NEUROBIOLOGY FINAL EXAM
QUESTIONS & ANSWERS
Synaptic plasticity - Correct Answers -Structural/functional changes at a synapse
involved in learning, memory, development. Changes can be
presynaptic/postsynaptic/both
Facilitation - Correct Answers -different than linear summation--temporary increase in
size of successive psps with rapid, repeated stimulation. Not simply summing up.
Synaptic depression - Correct Answers -opposite of potentiation/facilitation: temporary
decrease in size of successive psps with rapid, repeated stimulation. Simple synaptic
depression only lasts msec or seconds. Seems to be due to depletion of pool of
synaptic vesicles that are ready to be released. can be demonstrated by reducing
extracellular Ca2+--leads to decrease or elimination of synaptic depression. due to
changes in presynaptic neuron (like facilitation). doesn't necessarily decrease overall
output of the circuit. e.g., depression at inhibitory synapse can enhance responding of
postsynaptic cell. e.g., in a simple CPG circuit with reciprocal inhibition, rate of activity of
CPG can speed up if synaptic depression occurs at one or both synapses
broadening of action potential - Correct Answers -broadening=AP lasts longer. Results
in more Ca2+ entering through voltage-dependent Ca2+ channels and more NT
released from sensory cell
mechanism of broadening AP - Correct Answers -5HT receptor activates PKA, PKC,
which phosphorylate K+ channels. Channels close, K+ can't get out. Cell stays
depolarized longer when AP fired. (5HT receptor activates cascade, phosphorylates K+
channel; K+ can't get out, cell stays depolarized longer when AP fired; more Ca2+
enters; more NT released from sensory cell. similar to mechanism of facilitation in that
presynaptic cell affected. end result is increased response by postsynaptic cell--L7
motor neuron)
NR2A and 2B subunits of NMDA receptor and their role in development and learning -
Correct Answers -Tang et al. made mice in which they replaced NR2A subunit of NMDA
receptor with NR2B subunit--called them Doogie mice. NR2B subunit normally gets
replaced with 2A during development. Channels with NR2B subunit stay open longer
than with NR2A. Easier to induce LTP in Doogie mice. performed better than controls in
learning tasks: morris water maze, recognition of objects, pairing foot shock with tone. is
this why young animals learn better/faster than adults?
,presynaptic and postsynaptic changes - Correct Answers -simple forms of plasticity
seem to involve changes in presynaptic cell. more complex forms involve changes in
both pre/post. Long term changes require changes in both cells. Retrograde signal often
sent from post to pre
role of calcium in facilitation and potentiation - Correct Answers -Ca2+ enters
presynaptic cell, builds up faster than it can be buffered or sequestered. When next AP
arrives more Ca2+ available, more NT is released, larger epsp evoked. increased
response in postsynaptic cell due to buildup of calcium in presynaptic cell
Aplysia - Correct Answers -cellular mechanisms of learning explored here. Water
squirted onto siphon causes reflex withdrawal of siphon and gill. Used as response in
learning studies
BDNF - Correct Answers -BDNF activates receptor called tyrosine receptor kinase B.
BDNF production required for LTP: don't know where it is made (maybe small
organelles in dendrites [not axons] called Golgi outposts). Affects both pre/post synaptic
cells. Presynaptic: enahnces release of glutamate. postsynaptic: phosphorylates NMDA
receptor making it easier to open. Also activates PLC which causes release of Ca2+
from IC stores, causingmore AMPA receptors to be inserted into the membrane. Also
opens TRPC3 channels allowing more cations into the cell
TrkB - Correct Answers -Tyrosine receptor kinase B activated by BDNF. TrkB receptors
on both presynaptic and postsynaptic cell membranes. TrkB binding causes receptor to
autophosphorylate: receptor binding activates at least 3 pathways leading to protein
synthesis and alters gene expression
classical (Pavlovian) conditioning - Correct Answers -learned association between two
stimuli that are paired repeatedly. E.g., Pavlov's dogs learned that being taken out of
cage meant food coming--started to salivate.
conditioned and unconditioned stimuli - Correct Answers -Unconditioned stimulus elicits
automatic unlearned reaction. Conditioned stimulus comes to elicit same reaction if
paired enough with US. CS predicts US, animal learns and starts to respond to CS
(harness in this case)
declarative (explicit) memory - Correct Answers -conscious, explicit, e.g., facts, people,
places, things. Primarily studied in mammals
dendritic sprouting - Correct Answers -causes new synapses to be made. Protein
synthesis required--happens right in dendritic spines
excitotoxicity - Correct Answers -Glutamate often implicated in excitotoxicity--involved in
epilepsy, stroke, traumatic brain damage, some neurodegenerative diseases. glutamate
spilling out of damaged or dying cells can cause excitotoxicity. This can allow too much
,Ca2+ in cell, which activates classes of enzymes inside cell and can damage cell
structure (cytoskeleton/membrane) if in excess.
