Neuron Physiology Terms & Definitions - Biology Study Set

a difference in electrical charge between one point to another

voltage

a flow of charged particles from one point to another

electrical current

pumps

move substances across their concrentration gradient. require ATP.

channels

protein pores in the membrane that allow ions to move down their cnocrentration graident. do not require energy

leak channels

always open for continuous diffusio

chemically gated channels

normally closed by open when a neurotransmitter binds to it

voltage gated channels

are normally closed but open when the membrane charge changes

how many gates does a voltage gated channel have

2 gates: activation and inactivation gate

resting state of voltage gated channel

AG closed; IG open. Na+ entry prevented

activation state of voltage gated channel

AG: open. IG: open. Na moves thoruhg

inactivation state

AG: Open. IG: closed. entry of Na prevented. very short before resetting to resting state.

modality gated channels

normally closed but can open due to a stimulus otheer than chemical/voltage chnages. usally something in the encironment (pressure)

receptive segment

dendrite and cell body.

what kind of channels are on the receptive segment

chemically gated channels

initial segment

axon hillock

what kind of channels are on the initial segment

voltage gated Na and K channels

conductive segment

axon and its branches

what kind of channels are on the conductive segment

voltage gated Na and K channel s

transmissive segment

synaptic knob

what kind of channels are on the transmissive segmnet

voltage gated Ca2+ channels and Ca2+ pumps

what kind of channels do you see in general throughout the whole neuron

Na and K leak channles, along with NaK pumps

what is the distribution of Na and K in aneuron that is at rest

more K in the cell, more Na outside the cell

what is the resting membrane potential of a neuron

-70 mv

where does summation of graded potentials occur

the initial segment

small, short lived changes in RMP

graded potentials

where are graded potentials established

in the receptive segment by the opening of chemically gated ion channels

T OF F: graded potentialls vary in degree ; large or small

true

EPSP

excitatory postsynaptic potential. results in depolarization (more +)

IPSP

inhibitory postsynaptic potential. results in hyperpolarization (-)

how is an EPSP generated

when neurotransmitters are released from the presynaptic neuron, cheical channels on the postsynaptic ions open. Na also flows into it. inside of neuron becomes more positive called EPSP. EPSP will move toward initial segment.

how is an IPSP generated

neurotransmitters cause either chemically gated K+ or Cl- chsnnels open. K+ either leaves of Cl- comes in. inside of of neuron gets more negative and moves toward initial segment.

how can an action potential be produced at the axon hillock

if the summation of the EPSP and IPSPs reach the threshold for an action potential. the threshold is about -55 mV. you need to have more EPSP than IPSP

what happens if threshold membrane potential is reached at the initial segment

voltage gated channels open and an action potential is generated.

spacial summation

multiple locations on the cells receptive regions receive EPSP and IPSPs (multiple stimulus, different locations

temporal summations

a single presynaptic neuron repeatedly releases neurotransmitter and produces multiple EPSP in a short period of time. (same place, multiple stimulus)

T or F: the action potential is the same intensity even if its greater than threshold

true

depolarization

gain of posiitve charge as Na enters the coltage gated Na channels

repolarization

return to negative poential as K+ exits through voltage gated K channels

nerve signal

the propogation of action potential down the axon

what is the potenial at depolarization

+30

What is the value for hyperpolarization of the nervous cell

-80

refractory period

period of time after the action potential when it is impossible/difficult to fire another action potential

absolute refractory period

no stimulus can initiate another action potensital.

relative refractory period

the cell is still in hyperpolarization, so you can have another stimulus but you now need a greater amount to reach the threshold.

continuous conduction

occurs on unmyelinated axons. takes more ATP and is slower.

saltatory conduction

occurs on myelinated sheaths. AP only occurs at the neurofibril nodes which is where the voltage gated channels are. jumping from node to node. faster and uses less ATP.

what happens at the transmissive segment after an action potential

arrival of action potential at teh Ca channels. Ca diffuses into the knob and binds to the synaptic vessicles. and they are storing neurotransmitters and let them out via exocytosis.

T or F: thicker fibers conduct faster signals than thin oens

true

explain amplitude and frequency of action potential

amplitude of AP always stays the same, but the frequency (action potentials per second) can speed up ro slow down.