Ch 13

Myocardium

The medical term for cardiac muscle.

Pericardium

A tough membranous sac that encases the heart.

AV Node

Atrioventricular node; slows action potential transmission to allow for atrial contraction before ventricular contraction.

Pulmonary Circuit

The pathway of blood flow between the right side of the heart and the lungs for oxygenation.

Systemic Circuit

The pathway of blood flow between the left and right heart sides that distributes blood throughout the body.

Tricuspid Valve

The right atrioventricular valve that prevents backflow into the right atrium.

Bicuspid (Mitral) Valve

The left atrioventricular valve that prevents backflow into the left atrium.

Semilunar Valves

Valves located between the ventricles and the arteries (pulmonary and aortic) that prevent backflow.

Chordae Tendineae

Fibrous strings that prevent AV valves from inverting, attached to papillary muscles.

Pacemaker Cells

Autorhythmic cells that generate spontaneous signals to initiate heart contraction.

Stroke Volume (SV)

The amount of blood pumped by each ventricle per contraction.

End-Diastolic Volume (EDV)

The volume of blood in the ventricles at the end of diastole, just before contraction.

End-Systolic Volume (ESV)

The volume of blood remaining in the ventricles after contraction.

Cardiac Output (CO)

The volume of blood pumped by the heart per minute, calculated as SV × HR.

Einthoven Triangle

A hypothetical triangle around the heart formed by electrodes placed on the arms and left leg for ECG measurement.

Frank-Starling Law

States that increased ventricular filling leads to stronger contractions due to muscle stretch.

Atrial Systole

The phase of the cardiac cycle when the atria contract, pushing blood into the ventricles.

Ventricular Systole

The phase of the cardiac cycle when the ventricles contract, ejecting blood into the arteries.

Diastole

The phase of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood.

Systolic Pressure

The pressure in the arteries during ventricular contraction.

Diastolic Pressure

The pressure in the arteries during ventricular relaxation.

Autorhythmic Cells

A type of cardiac muscle cell that generates its own electrical impulses.

Gap Junctions

Cellular connections that allow electrical signals to pass quickly between cardiac muscle cells.

Coronary Arteries

Arteries that supply oxygen-rich blood to the heart muscle itself.

Pulmonary Valve

The semilunar valve located between the right ventricle and the pulmonary trunk.

Aortic Valve

The semilunar valve located between the left ventricle and the aorta.

ECG Waveforms

P wave (atrial depolarization), QRS complex (ventricular depolarization), T wave (ventricular repolarization).

Cardiac Glycosides

Medications that increase cardiac contractility by affecting calcium levels in cardiac cells.

Inotropic Agents

Substances that affect the contractility of the heart muscle.

Sympathetic Nervous System

The division of the autonomic nervous system that increases heart rate and contractility.

Parasympathetic Nervous System

The division of the autonomic nervous system that decreases heart rate.

Calcium-Induced Calcium Release

Mechanism where calcium influx triggers further calcium release from the sarcoplasmic reticulum in cardiac muscle cells.

T-Tubules

Extensions of the cell membrane in cardiac muscle cells that facilitate calcium influx.

Intercalated Disks

Specialized connections between cardiac muscle cells that contain gap junctions and desmosomes.

Atrial Fibrillation

An irregular and often rapid heart rate that can lead to poor blood flow.

Ventricular Filling

The phase of the cardiac cycle when the ventricles are refilled with blood during diastole.

Isovolumetric Contraction

A phase in the cardiac cycle where the ventricles contract with no volume change, as all valves are closed.

Isovolumetric Relaxation

A phase in the cardiac cycle where the ventricles relax with no volume change, as all valves are closed.

Pulmonary Circulation

The route of blood flow from the right heart to the lungs and back to the left heart.

Systemic Circulation

The route of blood flow from the left heart to the rest of the body and back to the right heart.

Baroreceptors

Sensors that detect changes in blood pressure and help regulate heart rate.

Oxygen Consumption

The amount of oxygen utilized by heart muscle cells during metabolic processes.

Endocardium

The inner layer of the heart that lines the chambers and valves.

Pericarditis

Inflammation of the pericardium.

Coronary Veins

Veins that drain deoxygenated blood from the heart muscle.

Ejection Fraction

A measurement of the percentage of blood pumped out of a filled ventricle with each heartbeat.

Aneurysm

An abnormal blood-filled bulge in the wall of a blood vessel.

