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Physiology

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Cardiovascular System

Question
1 out of 13
 

TRUE regarding human heart (AIPG 2008)



A Conduction of impulse from endocardium to inwards

B During exercise duration of systole is reduced more than diastole

C HR increases with parasympathetic denervation

D Vagal stimulation decreases force of contraction

Ans. C HR increases with parasympathetic denervation

I. Impulses in the noradrenergic sympathetic nerves to the heart increase the cardiac rate (chronotropic effect) and the force of cardiac contraction (inotropic effect).

II. They also inhibit the effects of vagal stimulation, probably by the release of neuropeptide Y, which is a co-transmitter in the sympathetic endings.

III. Impulses in the cholinergic vagal cardiac fibers decrease the heart rate.

IV. A moderate amount of tonic discharge takes place in the cardiac sympathetic nerves at rest, but there is a good deal of tonic vagal discharge (vagal tone) in humans and other large animals.

V. When the vagi are cut in experimental animals, the heart rate rises, and after the administration of parasympatholytic drugs such as atropine, the heart rate in humans increases from 70 (its normal resting value)to 150 –180 beats/min because the sympathetic tone is unopposed.

VI. In humans in whom both noradrenergic and cholinergic systems are blocked, the heart rate is approximately 100/min.

Cardiovascular System Flashcard List

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