Download Ch 3 Biological Bases of Behavior

Chapter 3
The Biological Bases
of Behavior
AP EXAM
Biological Bases of Behavior (8–10%)
•An effective introduction to the relationship between physiological processes and
•behavior — including the influence of neural function, the nervous system and the
•brain, and genetic contributions to behavior — is an important element in the AP
•course.
•AP students in psychology should be able to do the following:
•• Identify basic processes and systems in the biological bases of behavior,
•including parts of the neuron and the process of transmission of a signal
•between neurons.
•• Discuss the influence of drugs on neurotransmitters (e.g., reuptake
•mechanisms, agonists, antagonists).
•• Discuss the effect of the endocrine system on behavior.
•• Describe the nervous system and its subdivisions and functions:
•— central and peripheral nervous systems;
•— major brain regions, lobes, and cortical areas;
•— brain lateralization and hemispheric specialization.
•• Discuss the role of neuroplasticity in traumatic brain injury.
•• Recount historic and contemporary research strategies and technologies that
•support research (e.g., case studies, split-brain research, imaging techniques).
•• Discuss psychology’s abiding interest in how heredity, environment, and
•evolution work together to shape behavior.
•• Predict how traits and behavior can be selected for their adaptive value.
•• Identify key contributors (e.g., Paul Broca, Charles Darwin, Michael Gazzaniga,
•Roger Sperry, Carl Wernicke).
Our Neurons
All thoughts, feelings, and actions are traced
to the electrical impulses in neurons. Your
brain contains 100 billion neurons and
each neuron is linked to about 15,000
other neurons.
Nerves
• Nerves: Large bundles of axons and
dendrites
• Myelin sheath: Fatty layer that coats some
axons
– Multiple Sclerosis (MS) may occur when
myelin layer is destroyed; numbness,
weakness, and paralysis occur
Communication in the Nervous System
• Hardware:
–
–
–
–
–
Glia – structural support and insulation
Neurons – communication
Soma – cell body
Dendrites – receive
Axon – transmit away
Neural Communication: Insulation and Information Transfer
• Myelin sheath – speeds up transmission
• Terminal Button – end of axon; secretes
neurotransmitters
• Neurotransmitters – chemical
messengers
• Synapse – point at which neurons
interconnect
Neuron and Its Parts
• Neuron: Individual nerve cells that receive, integrate, and transmit
information.
– Soma: Egg shaped cell/body of the neuron. Receives messages and sends
messages down axon. Provides fuel
– Axon: Carries information away from the cell body at speeds up to 200 mph.
– Axon Terminals: Branches that link the dendrites and somas of other
neurons
– Synapse: the meeting point between neurons; where neurons “talk”
– Neurotransmitters: the chemical signal that transmits across the synapse
– Dendrites: receive messages from other neurons
– Glial Cells: Supports neuron structure; cleans up unused neurotransmitters
!
!
An example of a
neuron, or nerve cell,
showing several of its
important features. The
right foreground shows
a nerve cell fiber in
cross section, and the
upper left inset gives a
more realistic picture of
the shape of neurons.
The nerve impulse
usually travels from the
dendrites and soma to
the branching ends of
the axon. The neuron
shown here is a motor
neuron. Motor neurons
originate in the brain or
spinal cord and send
their axons to the
muscles or glands of
the body.
See Fig 3.1
The Nerve Impulse
• Resting Potential: Electrical charge of an inactive
neuron
• Threshold: Trigger point for a neuron’s firing
• Action Potential: Nerve impulse/the firing
• Ion Channels: Axon membrane has these tiny
holes or tunnels
• Absolute refractory period: When a neuron is
cannot fire
A highly magnified view of the synapse shown above. Neurotransmitters are stored in tiny sacs called synaptic
vesicles. When a nerve impulse arrives at an axon terminal, the vesicles move to the surface and release
neurotransmitters. These transmitter molecules cross the synaptic gap to affect the next neuron. The size of the
gap is exaggerated here; it is actually only about one millionth of an inch. Transmitter molecules vary in their
effects: Some excite the next neuron and some inhibit its activity. Receptor sites only accept neurotransmitters
which “fit” the site.
Neurotransmitters
• Chemicals that alter activity in neurons; brain
chemicals
– Acetylcholine: Activates muscles (walking, breathing, etc.)
– Dopamine: Large Muscle movement and control. In
Parkinson’s Disease, the dopamine receptors die.
– Serotonin: Mood and appetite control. A lack of serotonin
may lead to depression. Drugs such as Paxil either
encourage the production of serotonin or slow the reuptake of
serotonin.
– Endorphins: similar in structure and effects of opiates, pain
suppression and pleasure.
• Receptor Site: Areas on the surface of neurons and
other cells that are receive neurotransmitters. It is a
“lock and key” mechanism.
