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Chapter 3
The Biological basis of Behavior
8%-10% on the AP EXAM
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DID
– DENDRITES
SOMEONE
– SOMA
ASK
– AXON
MY SISTER
– MYELIN SHEATH
TO BE
– TERMINAL BUTTON
NICE TODAY
– NEUROTRANSMITTER
SURE
– SYNAPSE
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Communication in the Nervous
System
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Hardware:
– Glia (glue) – structural support and insulation
– Neurons – communication
– Soma – cell body
– Dendrites – receive
– Axon – transmit away
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Neural Communication: Insulation
and Information Transfer
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Myelin sheath – protects & speeds up transmission
Terminal Button – end of axon; secretes
neurotransmitters
Neurotransmitters – chemical messengers
Synapse – point at which neurons interconnect
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The Neural Impulse: Electrochemical
Beginnings
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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
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The Neural Impulse: The Action
Potential
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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
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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.
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The Synapse: Chemicals as Signal
Couriers
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Synaptic cleft (Synapse)
Presynaptic neuron
– Synaptic vesicles
– Neurotransmitters
Postsynaptic neuron
– Receptor sites
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TWO MINUTE DRILL:
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BRIEFLY DEFINE EACH OF THE FOLLOWING
TERMS AS THEY RELATE TO A NEURAL
IMPULSE
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RESTING POTENTIAL
ABSOLUTE THRESHOLD
ALL-OR-NONE LAW
SODIUM
POTASSIUM
ACTION POTENTIAL
REFRATORY PERIOD
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When a Neurotransmitter Binds: The
Postsynaptic Potential
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Voltage change at receptor site – postsynaptic
potential (PSP)
– Not all-or-none
– Changes the probability of the postsynaptic neuron firing
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Positive voltage shift – excitatory PSP
Negative voltage shift – inhibitory PSP
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Signals: From Postsynaptic Potentials
to Neural Networks
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One neuron, signals from thousands of other neurons
Requires integration of signals
– PSPs add up, balance out
– Balance between IPSPs and EPSPs
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Neural networks
– Patterns of neural activity
– Interconnected neurons that fire together or sequentially
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Synaptic connections
– Elimination and creation
– Synaptic pruning
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Neurotransmitters
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Specific neurotransmitters work at specific synapses
– Lock and key mechanism
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Agonist – mimics neurotransmitter action
Antagonist – opposes action of a neurotransmitter
– curare – extracted from vines in South America – extreme muscle
relaxant – death by suffocation
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15 – 20 neurotransmitters known at present
Interactions between neurotransmitter circuits
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Basic Neurotransmitters
 Acetylcholine
(ACh)
Controls skeletal
muscles
 Contributes to the
regulation of attention,
arousal and memory
 Some ACh receptors are
stimulated by nicotine
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Dopamine (DA)
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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
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 Norepinephrine
(NE)
 Contributes
to
modulation of mood
and arousal
 Cocaine and
amphetamines
elevate the activity at
NE synapses
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 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
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serotonin circuits
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 Serves
as widely
aminobutyic distributed inhibitory
transmitter
acid
 Valium and similar
 (GABA)
antianxiety drugs
work at GABA
synapses
 Gamma-
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 Endorphins
 Resemble
opiate drugs
in structure and effect
 Contribute to pain relief
and perhaps to some
pleasurable emotions
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Organization of the Nervous System
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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
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Figure 3.6 Organization of the human nervous system
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The Nervous System
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Reflex
 a simple, automatic, inborn response to a sensory stimulus
Brain
Sensory neuron
(incoming information)
Muscle
Motor neuron
(outgoing
information)
Interneuron
Spinal cord
Skin
receptors
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Studying the Brain: Research
Methods
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Electroencephalography (EEG)
Damage studies/lesioning
Electrical stimulation (ESB)
Brain imaging –
– (CT) computerized tomography - computer enhanced Xray
– (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 – RealTable of Contents
time MRI
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Schizophrenia
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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
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Amanda has an excess amount of this
neurotransmitter which is associated with her
schizophrenia
 A. Acetylcholine
 B. Serotonin
 C. Dopamine
 D. Endorphins
 E. GABA
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C.Dopamine
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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
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E. Acetylcholine
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Metabolic activity in different areas of the brain
can best be visualized by means of:
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(A) magnetic resonance imaging (MRI)
 (B) computed tomography (CT)
 (C) positron emission tomography (PET)
 (D) electroencephalography (EEG)
 (E) electrical stimulation of the brain (ESB)
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C. PET scan
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Which of the following correctly pairs subdivisions
 within the major divisions of the human nervous
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 (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
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Brain Regions and Functions
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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
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The Cerebrum: Two Hemispheres,
Four Lobes
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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
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Four Lobes:
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Occipital – vision
Parietal - somatosensory
Temporal - auditory
Frontal – movement, executive control systems
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The Cerebral Cortex
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Prefrontal Cortex
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Mirror Neurons
 frontal lobe neurons that fire when
performing certain actions or when
observing another doing so
 may enable imitation, language
learning, and empathy
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Our Divided Brain
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The information
highway from the
eye to the brain
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Association Areas
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More intelligent animals have increased
“uncommitted” or association areas of the cortex
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Brain Reorganization
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Plasticity
 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
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A review
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Carl Sagen 11 mins
NAT GEO web site for review
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Brain Surgery
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The Endocrine System: Glands and
Hormones
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Hormones – chemical messengers in the
bloodstream
– Pulsatile release by endocrine glands
– Negative feedback system
– Hypothalamus – controls the system
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Endocrine glands
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Pituitary – “master gland,” growth hormone
Thyroid - metabolic rate
Adrenal - salt and carbohydrate metabolism
Pancreas - sugar metabolism
Gonads - sex hormones
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Genes and Behavior: The
Interdisciplinary Field of Behavioral
Genetics
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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
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Dominant, recessive
Homozygous, heterozygous
Genotype/Phenotype and Polygenic Inheritance
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Research Methods in Behavioral
Genetics
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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
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Modern Approaches to the Nature vs.
Nurture Debate
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Molecular Genetics = the study of the
biochemical bases of genetic inheritance
– Genetic mapping – locating specific genes - The
Human Genome Project
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Behavioral Genetics
– The interactionist model
– Richard Rose (1995) – “We inherit dispositions, not
destinies.”
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Evolutionary Psychology: Behavior in
Terms of Adaptive Significance
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Based on Darwin’s ideas of natural selection
– Reproductive success key
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Adaptations – behavioral as well as physical
– Fight-or-flight response
– Taste preferences
– Parental investment and mating
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