gill-withdrawal reflex - Correct Answers -electric shock to tail in Aplysia sensitizes gill
withdrawal in response to stimulation of the siphon. Tail shock delivered along with
siphon tickle causes dishabituation. When delivered before siphon tickle, causes
sensitization
habituation - Correct Answers -reduction in responding to stimulus over time. Not due to
sensory adaptation, e.g, may habituate to sound of student in next seat tapping pencil
L7 motor neuron - Correct Answers -motor neuron that stimulates gill withdrawal
(Aplysia)
LTP - Correct Answers -hours-months. Enhanced response will be specific to the input
or synpases that were subject to high frequency stimulation. If a different set of inputs is
stimulated, response is unchanged. Glutamate is main excitatory NT in hippocampus--
binds AMPA and NMDA receptors on postsynaptic membrane of CA1 cell at synapse
between Schaffer collateral and CA1 cell. Ca2+ entering through NMDA receptor
channel facilitates synapse (makes it easier to get system going next time). BDNF
production required for LTP
LTD - Correct Answers -inverse of LTP, form of synaptic depression lasting
hours/months
Morris water maze - Correct Answers -test of memory: mouse or rat put in tub of water
with hidden platform. Learns location of platform relative to other cues in room. After
several trials, learns to swim straight to platform. Drugs that mess with NMDA receptors
mess up performance
operant conditioning - Correct Answers -learning to perform a task to earn reward or
avoid punishment, e.g., pigeon pecks a key to get a food pellet
potentiation - Correct Answers -type of facilitation that lasts a long time. More
complicated than facilitation. Mechanisms only unravelled in past 2 decades. Short
term: seconds-minutes. Long term: hours-months
procedural (implicit) memory - Correct Answers -reflexive, unconscious, implicit
information on "how to do things" e.g., riding a bike. Studied in Aplysia, Drosophila
retrograde signaling - Correct Answers -CAM kinase causes production of nitric oxide
(signal sent to presynaptic cell) and contributes in several ways to make changes long
lasting: caues production of trophic factors (e.g., brain-derived neurotrophic factor or
BDNF), alters protein synthesis, in some cases also causes new synapses to be made
(retrograde signal to presynaptic cell also importan in making CC related changes
permenant in Aplysia)
, Schaffer collaterals - Correct Answers -high frequency stimulation of Schaffer collateral
results in changes in synapses between Schaffer collateral and CA1 cell. Activity of CA1
cell is increasedin a semi permanent way: LTP
sensitization - Correct Answers -increase in reflex responding due to presentation of a
different strong stimulus, e.g., if car alarm going off outside, might jump when someone
taps you on shoulder.
H.M. - Correct Answers -had ventral temporal lobes (including hippocampus) removed
in 1953 to stop seizures died in 2008. studied by Brenda Milner/students. Found that
HM had profound deficits in declarative memory--found hippocampus important in
consolidation of memory. Always thinks hes about 30--shocked looking in mirror,
grieved every time learned mother had died, learned procedural memory tasks (mirror
writing), could recognize people he met before surgery but not those since (after a few
hours), had trouble with spatial tasks--took 8 years to learn floor plan of new home.
couldnt find way home from more than 2 blocks away
Susumu Tonegawa - Correct Answers -experiments show role of LTP: made knock out
mice that lack CAM kinase II only after first few weeks of development. Couldn't induce
LTP in these animals. They performed poorly in water maze. Couldn't induce stable
receptive fields in hippocampal neurons (normally respond to locatin in space)
Gina Turrigiano - Correct Answers -synaptic scaling: After LTP. If number of AMPA
receptors increases at one synapse, will be decreased at other synapses of same cell
over next several days to preserve overall activity rate of cell. Underlying mechanisms
not understood but seems that Ca2+ and BDNF involved
learning - Correct Answers -a change in behavior as a result of experience
memory - Correct Answers -stored representation of learning
associative learning - Correct Answers -classical and operant conditioning
linear summation - Correct Answers -linear addition of psps, most basic. Ca2+ enters
presynaptic cell, rapidly buffered or sequestered
sensitization L7 motor neuron - Correct Answers -sensory neuron from siphon makes
synapse on L7 and on an interneuron that makes a synapse on L7--simple reflex circuit.
Sensory neuron from tail makes synpase onto facilitation interneuron that has
presynaptic contact with sensory neuron--L7 synapse. shock to tail causes change in
activity of synapse between siphon sensory neuron and L7. facilitation interneuron
functions to modulate activity of sensory neuron. releases serotonin onto sensory
neuron; binds to metabotropic receptor. release of 5HT caues siphon sensory neuron to
release more NT. increased NT release causes L7 to fire more, causing stronger
withdrawal of gill
QUESTIONS & ANSWERS
Synaptic plasticity - Correct Answers -Structural/functional changes at a synapse
involved in learning, memory, development. Changes can be
presynaptic/postsynaptic/both
Facilitation - Correct Answers -different than linear summation--temporary increase in
size of successive psps with rapid, repeated stimulation. Not simply summing up.
