lecture 10 postsynaptic

Question 1

Reuptake

Answer 1

method of removing neurotransmitter from the synaptic cleft through
transporters located the presynaptic termina

Question 2

where neurotransmitter is taken
up by glia may occur instead (or in addition)

Answer 2

Uptake

Question 3

Enzymatic breakdown

Answer 3

there are enzymes in the synaptic cleft that break down
neurotransmitter molecules so they are no longer able to bind to postsynaptic
receptors

Question 4

Excitatory synapse

Answer 4

a synapse where the release of neurotransmitter increases the
likelihood that the postsynaptic neuron fires an action potential. Usually by bringing the
membrane potential closer to or beyond the threshold potential

Question 5

type of neurotransmitter receptor in the
postsynaptic membrane, also known as
inotropic receptor, where the binding of
a neurotransmitter molecule, causes
the opening of a channel and allows
ions to flow through the channel

Answer 5

Ligand-gated ion channel

Question 6

Acetylcholine (ACh)

Answer 6

the excitatory
neurotransmitter at the neuromuscular
junction (NMJ)

Question 7

Acetylcholine receptor (AChR)

Answer 7

type of synaptic receptor at the NMJ,
located on the muscle. NMJ AChR are
ligand-gated ion channels that
desensitize and are activated by
nicotine so sometimes referred to as a
nicotinic AChR or nAChR. This channel,
when opened, permits the flow of Na+
and K+ currents.

Question 8

Alpha-bungarotoxin

Answer 8

competitive antagonist for nAChRs that are purified from snake
venom. α-bungarotoxin specifically binds to and blocks the receptor

Question 9

Excitatory postsynaptic potential (EPSP)

Answer 9

a transient depolarization of the membrane
potential as a result of the activation of an excitatory chemical synaptic. An EPP is an EPSP at
the NMJ. An EPSP typically has a fast rise and a slower decay and is typically at least 10 ms
(all the way up to 100-200 ms) in duration

Question 10

Reversal potential (VRev)

Answer 10

membrane potential where the net current through an open ligandgated ion channel (or receptor) would be zero. Depends on the permeability of the channel to
different ions and the equilibrium potential for those ions. For example the reversal potential at
the NMJ is ~ -10 mV because the conductance of sodium equals the conductance of
potassium through the nAChR

Question 11

Desensitization

Answer 11

property of some ligand-gated ion channels such that if they are open for a
long time, they will desensitize or close even though neurotransmitter molecules may still be
bound to the receptor. Typically, AChRs and AMPA receptors desensitize

Question 12

major neurotransmitter at excitatory synapses in the central nervous system

Answer 12

Glutamate

Question 13

AMPA receptor

Answer 13

glutamate-gated ion channel. Typical AMPA receptors desensitize, are
permeable to Na+ and K+ but impermeable to Ca2+. Has fast rise and decay times. AMPA
channels are the most common receptor type in the brain

Question 14

NMDA receptor

Answer 14

glutamate-gated ion channel, that is also voltage dependent. Mg2+ blocks
the receptor unless depolarization pushes the Mg2+ out of the pore. Typical NMDA receptors
do not desensitize, are permeable to Na+ and K+ and Ca2+. NMDA receptors also have slower
rise and decay times than AMPA receptors. NMDA receptors are important in learning and
synaptic plasticity

Question 15

Describe the structure of an acetylcholine receptor (AChR), including what makes it
selective to cations and how it differs from a voltage-gated sodium channel

Question 16

structure of achr receptor

Answer 16

5 separate proteins (vs 1 protein for VGna)
each subunit has 4 membrane domains (VGna has 6)
m2 domains line the pore (s4 lines the pore)

Question 17

What is a reversal potential? What ions are responsible for the reversal potential at fast
excitatory synapses?

Question 18

List the most common excitatory neurotransmitters in the CNS and PNS.

Answer 18

Acetylcholine cns, glutamate pns

Question 19

Draw a sub-threshold excitatory postsynaptic potential (EPSP) including appropriate size
and timescale. Explain why the rise time is faster than the falling phase

Question 20

if a neurotransmitter doesnt connect to a receptor what might happen to it

Answer 20

1) reuptake
2) broken down by cleft enzymes3
3) diffuse out
4) taken up by glial cells
5) removed by multiple factors like cleaved by enzyme then reuptaken

Question 21

what is the channel pore of an achr liined wih

Answer 21

negatively charged amino acids (like VGna) because an excitatory synapse needs to allow the postsynaptic cell to reach threshold which is more depolarized than resting potential (so needs na current)

Question 22

equation for reversal potential

Answer 22

equilibrium potential of x + equilibrium potential of y / 2

Question 23

which ligand isnt cleaved easily and causes desensitization of achr and paralysis

Answer 23

succinyl choline (muscle relaxant used in surgery)

Question 24

glutamate receptors

Answer 24

ampa and nmda

Question 25

main glutamate receptor

Answer 25

ampa

Question 26

voltage and ligand gated receptor that lets calcium enter during large depolarization

Answer 26

nmda

Question 27

ionotropic

Answer 27

lets ions flow