NEUROMUSCULAR JUNCTION

Question 1

skeletal muscle structure

Answer 1

skeletal muscle is surrounded by a connective tissue epimysium and within the muscle, there is a muscle fascicle which is surrounded by perimysium, within the fascicle there is muscle fiber, between muscle fascicle is the endomysium

Question 2

muscle fiber

Answer 2

it is surrounded by sarcolemma

within the muscle fiber is the myofibril

Question 3

myofibril

Answer 3

has sarcomere
the A-band consists of thick and thin filaments
within the A-zone there is H- vertical zone with an M-line that is a thick filament

I-band consists only of thin filaments

Z-disc separate sarcomere within myofibril from each other

Question 4

thick filament

Answer 4

made up of myosin with the globular head that has a myosin ATPase binding site

Question 5

an action potential occurs at the

Answer 5

sarcolemma

Question 6

thin filaments

Answer 6

are made up of actin with actin-binding site

they contain tropomyosin which blocks the actin-binding site

there is also troponin which is made up of three molecules

a. one molecule is attached to actin.
b. another to tropomyosin
c. the last one binds calcium

Question 7

what happens when calcium is not bound to troponin

Answer 7

it will stabilize tropomyosin in its blocking position over the actin-binding site

Question 8

neuromuscular junction

Answer 8

occurs the terminal end of a motor neuron and motor endplate of the sarcolemma of muscle fiber

Motor unit= motor neuron+muscle fibers innervated by neuron

Question 9

motor neuron axon can branch to contract several skeletal muscle fibers and the more motor neuron are stimulated

Answer 9

the more contraction occurs

Question 10

neuromuscular junction process

Answer 10

1. Action potential(AP) propagation in motor neuron
2. When AP reaches the axon terminal, causes voltage gatedCa2+channels to open. Increases intracellular [Ca2+]

3. Increase in Ca2+ causes
exocytosis of synaptic
vesicles releasing
Acetylcholine (ACh) into the
synaptic cleft

4. ACh binds to nicotinic receptors (ligand-gated
   channels) on the motor endplate
5. Na+ enters the cell
   causes end plate
   potential
   (excitatory)
6. when threshold potential is reached Opening of voltage-gated Na+ channels →Na+ enters the cell→generates an AP

Question 11

action potential of skeletal muscle

Answer 11

1. resting membrane potential is at -90 Mv

2. threshold potential is at -75 Mv

Question 12

what maintains skeletal muscle RMP

Answer 12

Cl, if it is not there, muscle won’t repolarize to generate the active state of the channel responsible for generating a succeeding action potential