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Inhibitory Postsynaptic Potential: Definition & Examples

Instructor: Amanda Robb
In this lesson, we'll define the inhibitory postsynaptic potential of neurons. We'll examine how inhibitory postsynaptic potentials impact important aspects of physiology, including the physiology evident in examples of drug and alcohol abuse.

What Is a Postsynaptic Potential?

The inhibitory postsynaptic potential is a mouthful of words! Basically it means that your brain is less likely to continue sending signals. In this lesson, we'll break down the postsynaptic potential step by step to help you understand the process that controls many aspects of conscious thought! This topic is also incredibly important in drug and alcohol abuse, so read on to learn more.

Neurons

To understand postsynaptic potential, we have to first understand the structure and function of brain cells. Neurons are the cells of the brain. Neurons communicate with each other to control our feelings, thoughts, and movements through both electrical and chemical signals. The signal starts with an electrical impulse when the neuron becomes more positive. If the neuron is negatively charged, it is less likely to send a signal, or action potential, to the next neuron.

You can think of it as a positive or negative reward. If a child has a behavior and we give the child a cookie, a positive reward, that child is more likely to continue that behavior. If a child gets a negative consequence, or punishment, then the child is less likely to continue the behavior. Remember, positive keeps the signal going and negative makes it stop!

The Synapse

One neuron connects to another at a place called the synapse. Each neuron starts with dendrites that receive signals; a cell body containing the nucleus; an axon that carries the electrical part of the signal; and the final terminal of the neuron, called the axon terminal. Below is a diagram of the structures in a neuron.

Structure of a neuron
neuron structure

Postsynaptic Potentials

The synaptic terminal of the first neuron, or presynaptic neuron, connects to the dendrites of the next neuron, the postsynaptic neuron, to send the message. At the synapse, the electrical signal of the presynaptic neuron is converted to a chemical signal, called a neurotransmitter. Neurotransmitters attach or bind to proteins on the postsynaptic dendrites, called receptors. Below is a diagram of a signal being communicated between two neurons.

Structure
Structure of a synapse

The postsynaptic receptors allow positively or negatively charged ions into the next cell. The charge in the postsynaptic neuron resulting from this is called the postsynaptic potential. The neurotransmitters are like the reward or consequence we give our child. The reward is like a neurotransmitter that causes positive ions to enter the postsynaptic cell, and the punishment is like a neurotransmitter that causes negative ions to enter the cell. The postsynaptic potential is like the behavior of the child - either it continues or does not based on the reward or punishment, the type of ions.

Below is a diagram of the postsynaptic neuron sending neurotransmitters to the dendrites of the postsynaptic cell.

Electrical and Chemical Communication Between Neurons
synapse structure

Inhibitory Postsynaptic Potentials

If the post synaptic potential makes the postsynaptic neuron more negative, it is called an inhibitory postsynaptic potential. Remember our example of the child. If he gets a punishment, he doesn't continue the behavior. So, our neuron is not going to continue the signal (as suggested by the name, inhibitory postsynaptic potential, the signal is inhibited, or stopped).

Neurotransmitters

There are several kinds of neurotransmitters that can cause an inhibitory postsynaptic potential, just like there are lots of different punishments for our child. The most prominent neurotransmitter is called GABA, or gamma-aminobutyric acid. GABA is released from a presynaptic neuron and binds to receptors on the postsynaptic neuron. The receptors open, and negative ions go into the postsynaptic neuron, making it less likely to continue the signal. Usually, the ion that comes into the cell is chloride. The chloride channels open when neurotransmitters like GABA bind them, enter the cell, and make it more negative.

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