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Chapter 2
Biology and Behavior
Chapter 2 Overview
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The Neurons and Neurotransmitters
The Human Nervous System
Discovering the Brain’s Mysteries
A Closer Look at the Brain
Age and Gender Differences in the Brain
The Endocrine System
Genes and Behavioral Genetics
What are the functions of the
various parts of the neuron?
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Cell body
– Carries out life-sustaining
functions
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Dendrites
– Receive signals from other
neurons
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Axon
– Sends signals to other
neurons, muscles, and
glands
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Synapse
– Junction between neurons
What are neurotransmitters?
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Neurotransmitters are
chemical substances that
transmit messages
between neurons
– Released into synapse by
axon terminals of sending
neuron
– Bind to receptor sites on
dendrites of receiving
neuron
– Taken back into axon
terminal by the process of
reuptake
What are the functions of some
major neurotransmitters?
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Acetylcholine
– Affects movement, learning, memory, REM Sleep
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Dopamine
– Affects movement, attention, learning, reinforcement,
pleasure
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Norepinephrine
– Affects eating, alertness, wakefulness
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Epinephrine
– Affects metabolism of glucose, energy release during
exercise
What are the functions of some
major neurotransmitters?
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Serotonin
– Affects mood, sleep, appetite, impulsivity, aggression
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Glutamate
– Active in areas of the brain involved in learning, thought,
and emotion
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GABA
– Facilitates neural inhibition in the central nervous system
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Endorphins
– Provide relief from pain and produce feelings of pleasure
and well-being
The Human Nervous
System
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Central nervous system
– The brain and spinal cord
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Peripheral nervous system
– The nerves connecting the central
nervous system to the rest of the body
Which brain structures are
found in the hindbrain?
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Medulla
– Controls heartbeat, blood
pressure, breathing,
coughing, swallowing
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Reticular formation
– Plays a crucial role in
arousal and attention
– Screens sensory messages
entering the brain
Which brain structures are
found in the hindbrain?
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Pons
– Plays a role in body
movement
– Influences sleep and
dreaming
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Cerebellum
– Helps the body execute
smooth, skilled movements
– Regulates muscle tone and
posture
What important structure is
located in the midbrain?
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The midbrain links
the physiological
functions of the
hindbrain to the
cognitive functions of
the forebrain
Substantia nigra
– Controls unconscious
motor movements
Which brain structures and
functions are found in the
forebrain?
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Thalamus
– A relay station for
information flowing into or
out of the brain
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Hypothalamus
– Regulates hunger, thirst,
sexual behavior, body
temperature, and a wide
variety of emotional
behaviors
Which brain structures and
functions are found in the
forebrain?
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Amygdala
– Structure in the limbic
system that plays an
important role in emotion
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Hippocampus
– Structure in the limbic
system that plays a central
role in storing new
memories, responses to new
or unexpected stimuli, and
navigational ability
The Peripheral Nervous
System
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The peripheral nervous system has
two subdivisions
– The somatic nervous system consists of
all sensory nerves and motor nerves
– The autonomic nervous system
transmits messages between the central
nervous system and the glands, the
cardiac muscle, and the smooth muscles
Two parts of the autonomic
nervous system
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Sympathetic nervous system
– Mobilizes the body’s resources during
stress and emergencies
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Parasympathetic nervous system
– Brings the heightened bodily responses
back to normal following an emergency
What is the difference between the
sympathetic and parasympathetic
nervous systems?
Discovering the Brain’s
Mysteries
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Modern researchers do not have to
wait to perform autopsies or wait for
injuries to occur to learn about the
brain
Today, researchers unlock the
mysteries of the brain using a variety
of techniques
What does the EEG reveal
about the brain?
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Electroencephalogram (EEG)
– A record of brain-wave activity made by a
machine called an electroencephalograph
– Electrical activity in the brain is detected
by electrodes placed on the scalp
How are imaging techniques
helpful in the study of brain
structure and function?
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CT scan
– Computerized axial tomography
– Uses X-rays to produce cross-sectional
images of the brain
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MRI
– Magnetic resonance imaging
– Produces high-resolution images of the
structures of the brain
How are imaging techniques
helpful in the study of brain
structure and function?
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PET scan
– Positron-emission tomography
– Reveals activity in various parts of the brain
based on blood flow, oxygen use, and glucose
consumption
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Functional MRI (fMRI)
– Provides images of both brain structure and
function
– Can identify locations of brain activity more
precisely and rapidly than PET scan
A Closer Look at the Brain
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The cerebrum
– The largest structure in the human brain
– Its functions include language, planning,
and logic
What are the components of
the cerebrum?
