Electrophysiology of the Conduction System; Action Potential

Question 1

What is the primary function of the conduction system in the heart?

Answer 1

To coordinate the contraction of the heart muscles and maintain a regular heartbeat.

Question 2

True or False: The sinoatrial (SA) node is known as the natural pacemaker of the heart.

Answer 2

True

Question 3

Fill in the blank: The action potential in cardiac muscle cells is primarily due to the movement of _____ ions.

Answer 3

sodium (Na+)

Question 4

What are the phases of the cardiac action potential?

Answer 4

Phase 0 (depolarization), Phase 1 (initial repolarization), Phase 2 (plateau), Phase 3 (repolarization), Phase 4 (resting potential).

Question 5

Which ion is responsible for the plateau phase of the cardiac action potential?

Answer 5

Calcium (Ca2+)

Question 6

What is the role of the atrioventricular (AV) node in the conduction system?

Answer 6

To delay the electrical signal from the atria to the ventricles, allowing time for the atria to contract and fill the ventricles.

Question 7

Multiple Choice: Which structure conducts the action potential from the AV node to the ventricles? A) Bundle of His B) Purkinje fibers C) Both A and B

Answer 7

C) Both A and B

Question 8

True or False: The Purkinje fibers have a faster conduction velocity than the atrial muscle.

Answer 8

True

Question 9

What is the resting membrane potential of a typical cardiac myocyte?

Answer 9

-90 mV

Question 10

Fill in the blank: The refractory period of cardiac muscle prevents _____.

Answer 10

tetany (sustained contraction)

Question 11

What initiates the depolarization phase of the action potential?

Answer 11

Rapid influx of sodium ions (Na+).

Question 12

Multiple Choice: What is the effect of sympathetic stimulation on the heart rate? A) Increases B) Decreases C) No effect

Answer 12

A) Increases

Question 13

True or False: The conduction system of the heart is influenced by hormonal factors.

Answer 13

True

Question 14

What is the significance of the refractory period in cardiac action potentials?

Answer 14

It ensures that the heart has time to relax and fill with blood before the next contraction.

Question 15

What is the primary ion involved in the repolarization phase of the cardiac action potential?

Answer 15

Potassium (K+)

Question 16

Fill in the blank: The conduction velocity is fastest in the _____.

Answer 16

Purkinje fibers

Question 17

Multiple Choice: Which part of the conduction system is responsible for the fastest rate of depolarization? A) SA node B) AV node C) Bundle of His

Answer 17

A) SA node

Question 18

What is the role of gap junctions in cardiac muscle?

Answer 18

They allow for the rapid transmission of electrical impulses between adjacent cells.

Question 19

True or False: Cardiac action potentials can be influenced by changes in extracellular ion concentrations.

Answer 19

True

Question 20

What effect does parasympathetic stimulation have on heart rate?

Answer 20

It decreases the heart rate.

Question 21

Fill in the blank: The action potential duration is longer in _____ than in skeletal muscle.

Answer 21

cardiac muscle

Question 22

What is the main purpose of the Bundle of His?

Answer 22

To transmit electrical impulses from the AV node to the ventricles.

Question 23

Multiple Choice: Which ion’s efflux is primarily responsible for the repolarization of the cardiac action potential? A) Sodium B) Potassium C) Calcium

Answer 23

B) Potassium

Question 24

What is the intrinsic firing rate of the SA node?

Answer 24

60 to 100 beats per minute.

Question 25

True or False: The action potential in cardiac cells can have a plateau phase.

Answer 25

True

Question 26

What is the primary action of calcium during the cardiac action potential?

Answer 26

To promote contraction of cardiac muscle cells.