Postsynaptic potential

Definition

A postsynaptic potential is a change in the membrane potential of a postsynaptic neuron that occurs in response to the binding of neurotransmitters released from a presynaptic neuron. This potential can be either excitatory, leading to depolarization and increased likelihood of an action potential, or inhibitory, resulting in hyperpolarization and decreased likelihood of firing an action potential. The nature of this change is crucial for signal transmission across synapses and ultimately influences neuronal communication and processing.

5 Must Know Facts For Your Next Test

1. Postsynaptic potentials can be graded, meaning they vary in magnitude depending on the amount of neurotransmitter released and the sensitivity of the postsynaptic receptors.
2. Excitatory postsynaptic potentials (EPSPs) typically result from the influx of sodium ions ($$Na^+$$) into the postsynaptic neuron, while inhibitory postsynaptic potentials (IPSPs) often result from the influx of chloride ions ($$Cl^-$$) or efflux of potassium ions ($$K^+$$).
3. The summation of multiple postsynaptic potentials can lead to a stronger overall signal, influencing whether or not an action potential will occur.
4. Temporal and spatial summation are two mechanisms by which postsynaptic potentials combine to reach threshold for action potential generation.
5. The duration and strength of a postsynaptic potential can be influenced by factors such as receptor desensitization and the reuptake or degradation of neurotransmitters.

Review Questions

• How do excitatory and inhibitory postsynaptic potentials differ in their effects on a neuron's likelihood to fire an action potential?
  • Excitatory postsynaptic potentials (EPSPs) increase a neuron's likelihood to fire an action potential by causing depolarization, while inhibitory postsynaptic potentials (IPSPs) decrease this likelihood through hyperpolarization. EPSPs typically occur when neurotransmitters promote the influx of sodium ions ($$Na^+$$), making the inside of the neuron more positive. In contrast, IPSPs often result from the influx of chloride ions ($$Cl^-$$) or efflux of potassium ions ($$K^+$$), making the inside more negative and further away from threshold.
• What role does neurotransmitter release play in generating postsynaptic potentials?
  • Neurotransmitter release is essential for generating postsynaptic potentials, as it involves neurotransmitters binding to specific receptors on the postsynaptic neuron. When an action potential reaches the axon terminal of a presynaptic neuron, it triggers the release of neurotransmitters into the synapse. These neurotransmitters then interact with receptors on the postsynaptic membrane, leading to either excitatory or inhibitory changes in membrane potential, depending on the type of neurotransmitter and receptor involved.
• Evaluate how temporal and spatial summation affect the overall impact of multiple postsynaptic potentials on neuronal firing.
  • Temporal summation occurs when multiple postsynaptic potentials happen in quick succession at the same synapse, potentially amplifying their effect and helping reach the threshold for an action potential. Spatial summation involves simultaneous activation of multiple synapses on a single postsynaptic neuron, allowing different EPSPs to combine their effects. Together, these summation mechanisms enhance signal integration within neurons, determining whether a neuron will fire based on cumulative input from various synapses.

Related terms

action potential: A rapid, temporary change in a neuron's membrane potential that occurs when the neuron is stimulated past a certain threshold, leading to the transmission of an electrical signal along the axon.

neurotransmitter: Chemical messengers released by neurons at synapses that bind to receptors on the postsynaptic neuron, initiating postsynaptic potentials.

synapse: The junction between two neurons, where communication occurs through the release of neurotransmitters from the presynaptic neuron and their binding to receptors on the postsynaptic neuron.