How do stimulatory neurotransmitters affect the membrane potential of postsynaptic membrane?

Stimulatory neurotransmitters exert their effects by increasing the membrane potential of the postsynaptic membrane, bringing it closer to the threshold potential and thus increasing the likelihood of an action potential being generated. This process involves the following steps:

Binding to Receptors: Stimulatory neurotransmitters, such as glutamate or acetylcholine, are released into the synaptic cleft upon the arrival of an action potential at the presynaptic terminal. These neurotransmitters bind to specific receptors on the postsynaptic membrane.

Ion Channel Opening: The binding of the neurotransmitter to its receptor causes a conformational change in the receptor protein, leading to the opening of ion channels. These channels are usually cation channels, allowing positively charged ions such as sodium or calcium to flow into the postsynaptic neuron.

Depolarization: The influx of positive ions into the postsynaptic neuron leads to depolarization of the membrane potential. This means that the inside of the neuron becomes less negative compared to the outside.

Graded Potential: The depolarization caused by stimulatory neurotransmitters is graded, meaning that the magnitude of the depolarization depends on the amount of neurotransmitter released and the number of receptors activated.

Excitatory Postsynaptic Potential (EPSP): The depolarization of the postsynaptic membrane in response to the binding of stimulatory neurotransmitters is referred to as an excitatory postsynaptic potential (EPSP). EPSPs bring the membrane potential closer to the threshold potential, increasing the likelihood of an action potential being generated.

It's important to note that the effects of stimulatory neurotransmitters are opposed by inhibitory neurotransmitters, which cause hyperpolarization (a decrease in membrane potential) and make it less likely for an action potential to occur. The balance between excitatory and inhibitory inputs determines the overall electrical activity of the neuron.