Loai Alzghoul Loai physiologyyahoo com Action Potential ALL

Loai Alzghoul Loai. physiology@yahoo. com

Action Potential = ALL x NOTHING

The Action Potential Equilibrium potential of sodium (+60 m. V) - 75 m. V K Na K K Na Passive increase in positive charge Electrotonic potential Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 3

The Action Potential Equilibrium potential of sodium (+60 m. V) - 55 m. V K threshold Electrotonic potential Na K K Na Opening of voltage-gated sodium channel Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 4

The Action Potential Equilibrium potential of sodium (+60 m. V) - 40 m. V K Na K K Na Depolarisation due to sodium influx Opening of voltage-gated sodium channel Electrotonic potential Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 5

The Action Potential voltage-gated sodium channels turn to the inactivation phase Equilibrium potential of sodium (+60 m. V) + 50 m. V K Na K K Na Depolarisation due to sodium influx Inactivation of voltage-gated sodium channel Electrotonic potential Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 6

The Action Potential Equilibrium potential of sodium (+60 m. V) + 50 m. V K Na K K Na Depolarisation due to sodium influx opening of voltage-gated potassium channel Electrotonic potential Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 7

The Action Potential Equilibrium potential of sodium (+60 m. V) - 85 m. V Repolarization due to potassium influx K Na K K Na Depolarisation due to sodium influx opening of voltage-gated potassium channel Electrotonic potential Resting potential (-75 m. V) Equilibrium potential of potassium (-95 m. V) 8

The Action Potential Membrane potential approaches the ENa and voltage-gated sodium channels turn to the Equilibrium potential of sodium (+60 m. V) inactivation phase - 75 m. V repolarization due to potassium influx K Na K K Na Depolarisation due to sodium influx closing of voltage-gated potassium channel Electrotonic potential Resting potential (-75 m. V) Hyperpolarising afterpotential Repolarisation due to potassium influx 9

The Action Potential Inactivation of voltage-controlled sodium channel Equilibrium potential of sodium (+60 m. V) Opening of voltagecontrolled potassium channel Opening of voltagecontrolled sodium channel threshold Electrotonic potential Resting potential (-75 m. V) Hyperpolarization due to more outflux of potassium ions Dentistry 07 10

Properties of action potentials • Action potentials: +60 • are all-or-none events 0 m. V threshold Stimulus -70 • APs do not summate - information is coded by frequency not amplitude. 11

Recording membrane potential m. V - 60 + - 30 + -0 - 30 - Electrotonic potential Localized non propagated Action potential - 60 - 90 - Dentistry 07 12

Graded Potentials

Excitable cell: NEURON and MUSCLE CELL

Neuron F 8 -2 • Axons carry information from the cell body to the axon terminals. • Axon terminals communicate with their target cells at synapses.

Communication Between Neurons • Electrical synapse Chemical

Recording of Resting and action potentials • It is recorded by cathode ray oscilloscope – -70 m. V + Voltmeter it is negative in polarized (resting, the membrane can be excited) state with the potential difference inside the cell membrane is negative relative to the outside. Dentistry 07 + + + – – – + – + – – + + 19

Terminology Associated with Changes in Membrane Potential F 8 -7, F 8 -8 • Depolarization- a decrease in the potential difference between the inside and outside of the cell. • Hyperpolarization- an increase in the potential difference between the inside and outside of the cell. • Repolarization- returning to the RMP from either direction. • Overshoot- when the inside of the cell becomes +ve due to the reversal of the membrane potential polarity.