The Heart

Flashcards covering key vocabulary terms and concepts related to the anatomy and physiology of the heart.

Cardiac Output (CO)

The volume of blood pumped by the left ventricle in one minute; calculated as CO=HR\times SV

(Heart Rate (bpm) × Stroke Volume (mL/beat))

Stroke Volume (SV)

The amount of blood ejected by each ventricle during contraction

calculated as SV = EDV - ESV

(End-Diastolic Volume - End-Systolic Volume).

End-Diastolic Volume (EDV)

The amount of blood in each ventricle at the end of ventricular diastole (relaxation), before contraction.

End-Systolic Volume (ESV)

The amount of blood remaining in each ventricle at the end of ventricular systole (contraction), after ejection.

Heart Location

in the mediastinum, slightly to the left of the midline, between the lungs and posterior to the sternum.

Pericardium

The membrane surrounding the heart, composed of an outer fibrous layer and an inner serous layer.

Layers of the Heart Wall

Epicardium, Myocardium, Endocardium

Chambers of the Heart

right atrium, right ventricle, left atrium, and left ventricle.

Heart Valves

Structures that ensure unidirectional blood flow/ prevent backflow of blood

including the tricuspid, pulmonary, mitral, and aortic valves.

Coronary Circulation

The circulation of blood to and from the tissues of the heart muscle itself, via coronary arteries and cardiac veins.

Blood Flow Pathway

The route blood takes through the heart and body, including: Pulmonary Circuit and Systemic Circuit

Conducting System of the Heart

A network of specialized cardiac muscle cells that initiate and distribute electrical impulses; Sinoatrial (SA) Node, Atrioventricular (AV) Node, AV Bundle (Bundle of His), Bundle Branches (left and right), Purkinje Fibers

Pacemaker Cells

Specialized cardiac muscle cells in the sinoatrial (SA) node that generate their own action potentials (autorhythmicity) and control the heart rate.

Impulse Conduction Pathway

1. SA node depolarizes

2. Electrical activity spreads through the atria to the AV node.

3. AV node delays the impulse.

4. AV bundle and bundle branches conduct the impulse to the apex.

5. Purkinje fibers spread the impulse throughout the ventricular myocardium, leading to contraction.

Electrocardiogram (ECG or EKG)

A graphic record of the electrical activity of the heart over time. Key waves include: P wave, QRS complex, T wave

Cardiac Contractile Cells

Cells that make up the bulk of the myocardial muscle, responsible for the actual pumping of blood. They contract in response to electrical impulses generated by pacemaker cells.

Action Potential of Contractile Cells

Distinct phases leading to muscle contraction:

1. Rapid Depolarization: Na+ influx

2. Plateau Phase: Ca2+ influx (prolongs contraction and prevents tetany)

3. Repolarization: K+ efflux

Action Potential of Pacemaker Cells

Characterized by an unstable resting potential (pacemaker potential) due to slow Na+ influx, followed by depolarization (Ca2+ influx) and repolarization (K+ efflux).

Role of Calcium Ions (Ca^{2+}) in Cardiac Contraction

Ca^{2+} influx during the plateau phase triggers sarcoplasmic reticulum Ca^{2+} release, initiating cross-bridge cycling and muscle contraction (excitation-contraction coupling).

Refractory Period

The time during which cardiac contractile cells cannot respond to a new stimulus, which is prolonged by the Ca^{2+} plateau phase. This prevents tetanic contractions in the heart.

Cardiac Cycle definition

The sequence of events during one complete heartbeat, including atrial systole, atrial diastole, ventricular systole, ventricular diastole, resulting in blood flow.

Autonomic Innervation of the Heart

The autonomic nervous system regulates heart rate and contractility: Sympathetic nervous system and Parasympathetic nervous system

Contractility

The intrinsic strength of the heart muscle contraction, independent of preload and afterload. Influenced by Positive inotropic agents and Negative inotropic agents

Cardiac Skeleton

A structure of dense connective tissue that supports the heart valves and great vessels, anchors cardiac muscle, and acts as an electrical insulator between the atria and ventricles.

Left Coronary Artery (LCA)

Arises from the aorta and branches into the anterior interventricular artery (LAD) and circumflex artery, supplying the left atrium, left ventricle, and interventricular septum.

