me007
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b?
beta 2 receptors on skeletal muscles when activated promote potassium uptake into cell.
K conductance is highest in cell membrane.
For normal repolarisation potassium outflow is important.
a - propranolol does not anything with dopamine release
b - conduction velocity will be brought to about normal
c - increasing refractory period in muscle i guess shouldn't be affected
d - alfa receptor activation will affect Ca in smooth muscle
is it like this or i'm messing with physio?
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| epica
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Please try again, I think it's tricky Q
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| me007
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ok, c. if not b .
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| new_n_lost
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i had to literally scratch my head n think of possiblity cos this question is truly tricky as we dont see much written abt muscle dynamics. so here is my theory
Stimulation of beta-receptors bycatecholamines ultimately results in increased intracellular calcium, which then causes the excitation-contraction coupling of the cell. intramembranous beta-adrenergic receptor activity, which may be blocked by drugs such as propranolol resulting in decreased intracellular cAMP with a resultant blunting of the effects of endogenous and exogenous catecholamines.
So the answer will be D my initial reaction was B too so i had this question wrong initially.
Good Question, Do post the Exact explanation ot this question. whether mine is correct or not
Edited by new_n_lost on 03/11/07 - 09:54 PM
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| epica
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Sorry, u know that B blocker Propranolol does not relate to A recepror.
No, it's not D.
Ans is E.
Simple ans but I was confused w this Q also.
The Pt suffers from physiologic tremor. I have only this. explan in the book. If u can add more ,will be great.
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| new_n_lost
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can u tell me where is this question from? i mean which book
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| new_n_lost
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wht explanation have they given in the book can u post it hear. cos i cant find anything on spinal reflex loops
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| epica
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From the old NBME released Q.
They told only " because of Physiologic tremor" ans is E
It's confused me also, but anyway, I will try to search PubMed for this Q.
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| new_n_lost
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http://www.aafp.org/afp/20031015/1545.html
PHYSIOLOGIC TREMOR
All normal persons exhibit physiologic tremor, a benign, high-frequency, low-amplitude postural tremor. Usually invisible to the naked eye, it can be amplified by holding a piece of paper on the outstretched hand or pointing a laser at a distant screen.
Enhanced physiologic tremor is a visible, high-frequency postural tremor that occurs in the absence of neurologic disease and is caused by medical conditions such as thyrotoxicosis, hypoglycemia, the use of certain drugs, or withdrawal from alcohol or benzodiazepines. It is usually reversible once the cause is corrected.
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| new_n_lost
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Even they say that it Propranolol may reduce the effects of Tremors
my conclusion is that the spinal reflex activity can only be accomplished by effecting the beta receptors which have to be present on muscle
Edited by new_n_lost on 03/11/07 - 10:45 PM
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| epica
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Oh, u already did it. Is this clear for u now?
I have to do some search but only tommor.
Thank u v much .
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| new_n_lost
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no the second part of my statement says that any spinal reflex activity will be inhibited if the Beta Blocker acts on the Muscle where it has its receptors n the mechanism will be not directly stimulating the spinal loop it will be either Ca+ influx inhibition or some other mechanism. there is no mention of it directly effecting the directly on the Reflex loop in Spine
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| new_n_lost
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here is a diagram which goes more in favor of Calcuim influx. I might i just trying to prove my theory but its fits more n more. lol Plz Guys look into this question.
Attached Files:
Activation of Beta Receptor n its effect.doc (47 KB, 5 downloads)
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| epica
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I already posted this Q to our professor. Wait. I hope he will ans this confusing Q.
I will reply his feedback.
I agrre with you now but keep going to another Q's We have to do as much as we can.
Is your exam close?
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| new_n_lost
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Yup I m getting geared up for Apr 1 wk which seems a bit impossible from the current situation of mine but nayways its going to be in Apr no matter wht.
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| nandrolone
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So the answer will be D my initial reaction was B too so i had this question wrong initially
Hi NNL
According to my knowledge the contraction of the skeletal muscle does not depend upon the the extracellular Ca levels. So "D " is never going to be an answer.. Right/
Please correct me if i am wrong.....
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| me007
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The mechanism of action in the reduction of ET is not known. The action is hypothesized to be mediated primarily by peripheral beta2 adrenoreceptors, but some evidence indicates that beta1-receptor antagonists such as metoprolol also have some efficacy. Peripheral beta2 adrenoreceptors are located in the extrafusal muscle fibers and on the intrafusal fibers of the muscle spindles.
from e-medicine
if it blocks peripheral beta receptors, it inhibit conduction of impulse.
i still have not understanding about mechanism via spinal cord
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