Cardiac Myocytes and Heart Conduction Mechanisms

Myocardium

Layer of heart composed mainly of cardiac myocytes.

Cardiac myocytes

Branching, mononucleate cells with myofibrils.

Striated muscle

Muscle with organized myosin and actin filaments.

Sarcomeres

Repeating units of myofibrils in muscle cells.

Intercalated discs

Structures linking cardiac myocyte plasma membranes.

Gap junctions

Channels allowing ion flow between cardiac cells.

Action potentials

Electrical signals generated by cardiac myocytes.

L-Type VGCCs

Calcium channels contributing to prolonged cardiac AP.

Calcium-induced calcium release

Mechanism amplifying calcium for muscle contraction.

Excitation-contraction coupling

Process linking electrical signals to muscle contraction.

Sinoatrial (SA) node

Pacemaker initiating heart rhythm through depolarization.

Pacemaker potential

Slow depolarization restarting after each repolarization.

Funny channel (HCN channel)

Cation channel activated by hyperpolarization in pacemaker cells.

Parasympathetic activity

Slows heart rate via acetylcholine release.

Sympathetic activity

Increases heart rate via norepinephrine release.

Atrioventricular (AV) node

Delays electrical signal between atria and ventricles.

Purkinje fibres

Conducting fibres transmitting signals through ventricles.

Electrocardiogram (ECG)

Recording of electrical activity in heart chambers.

P wave

Represents atrial depolarization in ECG.

QRS complex

Indicates ventricular depolarization in ECG.

T wave

Represents ventricular repolarization in ECG.

Arrhythmias

Irregular heart rhythms indicating potential health issues.

Sinus arrhythmia

Normal heart rate variation with respiration.

Tachycardia

Heart rate exceeding 100 bpm.

Bradycardia

Heart rate below 60 bpm.

Calcium channels

Proteins allowing calcium ion flow into cells.

Repolarization

Return to resting membrane potential after depolarization.

Sarcoplasmic reticulum

Organelle storing calcium ions in muscle cells.

T-tubules

Invaginations facilitating action potential transmission in muscle.

Functional syncytium

Coordinated action of interconnected cardiac myocytes.

Calcium concentration

Critical for initiating cardiac muscle contraction.