Right Coronary Artery (RCA)

Arises from the aorta and supplies the right atrium, right ventricle, and parts of the interventricular septum, inferior left ventricle, and often the SA and AV nodes.

Coronary Sinus

A large vein on the posterior surface of the heart

collects deoxygenated blood from cardiac veins and empties into the right atrium.

Interventricular Septum

The muscular wall separating the right and left ventricles, crucial for maintaining separate systemic and pulmonary circulations.

Papillary Muscles and Chordae Tendineae

Structures within the ventricles;

stabilize AV valves

Trabeculae Carneae

Irregular muscular ridges and folds on the internal surfaces of the ventricles, contributing to the turbulence of blood flow and potentially preventing suction effects.

Intercalated Discs

interconnect cardiac cells

membranes of adjacent cells are held together by desmosomes and linked by gap junctions

transfer force to contraction from cell to cell

propagate action potential

PR Interval

The duration from the beginning of atrial depolarization (P wave) to the beginning of ventricular depolarization (QRS complex), representing conduction time through the atria and AV node.

QT Interval

the total time required for ventricular electrical activity

The duration from the beginning of ventricular depolarization (QRS complex) to the end of ventricular repolarization (T wave)

ST Segment

The isoelectric period between the end of the S wave and the beginning of the T wave, representing the time when the entire ventricular myocardium is depolarized.

Ventricular Systole

ventricular ejection

pressure rises, opens semilunar valves allowing blood to exit

Ventricular Diastole

isovolumetric relaxation

all valves closed

ventricular filling (blood flows from atria to ventricles through open AV valves).

Coronary Artery Disease (CAD)

A condition characterized by the narrowing or blockage of the coronary arteries, typically by atherosclerosis, leading to myocardial ischemia.

Angina Pectoris

Chest pain or discomfort caused when the heart muscle doesn't get enough oxygen-rich blood, often a symptom of CAD.

Myocardial Infarction (MI)

Commonly known as a heart attack,

irreversible death of heart muscle tissue due to lack of oxygen, usually from a blockage of a coronary artery.

Modifiable Risk Factors for CVD

high blood pressure, high cholesterol, smoking, diabetes, obesity, and physical inactivity.

Non-modifiable Risk Factors for CVD

increasing age, male gender, and a family history of early heart disease.

Percutaneous Coronary Intervention (PCI) / Angioplasty with Stent

A minimally invasive procedure to open narrowed or blocked coronary arteries using a balloon catheter, often followed by the placement of a stent to keep the artery open.

Coronary Artery Bypass Graft (CABG)

A surgical procedure where a healthy blood vessel (from the leg, arm, or chest) is used to create a new path for bloodflow around a blocked/narrowed coronary artery, restoring blood flow to the heart muscle.

Heart Valve Surgery

Surgical repair or replacement of diseased or damaged heart valves (e.g., aortic, mitral), performed to restore proper blood flow through the heart.

Common Medications for CVD

statins (for cholesterol)

beta-blockers (for heart rate/blood pressure)

ACE inhibitors (for blood pressure)

antiplatelet drugs (to prevent clots).

Atrioventricular (AV) valves

Tricuspid (right) & Mitral/Bicuspid (left)

between atria and ventricles

Ensure one-way blood flow from the atria to the ventricles, preventing backflow during contraction.

Semilunar (SL) valves

Pulmonary (right) and Aortic (left), between ventricles and great arteries.

Prevent backflow of blood into the ventricles

Epicardium

Outermost layer, continuous with the visceral layer of the serous pericardium.

Myocardium

Middle layer, composed of cardiac muscle tissue, responsible for pumping action.

Endocardium

Innermost layer, lining the chambers and valves, continuous with the endothelium of blood vessels

Pulmonary Circuit

Blood from the right side of the heart to the lungs and back to the left atrium.

Systemic Circuit

Blood from the left side of the heart to the body and back to the right atrium

Sinoatrial (SA) Node

Primary pacemaker

Atrioventricular (AV) Node

Delays impulse to allow ventricular filling.

AV Bundle (Bundle of His)

transmit electrical impulses from the atria to the ventricles

Bundle Branches (left and right)

Conduct impulses through the ventricles to facilitate contraction.

