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Physiology Quiz -Skeletal Muscle Physiology - Part 3

Skeletal muscle cells are characterized by their striated appearance when visualized under the light and electron microscopes. Collectively, skeletal muscle cells make up approximately 50% of the body’s wet (i.e., soft tissue) weight. Skeletal muscle cells perform highly important functions including generating force, motion, and even heat. Test your basic knowledge of skeletal muscle physiology by taking this simple quiz.

(1) Action potentials travel along the skeletal muscle cell plasma membrane as well as along the t-tubules by saltatory conduction.

True

False

(2) The refractory period (total; absolute + relative) in a skeletal muscle cell is about:

(A) 1 ms

(B) 5 ms

(C) 10 ms

(D) 50 ms

(E) 100 ms

(3) At the neuromuscular junction (NMJ), the end-plate potential:

(A) Is at the end of the plate.

(B) Results from the activation of the nicotinic acetylcholine receptors.

(C) Results from the opening of the voltage-gated Na+ channels.

(D) Results from the opening of the voltage-gated K+ channels.

(E) All of the above.

(4) Arrival of an action potential at the axon terminal of a motor neuron causes the fusion of acetylcholine-containing synaptic vesicles with the pre-synaptic plasma membrane of the axon terminal. Acetylcholine then diffuses across the synaptic cleft to bind to and activate nicotinic acetylcholine receptors. Activation of the nicotinic acetylcholine receptors leads to an initial depolarization before a skeletal muscle action potential is initiated. The initial depolarization of the skeletal muscle plasma membrane at the neuromuscular junction (NMJ) is referred to as the: