Smooth muscles that act like skeletal muscles but are controlled by autonomic nerves and hormones are:?

Question

a. red muscles
b. white muscles
c. single-unit muscles
d. multiunit muscles

Answer 1

C. single unit muscles

Single-unit Smooth Muscle:


Fibers in the single-unit smooth muscle undergo synchronous electrical and/or mechanical activity. Thus, the whole muscle responds to stimulation as a single unit.
Each fiber is linked to its adjacent cell by gap junctions, as mentioned in page 1. So when one action potential occurs in one cell, it propagates to the next cell.
The contractile activity of single-unit smooth muscles can be altered by nerves, hormones, and local factors.
The contractile response can often be induced by stretching the muscle. One example is the muscles in the walls of the uterus. The stretching of the smooth muscles in the walls of the organ results from an increase in the volume of material in the lumen which initiates a contractile response.


Figure 2.
Single-unit smooth muscle. The action

potential is propagated to neighboring fibers.
You can find single-unit smooth muscle in the:
small intestine,

colon,

uterus,

urinary bladder,

ureters,

lymph vessels, and

smaller arterioles
The movement we know as peristalsis is caused by the alternating contractions of the single-unit smooth muscle layers. This ultimately propels the contents to one direction.


Figure 3.
The gastrointestinal tract contains
single-unit smooth muscle layers
that aid in the movment of
digestion products. (ref)