Question

Compare and contrast excitatory and inhibitory synapses and explain why both are necessary. Please answer this question in one paragraph in more detail

Answer 1

Excitatory synapses are the synapses that cause positive action potential in neurons that transmits the signal to another cell. At excitatory synapses ionic currents flow through ion gated channels that cause net depolarization of the post synaptic cell. For example there are many excitatory neurotransmitters like glutamate, acetylcholine etc that cause excitatory synapses. When excitatory neurotransmitters like acetylcholine binds to receptors that opens sodium channels and allow sodium ions influx and reduces membrane potential called excitatory postsynaptic potential (EPSP). They usually act on nicotinic receptors which are found at the neuromuscular junction of smooth muscles, other glands that are associated with sympathetic nervous system.

Inhibitory synapses are the synapses that cause decrease in the action potential in neurons that transmits the signal to another cell. At inhibitory synapses ionic currents flow through ion gated channels that cause net hyperpolarization of the post synaptic cell. For example there are many excitatory neurotransmitters like GABA, dopamine etc that cause inhibitory synapses. When inhibitory neurotransmitters like GABA binds to receptors increases the flow of chloride ions in the post synaptic cells that raises the membrane potential called inhibitory postsynaptic potential (IPSP) and inhibit the excitatory signals. They also activate secondary messengers by opening potassium channels. Sedative drugs like phenobarbital, hexobarbital etc bind directly to GABA and cause sedation effect.

These excitatory and inhibitory synapses are necessary because excitatory synapses helps in passing the information between the cells and inhibitory synapses helps in limiting and change in the flow of information in order to regulate the track of the data running.