Question

8 multiple choice 1 point
which one of the following most accurately describes a difference between smooth and cardiac muscle?
cardiac muscle requires stimulation of nerves to contract but smooth muscle does not.
smooth muscle is voluntary, whereas cardiac muscle is involuntary.
cardiac muscle contracts slowly compared to smooth muscle.
smooth filaments are arranged in sarcomeres, whereas cardiac filaments are not.
cardiac muscle requires relaxation periods, whereas smooth muscle is generally always partially contracted
9 multiple choice 1 point
intercalated discs
join cardiac muscle cells to each other.
stimulate the contraction of skeletal muscle.
stimulate pacemaker cells in cardiac muscle.
are characteristic of smooth muscle cells.
support fast-twitch fibers of skeletal muscle.

Explanation:

For question 8:

• Cardiac muscle can contract autonomously (doesn't need nerve stimulation), so the first option is wrong.
• Both smooth and cardiac muscle are involuntary, so the second option is wrong.
• Smooth muscle contracts slowly, cardiac muscle contracts at a steady, rhythmic pace faster than smooth, so the third option is wrong.
• Cardiac muscle has sarcomeres, smooth muscle does not, so the fourth option is wrong.
• Smooth muscle maintains tone (partial contraction) while cardiac muscle needs relaxation periods between contractions.

For question 9:

• Intercalated discs are specialized structures that connect adjacent cardiac muscle cells, enabling synchronized contraction. They are not related to skeletal or smooth muscle, nor do they stimulate pacemaker cells directly.

Answer:

1. Cardiac muscle requires relaxation periods, whereas smooth muscle is generally always partially contracted
2. join cardiac muscle cells to each other.