Author Question: Muscles that guard entrances and exits of internal passageways are ________ muscles. A) parallel B) ... (Read 91 times)

eruditmonkey@yahoo.com · **on:** Feb 28, 2019

Muscles that guard entrances and exits of internal passageways are ________ muscles.
A) parallel
B) convergent
C) pennate
D) bipennate
E) circular

Question 2

Many visceral smooth muscle cells lack motor neuron innervation. How are their contractions coordinated and controlled?

jaymee143 · **Reply #1 on:** Feb 28, 2019

Answer to Question 1

E

Answer to Question 2

Gap junctions interconnect visceral smooth muscle fibers. An action potential that begins in one will spread to its surrounding neighbors. The action potential can be triggered by stretching, hormones, chemical changes, or stimulation at a myoneural junction on a distant smooth muscle cell.