Cardiac Muscle and Cardiac Conduction System p1 wk2

These flashcards cover key terms and concepts from the lecture on cardiac muscle and its conduction system, focusing on the structure and function of cardiac muscle cells, their electrical properties, and the significance of different components in the cardiac cycle.

Cardiac muscle cells

Also known as cardiac muscle fibers, they are shorter and smaller compared to skeletal muscle cells, usually have one nucleus, and many mitochondria.

Functional syncytium

A term describing how the myocardium functions as a single unit despite individual cells being separate due to intercalated discs.

Intercalated disks

Specialized cell membranes that connect individual myocytes and provide structural attachment via desmosomes and electrical connection through gap junctions.

Autorhythmicity

The ability of certain heart cells (autorhythmic cells) to contract spontaneously and generate action potentials, even without neural input.

SA node

The sinoatrial node, the primary pacemaker site in the heart that generates action potentials faster than other autorhythmic cells.

Sarcoplasmic reticulum

Organelles in cardiac muscle cells that store calcium, playing a crucial role in muscle contraction.

Resting membrane potential

The electrical charge across the membrane when a cell is at rest; approximately -90mV in cardiac myocytes due to high permeability to potassium.

Excitation-contraction coupling

The process whereby an action potential in the cardiac muscle leads to muscle contraction, involving interactions between actin and myosin.

Sarcomere

The basic contractile unit of muscle fibers, defined as the distance between two Z lines.

Desmosomes

Protein structures within intercalated discs that provide structural support by gluing cardiac muscle cells together.

Action potential duration

The time it takes for an action potential to occur, approximately 200-400 milliseconds in cardiac myocytes, compared to 1-2 milliseconds in nerve cells.