An inhibitory post-synaptic potential (IPSP) is a crucial process that reduces the likelihood of an action potential occurring in a post-synaptic neuron. This occurs primarily through the action of inhibitory neurotransmitters, which bind to specific receptors on the post-synaptic membrane.
When an inhibitory neurotransmitter is released from a pre-synaptic neuron, it binds to receptors on the post-synaptic cell, leading to the opening of chloride ion (Cl-) channels. This allows Cl- ions, which are negatively charged, to flow into the post-synaptic neuron.
As Cl- ions enter the cell, they contribute to the hyperpolarization of the post-synaptic membrane. Hyperpolarization means that the membrane potential becomes more negative, moving further away from the resting membrane potential. The resting membrane potential of a neuron typically hovers around -70 mV, and for an action potential to occur, the membrane potential needs to reach a certain threshold voltage (usually around -55 mV).
By facilitating the influx of negatively charged Cl- ions, IPSPs make it more challenging for the membrane potential to reach this threshold voltage. Instead of depolarizing toward the threshold, the hyperpolarization that occurs makes it necessary for a larger excitatory stimulus to trigger an action potential or may prevent it altogether. This mechanism is crucial in the regulation of neuronal activity, preventing excessive firing and fine-tuning responses in neural circuits. Overall, the presence of IPSPs, through the actions of inhibitory neurotransmitters and the dynamics of Cl- channels, acts to maintain balance in the excitability of neurons and contributes to the overall inhibitory signaling within the nervous system.
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