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Physiology

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Nerve Muscle Physiology

Question
13 out of 19
 

In isometric exercise the following changes occur EXCEPT: (DNB Dec-2008)



A Increase in muscle tone

B Staircase phenomenon

C Summation of contractions

D Relaxation heat

Ans. D Relaxation heat

"If a muscle that has contracted isotonically is restored to its previous length, extra-heat in addition to heat is produced (known as Relaxation heat)"

I. e.

a. In Isotonic contraction both Recovery heat and Relaxation heat (extra heat) are produced that restore the muscle to its precontraction state. External work must be done on the muscle to return it to its previous length, and relaxation heat is mainly a manifestation of this work.

b. In Isometric contraction (same length but in tension) - only Recovery heat is liberated that restore the muscle to its pre-contraction state.

i. Summation of contractions and Staircaise (Treppe) phenomenon occur in both of muscle contraction"

Work = Force x (distance).

ii. Therefore

In Isometric contraction

W = Force x a (distance)

= 0 i. e. energy is used with work.

In Isotonic contraction

W = Force x distance (muscle is shortened)

= Work done.

Nerve Muscle Physiology Flashcard List

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