Question 1

Which of the following best describes the sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Motor nerve signal, release of Ach, depolarization of the sarcolemma, release of intracellular calcium

Question 2

At the neuromuscular junction, what is the role of acetylcholine (Ach)?

Accepted Answer

It binds to receptors on the motor endplate, causing chemically gated channels to open

Question 3

Which structure is specifically referred to as the 'motor endplate' at the neuromuscular junction?

Accepted Answer

The postsynaptic membrane of the muscle fiber

Question 4

What is the primary function of cholinesterase at the neuromuscular junction?

Accepted Answer

To break down acetylcholine in the synaptic cleft, terminating the signal

Question 5

Which equation best represents the depolarization of the sarcolemma due to sodium influx?

Accepted Answer

$$\Delta V = V_{Na^+} - V_{rest}$$

Question 6

A patient is exposed to a toxin that blocks acetylcholine receptors at the motor endplate. What is the most likely physiological consequence?

Accepted Answer

Failure of muscle contraction due to lack of depolarization

Question 7

Which of the following best explains why skeletal muscle fibers are described as having a 1:1 ratio of innervation?

Accepted Answer

Each muscle fiber receives input from one motor neuron, and each motor neuron can innervate multiple fibers

Question 8

During muscle contraction, which molecule binds to troponin to expose the myosin binding sites on actin?

Accepted Answer

$$Ca^{2+}$$

Question 9

Which of the following is TRUE regarding the action potential at the neuromuscular junction?

Accepted Answer

It is initiated by the influx of sodium ions after acetylcholine binds to its receptor

Question 10

Which process directly requires ATP during the muscle contraction cycle?

Accepted Answer

Release of myosin head from actin

Question 11

A sprinter’s muscles are primarily composed of which type of muscle fibers, and what is their main source of ATP?

Accepted Answer

Type II fibers; glycolysis

Question 12

Which of the following best describes the latent period in a muscle twitch?

Accepted Answer

The brief delay between the stimulus and the onset of contraction

Question 13

If calcium ions ($$Ca^{2+}) $$are not returned to the sarcoplasmic reticulum after contraction, what will happen?

Accepted Answer

The contraction cycle will continue and the muscle will remain contracted

Question 14

Which of the following is a characteristic of slow-twitch (Type I) muscle fibers?

Accepted Answer

High fatigue resistance

Question 15

What is the effect of cholinesterase inhibitors on muscle contraction?

Accepted Answer

They prolong muscle contraction by preventing breakdown of acetylcholine

Question 16

Which of the following best explains the difference in fatigue resistance between slow-twitch and fast-twitch muscle fibers?

Accepted Answer

Slow-twitch fibers have a higher capillary supply and myoglobin content, supporting aerobic metabolism

Question 17

Which equation represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$$ATP + H_2O \rightarrow ADP + P_i + energy$$

Question 18

Which of the following events occurs FIRST during the transmission of a motor nerve signal to a skeletal muscle fiber?

Accepted Answer

Arrival of the action potential at the axon terminal

Question 19

Which of the following is TRUE regarding the function of the myelin sheath in motor neurons?

Accepted Answer

It insulates the axon and increases the speed of nerve impulse conduction

Neuromuscular Junction and Physiology of Muscle Contraction

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