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PSYC 2012: FINAL EXAM
What are neurons?
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basic building blocks of the nervous system
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cell body
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(somas) includes nucleus and cytoplasm
elicits post synaptic potential
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dendrites |
branches that receive messages
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Axon |
A single extension, leads away from the cell body and serves as a conduction zone, transmitting the cell's electrical impulse away from the cell body
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axon hillock
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conical structure at the junction between the cell body and the axon
where EPSP and IPSP is summed
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myelin
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(multiple sclerosis (MS): deterioration of myelin)
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nodes of Ranvier
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the gaps between adjacent myelin segments that concentrates axonal sodium and conducts action potential signals
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buttons |
knobby ending of axon branches that are efficient for drawing back and recycling neurotransmitters or their breakdown products
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neurotransmitter
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chemical that sends signal
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Synapse
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Junction between two neurons
Includes membrane of terminal button of presynaptic neuron, membrane containing receptor on dendrite of postsynaptic neuron, and space between (synaptic cleft)
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synaptic cleft
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gap where neurotransmitters diffuse
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synaptic vesicles
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small molecule neurotransmitters that have been synthesized are packaged
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lipid bilayer
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makes up the membrane of neurons
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lipid molecule
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(head – hydrophilic, tail - hydrophobic unipolar)
helps keep lipids lined up, and molecules from crossing membrane
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Channel Proteins
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Selectively permeable hydrophilic channel through the lipid bilayer.
Like a hole through the membrane. Only involved with diffusion
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signal proteins
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proteins in neurons that cause a neuron to fire
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unipolar, bipolar, and multipolar neurons, in humans which is the most common?
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types of structures
multipolar = most common
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Sensory, motor, interneurons - which are the most common in humans?
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interneurons make up most of human brain
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What are support cells and their functions?
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glial cells and satellite cells
form myelin and speed action potential
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What is a Golgi stain? Nissl stain? myelin stain? tracing techniques? What does each type of stain show?
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GS: lets you see the entire neuron (soma and dendrites clear; axon more difficult to see)
NS: lights up soma of cells
MS: darkens myelinated axons
TT: easier to photograph and trace/visualize dendrites
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What is a membrane potential and why was it originally measured in squids?
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a selectively permeable membrane
Squids have neurons with large diameter axons – easier to get an electrode inside these axons
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What is the potential difference between the inside and outside of a neuron at rest?
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sodium and chloride ions outside the membrane, potassium and protein ions within the neuron
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What are ions? positive ions? negative ions?
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salts in neural tissue separated into positively and negatively charged particles
positive ions are positively charged and negative
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What is the charge on sodium ions (Na+)? on potassium ions (K+)? on chloride ions (Cl-)?
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positive, positive, negative
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Why don’t protein ions rush out of the resting neuron?
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too big to fit across through the channels in the neuron’s membrane
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Why don’t chloride ions rush into the resting neuron?
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Have the same charge as the inside of the neuron, so are repelled from entering
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What is the function of sodium-potassium pumps?
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pump sodium ions out of the neuron, pump potassium ions into the neuron
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What are EPSPs? IPSPs?
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Postsynaptic depolarizations that increase the likelihood of the neuron firing
Postsynaptic hyperpolarizations that decrease the likelihood that the neuron will fire
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What does graded potential mean?
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that the amplitudes of EPSPs and IPSPs are proportional to the intensity of the signals that elicit them
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What is integration and at which part of the neuron does it occur?
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combining a number of individual EPSP and IPSP into one overall signal
occurs at the axon hillock
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What is action potential?
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a reversal of the membrane potential and their magnitude isn't related to the intensity of the stimuli
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What is the all-or-none response?
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potentials occur to their full extent or do not occur at all
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What is a neural signal based on?
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frequency and which neurons are firing
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What are voltage-activated ion channels?
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ion channels that open or close in response to changes in the level of the membrane potential
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What is the voltage threshold for initiating an action potential?
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(-65mV)
-70 to +50 mV
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How are sodium and potassium channels involved in the production and conduction of the action potential?
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The channels in the membrane open wide allowing Na+ ions to rush in and driving the membrane potential higher then triggering the opening of the channels. and K+ ions are driven out through them
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What is the voltage of an action potential at its peak?
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(+50mV)
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What are the 7 steps in an action potential?
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(1) Sodium channels open with summed excitatory potential -Sodium ions rush in (2) This reverses the polarity of this small area of the membrane (3) Voltage-activated potassium channels open-potassium ions rush out (4) Sodium channels close-height of action potential (5) Potassium ions continue to leave cell, causing membrane to return to baseline polarity (6) Potassium channels close gradually (7) Sodium channels next to the reversal area open and the same series of actions take place (steps 1-6)
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What is the absolute refractory period and relative refractory period? What is their function?
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absolute: brief period after initiation of an action potential - it's impossible to initiate a second one
relative: period after where it's possible to fire the neuron again but only by applying higher than normal levels of stimulation
Function: Neural activity - responsible for action potential travels in one direction and rate of the neural firing related to the intensity of stimulation
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Two differences between action potentials and post-synaptic signaling
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(1) action potentials are non decremental (2) action potentials are slower
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What is the speed of the fastest human action potential?
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60 meters per second
Bigger the axon’s diameter, the faster the action potential
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How does myelin increase the speed of an action potential?
