How do inhibitory synapses affect the action potential?

Inhibitory synapses decrease the likelihood of an action potential being generated in the post-synaptic neuron.

Inhibitory synapses play a crucial role in the functioning of the nervous system. They work by reducing the chance of an action potential, or nerve impulse, being generated in the post-synaptic neuron. This is achieved through the release of neurotransmitters that hyperpolarise the post-synaptic neuron, making it more negative and thus further from the threshold needed to trigger an action potential.

Neurotransmitters are chemical messengers that transmit signals across a synapse, from one neuron (pre-synaptic) to another (post-synaptic). In the case of inhibitory synapses, the neurotransmitters involved are typically gamma-aminobutyric acid (GABA) or glycine. When these neurotransmitters bind to their respective receptors on the post-synaptic neuron, they cause an influx of negatively charged chloride ions or an efflux of positively charged potassium ions. This increases the negative charge inside the neuron, a process known as hyperpolarisation.

Hyperpolarisation moves the membrane potential of the post-synaptic neuron further away from the threshold potential. The threshold potential is the critical level to which a membrane potential must be depolarised to initiate an action potential. By making the inside of the neuron more negative, inhibitory synapses make it harder for excitatory synapses to depolarise the neuron to the threshold potential. Therefore, the likelihood of an action potential being generated is decreased.

Inhibitory synapses are essential for the balance and precision of neural networks. Without them, our nervous system would be in a constant state of over-excitation, leading to uncontrolled and excessive neuronal firing. This could result in conditions such as epilepsy. Therefore, inhibitory synapses play a vital role in maintaining the balance of excitation and inhibition in the brain, allowing it to function correctly.