Muscles that guard entrances and exits of internal passageways ...

[eruditmonkey@yahoo.com]

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]

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.

[eruditmonkey@yahoo.com]

Thanks for the timely response, appreciate it

[xiaomengxian]

Excellent