Question

describe how the nerve cell membeane acts as an integrator of both inhibitory and excitatory post synaptic potentials. What determines which way the membrane will go?

Answer 1

The junction between any two neurons is called as a synapse. There are chemical synapses as well as electrical synapses. Like wise there are excitatory synapses and inhibitory synapses. The choice of stimuli either be excitatory or inhibitory depends on the net polarisation of the cell membrane.

The neurotransmitters generate an action potential. Generally at the excitatory synapse they binds with the non specific cation channels. This binding permits the simultaneous passage of cations such as Na⁺, K⁺ through these synapses. At the start of the potential generation the membrane is at resting potential where the electrical gradient ( Voltage across the cell membrane ) and concentration gradients favours the movement of cations into the post synaptic neuron by the signal developed by the potential generated. This movement causes a slight depolarization of the membrane. This is called the Excitatory Post Synaptic Potential where the nervous transmission continues in this manner by post synaptic potentials across different neurons.

During an inhibitory post synaptic potential, the binding of neurotransmitters to the neuron causes hyperpolarisation of the membrane. This is a result of increase in the permeability of the post synaptic neuronal membrane to K⁺ or Cl^- . This membrane hyperpolarisation inhibits the generation of action potential on the post synaptic neuron.

In such a way never cell acts as an integrator for both inhibitory and excitatory post synaptic potentials. The net polarisation of the membrane determines in which way the membrane would goes to.