Describe the events of the muscle stimulation and contraction starting with the influx of Ca at the synaptic knob (of the neuron) and ending with the release of Ca into the sarcoplasm. What effect does botox have on the neuromuscular junction and its function?

Nerve stimulation, that is, the appearance of an action potential in the motor plate (nerve terminal + muscle fiber) triggers the release of calcium by the REL into the intracellular compartment, causing myosin and actin to bind, and that the topoisomerase that intervenes in the active site of both be displaced, thus generating a perfect shortening of the sarcomero.

The shortening of the sarcomero causes the Z lines to get closer, simultaneously all the sarcomeros will work the same and therefore muscle contraction is achieved.

Calcium is the generator of the bond between myosin and actin, which without it cannot be met with muscle contraction.

Explanation:

Muscle contraction will end once intracellular calcium concentrations decrease and myosin and actin are forced to detach, therefore the Z lines return to the initial position from where they were at rest, this coincides with the motor plate it is not in action potential but in a reflective period of stimuli, called resting potential.