GENERAL HISTOLOGY

MUSCLE

SKELETAL MUSCLE

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

Where are the calcium ions in a muscle fiber stored when the muscle isn’t contracting?

A	mitochondria
B	myofibrils
C	T-tubules
D	sarcoplasmic reticulum

Explanation:

Detailed explanation-1: -Sarcoplasmic reticulum is the organelle in which Ca++ ions are stored in the muscle fibers.

Detailed explanation-2: -Calcium ions at rest are stored in the sarcoplasmic reticulum (SR) from which they are rapidly released upon the depolarisation of the sarcolemmal and transverse (T-) tubular membranes of the muscle cell.

Detailed explanation-3: -Impaired calcium release from the sarcoplasmic reticulum (SR) has been identified as a contributor to fatigue in isolated skeletal muscle fibers.

Detailed explanation-4: -High concentrations of calcium in skeletal muscle are stored in a specialized type of smooth endoplasmic reticulum organelle called the sarcoplasmic reticulum (SR). The SR structure surrounds the myofibrils, allowing storage and release of calcium directly at sites of actin and myosin overlap.

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