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Conduction along myelinated segments of the axon is passive so it occurs instantly, causing the signal to "jump" along the axon from node to node
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What is the function of the nodes of Ranvier during the conduction of action potentials?
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in myelinated axons ions can pass through the axonal membrane only at the gaps of the nodes of Ranvier
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What is the presynaptic neuron?
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neuron before synapse that sends signal
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What is a postsynaptic neuron?
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the synapse that receives signal
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What are dendritic spines? What is their function?
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nodules of various shapes that are located on the surfaces of many dendrites where many axodendritic synapses terminate
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What is the most common synaptic connection?
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axon to dendrite
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neurotransmitter |
chemicals that transmit information across the synapse to a receiving neurons dendrites
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neuromodulator
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a chemical that influences the activity of neurotransmitters; it is not a neurotransmitter itself
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What is exocytosis and the steps involved?
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the process of neurotransmitter release
neuron at rest, action potential stimulates open channels of neurotransmitters in presynaptic membrane, Ca2+ ions enter the button causing synaptic vesicles to fuse with the presynaptic membrane and empty their contents into the synaptic left
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What do receptors receive?
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neurotransmitters
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Lock and key analogy
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lock = receptor, key = neurotransmitter
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What are the differences between ionotropic and metabotropic receptors?
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More metabotropic receptors than ionotropic receptors in human brain
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What are the functions of G proteins?
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Receptors on membrane signal proteins are linked to G proteins
After a neurotransmitter binds to a receptor then some G proteins breaks off into a neuron to bind to an ion channel or stimulates the synthesis of a second messenger
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What are second messengers and how do they function? What is a first messenger?
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a chemical that diffuses through the cytoplasm and influences the activities of the neuron (eg. genetic expression)
a first messenger is a neurotransmitter
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What are autoreceptors? What is their function?
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metabotropic receptors
monitor the # of neurotransmitter molecules in the synapse to reduce subsequent release when the levels are high or induce release when levels are low
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How does caffeine work?
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blocks the effects of adenosine
competes for autoreceptors
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Caffeine’s physiological and psychological effects
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increases the release of dopamine, acetylcholine, norepinephrine
so, affects alertness, motivation, thinking, and mildly reinforcing
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What are the symptoms of caffeinism? How much coffee must be consumed? What is the cure?
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nervous irritability,tremulousness, and occasional muscle twitching
the equivalent of about 12 cups of coffee per day
cure: stop consuming caffeine
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What is a lethal dose of caffeine?
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the equivalent of about 100 cups of coffee
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Which process is most common in the brain, enzymatic deactivation or reuptake?
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reuptake |
glutamate
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most prevalent excitatory NT in mammals
effects:
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GABA |
most prevalent inhibitory neurotransmitter in mammals
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dopamine
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monoamine neurotransmitter that
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acetylcholine
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Neurotransmitter at the neuromuscular junction that
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endorphins
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naturally occurring (endogenous) morphine
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What neurotransmitter does Prozac affect and how?
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serotonin by blocking the reuptake of serotonin
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What NT does cocaine affect and how?
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blocks the reuptake of dopamine
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What are agonists and antagonists?
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drugs that facilitate the effects of a particular neurotransmitter
(e.g., Black Widow Spider venom and acetylcholine)
drugs that inhibit the effects of an NT
(e.g., curare and acetylcholine, botulism toxin and acetylcholine, naloxone and endorphins)
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What is learning?
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deals with how experience changes the brain
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What is memory?
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deals with how changes from experience (learning) are stored and then reactivated
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infantile (childhood) amnesia
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Inability to recall genuine memories of events occurring before the age of three years
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anterograde amnesia
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forward acting amnesia (difficulty remembering things learned after surgery/trauma)
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retrograde amnesia
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difficulty remembering things learned before surgery/trauma
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What parts of the brain does the temporal medial lobe include that are related to memory?
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hippocampus, amygdala, and adjacent parts of the cortex
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What deficit do people with temporal medial amnesia show?
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Anterograde amnesia for explicit memories
Can perform implicit memory tasks.
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What are explicit memory and implicit memory?
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explicit: conscious memories
implicit: memories that are expressed by improved performance without conscious recall or recognition
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What is memory consolidation?
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transfer of short-term memories to long-term storage
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What's the H.M. case? What could he learn and not learn? How did Hebb explain it? (p. 270)
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Hippocampus was removed from both sides of his brain; is an example of temporal medial amnesia
COULD LEARN: digit span task, classical conditioning, mirror writing, rotary pursuit task, playing tennis, incomplete picture test, tower of Hanoi, implicit memory tasks
COULD NOT LEARN: explicit memory tasks
WHY? - reverberating circuits
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How can memories be disrupted?
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blow to head, electroconvulsive shock
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How has memory been disrupted in lab animals?
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electroconvulsive shock was used to disrupt memory in the rat research described in class
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What is the relationship of the hippocampus/amygdala with memory and how was this tested with brain-damaged human subjects?
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hippocampus: explicit memories
amygdala: emotional memories
damage to amygdala in patient = could not acquire conditioned autonomic startle responses to stimuli but had good explicit memory for the training - amygdala does not store memory but strengthens emotional memories stored elsewhere
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What is long-term potentiation? How is related to memory?
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facilitation of synaptic transmission following high frequency electrical stimulation applied to presynaptic neurons
LTP induction causes structural changes (eg. increases in number and size of synapses, dendritic branching changes)
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