Thrombus

A blood clot that forms in a blood vessel.

Arrhythmia

An irregular heartbeat that can disrupt normal heart function.

Vascular Resistance

The resistance to blood flow in blood vessels.

Myocytes

Muscle cells, including cardiac muscle cells.

Collagen Fibers

Connective tissue proteins that provide structural support in cardiac tissue.

Epicardium

The outer layer of the heart, which is also part of the pericardium.

Blood Pressure

The force exerted by circulating blood on the walls of blood vessels.

Cardiac Cycle

The sequence of events in one heart beat, including contraction and relaxation phases.

Ventricular Hypertrophy

The thickening of the heart muscle due to increased workload.

Angina Pectoris

Chest pain or discomfort due to reduced blood flow to the heart muscle.

Heart Murmur

An unusual sound during a heartbeat, often caused by improper valve function.

Holter Monitor

A portable device used to continuously monitor heart activity.

Hypertension

High blood pressure, a risk factor for heart disease.

Bradycardia

A slower than normal heart rate, typically less than 60 beats per minute.

Tachycardia

A faster than normal heart rate, typically over 100 beats per minute.

Apical Pulse

The pulse located at the apex of the heart, heard with a stethoscope.

Pacemaker Potential

The gradual depolarization and spontaneous firing of pacemaker cells.

Resting Membrane Potential

The voltage difference across the membrane of a non-excited cardiac cell.

Sinoatrial Nucleus (SA Node)

The primary pacemaker of the heart that sets the rhythm.

Ventricular Conduction System

The network of fibers ensuring coordinated contraction of ventricles.

Vasodilation

The widening of blood vessels; decreases blood pressure.

Vasoconstriction

The narrowing of blood vessels; increases blood pressure.

Cardiac Resynchronization Therapy

A treatment for heart failure that coordinates contractions of the heart chambers.

Compensatory Mechanisms

The body's adjustments to maintain hemodynamic stability in heart failure.

Stroke Volume Index (SVI)

A measure of stroke volume relative to body surface area.

Hemodynamic Parameters

Measurements related to blood flow and pressure in the cardiovascular system.

Neurohumoral Activation

The hormonal and neuronal responses that affect cardiac function.

Epinephrine

A hormone that increases heart rate and contractility.

Hypokalemia

Low potassium levels, which can affect cardiac function.

Cardiac Reserve

The heart's ability to increase output above resting levels.

Electrophysiology

The study of electrical activity in the heart.

Myocardial Infarction

A heart attack due to lack of blood flow to the heart muscle.

Troponin

A protein that regulates contractile activity in cardiac muscle.

Calmodulin

A protein that mediate smooth muscle contraction but not in cardiac muscle.

Tachyarrhythmia

Rapid heart rhythms that can potentially lead to complications.

Holter Monitor

Portable ECG device that records heart activity over 24-48 hours.

Electrode Leads

Wires connected to the ECG that monitor the heart’s electrical activity.

R-R Interval

The time difference between two successive R waves in the ECG, used to measure heart rate.

Vascular Compliance

The ability of blood vessels to expand under pressure.

Sphygmomanometer

An instrument used to measure blood pressure.

Internal Jugular Vein

Vein that drains blood from the brain.

Venipuncture

The procedure of obtaining intravenous access for intravenous therapy or venous blood sampling.

Lactate Threshold

The point during exercise at which lactic acid starts to accumulate in the bloodstream.

Capillary Blood Flow

The flow of blood through capillaries, facilitating nutrient and gas exchange.

Coagulation Cascade

The complex series of events that lead to blood clotting.

Thromboembolism

A blockage caused by a blood clot that travels through the bloodstream.

Pleurisy

Infection or inflammation of the pleura surrounding the lungs, affecting respiratory physiology.

Orthostatic Hypotension

A drop in blood pressure that occurs when standing up quickly.

Respiratory Sinus Arrhythmia

A natural variation in heart rate that occurs during breathing.

Atrial Septal Defect (ASD)

A congenital heart defect characterized by an opening in the atrial septum.

Coronary Artery Disease (CAD)

A condition characterized by narrowed coronary arteries, leading to reduced blood flow to the heart.

Ventricular Septal Defect (VSD)

A congenital heart defect characterized by a hole in the ventricular septum.

Valvular Heart Disease

Any disease involving one or more of the heart valves.