BRAINCAKEContraction of Cardiac Muscle
The walls of the heart are made of cardiac muscle, a type of muscle found only in the heart. It has special properties that allow it to contract rhythmically, around 70 times a minute at rest, for a whole lifetime.
Myogenic. Cardiac muscle is myogenic: it contracts without needing to be stimulated by nerve impulses. The signal to contract starts within the heart itself. Nerves can speed up or slow down the heart rate, but they do not start each beat.
Branched cells joined by intercalated discs. Cardiac muscle cells are branched and joined end to end by intercalated discs. These contain gap junctions that allow electrical impulses to pass very quickly from cell to cell. As a result, the cells in a chamber wall contract together, producing a strong, coordinated squeeze.
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More in The Heart
- Structure of the Human Heart
- Blood Flow through the Heart
- The Cardiac Cycle
- Control of the Heartbeat
- Electrocardiograms
- Electrical and Pressure Changes in the Heart
All 7 lessons in The Heart · All Edexcel AS-level Biology topics