Transcript Chapter 2

Chapter 3
Biopsychology and the
Foundations of Neuroscience
Copyright © Allyn & Bacon 2007
The Structure of a Neuron
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Soma (Cell Body): Contains the nucleus,
which includes the chromosomes
Axon: Extended fiber that conducts
information from the soma to the terminal
buttons; information travels along this in the
form of an electric charge called the action
potential.
Axon Terminal/Buttons: Tiny bubble-like
structures at the end of the axon which
contain neurotransmitters that carry the
neuron’s message into the synapse.
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Synaptic Vesicles: Small containers holding
neurotransmitters that connect to the
presynaptic membrane, releasing the
neurotransmitter into the synapse.
Myelin Sheath: Insulating covering of the axon
for neurons; facilitates the electrical impulse
and protects the neuron.
Dendrites: Branched fibers that carry
information into the neuron and extend
outward from the main cell body.
Neurotransmitters: Chemical messengers that
relay neural messages across the synapse
The Neuron
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Specialized cell that responds to and
sends signals
• Sensory neurons: carry messages
from sense receptors towards the
CNS (afferent – approach CNS)
• Motor neurons: carry messages
from CNS toward muscles and
glands (efferent – exit CNS)
• Interneurons: carry messages
between nerve cells
The Neural Impulse
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Resting potential: Electrical charge of a neuron when
it is ready to fire; it’s inactive state (-70mv)
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(+) potassium inside; (+) sodium outside; sodium wants in!
Action potential: Nerve impulse caused by a reversal
in the electrical charge across the axon (- to +)
Depolarization: sodium gates open; let sodium (+) in
 Repolarization: sodium gates close, potassium gates
open and let potassium (+) out; potassium gates
close when charge is leveled (back to -)
Refractory period: time period in which the neuron
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cannot reach its action potential; repolarizing to return
to its resting potential (polarized)
The Neural Impulse
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All-or-none principle: Action potential occurs
full blown or not at all; must cross threshold
(minimum level of stimulation needed)
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Synapse: Communication link between neurons
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Impulses only move in one direction!!!
Happens in the synaptic gap
b/w terminal buttons of one neuron and dendrites
of another neuron
Synaptic transmission: relaying of info across
the synapse by means of neurotransmitters
Plasticity and Glial Cells
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Plasticity: Ability of the nervous system to
adapt or change as the result of experience
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Helps the nervous system adapt to physical damage
Restructured/programmed by experience
Neurons make new connections
Example - sprout new dendrites
Glial cells
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Provide structural support for neurons
Help in forming new synapses
Form myelin sheath
Clean up dead cells
Neurotransmitters
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Neurotransmitters: Chemical messengers that
relay neural messages across the synapse
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Diffuse across synapse & connect like lock and key
Agonist: drug/chemical that enhances or mimics
the effects of NTs – facilitates messages; turns up
volume
Antagonist: drug/chemical that inhibits the effects
of NTs – blocks receptor sites; turns down volume
Reuptake: recycling of NT back into the presynaptic neuron
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Turns message volume down
SSRI – inhibits reuptake, so turns
up volume of serotonin
Reuptake in the Synapse
Neurotransmitters
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Dopamine: pleasure and reward, voluntary
movement; Schizophrenia & Parkinson’s
Serotonin: sleep, dreaming, mood, pain,
aggression, appetite, sexual behavior;
depression
Norepinephrine: heart rate, sexual
responses, stress
Acetylcholine: learning, memory, motor
movement; Alzheimer’s & muscular disorders
Endorphins: pleasure, pain control; lower
levels from opiate addiction
Neurotransmitters
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GABA: inhibitory; anxiety & epilepsy
Glutamate: excitatory, learning, memory;
brain damage after a stroke
Two forms:
 Excitatory – more likely for the next neuron
to fire
 Inhibitory – less likely for the next neuron
to fire
The Organization of the
Nervous System
Nervous system
Peripheral nervous
system
Autonomic
nervous system
Sympathetic
nervous system
Central nervous
system (CNS)
Somatic
nervous system
Parasympathetic
nervous system
The Endocrine System
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The body’s chemical messenger system
The Endocrine System
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Pituitary gland :
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Master gland
Produces hormones influencing the
secretions of all other endocrine
glands
Produces hormones that influences
growth
Attached to hypothalamus
How Does the Brain
Produce Behavior and
Mental Processes?