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Cerebral hemispheres
– The left and right halves of
the cerebrum
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Corpus callosum
– Connects the two
hemispheres
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Cerebral cortex
– Thin outer covering of
cerebrum
– Responsible for higher
mental processes of
language, memory, and
thinking
What are the specialized
functions of the left and right
hemispheres?
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The left
hemisphere
– Controls the right
side of the body
– Handles most
language functions
– Is specialized for
mathematics and
logic
What are the specialized
functions of the left and right
hemispheres?
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The right
hemisphere
– Controls the left side of
the body
– Processes music
– Interprets emotional
messages conveyed by
tone of voice and
gestures
– Is specialized for
visual-spatial relations
Which psychological functions
are associated with the frontal
lobes?
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Motor cortex
– Area that controls
voluntary body
movement
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Broca’s area
– Area in the frontal
lobe, usually in the left
hemisphere, that
controls the production
of speech
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Association areas
– Areas involved in
thinking, planning for
the future, impulse
control
What important structure is
found in the parietal lobes?
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Somatosensory
cortex
– Strip of tissue at
the front of the
parietal lobes
where touch,
pressure,
temperature, and
pain register in the
cortex
Why are the occipital lobes
critical to vision?
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The occipital lobes
are involved in the
reception and
interpretation of
visual information
Primary visual
cortex
– Area at the rear of the
occipital lobes where
vision registers in the
cortex
What are the major areas
within the temporal lobes, and
what are their functions?
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Primary auditory
cortex
– Area in each
temporal lobe where
hearing registers in
the cortex
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Wernicke’s area
– Language area in the
left temporal lobe
involved in
comprehending
spoken language and
formulating coherent
speech and written
language
Age and Gender
Differences in the Brain
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The brain grows from conception until
well into adulthood
Throughout development, the brains
of males and females differ to some
degree
How do the brains of men differ
from those of women?
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Women’s brains have equal proportions of gray and white
matter in the left and right hemispheres; men’s brains have a
lower proportion of white matter in the left hemisphere than
in the right
– This may explain men’s superior ability in spatial tasks
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Women have more gray matter in the area of the brain that
controls emotions
– This may explain women’s superior ability to perceive emotions
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Navigational information is processed in different parts of the
brain in men and women
– Women use right parietal cortex and right frontal cortex
– Men use left hippocampus
– Men and women use different areas to process location of sound
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More research is needed to understand the meaning of these
gender differences in the brain
The Endocrine System
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A system of ductless glands that
manufacture hormones and secrete
them into the bloodstream
What functions are associated
with the various glands of the
endocrine system?
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Pituitary gland
– The “master gland”
– Located in the brain
– Releases hormones that activate other endocrine glands
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Pineal gland
– Located deep in the brain
– Secretes the hormone melatonin which controls
sleep/wakefulness cycle
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Thyroid gland
– Located below the voice box
– Produces thyroxine, which regulates rate at which food is
metabolized
What functions are associated
with the various glands of the
endocrine system?
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Parathyroid glands
– Attached to the thyroid
– Produce parathyroid hormone which helps the body
absorb minerals from the diet
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Thymus gland
– Produces hormones that are essential to immune system
functioning
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Adrenal glands
– Release hormones that prepare the body for emergencies
and stressful situations
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Gonads
– The ovaries in females and testes in males
– Produce sex hormones
Genes and Behavioral
Genetics
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Genes
– segments of DNA located on chromosomes that
transmit all heredity traits
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Chromosomes
– rod shaped structures in the nuclei of cells that
contain all genes and carry genetic information
to make a human being
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Behavioral Genetics
– a field of research that uses twin and adoption
studies to investigate the relative effects of
heredity and environment on behavior
What patterns of inheritance
are evident in the transmission
of genetic traits?
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Dominant-recessive pattern
– a set of inheritance rules in which one dominant
gene causes a trait to be expressed, but two
recessive genes are required for expression of a
recessive trait
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Multifactorial inheritance
– A pattern of inheritance in which a trait is
influenced by both genes and environment
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Sex-linked inheritance
– Involves genes on the X and Y chromosomes
– Example: red-green color blindness
Ishihara Test
What kinds of studies are done
by behavioral geneticists?
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Twin studies
– Examine identical (monozygotic) and fraternal
(dizygotic) twins
– If identical twins are more alike on a trait, the
trait is assumed to be more influenced by
heredity
– If identical and fraternal twin pairs do not differ
on a trait, the trait is assumed to be more
influenced by environment
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Adoption studies
– Compare adopted children’s abilities and traits to
those of adoptive parents and biological parents