Cardiac Fibrillation and Excitation Sequence Quiz

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What is the primary function of the sinoatrial (SA) node?

Delay the electrical signal to allow for complete atrial contraction

Initiate electrical impulses that trigger cardiac muscle contraction (correct)

Conduct the electrical impulse from the AV node to the ventricles

Distribute the electrical impulse throughout the ventricles

Which structure is responsible for delaying the electrical signal to allow for complete atrial contraction before transmitting it to the ventricles?

Bundle of His

Atrioventricular (AV) node (correct)

Purkinje fibers

Sinoatrial (SA) node

Which structure conducts the electrical impulse from the AV node down the interventricular septum?

Right and left bundle branches

Atrioventricular (AV) node

Sinoatrial (SA) node

AV bundle (Bundle of His) (correct)

Which structure is responsible for rapidly distributing the electrical impulse throughout the ventricles, coordinating their contraction from the apex upward?

Subendocardial conducting network (Purkinje fibers) Signup and view all the answers

Which part of the brain controls sympathetic innervation of the heart, stimulating an increase in heart rate and contractility during times of stress or physical exertion?

Cardioaccelerator center Signup and view all the answers

Which phase of the cardiac action potential involves the influx of calcium ions through slow voltage-gated calcium channels and efflux of potassium ions, sustaining the depolarized state for prolonged contraction?

Plateau phase Signup and view all the answers

During which phase of the cardiac cycle do the ventricles contract, ejecting blood into the circulation?

Systole Signup and view all the answers

Which phase of the cardiac cycle involves the ventricles relaxing isometrically, marking the beginning of diastole?

Isovolumetric ventricular relaxation Signup and view all the answers

What is the term used to describe the chaotic electrical signals in the heart that impair its ability to pump blood effectively and can lead to life-threatening complications?

Fibrillation Signup and view all the answers

During which phase of the cardiac cycle does blood flow from the atria into the ventricles, filling them with blood?

Ventricular filling Signup and view all the answers

What does the term 'End Diastolic Volume (EDV)' represent?

The volume of blood in the ventricles at the end of diastole, just before ventricular contraction begins Signup and view all the answers

What is the relationship between End Diastolic Volume (EDV), End Systolic Volume (ESV), and Stroke Volume (SV)?

SV = EDV - ESV Signup and view all the answers

Which of the following statements about Cardiac Output is correct?

Cardiac Output is the total volume of blood pumped by the heart per unit time Signup and view all the answers

What is the equation for calculating Cardiac Output?

Cardiac Output (CO) = Heart Rate (HR) × Stroke Volume (SV) Signup and view all the answers

Which neurotransmitter is associated with the parasympathetic control of heart rate?

Acetylcholine Signup and view all the answers

What is the effect of catecholamines (norepinephrine and epinephrine) on heart rate?

They increase heart rate by binding to β1-adrenergic receptors and increasing sodium and calcium permeability Signup and view all the answers

Which of the following factors influence stroke volume?

Preload, contractility, and afterload Signup and view all the answers

What is the primary determinant of cardiac output that can be influenced by factors such as autonomic nervous system activity, hormonal regulation, and physical activity?

Heart rate Signup and view all the answers

Which of the following statements about End Systolic Volume (ESV) is correct?

ESV represents the volume of blood remaining in the ventricles at the end of systole, just after ventricular contraction Signup and view all the answers

What is the effect of acetylcholine on cardiac cells?

It increases the permeability of potassium channels, leading to hyperpolarization and a decrease in heart rate Signup and view all the answers

Which statement accurately describes the role of autorhythmic cells within the heart?

They spontaneously generate electrical impulses to coordinate rhythmic contractions. Signup and view all the answers

What is the primary characteristic that distinguishes autorhythmic cells from contractile cardiac cells?

Autorhythmic cells exhibit an unstable resting membrane potential. Signup and view all the answers

Which event initiates the process of action potential generation in autorhythmic cells?

The gradual depolarization of the cell membrane, known as the pacemaker potential. Signup and view all the answers

What is the primary event that occurs during the depolarization phase of an action potential in autorhythmic cells?

Voltage-gated calcium channels open, allowing calcium ions to enter the cell. Signup and view all the answers

Which process is primarily responsible for the repolarization phase of an action potential in autorhythmic cells?

The opening of potassium channels, allowing potassium ions to exit the cell. Signup and view all the answers

What percentage of cardiac muscle tissue is composed of autorhythmic cells?

Approximately 1% Signup and view all the answers

What term is used to describe irregularities in the heart's rhythm that can result from abnormalities in the intrinsic conduction system?

Arrhythmias Signup and view all the answers

Which ion primarily contributes to the depolarization phase of an action potential in autorhythmic cells?

Calcium ions Signup and view all the answers

Which statement accurately describes the role of potassium channels during the repolarization phase of an action potential in autorhythmic cells?

Potassium channels open, allowing potassium ions to exit the cell. Signup and view all the answers

Which statement regarding the pacemaker potential in autorhythmic cells is accurate?

The pacemaker potential is the gradual depolarization that triggers an action potential. Signup and view all the answers