The brain is composed of
many specialized modules
that work together to create
mind and behavior.
Three Layers of the Brain
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Hindbrain – vital functions
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Heart rate, breathing, digestion
 Brain stem (medulla, reticular formation)
pons, cerebellum
Midbrain
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Portion of the brain stem that connects the
hindbrain and the forebrain
Three Layers of the Brain
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Forebrain – very highly
developed part
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Limbic system – regulates
emotions, motives, memory
(amygdala, hippocampus)
 Also included:
Hypothalamus, thalamus
Cerebrum (top of forebrain)
 Reasoning, planning,
creating, problem solving
 Cerebral cortex
Important Structures
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Thalamus
Pons
Cerebellum
Medulla
Brain stem
Reticular
Formation
Important Structures
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Hypothalamus –
Serves as the
brain’s bloodtesting
laboratory,
constantly
monitors blood
to determine the
condition of the
body
The Limbic System
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Amygdala –
Involved in
memory and
emotion,
particularly fear
and aggression
The Limbic System
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Hippocampus –
Involved in establishing
long-term memories
Four Lobes of the Cerebral Cortex
Frontal lobes (AKA pre-frontal cortex): planning,
deciding, thinking, motor cortex, personality?
 Parietal lobes: touch sensation, spatial relationships,
somatosensory cortex
 Occipital lobes: contain visual cortex
 Temporal lobes: sounds, including speech, auditory
cortex; memory, speech production
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• Gyri and Sulci: ridges and
valleys that divide the
cortex into the lobes
The Cooperative Brain
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Association cortex: Cortical regions that
combine information from various other parts
of the brain
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Deciding what to do when your phone rings in class
Contralaterality: control of one side of your
body by the other side of your brain
Cerebral dominance: Tendency of each brain
hemisphere to exert control over different
functions
Specialization of the
Cerebral Hemispheres
Left Hemisphere
Right Hemisphere
• Spontaneous
speaking and
writing
• Responses to
complex commands
• Word rec./ speech
• Memory for words
and numbers
• Sequences of
movements
• Feelings of anxiety
• Positive emotion
• Repetitive but not
spontaneous
speaking
• Responses to simple
commands
• Facial recognition
• Memory for shapes
and music
• Spatial interpretation
• Emotional
responsiveness
• Negative emotion
Windows on the Brain
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Brain waves: Patterns of electrical activity
generated by the brain
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EEG (electroencephalograph): Records brain
waves; electrodes placed on scalp
Windows on the Brain
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Brain scans: Recordings of the brain’s electrical
or biochemical activity at specific sites
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CAT/CT (computerized tomography) – soft tissue,
structure, x-ray
PET (positron emission tomography) – activity, not
structure, detects glucose in active circuits
fMRI (magnetic resonance imaging) – moving pic.
of brain in action
Aphasia
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The impairment of language (speech
or understanding)
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Broca’s Area – interferes w/ speech
production (frontal lobe damage)
 can understand language
 words not properly formed
 speech is slow and slurred
 some aware of deficits
Wernicke’s Area – loss of ability to
understand language (parietal/temporal)
 can speak clearly most of the time
 words put together make no sense;
word salads
 not aware of deficits
The Split Brain
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Split-brain patients:
Individuals who have had
the corpus callosum
surgically severed; usually
epileptic
Duality of consciousness:
Condition in which a splitbrain patient has a
separate consciousness in
each hemisphere