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quickie question - amcas 4

Discussion in 'MCAT Discussions' started by misscalipig, Aug 15, 2002.

  1. bio amcas 4:

    pg 65 passage VII

    i thought the sympathetic NS would lead to vasodilation, not vasoconstriction...but the passage indicates NE (rorepinephrine) causes vasoconstriction...but when you are in the "flight or fight" mode, you should have more blood pumping...can you guys helps me out!

    thanks! =D and thanks to all of you who saw that it was my birthday the other day and said happy birthday...very thoughtful =D

    p.s. do you think amcas 4 verbal was easy?
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  3. Toejam

    Toejam Terminal Student

    May 12, 2002
    Likes Received:
    The way I see it is it's good to think of it as "fight or flight". The sympathetic nervous system increases heart rate and blood flow to the muscles (which, I believe, is vasodilatory), but it CONSTRICTS blood flow to the unecessary tissues like the digestive system and excretory system.
  4. Lavndrrose

    Lavndrrose Senior Member

    Feb 9, 2002
    Likes Received:
    Epinephrine is a vasoconstrictor in the arteries, but larger arteries are less affected by the sympathetic innervation because they have less smooth muscle per volume. I hope this answers your question.

  5. but if ephinephrine constricts arteries, that would decrease blood flow and this is NOT what you want for sympathetic stimulation....
  6. Mr. Z

    Mr. Z Senior Member

    Apr 19, 2002
    Likes Received:
    Here is the low down on sympathetic nervous stimulation:

    When activated, from anger, fear, or stress (my is stimulated right now thanks to mcat), heart rate is accelerated, blood pressure is increased, perfusion to skeletal muscle increases as blood flow is redirected from the skin and spleen, blood glucose goes up, bronchioles and pupils dilate.

    so yes, vasoconstriction does occur, but only in order to give more blood to the muscles and other organs of "fight or flight"

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