1.1 Synapses and APs

Briski (still)

how are neurotransmitters released from the synaptic cleft

exocytosis

types of synaptic transmission

axodendritic

axoaxonic

axosomatic

axodendritic transmission meaning

axon of one neuron to the dendrites of another

axoaxonic transmission meaning

axon of one neuron to the axon of another

axosomatic transmission meaning

axon of one neuron to the soma (cell body) of another neuron

fast chemical transmission synapses typically occur when the transmitter binds to…

receptors associated with ligand gated ion channels

fast chemical transmission synapses transmit which type of vesicles

low MW, and small

slow chemical transmission synapses have the transmitters packaged in ____ vesicles at a ____ distance from the cleft

larger, greater

slow chemical transmission synapses usually transmit..

high MW peptides

slow chemical transmission synapses act on ___ receptors

G protein linked

EPSP

excitatory post synaptic potential

EPSPs are mostly due to

Na conductance

IPSP

inhibitory post synaptic potential

IPSPs occur when…

a voltage change that hyperpolarizes the membrane and decreases the probability of an action potential

quantum

number of neurotransmitter molecules in a single synaptic vesicle

single channel current

ion flow due to activation of a single receptor

synaptic current

sum of all single channel currents at a single synapse

unitary post synaptic potential

the graded electrical response in a postsynaptic neuron that results from the activation of a single presynaptic input, usually by the release of one or a few vesicles of neurotransmitter from that single input

chemically activated ion channels remain…

open as long as a transmitter is bound to it

chemically activated ion channels are not sensitive to…

changes in membrane voltage

EPSP and IPSP are short lived because…

transmitters are always removed form the cleft

how are transmitters removed from the clef during synaptic transmission

transpport back into the presynaptic terminal (reuptake)

passive ion channels are located…

throughout the nerve cells

how are passive ion channels identified

according to the specific ions that allow it to pass

chemically activated ion channels are found…

primarily on cell bodys of axons and dendrites

chemical activated ion channels are generally closed by ____ that prevent ion flow through the membrane

gates

chemically activated ion channels open due to

neurotransmitter binding to receptors

where are voltage gated ion channels found

primarily on the axons

when do voltage gated ion channels open

when membrane voltage reaches a crucial or activating value

membrane potential is maintained by

K ion distrubutoin

resting potential of an AP is about

-75

resting potential is maintained by..

energy dependent Na/K ATPase-mediated movement of 2 K ions in and 3 Na ions out of the neuron

the membrane is freely permeable to ___

Cl-

Cl- is able to….

move out of the cell down and electrical gradient

threshold

-55

explain the purpose of the threshold

if a sufficient change in the positive direction occurs then depolarization can occur, this happens in the initial segment of the axon

voltage gated Na channels have ___ gates and ___ operational states

3, 2

what are the voltage gated Na channel gates

activation and inactivation

what are the operational states of voltage gated Na channels

resting, activation, inactive

voltage gated K channels have ____ gates and ___ operational states

1,2

what are the operational states of the voltage gated K channels

open and closed

stage 1 of an AP

resting stage

what occurring in the resting stage of an AP

Na channels are at a resting state

stage 2 and 3 of an AP

depolarization

what happens during depolarization

slow initial stage where stimuli activate the Na channels, threshold is met and leads to more Na channels activating due to positive feedback or regenerative processes

stage 4 of AP

repolarization

what happens in the repolarization stage of a AP

Na inactivation gates close independently of the activation gates, K efflux increases

5th stage of AP

hyperpolarization

what happens during the hyperpolarization stage

more K than requires leaves than needed to to assume resting potential, increased internal negative charge

nerve impulse

an AP that travels distally along the axon, starting at the initial segment

sink

depolarized area where Na ions flow inward

source

neighboring areas that supply Na ions, positive charges move along the interior of membrane from sink to source which depolarizes the source