Synaptic depression - Correct Answers -opposite of potentiation/facilitation: temporary
decrease in size of successive psps with rapid, repeated stimulation. Simple synaptic
depression only lasts msec or seconds. Seems to be due to depletion of pool of
synaptic vesicles that are ready to be released. can be demonstrated by reducing
extracellular Ca2+--leads to decrease or elimination of synaptic depression. due to
changes in presynaptic neuron (like facilitation). doesn't necessarily decrease overall
output of the circuit. e.g., depression at inhibitory synapse can enhance responding of
postsynaptic cell. e.g., in a simple CPG circuit with reciprocal inhibition, rate of activity of
CPG can speed up if synaptic depression occurs at one or both synapses
broadening of action potential - Correct Answers -broadening=AP lasts longer. Results
in more Ca2+ entering through voltage-dependent Ca2+ channels and more NT
released from sensory cell
mechanism of broadening AP - Correct Answers -5HT receptor activates PKA, PKC,
which phosphorylate K+ channels. Channels close, K+ can't get out. Cell stays
depolarized longer when AP fired. (5HT receptor activates cascade, phosphorylates K+
channel; K+ can't get out, cell stays depolarized longer when AP fired; more Ca2+
enters; more NT released from sensory cell. similar to mechanism of facilitation in that
presynaptic cell affected. end result is increased response by postsynaptic cell--L7
motor neuron)
NR2A and 2B subunits of NMDA receptor and their role in development and learning -
Correct Answers -Tang et al. made mice in which they replaced NR2A subunit of NMDA
receptor with NR2B subunit--called them Doogie mice. NR2B subunit normally gets
replaced with 2A during development. Channels with NR2B subunit stay open longer
than with NR2A. Easier to induce LTP in Doogie mice. performed better than controls in
learning tasks: morris water maze, recognition of objects, pairing foot shock with tone. is
this why young animals learn better/faster than adults?
,presynaptic and postsynaptic changes - Correct Answers -simple forms of plasticity
seem to involve changes in presynaptic cell. more complex forms involve changes in
both pre/post. Long term changes require changes in both cells. Retrograde signal often
sent from post to pre
role of calcium in facilitation and potentiation - Correct Answers -Ca2+ enters
presynaptic cell, builds up faster than it can be buffered or sequestered. When next AP
arrives more Ca2+ available, more NT is released, larger epsp evoked. increased
response in postsynaptic cell due to buildup of calcium in presynaptic cell
Aplysia - Correct Answers -cellular mechanisms of learning explored here. Water
squirted onto siphon causes reflex withdrawal of siphon and gill. Used as response in
learning studies
BDNF - Correct Answers -BDNF activates receptor called tyrosine receptor kinase B.
BDNF production required for LTP: don't know where it is made (maybe small
organelles in dendrites [not axons] called Golgi outposts). Affects both pre/post synaptic
cells. Presynaptic: enahnces release of glutamate. postsynaptic: phosphorylates NMDA
receptor making it easier to open. Also activates PLC which causes release of Ca2+
from IC stores, causingmore AMPA receptors to be inserted into the membrane. Also
opens TRPC3 channels allowing more cations into the cell
TrkB - Correct Answers -Tyrosine receptor kinase B activated by BDNF. TrkB receptors
on both presynaptic and postsynaptic cell membranes. TrkB binding causes receptor to
autophosphorylate: receptor binding activates at least 3 pathways leading to protein
synthesis and alters gene expression
classical (Pavlovian) conditioning - Correct Answers -learned association between two
stimuli that are paired repeatedly. E.g., Pavlov's dogs learned that being taken out of
cage meant food coming--started to salivate.
conditioned and unconditioned stimuli - Correct Answers -Unconditioned stimulus elicits
automatic unlearned reaction. Conditioned stimulus comes to elicit same reaction if
paired enough with US. CS predicts US, animal learns and starts to respond to CS
(harness in this case)
declarative (explicit) memory - Correct Answers -conscious, explicit, e.g., facts, people,
places, things. Primarily studied in mammals
dendritic sprouting - Correct Answers -causes new synapses to be made. Protein
synthesis required--happens right in dendritic spines
excitotoxicity - Correct Answers -Glutamate often implicated in excitotoxicity--involved in
epilepsy, stroke, traumatic brain damage, some neurodegenerative diseases. glutamate
spilling out of damaged or dying cells can cause excitotoxicity. This can allow too much
,Ca2+ in cell, which activates classes of enzymes inside cell and can damage cell
structure (cytoskeleton/membrane) if in excess.
