Cardiac Muscle Physiology Quiz

Heart Function and Structure

• At 0mV in heart cells, the resting potential is reached, and the cell is not permeable to sodium.
• Slow Ca++ channels play a crucial role in the heart's action potential, specifically in the plateau phase.

Heart Rate Regulation

• Without endocrine control, the SA node would fire around 100 times per minute.
• The AV node would fire around 40-60 times per minute without regulation.
• The atrial rate would be around 20-30 times per minute without regulation.

Electrocardiogram (ECG)

• An ECG is used to measure the heart's electrical activity.

Heart Structure

• The atria are the upper chambers of the heart, responsible for receiving blood.
• The base of the heart is located at the top of the heart, where the atria meet.
• The epicardium produces lubricating fluid to reduce friction between the heart and surrounding tissues.
• The ventricles are the lower chambers of the heart, responsible for pumping blood throughout the body.

Blood Flow

• The atrioventricular valves close due to muscle contractions.
• The semilunar valves close during ventricular diastole.
• The stroke volume is the normal amount of blood pushed out by the ventricles in one stroke.

Heart Layers

• The endocardium lines the chambers filled with blood, covers heart valves, and is continuous with the lining of blood vessels.

Heart Conduction

• The atrioventricular valves separate the heart into chambers and are physical extensions of myocardium.
• The septum separates the right atrium from the right ventricle.
• Purkinje fibers have a primary function of conducting electrical signals rapidly, allowing for coordinated contraction.

Cardiac Cycle

• Atrial contraction occurs during the atrial systole phase of the cardiac cycle.
• The T-wave corresponds to the repolarization of the ventricles.

Cardiac Assistive Devices

• An artificial pacemaker is used to regulate heart rhythm.
• An Automatic External Defibrillator (AED) is used to restore normal heartbeat in cardiac emergencies.

Heart Function Abnormalities

• Heart murmurs are primarily caused by abnormal blood flow through the heart valves.
• The closing of atrioventricular valves marks the end of diastole and the start of systole.
• A stiff or hypertrophic ventricle increases blood pressure, making it harder for the heart to pump blood.

Cardiac Output and Blood Pressure

• The normal ejection fraction range is 55-70%.
• Cardiac Output (CO) is calculated using the formula: CO = Heart Rate x Stroke Volume.
• The Baroreceptor reflex primarily responds to changes in blood pressure to regulate heart function.
• The vagus nerve releases acetylcholine (ACh) to slow heart rate.

Test your knowledge on the physiology of cardiac muscle including topics like repolarization, calcium channels, refractory period, conduction system, and endocrine control of heart rate.