Lock & Key Mechanism
Neurotransmitters bind to the receptors of the
receiving neuron in a key-lock mechanism.
The neurotransmitters that do not bind are reabsorbed by the original
Neuron. This process is know as “reuptake”.
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Neurotransmitters and You
!
• One of the 100 neurotransmitters in your brain is
“GABA” (Gama-aminobutyric acid).
– It is a common behavior inhibitor
– GABA and alcohol have very similar shapes
– As alcohol binds to the receptors in the brain, the brain
reduces production of GABA in chronic stages of
alcoholism. When we stop drinking, GABA receptors
react to “no” neurotransmitters and we feel discomfort
and withdrawal.
Alcohol’s Immediate Effects
• Alcohol displaces the GABA and as a result we
feel more “friendly”; and certainly less inhibited.
• This explains why drinking encourages different
behaviors – our loss of inhibitions
• And as you may guess, other drugs (such as
opiates, morphine, cocaine, etc.) act similar to
alcohol in blocking receptor sites by blocking
neural impulses and creating altered behaviors
Organization of the Nervous System
• Central nervous system (CNS) – brain and spinal cord
– Afferent = toward the CNS
– Efferent = away from the CNS
– Interneuron = connects afferent neurons and
efferent neurons in neural pathways. Found within
the central nervous system
• 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
Subparts of the nervous system.
Two Divisions of the
Autonomic System
• Runs internal organs and glands; controls
involuntary activities such as heart,
digestion, breathing, etc.
– Sympathetic: Arouses body; emergency system
– Parasympathetic: Quiets body; most active
after an emotional event
Autonomic Nervous System (ANS)
Sympathetic NS
“Arouses”
(fight-or-flight)
!
!
Parasympathetic NS
“Calms”
(rest and digest)
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Central Nervous System
The Spinal Cord and Reflexes
Simple Reflex
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Figure 3.6 Organization of the human nervous system
Characteristics of the Brain
• Do we only use 10% of our brain?
• The brain is like 3 pounds (the size of a grapefruit) of firm
tofu, like crumpled, compacted paper. The brain is
divided into two hemispheres.
• Does damage to the brain necessarily cause death?
– Phineas Gage Experience: He was a railroad construction
foreman now remembered for his incredible survival of an
accident in which a large 3 ½ foot iron rod was driven completely
through his head, destroying one or both of his brain's frontal
lobes, and for that injury's reported effects on his personality and
behavior—effects said to be so profound that friends saw him as
"no longer Gage.“
– http://en.wikipedia.org/wiki/Phineas_Gage
– Frontal Lobotomies in the 40s and 50s
• Over 18,000 performed
Tools for Researching the Brain
• Ablation: Surgical removal of parts of the brain
– The brain has no pain receptors (only on scalp and skull)
– Patients can be awake during surgery on brain
• Deep Lesioning: A thin wire electrode is lowered into a
specific area inside the brain; Electrical current is then
used to destroy a small amount of brain tissue
• Electrical Stimulation of the Brain (ESB): When an
electrode is used to activate target areas in the brain
• Electroencephalograph (EEG): Detects, amplifies, and
records electrical activity in the brain
Researching the Brain (cont.)
• Computed Tomographic Scanning (CT): Computerenhanced X-ray of the brain or body
• Magnetic Resonance Imaging (MRI): Uses a strong
magnetic field, not an X-ray, to produce an image of
the body’s interior
• Functional MRI: MRI that makes brain activity visible
• Positron Emission Tomography (PET): Computergenerated color image of brain activity, based on
glucose consumption in the brain
Neural Transmissions
• Tap your right finger when you see a command on a
screen. It's a simple maneuver, yet carrying it out
requires a vastly complicated series of actions. First,
the image of the words on the screen (telling you to tap
your finger) enters your eyes and strikes the retinas.
The retinas then convert the image into electrical
impulses. These impulses are sent to your brain. Your
brain "sees" the words and gives meaning to them.
Your brain then decides whether or not to carry out
what it has read. If it decides yes, your brain's motor
cortex, a small area that exists on the outer part of your
brain, calls for messages to be sent through your spinal
cord and down your arm to the muscles that control the
finger. Only then does the finger move.
This simplified drawing shows the main structures of the human brain and describes
some of their most important features. (You can use the color code in the foreground
to identify which areas are part of the forebrain, midbrain, and hindbrain.)
Parts of the Brain
Older Brain Structures
Brainstem the oldest part of the brain, beginning where
the spinal cord swells and enters the skull. Responsible
for automatic survival functions.
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Brain Stem
Medulla [muh-DUL-uh]
base of the brainstem,
controls heartbeat and
breathing.
!
Reticular Formation a nerve
network in the brainstem
that plays an important role
in controlling arousal.
