Lesson 15, 16, and 17. Regulation of the Cardiovascular System. 1. Arteriolar resistance helps provide constant flow despite changes in perfusion pressure. The depolarization of smooth muscles increases the frequency of spike discharge which leads to increased contractions. How can distention promote smooth muscle repolarization? a. Stretch-sensitive cationic channels b. Cl- channels c. Rise in perfusion pressure and increased flow d. All of the above 1. D: A rise in perfusion pressure and increased flow initially pushed on stretchsenstivie cationic or Cl- channels and leads to narrowing of the vessel which increases resistance and allows flow to return to constant state. Less area at the same velocity (P=A*V) causes a decrease in pressure. This decrease in pressure removes activation of stretch-sensitive cationic channels and thus lowers membrane potential -> lowers probability of spike discharge -> relaxes smooth muscle and increases area -> resistance falls and flow goes back up.
2. What statement best explains this figure:
a. Dotted line is the steady state flow at a new perfusion pressure b. Dotted line is the flow after abrupt changes in perfusion pressure c. Solid line is the steady state flow at a new perfusion pressure d. b & c