Chapter 4 - Electrical Properties of Neurons Flashcards

neural membrane sensitive to electrical change

bigger molecules can pass if energetically favorable, eg. water molecules surrounding molecules such as K+, easier to pass through than Na+ since energetically favorable to do so

persistently open

sensitive to electrical potential, depends on membrane charge

iontropic receptors, open in response to ligands (neurotransmitters)

sensory systems, respond to unique stimuli

eg. skin, hair cells...

constant movement of ions, no net movement of charge, balanced

Ex = 58 log ([x]o/[x]i)

Ex = RT/zF ln([x]o/[x]i); calculates reversal potential for given ion x; assumes all channels are open

ideal gas constant; 8.314 J/K*mol; way to convert # of molecules and energy that molecules exert

temperature; ~292K

electrical charge; predict direction of ion movement based on ion charge; represents influence exerted by electrical gradient

Na+ and K+; z = +1

Cl- = -1

Ca2+ = +2

faradays constant; 96,485 coulombs/mol

combines Nernst equation w/ 3 relevant ions (K+, Na+, Cl-)

gives value of membrane potential Vm; explains how movement of Na+ across membrane causes cell to become more positive.

permeability; the higher the permeability the higher the Vm is to the Ex of that ion

-70mV, dominated by

pk = 1, pcl = 0.55, pNa = 0.04

-80mV, -60mV, +55 mV

around -55 mV

short lasting change in membrane potential that travels down axon; driven by ion movement

subthreshold changed in Vm

Vm becomes more positive

Vm becomes more negative

...

neurotransmitters from presynaptic neurons cause ion movement via postsynaptic ligand-gated ion channels. postsynaptic potentials PSPs - small deviations in membrane voltage, release of EPSPs cause small depolarizations, IPSPs cause small hyperpolarizations

2 EPSPs from 2 adjacent inputs

multiple EPSPs from same input close in time

depolarization past threshold opens these channels leading to the influx of Na+ into the cell leading to further depolarization with a peak of around +40 mV

large depolarization leads to a more positive cell, this positive charge pushes K+ out of the cell; the opening of these channels leads to the Vm becoming more negative than resting potential (closer to Ek)

when cell reaches + potential, channels innactivate, prevents movement of excitatory, depolarizing Na+ ions

cell becomes negative again, since K+ leaves the cell. hyperpolarization stops, membrane potential returns to equilibrium of resting potential

depolarization, repolarization, and afterhyperpolarization

Vm becomes more positive due to Na+ influx

K+ channels open

Na+ channels inactivate

K+ driven out of the cell

Vm becomes more negative

gradual deactivation of K+ channels

time window where 2nd action potential cnanot be fired

happens because Na+ voltage-gated channels are innactivated

exists on a gradient, more difficult to fire action potential

Na+ channels reset @ inactive state

K+ channels still open, movement still happening

movement of K+ hinders depolarization

1. Na+ moves to lower conc. unlikely to move backward

2. previous patch is in absolute refractory period, impossible for action potential to travel backwards

layer of lipid coatory axon. increases conduction velocity, speed by which action potential travels down length of axon.

works by blocking K+ leak channels in membrane

causes + charge to be unable to exit cell

signal moves rapidly

AP jumps from node to node