Question

If your body was depleted of Ca++ ions, how would this affect communication between a presynaptic neuron and a post-synaptic neuron?

Answer 1

Release of acetylcholine by the nerve terminals:

When the nerve impulse (action potential) travelling in the nerve fibre (axon) reaches the terminal buttons, the voltage-gated Ca2+ channels present on the presynaptic membrane open up, increasing its permeability to Ca2+ ions. Consequently, the Ca2+ ions present in the extracellular fluid (ECF) of the synaptic cleft enter the terminal buttons. The elevated Ca2+ levels in the cytosol of terminal buttons trigger a marked increase in exocytosis of vesicles releasing acetylcholine in the synaptic cleft.

Effect of acetylcholine on the postsynaptic membrane:

The acetylcholine so released diffuses in the synaptic cleft and binds to the nicotinic–acetylcholine receptors located mainly on the junctional folds of the motor end plate (post synaptic membrane) leading to opening up of the tubular channels.

Development of end plate potential:

Due to opening of the acetylcholine-gated channels in the end plate membrane, a large number of Na+ ions from the ECF enter inside the muscle fibre causing a local positive potential change inside the muscle fibre membrane called the end plate potential.

Thus Ca+ ions are required to transmit the electro chemical signal across the synaptic cleft by releasing the acetylcholine. Thus if the conc of Ca+2 gets decreased, then there will be disruption of communication between pre and post synaptic neuron.