NEET BIOLOGY

Detailed explanation-1: -Source of Ca2+ for muscle contraction is both sarcoplasmic (endoplasmic) reticulum as well as extracellular fluid in case of. a. Skeletal muscles.

Detailed explanation-2: -In smooth muscle the sarcoplasmic reticulum is the major intracellular source of Ca2+; mitochondria do not play a significant role in the physiological regulation of [Ca2+]i.

Detailed explanation-3: -Skeletal muscle stores Ca2+ in the sarcoplasmic reticulum (SR) and releases it to initiate contraction, but the concentration of luminal Ca2+ in the SR ([Ca2+]SR) and the amount that is released by physiological or pharmacological stimulation has been difficult to measure.

Detailed explanation-4: -Ca2+ binds with the protein participating in muscle contraction to induce muscle contraction and is then reabsorbed into the sarcoplasmic reticulum via Ca2+ ATPase.

Detailed explanation-5: -When the muscle is stimulated, calcium ions are released from its store inside the sarcoplasmic reticulum, into the sarcoplasm (muscle ). Invaginations of the plasma membrane (sarcolemma) of the muscle fibres are called T (or transverse) tubules.