Cardiac Muscle & Circulatory Physiology Review

Thirty question-and-answer flashcards covering cardiac circulation, pressure-volume relationships, cardiac output, and cellular physiology of cardiac muscle.

What is the primary purpose of the heart in the human body?

To pump blood throughout the body, maintaining systemic circulation.

Which chamber of the heart pumps oxygen-rich blood into systemic circulation?

The left ventricle.

Which chamber pumps oxygen-poor blood to the lungs in pulmonary circulation?

The right ventricle.

What is the largest artery that receives blood directly from the left ventricle?

The aorta.

In which thoracic space does the heart sit between the lungs?

The mediastinum.

Trace the normal pathway of blood beginning with the left ventricle and ending with its return to the right atrium.

Left ventricle → aorta → systemic arteries → capillaries → systemic veins → superior & inferior vena cavae → right atrium.

Why does blood flow from one cardiac chamber or vessel to another?

Because it moves down a pressure gradient—from higher to lower pressure.

What is meant by systolic pressure?

The arterial pressure when the left ventricle is contracted (about 120 mm Hg in a typical 120/80 reading).

What is meant by diastolic pressure?

The arterial pressure when the left ventricle is relaxed (about 80 mm Hg in a typical 120/80 reading).

In what units is blood pressure conventionally reported?

Millimeters of mercury (mm Hg).

How does increasing the volume of a container (e.g., a ventricle) affect pressure inside it?

It decreases pressure—an inverse relationship.

How does increasing the volume of the fluid inside a fixed container affect pressure?

It increases pressure—a direct relationship.

Define end-systolic volume (ESV).

The volume of blood left in a ventricle immediately after it contracts.

Define end-diastolic volume (EDV).

The volume of blood in a ventricle at the end of diastole, just before it contracts.

What is stroke volume (SV) and how is it calculated?

The volume of blood ejected by one ventricle per beat; SV = EDV − ESV.

Define cardiac output (CO) and give its formula.

The amount of blood ejected by the left ventricle per minute; CO = Heart Rate (HR) × Stroke Volume (SV).

Using EDV = 100 mL, ESV = 20 mL, and HR = 70 bpm, what is the cardiac output?

5.6 L / min.

Name the two main types of myocardial cells.

Myocardial contractile cells (MCCs) and myocardial autorhythmic cells (MACs).

What is the primary role of myocardial autorhythmic cells?

To set the heart’s rate and rhythm by initiating electrical impulses.

What is the primary role of myocardial contractile cells?

To generate force and pump blood when they contract.

What triggers calcium release from the sarcoplasmic reticulum in cardiac muscle?

Calcium-induced calcium release: extracellular Ca²⁺ entering through voltage-gated Ca²⁺ channels binds to and opens ryanodine receptors on the sarcoplasmic reticulum.

What type of channel allows extracellular Ca²⁺ to enter the myocardial contractile cell during depolarization?

A voltage-gated calcium channel in the T-tubule membrane.

How is the ryanodine receptor in cardiac muscle opened?

By binding of Ca²⁺ (it is a ligand-gated channel in cardiac tissue).

What is the function of the sarcoplasmic reticulum in myocardial cells?

To store Ca²⁺ and release it during excitation, enabling contraction.

What transporter removes Ca²⁺ from the cytosol back to the extracellular fluid after contraction?

The sodium-calcium exchanger (NCX), an antiporter.

How many sodium ions enter the cell for each calcium ion exported by the NCX?

Three Na⁺ in for one Ca²⁺ out.

What type of transport is performed by the NCX?

Secondary active transport driven by the inward Na⁺ gradient.

Why doesn’t the Na⁺ that enters via the NCX cause unwanted depolarization?

Because it is promptly pumped back out by the sodium-potassium ATPase, restoring ionic balance.

Approximately what peak pressure does the left ventricle generate during systole in a healthy adult?

About 120 mm Hg.

Through which vessels does the right ventricle deliver blood to the lungs?

The pulmonary arteries.