For each question choose skeletal, smooth, cardiac muscle or a combination of them…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
For each question choose skeletal, smooth, cardiac muscle or a combination of them.
- Which muscle cells have many nuclei?
- Which muscle has intercalated discs?
- Which muscle is found in the walls of the blood vessels?
- Which muscles are involuntary?
- Why do the cells of the heart contract together?
Need a reminder? The key ideaShow
Muscular tissue is made of long cells called fibres that contract and shorten. Skeletal muscle is attached to bones, and its fibres are striated, long, cylindrical, unbranched and multinucleate. It is voluntary. Smooth muscle lies in the walls of internal organs such as blood vessels, the stomach and the intestine. Its cells are spindle shaped with one nucleus and no stripes. It is involuntary. Cardiac muscle forms the wall of the heart. Its cells are striated and branched, and they are joined end to end by intercalated discs with gap junctions, so that they contract as a unit. It is involuntary. The output of the heart is the rate times the stroke volume.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Skeletal muscle. The other two have one nucleus in each cell.
Step 2. (b) Cardiac muscle, where the ends of two cells meet.
Step 3. (c) Smooth muscle.
Step 4. (d) Smooth and cardiac muscle.
Step 5. (e) The intercalated discs have gap junctions. A signal passes quickly from cell to cell, so the cells contract as a unit.
Answer: (a) skeletal; (b) cardiac; (c) smooth; (d) smooth and cardiac; (e) gap junctions in the intercalated discs.
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