Cardiac Muscle Physiology

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What happens at 0mV in the cardiac action potential?

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

K+ channels close

Ca++ channels open

Both Ca++ channels open and K+ channels close

What role do slow Ca++ channels play in the cardiac action potential?

Maintaining the resting membrane potential

Causing hyperpolarization

Allowing for the plateau phase (correct)

Initiating depolarization

If not for endocrine control, how many times per minute would the SA node fire?

50 - 70 times

80 - 90 times (correct)

120 - 130 times

100 - 110 times

Which component of the heart's conduction system has the lowest firing rate?

Purkinje fibers Signup and view all the answers

What is another term used to refer to recording electrical signals of the heart?

ECG or EKG Signup and view all the answers

What event marks the depolarization of the ventricles in the cardiac cycle?

QRS complex Signup and view all the answers

What is the function of the atria in the heart?

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

Which device is designed to correct fibrillations in the heart?

Artificial pacemaker Signup and view all the answers

Where is the base of the heart located?

Superior and medial to the apex Signup and view all the answers

What represents the amount of blood pushed out by the ventricles in one cycle?

Stroke volume Signup and view all the answers

Which artery carries deoxygenated blood?

Pulmonary artery Signup and view all the answers

What occurs during ventricular diastole in the cardiac cycle?

Semilunar valves open Signup and view all the answers

Where is the myocardium located in the heart?

Middle thickest layer with muscle cells and blood vessels Signup and view all the answers

What signifies the interruption in the normal conduction pathway of the heart?

Heart block Signup and view all the answers

What is the purpose of the serous pericardium layer in the heart?

Produce lubricating fluid Signup and view all the answers

During which phase of the cardiac cycle does blood flow into the atria and through into the ventricles?

Atrial diastole Signup and view all the answers

What are auricles in the heart?

Thin walled structures that hold blood and empty into atria Signup and view all the answers

Which heart sound is heard at the closing of the atrioventricular valves?

S1 Signup and view all the answers

What is the cause of heart murmurs?

Turbulent blood flow Signup and view all the answers

What is the equation for Cardiac Output (CO)?

CO = HR * SV Signup and view all the answers

What does the ejection fraction represent?

Percentage of blood pumped in each heartbeat Signup and view all the answers

What happens to Stroke Volume (SV) as heart rate increases during exercise?

SV decreases proportionally Signup and view all the answers

What is the normal range for Ejection Fraction (EF)?

50% - 70% Signup and view all the answers

Which layer lines the chambers filled with blood and covers the heart valves?

Endocardium Signup and view all the answers

What is the function of endothelins released by the endothelium?

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

What is the function of the septum in the heart?

Separates atria from ventricles Signup and view all the answers

Which chamber of the heart receives deoxygenated blood from the systemic circulation?

Right atrium Signup and view all the answers

What purpose do semilunar valves serve in the heart?

Separate ventricles from blood vessels Signup and view all the answers

Which structure connects chordae tendineae to close the mitral valve in the heart?

Papillary muscles Signup and view all the answers

What is the function of coronary circulation in the body?

Deliver oxygenated blood to organs Signup and view all the answers

Plateau phase in cardiac contractile cells involves which of the following ion channels?

$Na^+$ channels close, $Ca^{++}$ channels are open, few K$^+$ channels are open Signup and view all the answers