Question

physiology of muscles contraction and relaxation​

Answer 1

Answer:

Relaxation occurs when stimulation of the nerve stops. Calcium is then pumped back into the sarcoplasmic reticulum breaking the link between actin and myosin. Actin and myosin return to their unbound state causing the muscle to relax.

Answer 2

muscle contraction means shortening of the muscle where muscle relaxation means lengthening of muscle or relieve the tension.

Explanation:

• In response to a particular stimulation(passive stretch), sensory neurons gets activated and then activate alpha motor neuron that innervate the muscle cell.
• Alpha motor neuron release neurotransmitter acetylcholine that binds to the muscle cells and generate action potential in muscle cell that ultimately result in the release of Ca2+ ions from smooth endoplasmic reticulum of muscle cell.
• Binding of calcium to troponin C, uncovering myosin binding site on actin and formation of linkage between actin and myosin and sliding of thin on thick filament that result in muscle contraction.
• In response to active tension, sensory neuron activate inhibitory interneuron that inhibit the activity of alpha motor neuron.
• Alpha motor neuron does not release acetylcholine, so can not generate action potential. No release of calcium takes place. Remaining calcium pumped back to SER by an ATPase pump.
• In absence of calcium, formation of linkage does not take place between actin and myosin, so no muscle contraction take place and in absence of contraction muscle gets relaxed.