What is Cardiac Muscle?

Cardiac Muscle

DEFINITION

Cardiac muscle is a type of involuntary striated muscle found only in the heart. It contracts rhythmically to pump blood throughout the body.

EXPLANATION

• Cardiac muscle cells are connected by intercalated disks that transmit electrical impulses between cells to synchronize contractions.
• Unlike skeletal muscle, cardiac muscle contracts and relaxes spontaneously without nerve stimulation.
• Cardiac muscle relies on aerobic metabolism for energy and has a rich blood supply. It does not fatigue easily.
• Cells are branched and form a network that contracts as a unit to squeeze blood out of chambers.

EXAMPLES

• The left ventricular cardiac muscle contracts to pump oxygenated blood to the body.
• The right atrial cardiac muscle relaxes to allow blood to flow in from the body.

RELATED TERMS

• Myocardium – entire muscular tissue of the heart.
• Sinoatrial node – the pacemaker that generates electrical impulses.

COMMON QUESTIONS

• Why is cardiac muscle involuntary? Coordinated pumping does not require conscious control.
• What causes cardiac muscle fatigue? Ischemia from blockages can prevent blood flow to myocardium.

DO NOT CONFUSE WITH

• Skeletal muscle – voluntary striated muscle attached to bones by tendons.
• Smooth muscle – involuntary non-striated muscle in walls of internal organs.

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