Cardiac Myocytes and Electrophysiology

These flashcards cover the key terms and concepts related to cardiac myocytes and cardiac electrophysiology, useful for exam preparation.

Epicardium

The thin layer of serous membrane that lubricates and protects the outside of the heart.

Myocardium

The muscular middle layer of the heart, containing cardiac muscle tissue, responsible for pumping blood.

Endocardium

The simple squamous endothelium layer lining the inside of the heart, preventing blood from sticking and forming clots.

AV valve

Valves located between the atria and ventricles that prevent backflow of blood.

Semilunar valves

Valves located between the ventricles and arteries, shaped to catch blood.

SA node

A collection of pacemaker cells that can generate impulses autonomously.

AV node

The node that delays electrical impulses to allow full ejection of blood from the atria.

Bundle of His

A pathway for electrical impulses from the AV node to the ventricles.

Purkinje fibres

Specialized cells that transmit cardiac action potentials rapidly to the myocardium.

Pacemaker potential

The slow depolarization phase that occurs at the end of one action potential and the start of the next.

HCN channels

Channels that allow Na+ entry into cells, contributing to the pacemaker potential.

Calcium entry

Initiates the depolarization phase in pacemaker cells.

Action potential in cardiomyocytes

The sequence of electrical events leading to contraction, lasting 200-400ms.

Myofibrils

Structures within cardiac myocytes composed of myofilaments responsible for contractions.

Sarcomere

The structural unit of a myofibril in striated muscle, between two Z lines.

Myosin

A thick filament protein that interacts with actin during muscle contraction.

Troponin

A protein complex that regulates muscle contraction by controlling the interaction between actin and myosin.

Excitation-contraction coupling

The process by which an action potential triggers muscle contraction in cardiomyocytes.

Sarcoplasmic Reticulum

An organelle that stores calcium ions, critical for muscle contraction.

Calcium influx

The entry of calcium ions into muscle cells that triggers contraction.

Sodium-calcium pump

A mechanism that transports calcium out of the cell, contributing to muscle relaxation.

Myogenic

The characteristic of cardiac muscle that allows it to generate its own action potentials.

Chronotropy

The term that refers to the rate at which the heart beats.

M2-AChR

The receptor through which the parasympathetic system acts to influence heart rate.

AV delays

A delay introduced at the AV node to synchronise atrial and ventricular contractions.

Gap junctions

Connections that allow electrical activity to be synchronized between cardiac myocytes.

Cardiac muscle vs Skeletal muscle

Cardiac muscle is myogenic, has gap junctions, and action potential plateaus, while skeletal muscle is neurogenic and uses motor units.

Calcium-Activated Calcium release

A mechanism in cardiac muscle where calcium entry triggers further release of calcium from the sarcoplasmic reticulum.

ATP hydrolysis

The process that provides energy for changes in the actin-myosin complex during contraction.

Calcium sequestering

The process by which calcium is removed from the cytoplasm back to the sarcoplasmic reticulum.

Intercalated disks

Structures that facilitate electrical coupling between cardiac myocytes.

Sino-atrial (SA) node action potential

Includes depolarization due to calcium influx that triggers heartbeats.

Right atrium

The chamber that receives deoxygenated blood from the body.

Left ventricle

The chamber responsible for pumping oxygenated blood to the body.

Deoxygenated blood flow path

Blood flows from the inferior vena cava to the right atrium, right ventricle, and to the lungs.

Oxygenated blood flow path

Blood flows from the lungs to the left atrium, left ventricle, and to the aorta.

Cardiac output

The volume of blood the heart pumps per minute.

Myocardial infarction

A condition caused by reduced blood flow to the heart muscle, often indicated by elevated TN-I levels.

Chronic heart disease

A long-term condition affecting the heart's functioning and structure.