Synaptic Integration

electrotonic signal spread

membrane depolarization falls off exponentially with increasing distance along a dendrite

Dendritic length constant (lambda)

measure of how far a signal can spread passively before it fades

excitable dendrites

In order to boost the transmission of a excitatory synaptic event to the soma, _________ are at work

Na+, K+, and Ca2+

what type of voltage gated channels do dendrites have?

EPSP Summation

Allows for neurons to perform sophisticated computations

spatial summation

the adding together of EPSPs generated simultaneously at many different synapses on a dendrite

temporal summation

the adding together of EPSPs generated at the same synapse if they occur in rapid succession, within about 1-5 msec of one another

Synaptic Integration, summation

process by which multiple synaptic potentials combine within one postsynaptic neuron

GABA

What neurotransmitter commonly generates IPSPs in the brain?

GABA_A ​ receptor

What type of receptor does GABA bind to for IPSP generation?

Chloride (Cl⁻) channels

What type of ion channel is opened by GABAA_A​ receptors?

membrane becomes more negative (hyperpolarized), producing an IPSP

What happens when Cl⁻ enters the postsynaptic neuron?

decreases the likelihood by taking the membrane potential further from threshold

How does an IPSP affect the likelihood of an action potential firing?

Excitatory vs inhibitory synapses

bind different neurotransmitters, allow different ions to pass through channels

IPSP will have hyperpolarizing effect

What happens if membrane potential is less negative than -65mV (ex. -50mV)?

Shunting inhibition

Synapse inhibits current flow from soma to axon hillock

Synaptic Transmission Modulation

signalling events that modifies the

strength of synaptic transmission

(i.e. activating G-protein

coupled norepinephrine β-receptor)

Autoreceptors

presynaptic receptors sensitive to the neurotransmitter released by the presynaptic terminal

inhibition of neurotransmitter release

What is the common consequence of activating autoreceptors?

prevent the neuron from over-releasing neurotransmitter

Function of autoreceptors