gill-withdrawal reflex - Correct Answers -electric shock to tail in Aplysia sensitizes gill
withdrawal in response to stimulation of the siphon. Tail shock delivered along with
siphon tickle causes dishabituation. When delivered before siphon tickle, causes
sensitization
habituation - Correct Answers -reduction in responding to stimulus over time. Not due to
sensory adaptation, e.g, may habituate to sound of student in next seat tapping pencil
L7 motor neuron - Correct Answers -motor neuron that stimulates gill withdrawal
(Aplysia)
LTP - Correct Answers -hours-months. Enhanced response will be specific to the input
or synpases that were subject to high frequency stimulation. If a different set of inputs is
stimulated, response is unchanged. Glutamate is main excitatory NT in hippocampus--
binds AMPA and NMDA receptors on postsynaptic membrane of CA1 cell at synapse
between Schaffer collateral and CA1 cell. Ca2+ entering through NMDA receptor
channel facilitates synapse (makes it easier to get system going next time). BDNF
production required for LTP
LTD - Correct Answers -inverse of LTP, form of synaptic depression lasting
hours/months
Morris water maze - Correct Answers -test of memory: mouse or rat put in tub of water
with hidden platform. Learns location of platform relative to other cues in room. After
several trials, learns to swim straight to platform. Drugs that mess with NMDA receptors
mess up performance
operant conditioning - Correct Answers -learning to perform a task to earn reward or
avoid punishment, e.g., pigeon pecks a key to get a food pellet
potentiation - Correct Answers -type of facilitation that lasts a long time. More
complicated than facilitation. Mechanisms only unravelled in past 2 decades. Short
term: seconds-minutes. Long term: hours-months
procedural (implicit) memory - Correct Answers -reflexive, unconscious, implicit
information on "how to do things" e.g., riding a bike. Studied in Aplysia, Drosophila
retrograde signaling - Correct Answers -CAM kinase causes production of nitric oxide
(signal sent to presynaptic cell) and contributes in several ways to make changes long
lasting: caues production of trophic factors (e.g., brain-derived neurotrophic factor or
BDNF), alters protein synthesis, in some cases also causes new synapses to be made
(retrograde signal to presynaptic cell also importan in making CC related changes
permenant in Aplysia)
, Schaffer collaterals - Correct Answers -high frequency stimulation of Schaffer collateral
results in changes in synapses between Schaffer collateral and CA1 cell. Activity of CA1
cell is increasedin a semi permanent way: LTP
sensitization - Correct Answers -increase in reflex responding due to presentation of a
different strong stimulus, e.g., if car alarm going off outside, might jump when someone
taps you on shoulder.
H.M. - Correct Answers -had ventral temporal lobes (including hippocampus) removed
in 1953 to stop seizures died in 2008. studied by Brenda Milner/students. Found that
HM had profound deficits in declarative memory--found hippocampus important in
consolidation of memory. Always thinks hes about 30--shocked looking in mirror,
grieved every time learned mother had died, learned procedural memory tasks (mirror
writing), could recognize people he met before surgery but not those since (after a few
hours), had trouble with spatial tasks--took 8 years to learn floor plan of new home.
couldnt find way home from more than 2 blocks away
Susumu Tonegawa - Correct Answers -experiments show role of LTP: made knock out
mice that lack CAM kinase II only after first few weeks of development. Couldn't induce
LTP in these animals. They performed poorly in water maze. Couldn't induce stable
receptive fields in hippocampal neurons (normally respond to locatin in space)
Gina Turrigiano - Correct Answers -synaptic scaling: After LTP. If number of AMPA
receptors increases at one synapse, will be decreased at other synapses of same cell
over next several days to preserve overall activity rate of cell. Underlying mechanisms
not understood but seems that Ca2+ and BDNF involved
learning - Correct Answers -a change in behavior as a result of experience
memory - Correct Answers -stored representation of learning
associative learning - Correct Answers -classical and operant conditioning
linear summation - Correct Answers -linear addition of psps, most basic. Ca2+ enters
presynaptic cell, rapidly buffered or sequestered
sensitization L7 motor neuron - Correct Answers -sensory neuron from siphon makes
synapse on L7 and on an interneuron that makes a synapse on L7--simple reflex circuit.
Sensory neuron from tail makes synpase onto facilitation interneuron that has
presynaptic contact with sensory neuron--L7 synapse. shock to tail causes change in
activity of synapse between siphon sensory neuron and L7. facilitation interneuron
functions to modulate activity of sensory neuron. releases serotonin onto sensory
neuron; binds to metabotropic receptor. release of 5HT caues siphon sensory neuron to
release more NT. increased NT release causes L7 to fire more, causing stronger
withdrawal of gill
