Synaptic transmission IL

Question 1

Define neuromuscular junction
(NMJ)

Answer 1

synapse point between the axon terminal and end of a motor neuron and the muscle its sending a signal to

Question 2

a single axon can innervate multiple fibers in a muscle but each individual muscle fiber is controlled by only one ____

Answer 2

axon

Question 3

at the site of the NMJ the motor neuron has Ca2+ induced release of _____

Answer 3

Acetylcholine (ACh)

Question 4

how do we want to respond to motor impulses fast

Answer 4

Junctional folds that increase surface area + decrease distance between the motor neuron and the muscle membrane

Question 5

which receptors are fast responding

Answer 5

ionotropic receptros

Question 6

a myocyte is innervated by one axon but ____ neuron csn innervate multiple myocytes

Answer 6

a motor neuron

Question 7

are metabotropic receptors found in NMJ

Answer 7

no

Question 8

which receptors are stimulated by nicotine
attatched to an ion channel
2 ACh molecules bind to 1 receptor
demonstrate rapid desensitization

Answer 8

ionotropic receptors

Question 9

an action potential will travel down the axon to the synaptic terminal
____ the membrane by an ____ flux of sodium and ____ flux of potassium

Answer 9

depolarizing
inward
outward

Question 10

as the action potential reaches the axon terminal and Na+ reaches its reversal potential, voltage gates ____ channels will open and ____ will flow INTO the axon terminal

Answer 10

Ca2+

Question 11

free cytoslic calcium causes synaptic vesciles to fuse on the ____ membrane

Answer 11

presynaptic

Question 12

the ACh will diffuse across the synaptic cleft to the ____ membrane and binds to its receptor which causes an influx of sodium through depolarization of muscle cell, it produces End plate potential

Answer 12

postsynaptic

Question 13

once EPP reaches threshold _____ potential is generated and we have contraction

Answer 13

an all or nothing action potential

Question 14

T or F
an end plate potential is NOT an action potential

Answer 14

T
its a graded potential produced at the post synaptic level of the NMJ

Question 15

strength of action potential directly influences the ____ of the inward ___ current

Answer 15

size
Ca2+ current

Question 16

stronger action potential= longer time the membrane is depolarized = longer opening of the voltage gated calcium channels

Question 17

EPP is graded, it is dependent on the amount of ACh that is released into the synaptic cleft. what ensures we always have enough vesicles released and can always guarantee muscle contraction

Answer 17

safety factor

Question 18

what determines the amplitude of the EPP

Answer 18

strength of calcium current in the presynaptic cell
number of vesciles in the synapse
concentration of ACh in vesicle
concentration of ACh receptors on the post synaptic cell membrane

Question 19

T or F
binding of ACh binds to its receptor opens an ion channel that allows Na and K to pass this ion channel is equally permeable to both Na and K

Answer 19

T

Question 20

know the point of equal flux of sodium and potassium through Ach channel

Question 21

Ach vesicles fuse with

Answer 21

presynaptic terminals and release ACh into synaptic cleft

Question 22

ACh binds to AChR in the junctional folds on the post synaptic side causing ______

Answer 22

the nicotinic AChR to open a ligand gated ion channel

Question 23

initial depolarization due to inward flux of Na+ causes ____-

Answer 23

the EPP

Question 24

what happens when depolarization of the ligand gated channel depolarizes the membrane enough to open the voltage gated sodium channels located across the membrane

Answer 24

an action potential occurs

Question 25

what ends when Na+ and K+ battle for current they approach equilibrium so there is no change in membrane potential

Answer 25

EPP ends ( end plate potential)

Question 26

mediated by 2 voltage gated channels

Answer 26

action potential

Question 27

rapid depolarization with overshoot to +40 mV

Answer 27

action potential

Question 28

charge carried by Na+ (overshoot is close to Na+ equilibrium potential)

Answer 28

action potential

Question 29

repolarization due to increased gK+ (undershoot is close to K+ equilibrium potential)

Answer 29

action potential

Question 30

two independent Na+ and K+ Channels

Answer 30

action potential

Question 31

mediated by 1 ligand gated channel

Answer 31

End plate potential

Question 32

rapid depolarization with overshoot to 0 mV

Answer 32

End plate potential

Question 33

charge carried by both Na+ and K+ with Erev=(Ena+Ek)/2

Answer 33

End plate potential

Question 34

passive repolarization mediated by leak channel (which goes down along space and time constant)

Answer 34

End plate potential

Question 35

single channel permeable to both Na+ and K+

Answer 35

End plate potential

Question 36

calcium is an extrememly powerful ____ in the cell

Answer 36

second messenger

Question 37

calcium is sequestered by which two organelles

Answer 37

mitochondria and smooth Er (SER)

Question 38

memorize voltage gated ca2+ channels

Question 39

L - type or long lasting

Answer 39

important in maintaining action potentials

Question 40

p/q type or purkinje

Answer 40

p type is present in the presynaptic terminal of the NMJ

Question 41

t type or transient

Answer 41

important in intiating action potentials

Question 42

n type or neuronal

Answer 42

similar to P/ Q type invovled in neurotransmitter release
high threshold of activation
involved in calcium homeostatus
deactivated by conotoxin from snails