Q: Which equation best represents the Nernst equation for calculating the equilibrium potential of an ion across the cardiac cell membrane?

$$E = \frac{RT}{zF} \ln \left( \frac{[\text{ion}]_{\text{outside}}}{[\text{ion}]_{\text{inside}}} \right)$$

Question 1

Which structural feature is unique to cardiac muscle cells and is essential for their synchronized contraction?

Accepted Answer

Intercalated discs

Question 2

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

Accepted Answer

Cardiac muscle cells have a long absolute refractory period

Question 3

A patient suffers a myocardial infarction that blocks blood supply to part of the heart. Which cellular process is most likely to be impaired first?

Accepted Answer

Aerobic respiration in cardiac myocytes

Question 4

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

Accepted Answer

Ca$$^{2+}$$

Question 5

During the cardiac action potential, which event marks the transition from depolarization to repolarization?

Accepted Answer

Inactivation of Ca$$^{2+}$$ channels and opening of K$$^{+}$$ channels

Question 6

Which muscle type is characterized by spindle-shaped cells, a single central nucleus, and no striations?

Accepted Answer

Smooth muscle

Question 7

What is the primary function of gap junctions in cardiac muscle cells?

Accepted Answer

To electrically couple adjacent cells for coordinated contraction

Question 8

Which of the following statements about cardiac pacemaker cells is TRUE?

Accepted Answer

They possess auto-rhythmicity and can depolarize spontaneously

Question 9

Which neurotransmitter and receptor combination is responsible for decreasing heart rate?

Accepted Answer

Acetylcholine acting on muscarinic receptors

Question 10

A drug blocks voltage-gated Ca$$^{2+}$$ channels in cardiac myocytes. What is the most likely effect on the cardiac action potential?

Accepted Answer

Shortening of the plateau phase

Question 11

Which of the following best describes the sequence of electrical excitation in the heart?

Accepted Answer

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

Question 12

Which equation best represents the Nernst equation for calculating the equilibrium potential of an ion across the cardiac cell membrane?

Accepted Answer

$$E = \frac{RT}{zF} \ln \left( \frac{[	ext{ion}]_{	ext{outside}}}{[	ext{ion}]_{	ext{inside}}} ight)$$

Question 13

Which of the following is a direct effect of norepinephrine on cardiac muscle cells?

Accepted Answer

Increased force of contraction

Question 14

If the SA node fails, which structure will most likely take over as the pacemaker of the heart?

Accepted Answer

AV node

Question 15

Which process describes the mechanism by which extracellular Ca$$^{2+}$$ triggers further Ca$$^{2+}$$ release from the sarcoplasmic reticulum in cardiac myocytes?

Accepted Answer

Ca$$^{2+}-$$induced Ca$$^{2+}$$ release (CICR)

Question 16

Which of the following is TRUE regarding the energy requirements of cardiac muscle cells?

Accepted Answer

They have many mitochondria and depend on aerobic respiration

Question 17

A patient is given a muscarinic receptor inhibitor. What is the expected effect on heart rate?

Accepted Answer

Heart rate will increase

Question 18

Which of the following best explains why the atria contract before the ventricles during a normal heartbeat?

Accepted Answer

The AV node delays the impulse, allowing atrial contraction first

Question 19

Which of the following is a consequence of acidification (increased H$$^{+}) in $$cardiac muscle due to anaerobic respiration?

Accepted Answer

Blockage of gap junctions leading to arrhythmias

Question 20

Which of the following is TRUE regarding the excitation of cardiac muscle compared to skeletal muscle?

Accepted Answer

Cardiac muscle cells can contract automatically due to pacemaker cells

Lecture #21

Guida di studio - Domande di pratica

Study guide - Flashcard