Cardiac Action Potential and ECG Quiz

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Questions and Answers

Which layer of the heart consists of the main muscle layer?

Endocardium

Myocardium (correct)

Epicardium

Coronary arteries

Where are the coronary arteries located in relation to the heart's walls?

Epicardium (correct)

Right atria

Endocardium

Myocardium

Which coronary vessel supplies the lateral wall of the left ventricle?

LAD

LCA

LCx (correct)

RCA

What happens to the blood flow in coronary vessels during physical stress?

Increases (C) Signup and view all the answers

At what occlusion percentage does resting blood flow become insufficient to meet oxygen demand?

More than 85% (D) Signup and view all the answers

What role does the heart play in supplying blood to the body?

Supplying blood to all parts of the body (C) Signup and view all the answers

What is the primary cause of tissue hypoxia in the myocardium during activities like running?

Increased oxygen demand in the myocardium (D) Signup and view all the answers

What process may result in complete occlusion of the vessel supplying a specific region of the myocardium?

Atherosclerotic process (C) Signup and view all the answers

What is the main characteristic of Phase 0 of the fast-response action potential in cardiac cells?

Depolarization due to inward movement of Na+ (C) Signup and view all the answers

Which type of action potentials occur in atrial and ventricular myocardial fibers as well as Purkinje fibers?

Fast-response action potentials (C) Signup and view all the answers

What is responsible for the plateau phase in the fast-response action potential?

Inward movement of Ca++ through L-type calcium channels (A) Signup and view all the answers

What triggers the release of a large amount of calcium into the cytosol from the sarcoplasmic reticulum during myocardial contraction?

Inward movement of Ca++ through L-type calcium channels (C) Signup and view all the answers

During which phase is ventricular contraction sustained throughout the action potential?

Phase 2 - Plateau (C) Signup and view all the answers

Which ion is mainly responsible for repolarization during Phase 3 of the fast-response action potential?

Potassium (K+) (C) Signup and view all the answers

'Restoration of ionic concentrations' during Phase 4 is primarily mediated by which cellular mechanism?

$Na^+$-K$^+$-ATPase (B) Signup and view all the answers

'ATP-driven Ca++ Pump' mentioned in Phase 4 is responsible for which physiological process?

$Ca^{++}$ reuptake into sarcoplasmic reticulum during relaxation (D) Signup and view all the answers

Study Notes

Heart Structure and Function

The myocardium consists of the main muscle layer of the heart.
The coronary arteries are located in the epicardium, the outermost layer of the heart's walls.
The obtuse marginal branch of the left circumflex coronary artery supplies the lateral wall of the left ventricle.

Blood Flow and Oxygen Demand

During physical stress, blood flow in coronary vessels increases to meet the increased oxygen demand.
If the coronary artery is occluded by more than 70%, resting blood flow becomes insufficient to meet oxygen demand.
The heart plays a crucial role in supplying blood to the body, and any disruption in blood flow can lead to tissue hypoxia.

Tissue Hypoxia and Coronary Occlusion

The primary cause of tissue hypoxia in the myocardium during activities like running is the inability of the coronary circulation to meet the increased oxygen demand.
Atherosclerosis, a process of plaque buildup, may result in complete occlusion of the vessel supplying a specific region of the myocardium.

Action Potentials in Cardiac Cells

The main characteristic of Phase 0 of the fast-response action potential in cardiac cells is a rapid depolarization due to the influx of sodium ions.
Fast-response action potentials occur in atrial and ventricular myocardial fibers as well as Purkinje fibers.
The plateau phase in the fast-response action potential is primarily maintained by the influx of calcium ions.
The release of a large amount of calcium into the cytosol from the sarcoplasmic reticulum during myocardial contraction is triggered by the depolarization of the sarcolemma.
Ventricular contraction is sustained throughout the action potential during Phase 2.
Potassium ions are mainly responsible for repolarization during Phase 3 of the fast-response action potential.
'Restoration of ionic concentrations' during Phase 4 is primarily mediated by the Na+/K+ ATPase pump.
The 'ATP-driven Ca++ Pump' is responsible for the reuptake of calcium ions into the sarcoplasmic reticulum during Phase 4.

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Description

Test your knowledge of cardiac action potential and its relation to ECG with this quiz. Topics include heart chambers, myocardial layers, coronary arteries, and coronary anatomy.