Isoproterenol

Ycut

Full Member
Oct 20, 2012
101
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  1. Non-Student
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    Can someone explain why there is a fall in systolic pressure with isoproterenol ?
     

    dragon529

    MS-III
    10+ Year Member
    Jul 25, 2007
    715
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    Los Angeles, CA
    1. Medical Student
      Isoproternol only affects B1 and B2. Through B1, it increases heart rate and through B2 it vasodilates. The vasodilation cause drop in blood pressure.

      Compare with norepinephrine which affects alpha 1,2 and beta 1 so it vasoconstricts via alpha1 and there's a reflex decrease in heart rate because of that.

      I know you took this from FA and that little paragraph underneath sums it up.
       

      Ycut

      Full Member
      Oct 20, 2012
      101
      1
      1. Non-Student
        Isoproternol only affects B1 and B2. Through B1, it increases heart rate and through B2 it vasodilates. The vasodilation cause drop in blood pressure.

        Compare with norepinephrine which affects alpha 1,2 and beta 1 so it vasoconstricts via alpha1 and there's a reflex decrease in heart rate because of that.

        I know you took this from FA and that little paragraph underneath sums it up.

        B2 stimulation-Vasodilation-decreases (TPR) and as a result diastolic BP
        B1 stimulation-positive inotropism+ chronotropism-which must increase (Stroke volume) and as a result systolic BP
         
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        dragon529

        MS-III
        10+ Year Member
        Jul 25, 2007
        715
        2
        Los Angeles, CA
        1. Medical Student
          If you inject isoproternol, BP has to decrease for 2 reasons. Through beta1, you pump the heart stronger and faster then you'll get reflex vasodilation. Also, through beta2, it vasodilates because that's what it does.

          You have to think about the reflex the drug is indirectly causing because our body is constantly trying to maintain homeostasis.
           
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