OIA1004 (TERMS) CVS I

Cardiac Conduction System

Network facilitating electrical impulses in the heart.

Automaticity

Ability of heart to initiate its own contractions.

Excitability

Heart's capacity to respond to stimuli.

Conductivity

Speed of electrical impulse transmission in heart.

Contractility

Heart muscle's ability to contract forcefully.

SA Node

Primary pacemaker generating action potentials at 100 beats/min.

AV Node

Slows impulse conduction to allow ventricular filling.

Bundle of His

Conducts impulses from AV node to ventricles.

Purkinje Fibres

Specialized fibers for rapid impulse distribution in ventricles.

AV Nodal Delay

Delay at AV node allowing atrial contraction before ventricles.

Resting Membrane Potential (RMP)

Voltage across membrane when cell is at rest.

Action Potential (AP)

Rapid change in membrane potential during contraction.

Pacemaker Potential

Slow depolarization in SA node leading to AP.

Sodium Ion Leak

Na+ influx causes depolarization in SA node.

Calcium Channels

Open during depolarization, allowing Ca2+ influx.

Potassium Channels

Open during repolarization, allowing K+ efflux.

Ventricular Muscle

Muscle that contracts in response to SA node signals.

Atrial Muscle

Muscle that contracts simultaneously with ventricular filling.

Electrical Impulse Pathway

Route from SA node through AV node to ventricles.

Sympathetic Nervous System

Increases heart rate and contractility.

Parasympathetic Nervous System

Decreases heart rate and promotes relaxation.

Interventricular Septum

Wall separating right and left ventricles.

Fibrous Barrier

Prevents direct electrical conduction between atria and ventricles.

Endocardial Surface

Inner layer of heart where impulse spreads in ventricles.

Action Potential

Electrical impulse triggering muscle contraction in cardiac cells.

Phase 0

Rapid sodium influx due to fast voltage-gated sodium channels.

Phase 1

Brief repolarization as sodium channels inactivate.

Phase 2

Plateau phase from sustained calcium permeability increase.

Phase 3

Repolarization occurs with potassium efflux.

Phase 4

Resting membrane potential with stable ion permeability.

Excitation-Contraction Coupling

Process linking electrical excitation to muscle contraction.

Calcium-Induced Calcium Release

Calcium influx triggers further calcium release from SR.

Troponin

Protein that binds calcium, initiating muscle contraction.

Sarcoplasmic Reticulum

Calcium storage organelle in muscle cells.

Refractory Period

Time during which cardiac muscle cannot be re-excited.

Absolute Refractory Period

Period where no new action potential can occur.

Chronotropic Effect

Influence on heart rate by autonomic nervous system.

Parasympathetic Stimulation

Decreases heart rate via acetylcholine release.

Sympathetic Stimulation

Increases heart rate via noradrenaline release.

Voltage-Gated Calcium Channels

Channels that open in response to membrane depolarization.

Potassium Efflux

Movement of potassium ions out of the cell.

Crossbridge Cycling

Interaction between actin and myosin during contraction.

T-Tubules

Extensions of the plasma membrane in muscle cells.

Calcium ATPase

Enzyme that pumps calcium back into the SR.

Na+-Ca++ Exchanger

Exchanges sodium ions for calcium ions across membrane.

Myoglobin

Oxygen-binding protein in cardiac muscle cells.

Striated Muscle

Muscle type with organized thick and thin filaments.

Membrane Prepotential

Initial phase of depolarization in nodal cells.

Muscarinic Receptors

Receptors activated by acetylcholine in cardiac tissue.

β1 Receptors

Receptors that increase heart rate upon noradrenaline binding.