section bank B/B #4

[akimhaneul]

Confused about this one...If sympathetic nervous system is activated, shouldn't there be more blood flow to brain? So why would the blood flow be moderated?

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[lpp06]

Confused about this one...If sympathetic nervous system is activated, shouldn't there be more blood flow to brain? So why would the blood flow be moderated?

The sympathetic nervous system, as you will recall, controls the "fight or flight" response and will do things like increase heart rate, vasodilator skeletal muscle, inhibits digestion, etc. It doesn't activate brain function.

One sympathetic effect is an increase in blood pressure. The passage is a study of the response of cerebral arteries to changes in internal pressure (ie. blood pressure). The table shows that an increase in internal pressure is accompanied by a decrease in arterial diameter - which in turn moderates blood flow.

If I had to guess, I would venture to say that this is a safe guard against pressure related damage occurring to cerebral arteries and the brain.

 

[laczlacylaci]

^spot on. Exactly what I thought after doing this problem.