Question 1

Which of the following best describes a key physiological difference between cardiac muscle and skeletal muscle?

Accepted Answer

Cardiac muscle cells are connected by intercalated discs, allowing for synchronized contraction, while skeletal muscle fibers are not.

Question 2

During an action potential, which ion influx is primarily responsible for the plateau phase in cardiac muscle cells, and how does this differ from skeletal muscle?

Accepted Answer

Calcium ion influx in cardiac muscle; no plateau phase in skeletal muscle.

Question 3

Which of the following equations best represents the relationship between force of contraction and calcium ion concentration in cardiac muscle?

Accepted Answer

$$F = k \cdot [Ca$$^{2+}$$]$$

Question 4

A patient is given a drug that blocks gap junctions in cardiac muscle. What is the most likely physiological effect?

Accepted Answer

Loss of synchronized contraction of the heart muscle.

Question 5

Which of the following statements about the refractory period in cardiac muscle is correct?

Accepted Answer

The refractory period in cardiac muscle is longer than in skeletal muscle, preventing tetanus.

Question 6

Which structure is unique to cardiac muscle and is essential for the rapid transmission of electrical impulses between cells?

Accepted Answer

Intercalated disc

Question 7

A researcher measures the action potential duration in cardiac and skeletal muscle. Which result is most likely?

Accepted Answer

Cardiac muscle action potentials last longer due to a plateau phase.

Question 8

Which of the following best explains why cardiac muscle cannot undergo tetanus?

Accepted Answer

The long refractory period in cardiac muscle prevents summation of contractions.

Question 9

Which of the following is true regarding the source of calcium ions for contraction in cardiac versus skeletal muscle?

Accepted Answer

Cardiac muscle uses both extracellular and intracellular calcium, while skeletal muscle primarily uses intracellular calcium.

Question 10

A patient with a mutation affecting the function of intercalated discs would most likely experience which of the following symptoms?

Accepted Answer

Arrhythmias due to impaired electrical conduction in the heart.

Question 11

Which of the following best describes the mechanism of contraction initiation in cardiac muscle?

Accepted Answer

Initiated by pacemaker cells generating spontaneous action potentials.

Question 12

Which of the following best explains why skeletal muscle can be tetanized but cardiac muscle cannot?

Accepted Answer

Skeletal muscle has a shorter refractory period, allowing for summation of contractions.

Question 13

Which of the following is a direct result of the presence of intercalated discs in cardiac muscle?

Accepted Answer

Synchronous contraction of cardiac muscle cells.

Question 14

A drug that blocks voltage-gated calcium channels in cardiac muscle would most likely have which effect?

Accepted Answer

Decrease the force of cardiac contraction.

Question 15

Which of the following best describes the energy metabolism of cardiac muscle compared to skeletal muscle?

Accepted Answer

Cardiac muscle relies more heavily on aerobic metabolism than skeletal muscle.

Comparison of Cardiac and Skeletal Muscle Physiology

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