key term - EPSP

Definition

EPSP stands for Excitatory Postsynaptic Potential, which is a change in the electrical potential across the postsynaptic membrane of a neuron caused by the binding of excitatory neurotransmitters released from the presynaptic terminal. This depolarization of the postsynaptic membrane brings the neuron closer to the threshold for generating an action potential.

5 Must Know Facts For Your Next Test

1. EPSPs are caused by the binding of excitatory neurotransmitters, such as glutamate, to receptors on the postsynaptic membrane.
2. The depolarization of the postsynaptic membrane brought about by an EPSP brings the neuron closer to the threshold for generating an action potential.
3. EPSPs are additive, meaning that multiple EPSPs occurring in close temporal and spatial proximity can summate to reach the threshold for an action potential.
4. The magnitude of an EPSP is influenced by factors such as the number of neurotransmitter receptors, the conductance of the postsynaptic membrane, and the distance from the site of the EPSP to the action potential initiation zone.
5. Inhibitory Postsynaptic Potentials (IPSPs) can counteract the depolarizing effects of EPSPs, making it less likely for the neuron to reach the threshold for an action potential.

Review Questions

• Explain how the binding of excitatory neurotransmitters to the postsynaptic membrane leads to the generation of an EPSP.
  • When an excitatory neurotransmitter, such as glutamate, is released from the presynaptic terminal and binds to receptors on the postsynaptic membrane, it causes the opening of ion channels that allow positively charged ions, such as sodium or calcium, to flow into the postsynaptic cell. This influx of positive ions leads to a localized depolarization of the postsynaptic membrane, creating an Excitatory Postsynaptic Potential (EPSP). The EPSP brings the postsynaptic neuron closer to the threshold for generating an action potential, which can then be propagated along the neuron's axon to transmit the signal to the next cell in the neural circuit.
• Describe how the summation of multiple EPSPs can lead to the generation of an action potential.
  • EPSPs are additive, meaning that multiple EPSPs occurring in close temporal and spatial proximity can summate to bring the postsynaptic neuron closer to the threshold for generating an action potential. If the combined depolarization from several EPSPs is strong enough to reach the threshold, it will trigger the opening of voltage-gated sodium channels, leading to the generation of an all-or-nothing action potential. This action potential can then be propagated along the neuron's axon to transmit the signal to the next cell in the neural circuit. The summation of EPSPs is a crucial mechanism for integrating and processing information within the nervous system.
• Analyze how the characteristics of the postsynaptic membrane and the location of the EPSP can influence the likelihood of action potential generation.
  • The magnitude of an EPSP, and its ability to contribute to the generation of an action potential, is influenced by several factors related to the postsynaptic membrane and the location of the EPSP. The number and distribution of neurotransmitter receptors, the conductance of the postsynaptic membrane, and the distance from the site of the EPSP to the action potential initiation zone (usually the axon hillock) can all affect the strength and impact of the EPSP. For example, EPSPs that occur closer to the action potential initiation zone will have a greater influence on the neuron's likelihood of reaching the threshold for action potential generation. Additionally, the presence of inhibitory postsynaptic potentials (IPSPs) can counteract the depolarizing effects of EPSPs, making it less likely for the neuron to reach the threshold for an action potential. Understanding these factors is crucial for comprehending how the integration of excitatory and inhibitory inputs at the postsynaptic membrane ultimately determines the neuron's output.

Related terms

Action Potential:

A brief, all-or-nothing electrical signal that travels along the length of a neuron's axon, transmitting information to other neurons or effector cells.

Neurotransmitter:

A chemical substance released by the presynaptic terminal of a neuron that binds to receptors on the postsynaptic cell, triggering a response.

Postsynaptic Membrane: The membrane of the postsynaptic cell that receives signals from the presynaptic terminal across the synaptic cleft.