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Brain Stem
Thalamus [THAL-uhmuss] the brain’s sensory
switchboard, located on top
of the brainstem. It directs
messages to the sensory
areas in the cortex and
transmits replies to the
cerebellum and medulla.
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Cerebellum
The “little brain” attached
to the rear of the brainstem.
It helps coordinate
voluntary movements and
balance.
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The Limbic System
Limbic System a doughnutshaped system of neural
structures at the border of
the brainstem and cerebrum,
associated with emotions
such as fear, aggression and
drives for food and sex. It
includes the hippocampus,
amygdala, and
hypothalamus.
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Amygdala
Amygdala [ah-MIG-dahla] two almond-shaped
neural clusters linked to
emotion of fear and anger.
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Hypothalamus
Hypothalamus lies below
(hypo) the thalamus; directs
several maintenance
activities like eating, drinking
body temperature, and
emotions. Helps govern the
endocrine system via the
pituitary gland. This may be
part of the “pleasure center”
of the brain.
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The Cerebral Cortex
The intricate fabric of interconnected neural cells that covers the
cerebral hemispheres. The body’s ultimate control and information
processing center.
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Structure of the Cerebral Cortex
Each brain hemisphere is
divided into four lobes,
separated by prominent
fissures. They are frontal
lobes (forehead), parietal
lobes (top to rear head),
occipital lobes (back head)
and temporal lobes (side of
head).
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4 Lobes of the Cerebral Cortex
• Occipital Lobe: (Primary Visual Cortex)
Back of brain; visual association area;
not a “TV” screen as we will later learn.
• Temporal Lobe: (Primary Auditory Cortex)
Each side of the brain above the ears;
auditory and language centers; recognizes
and organizes sounds
Central Cortex Lobes (contd)
• Parietal Lobe: contains the sensory cortex and the
motor cortex. This area is at the top, read of our
brain and runs from ear to ear. Contains perception,
senses and motor skills; bodily sensations such as
touch, pain, and temperature
– Mapped while stimulating areas in wide-awake patients
• Frontal Lobe: Higher mental functions (Our
Intelligence), movement, sense of smell
– Contains Primary motor cortex; controls motor movement
– Personality, emotions
– Prefrontal Cortex may serve as an “executive function” of
the brain
Visual Function
Functional MRI scan
shows the visual cortex
activates as the subject
looks at faces.
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Auditory Function
Functional MRI scan shows
the auditory cortex is active in
patients who hallucinate.
They are “hearing” voices.
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Figure 3.19 – The cerebral cortex in humans
Functions of the Cortex
Motor Cortex area at the rear of the frontal lobes controls
voluntary movements. Sensory Cortex (parietal cortex)
receives information from skin surface and sense organs.
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Figure 3.20 – Primary motor cortex with homunculus
Specialization & Integration
Brain activity when hearing, seeing, and speaking words
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Association Areas
More intelligent animals have increased
“uncommitted” or association areas of the cortex.
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When the Brain Fails to Function
Properly
• Association Cortex: Combine and process information
from the five senses
• Aphasia: Language disturbance resulting from brain
damage (like from a stroke)
• Broca’s Area: Related to language and speech
production
– If damaged, person knows what s/he wants to say but can’t say
the words
• Wernicke’s Area: Related to language comprehension; in
left temporal lobe
– If damaged, person has problems with meanings of words, NOT
pronunciation
Three Regions of the Brain
Hindbrain, Midbrain, Forebrain
Your Textbook Organization
• The hindbrain includes the
– Cerebellum (little brain)
• Critical to coordination and movement
– Medulla
• Controls heartbeat and circulation, breathing, reflexes
– Pons
• Connects brainstem with the cerebellum
• Involved with sleep and arousal
• Coordinates movement
Midbrain
Reticular Formation (RF)
• Midbrain coordinates sensory processes.
Deterioration of this area has implications for
Parkinson’s disease.
• Reticular Formation: Inside hindbrain and
midbrain
– Associated with alertness, attention, and some
reflexes (breathing, coughing, sneezing, vomiting)
– Reticular Activating System (RAS): Part of RF that
keeps it active and alert
• RAS acts like the brain’s alarm clock
• Activates and arouses cerebral cortex
Forebrain
• Largest, most complex region of the brain
• Structures are part of Limbic System: System
within forebrain closely linked to emotional
response and motivating behavior
– Thalamus: Relays sensory information on the way to the
cortex; switchboard
– Hypothalamus: Regulates emotional behaviors and
motives (e.g., sex, hunger, rage, hormone release)
– Amygdala: Associated with fear responses and
aggression
– Hippocampus: Associated with storing permanent
memories; helps us navigate through space
Forebrain (contd.)
