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 brochioles,B-2 and sympathetic  



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Author5 Posts
  #1

hey friends

i have a question

i thought that beta 2 receptors were not innervated, they only can be stimulated by circulating epinephrine.

so beta 2 stimulation would casue bronchodilation
also sympathetic stimulation causes bronchodilation (bc it releases epinephrine from adrenal medulla that in turn acts on beta 2)

but sympathetic NERVE stimulation does not
but now i read in kaplan mcqs as brochodilation being the correct choice for sympathetic nerve stimulation...how come? plzzzzzz expalin




  #2

Remember this always for everywhere in the body for the Smooth Muscles (e.g. bronchial) :

Parasympathetic stimulation will cause contraction.

Sympathetic stimulation will cause relaxation.

Thats all.


  #3

sensational1982 wrote:
Remember this always for everywhere in the body for the Smooth Muscles (e.g. bronchial) :

Parasympathetic stimulation will cause contraction.

Sympathetic stimulation will cause relaxation.

Thats all.


Dude, this is wrong on so many levels.



  #4

Doc;

Beta 2 receptors are MOSTLY not innervated ,means some places they are innervated.
It is not innervated :-as in case of bronchial muscles.
Bronchioles have no sympathetic innervation, but are instead affected by circulating Adrenaline .
When they say sympathetic stimulation causes bronchodilation they are right as that releases neurotransmitters that act on beta 2 receptors present on the bronchioles.
Remember the question is not whether bronchioles have nerve innervation.
One more thing sympathetics stimulation causes relaxation of smooth muscle is not a correct statement to make.
Instead we can rephrase it by saying ALPHA 1 think smooth muscle contrtaction
BETA 2 think smooth muscle relaxation.

regards
Dr. J. Iyer






  #5

thanks alot dr.iyer smiling face

sensational 1982, ur statement is not entirely true e.g sympathetic stimulation of blood vessels smooth mscs causes contraction through alpha 1
its about the individual receptors like alpha 1, beta 2, not sympathetic as a whole smiling face

GL to all





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