Inhibitory Neurotransmitters Reduce Neuronal Firing by Generating IPSPs
- Neurotransmitters play a critical role in transmitting signals between neurons.
- While some neurotransmitters are excitatory and increase the likelihood of action potentials, others are inhibitory and reduce the likelihood of neuronal firing by generating inhibitory postsynaptic potentials (IPSPs).
Definition
Inhibitory neurotransmitters
Inhibitory neurotransmitters are chemicals that make it less likely for the postsynaptic neuron to generate an action potential.
- Imagine you’re trying to focus on a task in a noisy room.
- You need to filter out distractions to concentrate.
- Your brain does something similar with signals, using inhibitory neurotransmitters to prevent unnecessary or harmful nerve impulses.
Inhibitory Neurotransmitters Hyperpolarize Neurons to Prevent Action Potentials
- Instead of depolarizing the postsynaptic membrane (as excitatory neurotransmitters do), inhibitory neurotransmitters make the membrane potential more negative, a process known as hyperpolarization.
- This occurs through the opening of channels that allow negatively charged ions to enter or positively charged ions to leave the neuron.
- Think of inhibitory neurotransmitters as a brake on a car.
- The car (neuron) is ready to move (fire an action potential), but when the brake (inhibitory neurotransmitter) is applied, the car slows down and has difficulty moving forward, thus preventing an overreaction or overactivation of the system.
How Inhibitory Neurotransmitters Generate IPSPs
- Neurotransmitter Release: When an action potential reaches the presynaptic terminal, it triggers the release of inhibitory neurotransmitters into the synapse.
- Binding to Postsynaptic Receptors: These inhibitory neurotransmitters bind to specific receptors on the postsynaptic membrane.
- Common inhibitory neurotransmitters include gamma-aminobutyric acid (GABA) and glycine.
- Opening of Ion Channels: Upon binding to their receptors, the neurotransmitters cause the opening of chloride (Cl-) channels or potassium (K+) channels:
- Chloride ions (Cl-): When GABA binds to its receptor, it often opens chloride channels, allowing Cl- ions to flow into the postsynaptic neuron.
- Potassium ions (K+): In some cases, the neurotransmitter can open potassium channels, allowing K+ ions to flow out of the neuron.
- Hyperpolarization: The movement of negatively charged ions (Cl-) into the neuron or positively charged ions (K+) out of the neuron makes the inside of the cell more negative, causing a hyperpolarization of the postsynaptic membrane.
- This makes it more difficult for the neuron to reach the threshold potential required for an action potential, reducing the likelihood of firing.
