PHIL 1000X Study Guide - Final Guide: Conformational Change, Sarcolemma, Myofilament
10 May 2018
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BLOCK XC
MODULE X7 - MUSCLE PHYSIOLOGY
UNIT 1
Skeletal Muscle Function
Unit Objectives
When you have finished this unit, you should be able to:
1. Sketch the neuromuscular junction (NMJ) in cross-section, showing nerve terminal,
vesicles, synaptic cleft, and postsynaptic membrane (motor end plate) of the skeletal
muscle cell.
a. See here for picture:
https://t2.ftcdn.net/jpg/00/81/72/45/500_F_81724541_Kr4vsQwpTZlO1lXB7vhcx
w5vTA7fvNX6.jpg
b. Acetylcholine is released from the nerve terminal in vesicles → they diffuse
across the synaptic cleft → bind to receptors on the post-synaptic membrane
c. The motor end plate is the area where the nerve terminal touches the muscle cell
2. Describe the events at the NMJ, including the actions of ACh and acetylcholinesterase.
a. Acetylcholine released from the nerve terminal
b. Binds to receptors on the muscle cell
c. Those receptors are like sodium channels; once the acetylcholine binds to them
then they open up and let sodium in
d. Muscle cell is depolarized (called end plate potential)
e. If end plate potential depolarizes the muscle cell to threshold, get an action
potential
f. Acetylcholinesterase is an enzyme that breaks up acetylcholine in the cleft
because you don’t want your muscle to contract forever
3. Define motor unit, motor end plate, neuromuscular junction (NMJ), and end plate
potential (EPP).
a. Motor unit - all the muscle cells that are innervated by a single motor neuron
b. Motor end plate - where the neuron synapses onto the muscle
c. NMJ - connection between the two
d. End plate potential - depolarization that occurs because of the binding of
acetylcholine and opening of receptor channels, allowing Na+ in
4. Sketch a diagram and explain the relationship between muscle fiber, myofibril,
myofilament, sarcomere, thin (actin) filament, and thick (myosin) filament in a skeletal
muscle cell.
