EPSP & IPSP

Understanding Postsynaptic Potentials

Types of Postsynaptic Potentials

• Postsynaptic potentials caused by neurotransmitter chemicals can be either:

• Depolarizing: Often results in an excitatory postsynaptic potential (EPSP).

• Hyperpolarizing: Results in an inhibitory postsynaptic potential (IPSP).

Propagation and Integration of Signals

• Postsynaptic potentials diminish as they spread along the dendritic membrane, leading to:

• More distant synapses producing weaker signals compared to those closer to the axon hillock.

• Most synapses generating potentials that are below the threshold for action potentials.

Summation of Synaptic Inputs

• When two excitatory synapses activate simultaneously, their local depolarizations can sum up:

• This summation can reach the threshold at the axon hillock, triggering an action potential.

Role of Inhibitory Synapses

• Active inhibitory synapses stabilize the membrane potential below threshold:

• They induce hyperpolarizations or sub-threshold depolarizations that prevent reaching action potential levels.

Temporal and Spatial Summation

• The neuron integrates inputs through two types of summation:

• Temporal Summation: Occurs when postsynaptic effects happen close together in time, enhancing overlap and summation.