Question

Animal Physiology Question

1. Describe the process of skeletal muscle contraction starting from an action potential being sent down a motor neuron to the contraction of the sarcomere.

Answer 1

The action potential for a muscle contraction is generated and it reaches a neuromuscular junction. The action potential arrives at the axon ends of the neuron. There are synaptic vesicles in which acetylcholine is stored. It gets fused with the presynaptic membrane and the vessicles release acetylcholine to the synaptic cleft by the opening of voltage gated calcium channels. The acetylcholine then binds to the receptors in the motor end plate of post synaptic membrane. This cause the release of calcium to the sarcoplasm through T tubules which isvtge lead to the muscle contraction. The Ca2+ ions binds to the troponin and removes the troponin tropomyosin blockade that blocks the active sites of actin. This makes the site ready for the binding of myosin. The myosin head undergo hydrolysis process which converts ATP to ADP. This makes the myosin head at a high energy level and thus bind to the active sites of actin. Thus a cross bridge is formed. As strong the stimuli is the myosin binding to the actin increases making more crossbridge. The filaments now slide one over the other making the sarcomere to decrease it's length. The sacomere is the unit of muscle contraction. The reduced length of sarcomere marks the strength of a mucsle contraction.