Question 1

Which structural feature of cardiac muscle cells allows for rapid electrical communication between adjacent cells?

Accepted Answer

Gap junctions

Question 2

What is the primary function of phospholamban (PLN) in cardiac muscle relaxation?

Accepted Answer

It inhibits the SERCA pump when dephosphorylated, slowing Ca$^{2+}$ reuptake.

Question 3

During the action potential of an autorhythmic cardiac cell, which ion channel is responsible for the initial depolarization from the unstable resting membrane potential?

Accepted Answer

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels

Question 4

Which equation best represents the relationship between force of contraction and intracellular Ca$^{2+}$ concentration in cardiac muscle?

Accepted Answer

$F \propto [Ca^{2+}]$

Question 5

A patient is given a drug that increases phosphorylation of L-type Ca$^{2+}$ channels in cardiac muscle. What is the expected effect on cardiac contractility?

Accepted Answer

Increased contractility due to enhanced Ca$^{2+}$ influx

Question 6

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

Accepted Answer

The long duration of the action potential prevents summation of contractions

Question 7

In the crossed extensor reflex, what is the role of the contralateral limb?

Accepted Answer

Its extensors are activated to support the body as the other limb withdraws

Question 8

Which process is unique to excitation-contraction coupling in cardiac muscle compared to skeletal muscle?

Accepted Answer

Ca$^{2+}$-induced Ca$^{2+}$ release from the sarcoplasmic reticulum

Question 9

Which of the following best describes the effect of sympathetic stimulation on cardiac muscle?

Accepted Answer

Increases heart rate, conduction velocity, and contractility

Question 10

A mutation causes the HCN channels in autorhythmic cells to remain closed. What is the most likely consequence?

Accepted Answer

Decreased heart rate due to slower depolarization

Question 11

Which of the following is TRUE regarding the length-tension relationship in cardiac muscle?

Accepted Answer

A slightly stretched sarcomere increases Ca$^{2+}$ sensitivity and tension

Question 12

Which ion is primarily responsible for the plateau phase in the action potential of a cardiac contractile cell?

Accepted Answer

Ca$^{2+}$

Question 13

What is the main reason cardiac muscle cells have a high abundance of mitochondria?

Accepted Answer

To support oxidative metabolism for continuous ATP production

Question 14

Which of the following best describes the role of troponin in cardiac muscle contraction?

Accepted Answer

Troponin binds to Ca$^{2+}$, removing tropomyosin inhibition and allowing cross-bridge cycling

Question 15

Which of the following is a direct effect of increased cytosolic Ca$^{2+}$ in cardiac muscle cells?

Accepted Answer

Increased cross-bridge formation and contractile force

Question 16

Which step occurs LAST during the excitation-contraction coupling in cardiac muscle?

Accepted Answer

Cross-bridge cycling between actin and myosin

Question 17

Which of the following mechanisms is primarily responsible for the removal of Ca$^{2+}$ from the cytosol during cardiac muscle relaxation?

Accepted Answer

SERCA pump reuptake into the sarcoplasmic reticulum

Question 18

Which of the following statements about cardiac muscle cells is CORRECT?

Accepted Answer

They are striated, branched, and usually have a single nucleus

Question 19

Which neurotransmitter is released by the sympathetic nervous system to increase heart rate and contractility?

Accepted Answer

Norepinephrine

Question 20

A patient has a defect in ryanodine receptors in cardiac muscle. Which process would be most directly affected?

Accepted Answer

Ca$^{2+}$-induced Ca$^{2+}$ release from the sarcoplasmic reticulum

Cardiac Muscle Physiology and Reflexes: Study Notes for Anatomy & Physiology

Study Guide - Practice Questions

Study Guide - Flashcards