Cardiac Muscle and Circulatory Physiology

Vocabulary flashcards covering cardiac anatomy, circulation pathways, hemodynamic principles, and cellular mechanisms of cardiac muscle contraction.

Cardiac Muscle

Specialized involuntary striated muscle tissue that makes up the heart wall and contracts to pump blood.

Systemic Circulation

Pathway in which the left ventricle pumps oxygen-rich blood through the aorta to the body and returns oxygen-poor blood to the right atrium.

Pulmonary Circulation

Circuit in which the right ventricle pumps oxygen-poor blood to the lungs via pulmonary arteries and receives oxygen-rich blood back in the left atrium.

Left Ventricle

Heart chamber that generates high pressure to eject oxygen-rich blood into the aorta for systemic circulation.

Right Ventricle

Heart chamber that pumps oxygen-poor blood into the pulmonary arteries toward the lungs.

Left Atrium

Posterior heart chamber that receives oxygenated blood from the lungs and delivers it to the left ventricle.

Right Atrium

Heart chamber that receives systemic venous (oxygen-poor) blood via the superior and inferior venae cavae.

Aorta

Largest artery in the body; carries high-pressure, oxygen-rich blood from the left ventricle to systemic arteries.

Inferior and Superior Vena Cava

Large systemic veins that return oxygen-poor blood to the right atrium.

Coronary Arteries

Vessels that branch from the aorta and supply oxygen and nutrients to the myocardium itself.

Mediastinum

Central compartment of the thoracic cavity where the heart is located between the lungs.

Pressure Gradient

Difference in pressure that drives fluid (blood) from higher to lower pressure regions.

Systolic Pressure

Arterial pressure (≈120 mm Hg) measured when the left ventricle contracts (systole).

Diastolic Pressure

Arterial pressure (≈80 mm Hg) measured when the left ventricle relaxes (diastole).

Millimeters of Mercury (mm Hg)

Standard unit for measuring blood pressure.

Ventricular Systole

Phase when a ventricle contracts, reducing chamber volume and raising pressure to eject blood.

Ventricular Diastole

Phase when a ventricle relaxes, increasing chamber volume and filling with blood.

End-Systolic Volume (ESV)

Volume of blood remaining in a ventricle after contraction ends.

End-Diastolic Volume (EDV)

Volume of blood in a ventricle just before it contracts.

Stroke Volume

Amount of blood ejected by one ventricle during a single contraction; calculated as EDV – ESV.

Heart Rate

Number of cardiac cycles (beats) per minute.

Cardiac Output

Volume of blood pumped by a ventricle per minute; equal to heart rate × stroke volume (L min⁻¹).

Myocardium

Muscular middle layer of the heart wall composed of cardiac muscle cells.

Myocardial Contractile Cells (MCCs)

Cardiac muscle cells that generate force to pump blood when electrically stimulated.

Myocardial Autorhythmic Cells (MACs)

Pacemaker cells that spontaneously depolarize, setting the heart’s rhythm and triggering MCCs.

Sarcoplasmic Reticulum (SR)

Intracellular organelle that stores Ca²⁺ and releases it during excitation-contraction coupling.

Voltage-Gated Calcium Channel

Membrane channel in T-tubules of MCCs that opens on depolarization, allowing extracellular Ca²⁺ entry.

Ryanodine Receptor

Ca²⁺-release channel on the SR that opens when Ca²⁺ binds (calcium-induced calcium release).

Calcium-Induced Calcium Release

Mechanism where incoming Ca²⁺ triggers additional Ca²⁺ release from the SR in cardiac cells.

Calcium ATPase (SERCA)

Active pump that returns cytosolic Ca²⁺ to the SR after contraction.

Sodium-Potassium Pump (Na⁺/K⁺ ATPase)

Membrane pump that restores Na⁺ and K⁺ gradients by moving 3 Na⁺ out and 2 K⁺ into the cell using ATP.

Sodium-Calcium Exchanger (NCX)

Secondary active antiporter that uses inward Na⁺ movement to export Ca²⁺ from the cardiac cell.

Secondary Active Transport

Energy-coupled transport where one solute moves against its gradient using energy from another moving down its gradient.

Antiporter

Transport protein that moves two ions in opposite directions across a membrane.

Hypovolemia

Condition of abnormally low blood volume that lowers blood pressure and impairs perfusion.

Vasoconstriction

Narrowing of blood vessel diameter that increases vascular resistance and pressure.

Vasodilation

Widening of blood vessel diameter that decreases vascular resistance and pressure.