Page 83 - Teknik Menjawab Soalan PSPM Biologi

Describe the events that occur when a resting skeletal muscle is stimulated by a motor

neuron

At neuromuscular junction

● Action potential reaches at the axon terminal
● voltage-gated calcium ion (Ca ) channel open
2+
● Ca 2+ diffuse into axon terminal

● Ca 2+ stimulates synaptic vesicles to move towards presynaptic
membrane & fuse with it
● Acetylcholines (Ach) are released into synaptic cleft
● By exocytosis
● Acetylcholines bind to the receptor proteins on the sarcolemma
+
● Causes the ligand gated Na channels to open
+
● Na diffuse into sarcoplasm
● Depolarisation occur (known as end plate potential (EPP) )
● If depolarization exceeds threshold level, action potential is

generated

At Muscle

● Action potential spreads along the sarcolemma via T tubule
● Stimulate sarcoplasmic reticulum to release calcium ion into

sarcoplasm
● When Ca 2+ is released, it binds to troponin & changes its
conformation
● Tropomyosin move away to expos the myosin binding site on actin
● ATPase at myosin head is activated to hydrolyze ATP into

ADP & P i
● Energy released change myosin into high energy

configuration