Neuronal excitability

Galvani

Animal electricity

electrical currents triggered muscle spasms

aldini

public demonstrations galvanised criminal bodies

Action potential

Inside cell -ve K+ leakage channels allow K+ leave

V-Na+ channel opens & enters cell down a gradient

Na+ close, K+ opens & leaves cell making it more -ve

Na+/K+ ATPase restores ion gradients

hodgkin & huxley

giant squid axon 1mm thick

current and voltage controlled by experimenter using different clamps to measure the voltage and ionic currents

results of hodgkin & huxley experiment

Identified Na+ and K+ currents underlying AP

developed maths model for neuron excitability

how does Na+/K+ work

3 Na move outside whilst 2 K move inside

require energy from ATP hydrolysis

Ca²+ ATPase pump

ca²+ moves against gradient to move outside uses energy from atp hydrolysis

KCC

use K+ gradient from Na+/K+ pump to move Cl^- out of cell

excitable cells

have resting potential & can also generate action potential

tetrodotoxin

blocks V-gated Na+ channels stops generation of AP