Cerebral Cortex
• Definition: Outer layer of the cerebrum; contains
70% of neurons in CNS
• Contains the association areas where we do our
reasoning/thinking
• Cerebrum: Two large hemispheres that cover
upper part of the brain
• Corticalization: Increase in size and wrinkling of the
cortex
• Cerebral Hemispheres: Right and left halves of
the cerebrum
• Corpus Callosum: Bundle of fibers connecting
cerebral hemispheres
Teenage Brain Pt III
• Teenage Brain Part III (part 4 in video)
• Teens often perceive their environment
differently and thus react differently than
older individuals.
Speech Production
Understanding speech
Right Brain/Left Brain
• About 95 percent of our left brain is used for
language
• Left hemisphere better at math, judging time and
rhythm, and coordinating order of complex
movements
– Processes information sequentially and is involved with
analysis (speech, writing, math, sequencing, analyzing)
– Controls the right side of the body
• Right hemisphere good at perceptual skills, and at
expressing and detecting other’s emotions
– Processes information simultaneously and holistically
(music, puzzles, spatial tasks)
– Controls the left side of the body
Split Brains
• Corpus Callosum is thicker in females; classical
musicians
• Corpus Callosum can be severed; done to control
severe epilepsy (seizure disorder)
• Result: The person now has two brains in one
body
• This operation is rare and is often used as a last
resort.
• The Divided Brain (6 min)
Splitting the Brain
A procedure in which the two hemispheres of the brain are
isolated by cutting the connecting fibers (mainly those of the
corpus callosum) between them.
Martin M. Rother
Courtesy of Terence Williams, University of Iowa
Corpus Callosum
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Specialized Abilities of the Two
Hemispheres
• Left Hemisphere
–
–
–
–
Words, letters
Language sounds
Verbal Memory
Speech, grammar,
reading, writing
– Logic, explaining
events
• Right Hemisphere
–
–
–
–
–
–
–
Faces
Emotional expression
Geometric patterns
Music
Nonverbal memory
Emotion of tone/speech
Judgment of distance
The Brain’s Plasticity
• Plasticity refers to the brain’s ability to
modify itself after damage, especially in
young children. Also this is the process of
rehabilitation in stroke victims.
– If the motor cortex area that controls the
forefinger, the surrounding motor cortex areas
may take over that function
– If the language processing area in the left
hemisphere is damaged, the right hemisphere
may take over part of that task
Can Life Experience Affect your Brain
• Two groups of rats were studied. Group A
lived in an impoverished environment
(alone in a small cage); Group B lived in
an enriched environment with other rats
with new “toys” daily.
• At the end of the study, the Group B rats
had a heavier, thicker cortex. Even rats
that only lived in that environment for a few
days experienced gains.
The Endocrine System
Endocrine System is
the body’s “slow”
chemical
communication
system.
Communication is
carried out by
hormones synthesized
by a set of glands.
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Endocrine System
• The Body’s slower communication system. The
bloodstream carries these “messengers” whereas the
neurons are carried electrically.
• Glands that pour chemical messengers (hormones)
directly into the bloodstream or lymph system
• Pituitary Gland: Regulates growth via growth hormone.
Pituitary also governs functioning of other glands,
especially thyroid, adrenals, and gonads
• Pancreas: produces insulin to control metabolism of
sugar
• Gonads: ovaries and testes produce the hormones that
control secondary sex characteristics and reproduction
Endocrine System (cont.)
• Pineal Gland: Regulates body rhythms and sleep
cycles.
– Releases hormone melatonin, which responds to daily
variations in light
• Thyroid: In neck; regulates metabolism
– Hyperthyroidism: Overactive thyroid; person tends to
be thin, tense, excitable, nervous
– Hypothyroidism: Underactive thyroid; person tends to
be inactive, sleepy, slow, obese
Endocrine System (cont.)
• Adrenal glands: Arouse body, regulate salt
balance, adjust body to stress, regulate sexual
functioning; located on top of kidneys
– Releases epinephrine and norepinephrine (also known
as adrenaline and noradrenaline)
• Epinephrine arouses body; is associated with fear
• Norepinephrine arouses body; is linked with anger
Hormones
Hormones are chemicals synthesized by the endocrine
glands and secreted in the bloodstream. Hormones affect
the brain many other tissues of the body.
For example, epinephrine (adrenaline) increases heart
rate, blood pressure, blood sugar and feelings of
excitement during emergency situations.
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Heredity and Genetics
Nurture v. Nature
• Twin Studies help separate heredity and
the environmental effects.
– Identical (or monozygotic) twins develop from
the same fertilized egg
– Fraternal (or dizygotic) twins develop from two
different eggs.
• Adoption Studies assess genetic influence
by comparing traits to biological and
adoptive parents
Evolutionary Bases of Behavior
• Natural Selection suggests that
characteristics that provide a survival or
reproductive advantage are more likely to
be passed on to offspring.
• The concept of natural selection applies to
physical and behavioral characteristics.
• Examine behaviors conserved across a
related species to understand how that
behavior maximizes success
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