Purkinje Fibers

Distribute impulse to ventricular myocardium

P wave

Atrial depolarization

QRS complex

Ventricular depolarization (and hidden atrial repolarization)

T wave

Ventricular repolarization

Sympathetic nervous system

Increases heart rate and contractility (via norepinephrine /epinephrine).

Parasympathetic nervous system

Decreases heart rate (via acetylcholine).

Positive inotropic agents

Increase contractility (Ca^{2+}, sympathetic stimulation)

Negative inotropic agents

Decrease contractility (acidosis, some drugs)

Sinoatrial (SA) Node Depolarization Rate

depolarizes at the fastest rate, typically 60-100 beats per minute, making it the primary pacemaker of the heart. Establishing sinus rhythm

Atrioventricular (AV) Node Depolarization Rate

slower intrinsic depolarization rate, typically 40-60 beats per minute. It acts as a secondary pacemaker and delays the impulse to allow for complete ventricular filling.

Tachycardia

An abnormally fast heart rate, over 100 bpm in adults.

Bradycardia

An abnormally slow heart rate (under 60 bpm in adults), often due to SA node dysfunction, increased parasympathetic activity, or AV nodal blocks.

Ectopic Pacemaker

An active site of impulse generation in the heart outside the SA node, which can cause abnormal rhythms (arrhythmias) if its rate is faster than the SA node's or if the SA node becomes dysfunctional.

pericardium

surrounds the heart and has 2 layers: outer fibrous and inner serous.

inner serous pericardium

outer parietal and inner visceral layers that provide lubrication and reduce friction as the heart beats.

pericardial cavity

the space between the layers of the pericardium that pericardial serous fluid, allowing for smooth movement of the heart.

pericarditis

inflamed pericardial surfaces rub against each other, causing chest pain.  

functions of connective tissues of the heart

supports cardiac muscle fibers, blood vessels and nerves of myocardium

distributes forces of contraction

add strength and prevent overexpansion of heart

provides elasticity

sulci

grooves on the surface of the heart that marks border of the heart chambers and contain fat blood vessels.

anterior/posterior interventricular sulcus

grooves that separate the left and right ventricles

foramen ovale

a small opening in the atrial septum that allows blood to bypass the non-functioning fetal lungs, closing after birth.

pectinate muscles

muscular ridges found on the anterior atrial wall and inner surface of auricle

tricuspid valve

the valve located between the right atrium and right ventricle, preventing backflow of blood during contraction.

trabeculae carne

muscular ridges on internal surface of both ventricles

moderator band

a muscular band found in the right ventricle that delivers electrical signals/stimulus for contraction to papillary muscles

conus arteriosus

arteriosus is a conical structure in the right ventricle that directs blood toward the pulmonary artery.

aortic sinuses

saclike expansions at base of ascending aorta

reguritation

the backward flow of blood through a valve

valvular heart disease (VHD)

deterioration of valve function

carditis

inflammation of the heart muscle

rheumatic fever

inflammatory autoimmune response to streptococcal bacteria

coronary circulation

supplies blood to muscle tissue of the heart

right coronary artery 

supplies blood to the right atrium and right ventricle of the heart.

gives rise to marginal arteries and posterior interventricular artery.

left coronary artery

supplies blood to the left atrium and left ventricle,

gives rise to the anterior interventricular and circumflex arteries.

arterial anastomoses

interconnect anterior and posterior interventricular arteries

maintain constant blood supply to cardiac muscle

great cardiac vein

drains blood from region supplied by anterior interventricular artery and returns blood to the coronary sinus.

coronary ischemia

reduced circulatory supply from partial or complete blockage of coronary arteries

heartbeat

single 

autorhythmic cells

control and coordinate heartbeat

contractile cells

produce contractions that propel blood

conducting system

initiate and distribute electrical impulses that stimulate contraction

consists of specialized muscle cells

autorhythmicity

cardiac muscle tissue contracts without neural or hormonal stimulation

pacemaker potential

gradual depolarization of pacemaker cells

do not have a stable resting membrane potential, leading to spontaneous action potentials.

cardiac contractile cells

form bulk of atrial and ventricular walls

receives stimulus from purjinke fibers

resting membrane potential of ventricular cell ~90 mV, of atrial cell ~80 mV