place in correct order 1. ACH binds to receptors
place in correct order 1. ACH binds to receptors on the postsynaptic membrane 2. AP travels along the sarcolemma and T tubules 3. Ca++ ion bind to troponin 4. Ca++ ions diffuse into the sarcoplasm 5. voltage-gated Ca++ ion channels in the sarcoplasmic reticulum open
The muscle contraction is explained via tha Sliding Filament Theory of Huxley ans Huxley.
It talks about how the sarcomere, unit of muscle structure and function, consisting of thick and thin segments reduces in length due to sliding of myosin over the actin chain after a cross bridge is formed.
Each muscle fibre has a nerve ending bringing to it information in the form of impulse.
This nerve consists of the cyton(cell body) with the nucleus; and the axon with terminal endings. Impulse is carried along the axon till the nerve endings. The neuron communicates with the muscle fibre through the synapse in the neuro muscular junction.
This is the motor end plate or neuromuscular junction formed by the presynaptic membrane of the neuron terminal endings, the synaptic cleft in between, and the postsynaptic membrane of the muscle fibre (sarcolemma).
The impulse for muscle contraction travels in the form of the action potential through the neuron till the motor end plate.
Here the sarcoplasmic reticulum releases the Acetylcholine neurotransmitter molecules into the synaptic cleft, they bind to the post synaptic membrane and cause release of calcium into the sarcoplasm. These calcium molecules bind to troponin c which causes movement of tropomyosin to expose the myosin binding site in actin and thus actin myosin cross bridges are formed. The myosin head slides over the cross bridge thereby causing muscle contraction as discussed above.
The pooling of calcium back into the sarcoplasmic reticulum requires phosphorylation of ADP to ATP.
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