Cardiac Anatomy, Conduction, Cycle, and Regulation Flashcards

Vocabulary flashcards generated from lecture notes covering cardiovascular anatomy, cardiac cycle phases, EKG wave interpretation, action potential mechanics, and autonomic heart regulation.

Cardiac Cycle

The period between the start of one heartbeat and the start of the next heartbeat.

Systole

The contraction phase of the cardiac cycle during which blood pressure rises.

Diastole

The relaxation phase of the cardiac cycle during which blood pressure decreases.

Atrial Systole

The first phase of the cardiac cycle in which the atria contract to maximize blood volume in the ventricles while atrioventricular valves are open and semilunar valves are closed.

Atrial Diastole

The relaxation phase of the atria that occurs following atrial systole while the ventricles begin ventricular systole.

Early Ventricular Systole

The phase of ventricular contraction where intraventricular pressure rises, closing both atrioventricular valves while semilunar valves remain closed.

Late Ventricular Systole

The phase of ventricular contraction where ventricular pressure exceeds arterial pressure, opening the aortic and pulmonary valves to pump blood into the aorta and pulmonary trunk.

Isovolumetric Contraction

A event during early ventricular systole where ventricles contract to build pressure without altering blood volume because all heart valves are closed.

Early Ventricular Diastole

The phase where ventricles relax to drop internal pressure while all four valves remain closed, resulting in isovolumetric relaxation.

Isovolumetric Relaxation

An event during early ventricular diastole where ventricles relax to decrease pressure without changing blood volume because all heart valves remain closed.

Late Ventricular Diastole

The relaxation phase where both atrioventricular valves open and semilunar valves remain closed, allowing blood to flow passively from the atria into the ventricles.

End-Diastolic Volume (EDV)

The maximum volume of blood present in a ventricle at the end of ventricular diastole right before contraction.

End-Systolic Volume (ESV)

The minimum volume of blood left over in a ventricle after ventricular systole is complete.

Stroke Volume (SV)

The volume of blood ejected from the left ventricle during ventricular systole, calculated as $\text{SV} = \text{EDV} - \text{ESV}$.

S1 ("Lubb")

The first heart sound, produced by the closing of the atrioventricular (AV) valves.

S2 ("Dubb")

The second heart sound, produced by the closing of the semilunar valves.

Heart Murmur

An abnormal heart sound generated by turbulent blood flow or valve dysfunction.

Cardiac Output (CO)

The total volume of blood pumped by the left ventricle in 1 minute, calculated as $\text{CO} = \text{SV} \times \text{HR}$.

Cardioacceleratory Center

A brain region with sympathetic neurons innervating the SA node that releases norepinephrine (NE) to decrease repolarization and increase heart rate.

Cardioinhibitory Center

A brain region with parasympathetic neurons innervating the SA node that releases acetylcholine (ACh) to cause hyperpolarization and decrease heart rate.

Baroreceptors

Sensory receptors specialized to detect and monitor changes in blood pressure.

Chemoreceptors

Sensory receptors specialized to monitor arterial oxygen, carbon dioxide, and pH levels.

Autonomic Tone

The continuous baseline release of autonomic neurotransmitters (norepinephrine and acetylcholine) onto cardiac tissue.

Atrial Reflex

A cardiac reflex triggered by stretch receptors during increased venous return to the atria that causes an increase in heart rate.

Preload

The amount of blood in the ventricle right before contraction (EDV); increased preload leads to increased stroke volume and cardiac output.

Contractility

The forcefulness of ventricular contraction; increased contractility leads to increased stroke volume and cardiac output.

Afterload

The arterial pressure in the aorta that ventricles must overcome to eject blood; varies inversely with stroke volume and cardiac output.

Sinoatrial (SA) Node

The primary pacemaker of the heart located in the right atrium that establishes normal sinus heart rate.

Bradycardia

An abnormally low heart rate below $60\text{\thinspace BPM}$.

Tachycardia

An abnormally fast heart rate above $100\text{\thinspace BPM}$.

