Module 3 Lecture 2: The Cardiovascular System - Heart Valves, Blood Flow, Coronary Circulation, Electrical Conductance and ECG

Flashcards covering key vocabulary terms related to heart valves, blood flow, coronary circulation, cardiac muscle tissue, electrical conduction, and electrocardiograms (ECG) from the lecture 'The Cardiovascular System'.

Fibrous Skeleton of the Heart

Consists of 4 dense connective tissue rings surrounding the heart valves that fuse with one another and merge with the interventricular septum, preventing overstretching of the heart valves and acting as an electrical insulator.

Heart Valves

Open and close in response to pressure changes as the heart contracts and relaxes, preventing backflow and ensuring blood travels in one direction through the heart.

Atrioventricular (AV) Valves

Connect the atria and ventricles, consisting of the tricuspid valve (right AV valve) and mitral valve (left AV valve), attached to chordae tendineae and papillary muscles.

Tricuspid Valve

The right atrioventricular (AV) valve, which has 3 leaflets.

Mitral Valve

Also known as the bicuspid valve, it is the left atrioventricular (AV) valve, which has 2 leaflets.

Chordae Tendineae

Fibrous cords that attach AV valve leaflets to papillary muscles, allowing valves to remain closed during ventricular contraction and preventing their inversion into atria.

Papillary Muscles

Muscles in the ventricles that anchor the chordae tendineae, preventing AV valve flaps from everting into the atria during ventricular contraction.

Semilunar (SL) Valves

Prevent blood backflow from the pulmonary trunk and aorta into the ventricles, consisting of the pulmonary semilunar valve and the aortic semilunar valve, each with 3 leaflets.

Pulmonary Semilunar Valve

Located between the right ventricle and the pulmonary trunk, preventing blood backflow into the right ventricle.

Aortic Semilunar Valve

Located between the left ventricle and the aorta, preventing blood backflow into the left ventricle.

Pulmonary Circulation

A pathway where deoxygenated blood is pumped from the right ventricle to the lungs for reoxygenation, then returned to the left atrium.

Systemic Circulation

A pathway where oxygenated blood is pumped from the left ventricle to the body (including the heart) and deoxygenated blood is returned to the right atrium.

Coronary Circulation

The heart's own blood supply, involving coronary arteries that supply blood to the heart (mainly myocardium) and coronary veins that drain deoxygenated blood into the coronary sinus.

Coronary Arteries

Originate at the base of the aorta and supply blood to the heart, including the left coronary artery (anterior interventricular artery, circumflex artery) and the right coronary artery (right marginal artery, posterior interventricular artery).

Coronary Veins

Drain deoxygenated blood from the heart into the coronary sinus, which then empties into the right atrium; examples include the great, middle, small, and anterior cardiac veins.

Myocardium

The heart muscle, making up the majority of the heart, whose contraction leads to the mechanical work of pumping blood.

Cardiac Muscle Cells (Myocytes)

The individual cells of the heart muscle, characterized by being branched, containing one (sometimes two) nuclei, possessing numerous large mitochondria, and being fatigue resistant.

Intercalated Discs

Irregular transverse thickenings of the sarcolemma at the ends of cardiac muscle fibers that connect neighboring fibers, containing desmosomes and gap junctions.

Desmosomes

Found within intercalated discs, they hold cardiac muscle fibers together.

Gap Junctions

Found within intercalated discs, they allow muscle action potentials to conduct from one muscle fiber to the next, enabling the entire myocardium of the atria or ventricles to contract as a single, coordinated unit (syncytium).

Autorhythmicity (Automaticity)

The ability of cardiac muscle cells to create their own action potential without external excitation, repeatedly generating spontaneous action potentials to trigger heart contraction.

Electrical Conduction System

A specialized network of electrical pathways in the myocardium formed by autorhythmic fibers (SA node, AV node, AV bundle, bundle branches, Purkinje fibers) that allows rapid transmission of electrical impulses across the heart.

Sinoatrial (SA) Node

The pacemaker of the heart, located in the right atrial wall, which depolarizes faster than the rest of the myocardium and generates impulses at about 60-100 bpm (sinus rhythm).

Atrioventricular (AV) Node

A component of the heart's electrical conduction system that delays the impulse transmission from the atria to the ventricles, allowing atrial contraction to complete before ventricular contraction begins.

Electrocardiogram (ECG)

A recording of the electrical signals generated by action potentials propagating through the heart, detected at the surface of the body, used to view the heart's electrical conductance and detect cardiac pathologies.

P Wave

Represents atrial depolarization, initiated by the SA node, on an ECG tracing.

QRS Complex

Represents ventricular depolarization and atrial repolarization (which is hidden) on an ECG tracing.

T Wave

Represents ventricular repolarization on an ECG tracing, which begins at the apex.

PR Segment

A flat (isoelectric) portion on an ECG between the end of the P wave and the start of the QRS complex, reflecting the AV nodal delay.

ST Segment

A flat (isoelectric) portion on an ECG between the end of the QRS complex and the start of the T wave, representing the ventricular depolarization plateau phase.

PR Interval

Measures the time on an ECG from the start of the P wave to the start of the QRS complex, including atrial depolarization and the AV delay.

QT Interval

Measures the time on an ECG from the start of the QRS complex to the end of the T wave, reflecting the total time for ventricular depolarization and repolarization.