Question 1

Which of the following best describes the role of the sodium-potassium pump in maintaining the resting membrane potential of a skeletal muscle cell?

Accepted Answer

It actively transports $3$ sodium ions out of the cell and $2$ potassium ions into the cell, maintaining a negative resting potential.

Question 2

A patient is exposed to a toxin that blocks voltage-gated sodium channels in skeletal muscle. Which phase of the action potential would be directly affected?

Accepted Answer

Depolarization

Question 3

Which of the following is TRUE regarding the differences between skeletal, cardiac, and smooth muscle tissues?

Accepted Answer

Skeletal muscle fibers are multinucleated and striated, while smooth muscle fibers are uninucleated and non-striated.

Question 4

At the neuromuscular junction, which event directly triggers the opening of ligand-gated sodium channels on the muscle fiber membrane?

Accepted Answer

Release of acetylcholine from the motor neuron terminal

Question 5

During the repolarization phase of an action potential in a muscle cell, which ion movement is primarily responsible for restoring the membrane potential?

Accepted Answer

Efflux of potassium ions ($K^+$)

Question 6

Which of the following best explains why acetylcholine is necessary for skeletal muscle contraction?

Accepted Answer

It binds to nicotinic receptors, opening ligand-gated sodium channels and initiating an action potential.

Question 7

A drug that blocks acetylcholine from binding to its receptor at the neuromuscular junction would most likely result in which of the following?

Accepted Answer

Inability of the muscle to contract (flaccid paralysis)

Question 8

Which of the following correctly matches the muscle type with its primary control mechanism?

Accepted Answer

Cardiac muscle: involuntary

Question 9

During excitation-contraction coupling in skeletal muscle, what is the role of calcium ions ($Ca^{2+}$)?

Accepted Answer

They bind to troponin, causing a conformational change that exposes myosin-binding sites on actin.

Question 10

A patient with a genetic defect in their voltage-gated potassium channels would most likely experience which of the following during muscle action potentials?

Accepted Answer

Prolonged depolarization due to delayed repolarization

Question 11

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

Accepted Answer

Action potential arrives at axon terminal → acetylcholine released → acetylcholine binds to nicotinic receptors → sodium influx → muscle action potential

Question 12

Which of the following is a key difference between ligand-gated and voltage-gated ion channels in muscle cell activation?

Accepted Answer

Ligand-gated channels open in response to neurotransmitter binding, while voltage-gated channels open in response to changes in membrane potential.

Question 13

A muscle fiber is unable to return to its resting membrane potential after contraction. Which process is most likely impaired?

Accepted Answer

Efflux of potassium ions through voltage-gated channels

Question 14

Which of the following best explains why the resting membrane potential of a muscle cell is negative?

Accepted Answer

The sodium-potassium pump creates an unequal distribution of ions, with more positive ions outside the cell.

Question 15

A patient is given a drug that increases the permeability of the muscle cell membrane to sodium ions at rest. What effect would this have on the resting membrane potential?

Accepted Answer

The resting membrane potential would become less negative (depolarized).

Question 16

Which of the following scenarios best illustrates the concept of excitation-contraction coupling in skeletal muscle?

Accepted Answer

A nerve impulse triggers acetylcholine release, leading to an action potential in the muscle fiber and subsequent contraction.

Question 17

Which of the following best describes the function of nicotinic receptors at the neuromuscular junction?

Accepted Answer

They are ligand-gated sodium channels that open when acetylcholine binds, allowing sodium influx.

Question 18

A patient with myasthenia gravis produces antibodies against nicotinic acetylcholine receptors. Which of the following symptoms would you expect?

Accepted Answer

Muscle weakness due to impaired synaptic transmission

Question 19

Which of the following best explains why smooth muscle can sustain contractions for longer periods than skeletal muscle?

Accepted Answer

Smooth muscle uses a different mechanism for calcium entry and has slower ATPase activity.

Question 20

During the relaxation phase of muscle contraction, which event occurs to allow the muscle fiber to return to its resting state?

Accepted Answer

Calcium ions are actively transported back into the sarcoplasmic reticulum.

Muscle Tissue Types, Neuromuscular Junction, and Action Potentials in Muscle Physiology

Study Guide - Practice Questions

Study Guide - Flashcards