1. The Biological basis of Behavior 8%-10% on the AP EXAM
Chapter 3
The Biological basis of Behavior
8%-10% on the AP EXAM

2. Before we start. . .
A website to help you review.
It’s COOL!

3. DID
DENDRITES
SOMEONE
SOMA
ASK
AXON
MY SISTER
MYELIN SHEATH
TO BE
TERMINAL BUTTON
NICE TODAY
NEUROTRANSMITTER
SURE
SYNAPSE

4. Communication in the Nervous System
Hardware:
Glia (glue) – structural support and insulation
Neurons – communication
Soma – cell body
Dendrites – receive
Axon – transmit away
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.

6. Neural Communication: Insulation and Information Transfer
Myelin sheath – protects & speeds up transmission
Terminal Button – end of axon; secretes neurotransmitters
Neurotransmitters – chemical messengers
Synapse – point at which neurons interconnect
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.

7. The Neural Impulse: Electrochemical Beginnings
Hodgkin & Huxley (1952) - giant squid
Fluids inside and outside neuron
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
Absolute Threshold – minimum amount of stimulus needed for AP to fire.
Positively charged sodium ions flow in, potassium ions flow out
Shift in electrical charge travels along neuron
The Action Potential
All – or – none law - it fires or it doesn’t
Refractory Period – the period of time after the AP fires in which it cannot fire again until it resets itself.
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.

10. The Synapse: Chemicals as Signal Couriers
Synaptic cleft (Synapse)
Presynaptic neuron
Synaptic vesicles
Neurotransmitters
Postsynaptic neuron
Receptor sites
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.

12. TWO MINUTE DRILL:
BRIEFLY DEFINE EACH OF THE FOLLOWING TERMS AS THEY RELATE TO A NEURAL IMPULSE
RESTING POTENTIAL
ABSOLUTE THRESHOLD
ALL-OR-NONE LAW
SODIUM
POTASSIUM
ACTION POTENTIAL
REFRATORY PERIOD

13. 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
Negative voltage shift – inhibitory PSP
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.

15. Signals: From Postsynaptic Potentials to Neural Networks
One neuron, signals from thousands of other neurons
Requires integration of signals
PSPs add up, balance out
Balance between IPSPs and EPSPs
Neural networks
Patterns of neural activity
Interconnected neurons that fire together or sequentially
Synaptic connections
Elimination and creation
Synaptic pruning
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.

17. Neurotransmitters Specific neurotransmitters work at specific synapses
Lock and key mechanism
Agonist – mimics neurotransmitter action
Antagonist – opposes action of a neurotransmitter
curare – extracted from vines in South America – extreme muscle relaxant – death by suffocation
15 – 20 neurotransmitters known at present
Interactions between neurotransmitter circuits
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.

18. Basic Neurotransmitters
Acetylcholine (ACh)
Controls skeletal muscles
Contributes to the regulation of attention, arousal and memory
Some ACh receptors are stimulated by nicotine

19. Dopamine (DA)
Contributes to control of voluntary movement, pleasurable emotions
Decreased levels associated with Parkinson’s Disease
Overactive at DA synapses associated with schizophrenia
Cocaine and amphetamines elevate activity at DA synapses

20. Norepinephrine (NE)
Contributes to modulation of mood and arousal
Cocaine and amphetamines elevate the activity at NE synapses

21. Serotonin
Involved in regulation of sleep and wakefulness, eating and aggression
Abnormal levels may contribute to depression and OCD
Prozac and similar antidepressant drugs affect serotonin circuits

22. Serves as widely distributed inhibitory transmitter
Valium and similar antianxiety drugs work at GABA synapses
Gamma-aminobutyic acid
(GABA)

23. Endorphins
Resemble opiate drugs in structure and effect
Contribute to pain relief and perhaps to some pleasurable emotions

26. Organization of the Nervous System
Central nervous system (CNS) – brain and spinal cord
Afferent (Sensory)= toward the CNS/ Efferent (Motor) = away from the CNS
SAME – Sensory=Afferent Motor=Efferent
Peripheral nervous system – nerves that lie outside the central nervous system
Somatic nervous system– voluntary muscles and sensory receptors
Autonomic nervous system (ANS) – controls automatic, involuntary functions
Sympathetic – Go (fight-or-flight)
Parasympathetic – Stop
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.
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.

