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physiology question

Discussion in 'Medical Students - MD' started by jesse14, Nov 30, 2005.

  1. jesse14

    jesse14 Senior Member
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    Hey med students,

    I was just wondering if anyone has a second to help me out with a question

    Here it is:

    Are the baroreceptors that detect MAP (mean arterial presure) mediated by stretch receptors, pressure receptors, or both? These baroreceptors are the aortic arch and carotid sinus ones just in case anyone was wondering.

    Thank you!
     
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  3. THP

    THP Senior Member
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    Considering that they are baroreceptors I am pretty sure they measure pressure. However, increased pressure causes distension of the vessels.
     
  4. thatuvicguy

    thatuvicguy Member
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    Hey Jesse,

    I haven't been around here in forever, good to see another Canadian med student. Anyways, about your question - we covered this at UBC a few weeks ago so I'll give it a shot: the baroreceptors (most importantly in the carotid sinus & aortic arch) indirectly respond to pressure in the sense that increased MAP causes stretching of the vessel walls and this in turn deforms the receptors. So you could say that they are in fact stretch sensitive. In fact tissues around the baroreceptors act as a slight buffer by sort of resisting stretch of the vessel walls. Our physiology text talked about how placing a plaster cast around the vessel wall (at point of receptor) will prevent increased baroreceptor firing even if MAP increases.

    Hope that helps,
    thatuvicguy

     
  5. ucsb101

    ucsb101 Senior Member
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    We learned em as responding to both---> cuz u can affect BP by "massaging ur carotid"


     
  6. trudub

    trudub Senior Member
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    Massaging the carotid actually just stretches the receptor. The fundamental thing they respond to is stretch but pressure causes stretch. Just as one of the poster talked about placing a cast around the vessel, that is exactly what happens in atherosclerosis. With atherosclerosis, there is essentially a cast around the receptor and so the receptor is less sensitive to stretch. This is one of the hypotheses about how atherosclerosis contributes to hypertension by blunting the baroreceptor response. However, the baroreceptors are only involved in short term regulation of BP and not long term because they very rapidly reset their set point.
     
  7. NRAI2001

    NRAI2001 3K Member
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    They indirectly detect BP by directly detecting stretch in the aortic arch and carotid sinus :thumbup:

    I think there are also ion receptors in these locations that detect Na+ and other ion levels which also indirectly reflect BP (not 100% sure about this, need to refer to my physio text).
     
  8. Southpawz

    Southpawz Member
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    Those are called chemoreceptors ;)
     

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