Nicotinic cholinergic receptors allow simultaneous passage o

Nicotinic cholinergic receptors allow simultaneous passage of Na^+ and K^+. What neurotransmitter do these receptors bind? Explain how stimulation of these channels leads to excitation. Fifteen different presynaptic neurons synapse on a single postsynaptic neuron. The postsynaptic neuron has a RMP of -70 mV. At the trigger zone, 14 of the presynaptic neurons produce excitatory postsynaptic potentials of 2 mV each, and the other one produces an inhibitory postsynaptic potential of 9 mV. The threshold for the postsynaptic neuronis is -50 mV. Will action potentials be produced in the postsynaptic neuron? Is this an example of temporal summation or spatial summation? Explain your answers.

Solution

1. The nicotinic cholinergic receptors belong to the family of cholinergic receptors. These receptors have property of binding with acetylcholine; as the function of neurotransmitting response. The nicotinic cholinergic receptors channels are having agonist property for nicotine, choline and epibatidine.

The process of excitation start when stimulation applied and a form of agonist binds. Binding causes the positive ion movement across the cell wherein sodium ions move inside and potassium ions outside. These channels are also a normal type of channels which are non-selective cation channel. So these also allowed the movement of calcium ions.

2. 14 presynaptic neurons produce = 14 x 2 mV = 28mV

An inhibitory postsynaptic potential= 9mV

Total difference when stimulation applied= 28-09 = 19 mV

The resting membrane potential is -70mV so,

After stmulation the resulting potential of the membrane is now

= -70 + 19 mV = -51 mV

The threshold for post synaptic neuron is -50mV which is 1 mv more than the stimulated potential (-51mV). So, the neuron will not excite; the action potential will not generate.

It is a case of spatial summation because postsynaptic neuron is stimulated by multiple neurons (presynaptic).