pair has a louder voice, always expressing itself and masking the other, different, member of the pair
Recessive: gene is one that is masked when the paired genes are different
Questions about how much of behavior is biologically based and how much is environmentally based are very old ones in psychology. Since the 1970’s, however, research methodologies have been developed in the field of behavioral genetics that shed new light on the age-old nature vs. nurture question.
Basic terminology necessary to discuss behavior genetics research:
Chromosomes are strands of Deoxyribonucleic Acid (DNA) carrying genetic information…each human cell contains 23 pairs, or 46 total, chromosomes…with the exception of sex cells which have 23 single chromosomes…not yet paired.
Each chromosome contains thousands of genes, which also occur in pairs…sometimes a member of a pair has a louder voice, always expressing itself and masking the other, different, member of the pair…this is a dominant gene. A recessive gene is one that is masked when the paired genes are different

42. Genes and Behavior: The Field of Behavioral Genetics
Homozygous: a person has two genes in a specific pair that are the same
Heterozygous: a person has two genes in a specific pair that are different
Genotype/Phenotype: Genotype refers to a person’s genetic makeup (lifelong), while phenotype refers to the ways in which a person’s genotype is manifested in observable characteristics (variable)
Polygenic Inheritance: most human traits are not so simple with regard to genetic transmission…they are polygenic, or influenced by more than one pair of genes.
When a person has two genes in a specific pair that are the same, the person is homozygous for that trait…if the genes are different, heterozygous
Genotype refers to a person’s genetic makeup, while phenotype refers to the ways in which a person’s genotype is manifested in observable characteristics. You can have different genotypes which yield the same phenotype (i.e., one person has 2 genes for detached earlobes (dominant) while another has one for attached and one for detached…both, outwardly, look the same in the earlobe department)…most human traits are not so simple with regard to genetic transmission…they are polygenic, or influenced by more than one pair of genes.

43. Figure 3.25 Genetic material

44. Research Methods in Behavioral Genetics
Family studies – Family studies simply assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait
Twin studies – compare resemblance of identical (monozygotic) and fraternal (dizygotic) twins on a trait (monozygotic are more correlated in terms of intelligence and personality, but not perfectly alike- environment plays a part)
Family studies simply assess hereditary influence by examining blood relatives to see how much they resemble one another on a specific trait…determine whether it runs in the family…many things run in families, however, that are not genetic…like dessert recipes or speaking a certain language.
Twin studies can yield better evidence about the possible influence of heredity, because identical twins have the exact same genotype…they share 100% of the same genes. Fraternal twins only share 50% genetic relatedness…the same as any two siblings born to a set of parents at different times. Twins of both types, however, are raised in more similar environments (same age, configuration of relatives, etc.). If identical twins are more similar on a given trait than fraternal, the assumption is that it is probably genetic. .

45. Research Methods in Behavioral Genetics
Adoption studies – examine resemblance between adopted children and their biological and adoptive parents
They have found very similar correlations between both adoptive (.20) and natural parents (.22)
Adoption studies assess genetic influence by comparing adopted children with both their biological and adoptive parents…if they are more like their biological parents (who they have never met) on a trait, it is probably genetic

46. Figure 3.27 Genetic relatedness

47. Figure 3.28 Family studies of risk for schizophrenic disorders

48. Figure 3.30 Twin studies of intelligence and personality

49. Modern Approaches to the Nature vs. Nurture Debate
Molecular Genetics = the study of the biochemical bases of genetic inheritance
Genetic mapping – locating specific genes and their chemical sequence of specific genes on specific chromosomes
The Human Genome Project: produced a working draft of all 3 billion letters of DNA in the human genome (a genetic atlas)
Modern advances in molecular genetic technology have allowed for genetic mapping…the locating of specific chromosomes and genes involved in phenotypic expression. While this is a promising area of research, initial progress points toward the complexity of polygenic inheritance rather than yielding simple answers to the nature nurture debate.

50. Modern Approaches to the Nature vs. Nurture Debate
Behavioral Genetics
The interactionist model
Genetic research has yielded no easy answers about nature vs. nurture
Instead, it has led to the interactionist model- people with certain genes are more likely to exhibit certain behaviors when environmental influences are present
Richard Rose (1995) – “Genes confer dispositions (we inherit dispositions), not destinies.”
The behavioral genetics field has yielded much the same conclusion…there will be no simple answer to the “is it nature or nurture” question…Richard Rose quote – “we inherit dispositions, not destinies.”

51. Evolutionary Psychology: Behavior in Terms of Adaptive Significance
Based on Darwin’s ideas of:
Natural selection
Successful transmission of genetic evolution depends on providing either a reproductive advantage (firefly’s light) or a survival advantage (turtle shell)
Change is very gradual

52. Evolutionary Psychology: Behavior in Terms of Adaptive Significance
Inclusive fitness
Used to explain self-sacrifice
An organism may succeed in helping natural selection by sacrificing itself to save others that share the same genes

53. Evolutionary Psychology: Behavior in Terms of Adaptive Significance
Adaptations (inherited characteristics) – behavioral as well as physical; more difficult to study behaviors b/c they are infrequent and relatively quick in length of display
Fight-or-flight response: helpful in primitive times, but now it is related to a number of stress-related diseases
Taste preferences: humans show a taste preference for fatty foods…this was adaptive in a hunter/gatherer society, when dietary fat was scarce
Evolutionary theorists study adaptations, or inherited characteristics, that increase in a population because they help solve a problem of survival or reproduction during the time they emerge…giraffes and long necks.
May extend even when no longer needed, for example the fight-or-flight response may have been very helpful in primitive times, but now it is related to a number of stress-related diseases. Similarly, humans show a taste preference for fatty foods…this was adaptive in a hunter/gatherer society, when dietary fat was scarce…before potato chips, etc.…resulting in obesity, heart disease, etc. While this may lead to decreased longevity, the effect on reproductive success is more difficult to gauge.

54. Evolutionary Psychology: Behavior in Terms of Adaptive Significance
Adaptations (cont.)
Parental investment and mating (Trivers- 1972)
When parental investment is high for females and low for males, polygyny results –each male seeks to mate with multiple females and each female seeks only one male.
Polyandry: female seeks to mate with multiple males and each male with only one female – this emerges when parental investment is high for males and low for females.
Monogamy emerges when male and female parental investment is roughly equal.
Parental investment refers to time, energy, survival risk, and forgone opportunities that each sex has to invest in order to produce and nurture offspring. Trivers (1972) suggests that a species courting and mating patterns are based in parental investment. When parental investment is high for females and low for males, polygyny results – a mating system whereby each male seeks to mate with multiple, females and each female seeks only one male. Polyandry occurs when each female seeks to mate with multiple males and each male with only one female – this emerges when parental investment is high for males and low for females. Monogamy emerges when male and female parental investment is roughly equal.