Question

Describe what happens in a postsynaptic cell when an excitatory neurotransmitter is released into the synapse by a presynaptic neuron. Describe what happens in a pos-synaptic cell when an inhibitory neurotransmitter is released into the synapse by a presynaptic neuron.

Answer 1

Answer: Neurotransmitters are important in neural communication. These are chemical messengers that carry messages between the nerve cells and other cells in the body. Excitatory neurotransmitters excite a signal called as action potential in the receiving neuron. A presynaptic neuron is a neuron that fires the neurotransmitter as a result of an action potential entering its axon terminal. A postsynaptic neuron is a neuron that receives the neurotransmitter after it has crossed the synapse (site where neuronal signals are transmitted from cell to cell) and may also experience an action potential if the neurotransmitter is strong enough. Excitatory neurotransmitters increase the probability that the cell with which it comes in contact will produce an action potential. Inhibitory neurotransmitter decreases the probability that the cell with which it comes in contact will produce an action potential, Type I synapse are excitatory in their actions, whereas type II synapses are inhibitory. The most common excitatory neurotransmitter, glutamate migrate via diffusion to the dendritic spine of the postsynaptic neuron and bind a transmembrane receptor protein that triggers the depolarization of that cell. In depolarization, the postsynaptic cell undergoes a shift in electric charge distribution resulting in less negative charge inside the cells. This is essential for the function of cells, cell to cell communication and body physiology.

In case of inhibitory synapse, the release neurotransmitter binds to the postsynaptic receptors that induces a change in the permeability of the postsynaptic neuron to particular ions. A negative postsynaptic potential is generated. The postsynaptic membrane potential becomes more negative than the resting membrane potential called as hyperpolarisation. For the generation of an action potential, the postsynaptic membrane must be depolarized.