What is an IPSP and how is it produced??
An IPSP (Inhibitory Postsynaptic Potential) is a type of electrical signal used by neurons to inhibit or reduce the firing of action potentials in the postsynaptic neuron. It is produced through a process known as synaptic inhibition.
When an action potential reaches the presynaptic terminal of a neuron, it triggers the release of neurotransmitters into the synaptic cleft. In the case of an IPSP, inhibitory neurotransmitters, such as GABA (gamma-aminobutyric acid), are released.
To understand how an IPSP is produced, here are the steps involved:
1. Action potential propagation: An action potential travels along the axon of a presynaptic neuron until it reaches the presynaptic terminal.
2. Neurotransmitter release: The arrival of the action potential at the presynaptic terminal triggers the opening of voltage-gated calcium channels. An influx of calcium ions into the terminal causes the synaptic vesicles to fuse with the presynaptic membrane, releasing neurotransmitter molecules into the synaptic cleft.
3. Receptor binding: The released inhibitory neurotransmitters, such as GABA, diffuse across the synaptic cleft and bind to specific receptors on the postsynaptic neuron. These receptors are called GABA receptors.
4. Ion channel activation: When inhibitory neurotransmitters bind to their receptors, ion channels associated with the receptors open. In the case of GABA receptors, the ion channel is permeable to chloride ions (Cl-).
5. Ion flow: The opening of chloride ion channels allows chloride ions to flow into the postsynaptic neuron. The influx of negatively charged chloride ions makes the inside of the neuron more negative, creating an inhibitory effect.
6. Post-synaptic membrane potential change: The influx of chloride ions hyperpolarizes the postsynaptic neuron, making it more difficult for the neuron to reach the threshold for generating an action potential. This inhibits the firing of action potentials by reducing excitability.
Overall, the production of an IPSP involves the release of inhibitory neurotransmitters, the binding of these neurotransmitters to their receptors, and the subsequent ion flow that leads to a change in the membrane potential of the postsynaptic neuron. This process ultimately results in the inhibition of action potential firing.