What is Cardiac Muscle?

Muscle Pump-elderly man with big muscles in the gym

Cardiac Muscle


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

man with big muscles resting after workout cardiac muscle


  • 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.


  • 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.


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


  • 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.
cardiac muscle


  • 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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