Chemical Synapses

EPSP

excitatory postsynaptic potentials

IPSP

inhibitory postsynaptic potentials

An EPSPs is a...

local depolarization of the postsynaptic membrane

What happens when a neurotransmitter binds to chemically gated channels at excitatory synapses?

It opens the channels, allowing simultaneous flow of Na+ and K+ in opposite directions.

What is the effect of Na+ influx compared to K+ efflux at excitatory synapses?

Na+ influx is greater than K+ efflux, causing a net depolarization.

What role does an EPSP play at the axon hillock?

An EPSP helps trigger an action potential if it is of threshold strength and opens the voltage-gated channels.

An IPSPs is a...

hyperpolarization of the postsynaptic membrane

What happens when a neurotransmitter binds to inhibitory synapses?

It opens channels for K+ or Cl-.

What effect does the opening of K+ or Cl- channels have on the postsynaptic membrane?

It causes hyperpolarization, making the inner surface of the membrane more negative.

How do inhibitory synapses affect a postsynaptic neuron's ability to produce an action potential?

They reduce the neuron's ability to produce an action potential.

Summation

add together

Summation by the postsynaptic neuron

A single EPSP cannot induce an AP, but EPSPs can summate to influence postsynaptic neuron

Two types of Summation

temporal and spatial

Temporal summation

One or more presynaptic neurons transmit impulses in rapid-fire order

Spatial summation

Postsynaptic neuron is stimulated by large number of terminals simultaneously

synaptic potentiation

Repeated use of synapse increases ability of presynaptic cell to excite postsynaptic neuron

Long-term potentiation

involved in learning and memory