Physiology Lecture on Cardiac Muscle Action Potential and Contractility

These flashcards cover key concepts related to the cardiac muscle action potential, contractility, and associated physiological mechanisms discussed in the lecture.

Action Potential (AP)

A rapid change in the electrical potential across the plasma membrane of a cardiac muscle cell, leading to contraction.

Pacemaker Cells

Specialized cardiac cells in the SA node that exhibit autorhythmicity and control heart rate.

All or None Law

The principle stating that a muscle fiber will fully contract or not at all, depending on whether the stimulus meets the threshold.

Staircase Phenomenon

The increase in contractility of the heart as the frequency of stimulation increases.

Starling's Law of the Heart

The relationship stating that the force of myocardial contraction is directly proportional to the initial length of cardiac muscle fibers.

Resting Membrane Potential (RMP)

The electrical potential difference across the plasma membrane of a resting myocyte, typically around -80 to -90 mV.

Conduction System of the Heart

A network of specialized cardiac cells that coordinate the contraction of heart muscle by conducting electrical impulses.

Ventricular Action Potential

The electrical activity of the ventricular muscle cells, characterized by a stable RMP and a long duration AP.

Excitation-Contraction Coupling

The process by which an action potential in a cardiac muscle cell leads to muscle contraction through the release of calcium.

Calcium-Induced Calcium Release (CICR)

The mechanism by which calcium entry during an action potential triggers further calcium release from the sarcoplasmic reticulum.

AV Node Delay

A brief delay in the conduction of electrical impulses at the atrioventricular node, allowing for proper ventricular filling before contraction.

Ion Channel Gating

The regulation of ion channels that control the flow of ions such as Na+, K+, and Ca2+ across the cardiac cell membrane during an action potential.

Intrinsic Cardiac Factors

Factors internal to the heart, such as heart rate and contractility, that affect cardiac performance.

Extrinsic Cardiac Factors

External factors, like sympathetic and parasympathetic nervous system influence, that affect heart function.

Myogenic

Referring to the ability of cardiac muscle to initiate its own contraction without external neural stimulation.