Cardiac Muscle Conduction and Refractory Period Quiz

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What happens at 0mV in the cardiac action potential?

Ca++ channels and K+ channels both open

Ca++ channels open and K+ channels close

Ca++ channels and K+ channels both close

Ca++ channels close and K+ channels open (correct)

What is the purpose of the long refractory period in the cardiac cycle?

To accelerate the heart rate

To initiate the plateau phase

To promote premature contractions

To prevent premature contractions (correct)

Which part of the heart's conduction system would typically fire the slowest?

SA node

AV node

Purkinje fibers (correct)

Atrioventricular bundle

What is the purpose of Ca++ binding to troponin in muscle contraction?

To allow myosin and actin cross bridge formation Signup and view all the answers

What is the purpose of an ECG or EKG recording?

To record electrical signals of the heart Signup and view all the answers

Where is the heart located in the body?

Between the lungs in the mediastinum Signup and view all the answers

What is the function of the atria in the heart?

Collect blood and push it into lower chambers Signup and view all the answers

Which chamber in the heart is responsible for pumping blood to the body or lungs?

Left ventricle Signup and view all the answers

What is the main function of the pulmonary vein?

Carry oxygenated blood Signup and view all the answers

What is the role of the epicardium in the heart?

Produces lubricating fluid Signup and view all the answers

Which layer of the heart is considered the most superficial?

Epicardium Signup and view all the answers

What is the main function of an artificial pacemaker?

To deliver electrical impulses for effective heart contractions Signup and view all the answers

During which phase of the cardiac cycle does systole occur?

During atrial contraction Signup and view all the answers

What is the main purpose of an AED (automated external defibrillator)?

To correct fibrillations Signup and view all the answers

Which wave represents the repolarization of the ventricles in an electrocardiogram?

T wave Signup and view all the answers

What phase of the cardiac cycle involves the closing of semilunar valves and opening of atrioventricular valves?

Ventricular systole Signup and view all the answers

What is the purpose of myoglobin in heart cells?

To store oxygen in muscle cells Signup and view all the answers

Which heart sound is associated with the closing of atrioventricular valves?

S1 Signup and view all the answers

What is the normal range for Cardiac Output (CO) in liters per minute?

4 - 8 L/min Signup and view all the answers

What is the formula to calculate Cardiac Output (CO)?

CO = HR * SV Signup and view all the answers

What does Ejection Fraction represent in cardiac physiology?

Percentage of blood pumped by the heart Signup and view all the answers

Which factor can decrease Heart Rate (HR) according to the text?

Hypoxia (lack of oxygen) Signup and view all the answers

Where does nervous control of Heart Rate come from?

Medulla oblongata Signup and view all the answers

What is the main effect of sympathetic stimulation on the heart?

Shortens the repolarization period Signup and view all the answers

Which response best describes Ejection Fraction?

The percentage of blood pumped out of the heart with each beat Signup and view all the answers

What is the impact of increased thyroid hormone levels on Heart Rate?

Increases HR and contractility Signup and view all the answers

What happens to Stroke Volume if there is less ventricular filling time?

It decreases Signup and view all the answers

Which layer lines the chambers of the heart and covers the heart valves?

Endocardium Signup and view all the answers

What are endothelins released by the endothelium known for?

Regulating growth patterns of cardiac muscle cells Signup and view all the answers

Which structure in the heart divides it into chambers?

Septum Signup and view all the answers

Which valve separates the left atrium from the left ventricle?

Mitral valve Signup and view all the answers

Why do semilunar valves make an audible sound when they close?

They have no muscular attachments Signup and view all the answers

What is the function of papillary muscles in the heart?

To close the tricuspid and mitral valves Signup and view all the answers

What is the main function of coronary circulation?

To bring blood to the myocardium and other components Signup and view all the answers

Which cell type initiates and propagates the action potential through the heart?

Myocardial conducting cells Signup and view all the answers

What is the main role of the SA node in cardiac conduction?

Sets normal cardiac rhythm Signup and view all the answers

What is the significance of gap junctions in cardiac muscle cells?

Allow ions to travel between cells for proper contractile rhythm Signup and view all the answers