Mapoob Sapling Learning macmilan learning Place the steps of smooth muscle contr
ID: 3477546 • Letter: M
Question
Mapoob Sapling Learning macmilan learning Place the steps of smooth muscle contraction in order from contraction initiation to relaxation. Contraction initiation Relaxation Calcium ions bind calmodulin Myosin light chain kinase phosphorylates myosin. Actin-myosin crossbridges form. Contraction cycles occur Myosin light chain phosphatase dephosphorylates myosin. Smooth muscle is stimulated by a somatic motor neuron. Calcium ions bind troponin. Smooth muscle is stimulated by an autonomic motor neuron. Calcium ions enter the sarcopla Previous Check Answer Next ExitExplanation / Answer
contraction initiation
Relaxation.
PS: Note that smooth muscle contraction does not involve stimulus by somatic motor neurons and neither does it involve the bonding of calcium to troponin This is the part of contraction of skeletal muscle cells where in acetylcholine released from the nerons acts to generate action potential in the skeltal muscle cell which leads to releas of calcium from only sacrcoplasmoc reticulum which binds to troponin to geenrate contraction.
- Smooth muscles is simulated by autonomic motor neurons releasing neurotransmitters(epiephrine/non epinephrine) which causes exitation of smooth muscle cells via depolarising the smooth muscle cell membrane. which leads to releasing of calcium from sarcoplasmic reticulum or calcium entering the cells form outside the cells through calcium chanels in the cell membrane.
- calcim in the cytosol binds to calmodulin.forming calcium calmdulin complex.
- this activates the phosphorylating enzyme myosin light chain kinase complex .which phospoorylates the myosin head
- Myosin head binds actin forming cross briges that where mysoin slide alon actin filaments
- generates muscle contraction
- as the stimulus diminishes, calcium is returned to the sarcoplasmic reticulum which lowers the sarcoplasmic concentration of calcium and hence Myosin light chain phosphatase counters the phosphorylation of myosin heads by dephosphrylysing them thereby leading to detachment of actin and myosin heads. ceasing the contraction.