Question

question 2 (1.7 points)
which of the following describes the cells of unitary smooth muscle?
a) they exhibit spontaneous action potentials.
b) they consist of muscle fibers that are structurally independent of each othe
c) they are used for vision and hair raising.
d) they depend upon recruitment using the autonomic nervous system.

Explanation:

• Option A: Unitary smooth muscle cells (also known as visceral smooth muscle) can exhibit spontaneous action potentials due to the presence of pacemaker cells within the muscle tissue. These pacemaker cells can depolarize spontaneously, leading to action potentials that then spread to other cells in the muscle sheet through gap junctions.
• Option B: Unitary smooth muscle cells are connected by gap junctions, so they are not structurally independent. Multi - unit smooth muscle cells (e.g., in the iris) are more structurally independent.
• Option C: The muscles used for vision (e.g., iris muscles) and hair - raising (arrector pili muscles) are multi - unit smooth muscles, not unitary smooth muscles.
• Option D: While the autonomic nervous system can influence unitary smooth muscle (e.g., by releasing neurotransmitters that modify the activity of pacemaker cells or the response of muscle cells to action potentials), unitary smooth muscle does not strictly "depend upon recruitment using the autonomic nervous system" in the same way as skeletal muscle depends on motor neuron recruitment. Unitary smooth muscle can contract spontaneously without direct autonomic nervous system recruitment in the classic sense.

Answer:

A. They exhibit spontaneous action potentials.