The heart's own muscle
Cardiac muscle beats all through life.
A tireless muscle
Your arm gets tired if you lift a heavy bag again and again. Your heart beats day and night, from birth.
What do you expect of the muscle in the heart?
What this lesson covers
The idea
Cardiac muscle, found only in the heart, has cylindrical, branched fibres with a single nucleus and faint striations, and works rhythmically throughout life without fatigue.
A tireless muscle
Your arm gets tired if you lift a heavy bag again and again. Your heart beats day and night, from birth.
What do you expect of the muscle in the heart?
- It works rhythmically without getting tired
- It gets tired and must rest like an arm
- It works only when you decide
Watch the heart beat
Press Play and watch the heart and its muscle fibre.
A different kind of muscle
The heart is made of cardiac muscle. It is found only in the heart. Its fibres are cylindrical like those of skeletal muscle, but they are branched, with a single nucleus and faint striations. They beat rhythmically all through life.
Cardiac muscle, found only in the heart, has cylindrical, branched fibres with a single nucleus and faint striations, and works rhythmically throughout life without fatigue.
Notes
Cardiac muscle is found only in the heart: branched fibres, single nucleus, faint striations, working rhythmically without fatigue.
Check yourself
Where is cardiac muscle found?
What are cardiac muscle fibres like?
What is special about how cardiac muscle works?
How are the striations of cardiac muscle described?
- In the stomach and intestines. Smooth muscles are found in organs like the stomach and intestines.
- Only in the heart — correct. Yes!
- Attached to the skeleton. Skeletal muscles are attached to the skeleton.
- Long and unbranched, with many nuclei and clear striations. These are skeletal muscle fibres.
- Spindle-shaped, with a single nucleus and no striations. These are smooth muscle cells.
- Cylindrical and branched, with a single nucleus and faint striations — correct. Yes!
- It works rhythmically all through life without fatigue — correct. Yes!
- It gets tired quickly and must rest every few minutes. The heart keeps beating throughout life without fatigue.
- It works only when we decide to move. The beating of the heart is an involuntary movement, which goes on without our conscious control.
- Absent, as in smooth muscle. Smooth muscle lacks striations, but cardiac muscle has faint ones.
- Faint — correct. Yes!
- Clear light and dark bands, as in skeletal muscle. Clear light and dark bands belong to skeletal muscle fibres.