Electrocardiogram (EKG or ECG)

A graphic recording of the electrical events occurring within the heart during the cardiac cycle.

P Wave

The deflection feature on an ECG representing atrial depolarization.

QRS Complex

The prominent wave feature on an ECG representing ventricular depolarization.

T Wave

The deflection feature on an ECG representing ventricular repolarization.

Contractile Cells

Heart muscle cells that comprise the majority of the cardiac tissue and generate mechanical force to pump blood.

Gap Junctions

Intercellular channels in intercalated discs that allow sodium ions ($Na^+$) to flow directly between cardiomyocytes for rapid electrical propagation.

Plateau Phase

A unique phase during cardiac contractile cell action potentials where calcium ($Ca^{2+}$) influx balances sodium ($Na^+$) efflux to hold voltage stable and prolong refractory period.

Absolute Refractory Period

The period post-contraction during which cardiomyocytes cannot respond to stimuli or contract, preventing summation and tetany.

Arteries

Blood vessels that transport blood away from the heart.

Veins

Blood vessels that transport blood back toward the heart.

Capillaries

Microscopic vessels forming interconnected networks between arteries and veins where material exchange occurs with interstitial fluid.

Pulmonary Circuit

The cardiovascular circuit that transports blood between the heart and the lungs.

Systemic Circuit

The cardiovascular circuit that transports blood between the heart and body tissues.

Atria

The two thin-walled superior receiving chambers of the heart.

Ventricles

The two thick-walled inferior pumping chambers of the heart.

Visceral Pericardium (Epicardium)

The serous membrane bound directly to the outer surface of the heart.

Parietal Pericardium

The membrane lining the inner surface of the fibrous pericardial sac.

Intercalated Discs

Specialized cellular junctions connecting branched cardiac muscle cells that contain desmosomes and gap junctions.

Desmosomes

Cellular structures in intercalated discs that mechanically hold adjacent cardiac cells together during contraction.

Myocardium

The thick middle layer of the heart wall composed of cardiac muscle tissue.

Endocardium

The simple squamous epithelial membrane lining the inner chambers and valves of the heart.

Interatrial Septum

The internal muscular wall separating the right atrium from the left atrium.

Interventricular Septum

The thick internal muscular wall separating the right ventricle from the left ventricle.

Tricuspid Valve

The right atrioventricular (AV) valve located between the right atrium and right ventricle that prevents backflow into the right atrium.

Bicuspid Valve

The left atrioventricular (AV) valve (mitral valve) located between the left atrium and left ventricle that prevents backflow into the left atrium.

Pulmonary Semilunar Valve

The valve at the base of the pulmonary trunk that prevents blood backflow into the right ventricle.

Aortic Semilunar Valve

The valve at the base of the aorta that prevents blood backflow into the left ventricle.

Chordae Tendineae

Fibrous tendinous strands connecting atrioventricular valve cusps to papillary muscles for structural stabilization.

Pectinate Muscles

Prominent muscular ridges found lining the internal walls of the atria.

Trabeculae Carneae

Irregular muscular ridges lining the inner surface of the ventricles.

Moderator Band

A vascular muscular band in the right ventricle that conducts electrical signals to papillary muscles before ventricular contraction.

Coronary Circulation

The intrinsic vascular network delivering oxygenated blood via coronary arteries and draining deoxygenated blood via cardiac veins to supply myocardium.

Conducting Cells

Specialized autorhythmic cardiac cells that generate and propagate electrical impulses through the conduction system.

Automaticity

The inherent ability of cardiac tissue to spontaneously generate action potentials without external nervous or hormonal input.

Atrioventricular (AV) Node

A node in the cardiac conduction system that receives SA node impulses and briefly delays conduction to allow complete atrial emptying.

Purkinje Fibers

Terminal conducting fibers that distribute electrical impulses directly to the ventricular myocardium from the apex toward the base.

Prepotential (Pacemaker Potential)

The gradual, spontaneous depolarization in SA and AV node cells resulting from continuous influx of sodium ($Na^+$) through leaky channels.