Electricity

what is key for nerve cell function

interaction between charged particles

intracellular ions

K+, PO4-

extracellular ions

Na+, Cl-

energy

the ability to do work

work

force of moving an object over a distance (FxD)

potential difference

difference in charge of the sides of the cell membrane

other terms for potential difference

electromotive force, electric potential

unit for potential difference

volts

current

the movement of electrical charges across a membrane

unit for current

amperes

current flow

net movement of positive charge

conductance

how well current flows through a given material

another term for conductance

intrinsic conductivity

factors that determines conductance

proportional to area, inversely proportional to length

resistance

blocks current flow (reciprocal of conductance)

ohm’s law equation

V=IR or V=I/g

what is involved in ohm’s law

current, voltage, conductance/resistance

what does ohm’s law do

determines how ions flow across a membrane

types of ion channels

resting, gated, Na/K pump

characteristics of resting channels

always open, bidirectional, maintains the resting membrane potential

types of gated channels

voltage, ligand, mechanical

how to open voltage gated channels

change in membrane potential (charge)

how to open ligand gated channels

binding of neurotransmitters

equation for resting potential

Vm = Vin - Vout

normal resting potential of nerve cells

-60 to -70 mV

major ions that help determine the resting potential

Na+, K+, Cl-, amino acids

driving forces of ions

electrical (potential difference) and chemical (concentration gradient)

nernst potential

the equilibrium potential where the net movement of ions is zero

what is needed to reach equilibrium potential

the chemical and electrical driving forces are equal and opposite

equilibrium potential of potassium (Ek)

-75 mV

equilibrium potential of sodium (Ena)

55 mV

why is the resting membrane potential not halfway between potassium and sodium

there are fewer sodium channels which means less conductance of sodium so the RMP stays closer to potassium

ion flux

(electrical + chemical driving force) x mechanical driving force

what determines membrane conductance

the number of channels that are open

function of the Na/K pump

maintain the correct concentration gradient for RMP

what is the goldman (GHK) equation used for

determines the RMP when multiple channels are open (at rest)