27. Figure 3.6 Organization of the human nervous system

31. The Nervous System Reflex
a simple, automatic, inborn response to a sensory stimulus
Skin
receptors
Muscle
Sensory neuron
(incoming information)
Motor neuron
(outgoing
information)
Brain
Interneuron
Spinal cord

32. Studying the Brain: Research Methods
Electroencephalography (EEG)
Damage studies/lesioning
Electrical stimulation (ESB)
Brain imaging –
(CT) computerized tomography - computer enhanced X-ray
(PET) positron emission tomography - radioactively tagged chemicals serve as markers of blood flow or metabolic activity in the brain that are monitored by X-ray
(MRI) magnetic resonance imaging - uses magnetic fields, radio waves, and computer enhancement to image brain structure
(fMRI)functional magnetic resonance imaging – Real-time MRI
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
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

35. Schizophrenia

37. Bill is suffering from depression and his psychiatrist prescribed Prozac to help him recover. What neurotransmitter will the drug affect?
A. Norepinephrine
B. Acetylcholine
C. Dopamine
D. Serotonin
E. GABA
C. Serotonin

38. Amanda has an excess amount of this neurotransmitter which is associated with her schizophrenia
A. Acetylcholine
B. Serotonin
C. Dopamine
D. Endorphins
E. GABA
C.Dopamine

39. 15. Researchers looking to create a drug to reduce
the symptoms of Alzheimer’s disease would
most likely focus their efforts on which of the
following neurotransmitters?
(A) GABA
(B) Serotonin
(C) Norepinephrine
(D) Dopamine
(E) Acetylcholine
E. Acetylcholine

40. Metabolic activity in different areas of the brain
can best be visualized by means of:
(A) magnetic resonance imaging (MRI)
(B) computed tomography (CT)
(C) positron emission tomography (PET)
(D) electroencephalography (EEG)
(E) electrical stimulation of the brain (ESB)
C. PET scan

41. Which of the following correctly pairs subdivisions
within the major divisions of the human nervous
system?
(A) Somatic . . endocrine and exocrine
(B) Central . . somatic and sympathetic
(C) Autonomic . . sympathetic and
parasympathetic
(D) Sympathetic . . parasympathetic and
autonomic
(E) Peripheral . . central nervous system
and the spinal cord
C. Autonomic – sympathetic and parasympathetic

42. Brain Regions and Functions
Hindbrain – vital functions – medulla, pons, and cerebellum
Midbrain – sensory functions – dopaminergic projections, reticular activating system
Forebrain – emotion, complex thought – thalamus, hypothalamus, limbic system, cerebrum, cerebral cortex
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.
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.
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…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.

43. The Cerebrum: Two Hemispheres, Four Lobes
Cerebral Hemispheres – two specialized halves connected by the corpus collosum
Left hemisphere – verbal processing: language, speech, reading, writing, math, logical, analytical
Right hemisphere – nonverbal processing: spatial, musical, visual recognition, intuition, creativity
Four Lobes:
Occipital – vision
Parietal - somatosensory
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.

48. The Cerebral Cortex

49. Prefrontal Cortex Mirror Neurons
frontal lobe neurons that fire when performing certain actions or when observing another doing so
may enable imitation, language learning, and empathy

51. Our Divided Brain
The information highway from the eye to the brain

53. Association Areas
More intelligent animals have increased “uncommitted” or association areas of the cortex

54. Plasticity Brain Reorganization
the brain’s capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development

55. A review
Carl Sagen 11 mins
NAT GEO web site for review
Brain Surgery

57. The Endocrine System: Glands and Hormones
Hormones – chemical messengers in the bloodstream
Pulsatile release by endocrine glands
Negative feedback system
Hypothalamus – controls the system
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.

58. Genes and Behavior: The Interdisciplinary Field of Behavioral Genetics
Behavioral genetics = the study of the influence of genetic factors on behavioral traits
Basic terminology:
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, recessive
Homozygous, heterozygous
Genotype/Phenotype and Polygenic Inheritance
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.
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.

60. Research Methods in Behavioral Genetics
Family studies – does it run in the family?
Twin studies – compare resemblance of identical (monozygotic) and fraternal (dizygotic) twins on a trait
Adoption studies – examine resemblance between adopted children and their biological and adoptive parents
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.
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.

64. Modern Approaches to the Nature vs. Nurture Debate
Molecular Genetics = the study of the biochemical bases of genetic inheritance
Genetic mapping – locating specific genes - The Human Genome Project
Behavioral Genetics
The interactionist model
Richard Rose (1995) – “We inherit dispositions, not destinies.”
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.
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.”

65. Evolutionary Psychology: Behavior in Terms of Adaptive Significance
Based on Darwin’s ideas of natural selection
Reproductive success key
Adaptations – behavioral as well as physical
Fight-or-flight response
Taste preferences
Parental investment and mating
The field of evolutionary psychology is a major new field in psychology focusing on analyzing human behavior in terms of adaptive significance.
Based on the work of Charles Darwin and the ideas of natural selection and reproductive fitness…i.e. that variations in reproductive success are what really fuels evolutionary change.
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.
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.