Section 4.2- Action Potentials

Proteins found in neuron cell membrane:

Sodium gated channels

Open/ close based on conditions to allow facilitated diffusion of Na+ ions

Proteins found in neuron cell membrane:

Potassium gated channels

Open/close to allow for facilitated diffusion on K+ ions

Proteins found in neuron cell membrane:

Sodium/potassium pump

Works constantly, uses ATP to move Na+ ions and K+ ions against concentration gradient through active transport

Resting Potential

Both protein channels closed

cell membrane is polarized meaning more negatively charged inside than outside as pump is moving Na+ to outside and K+ to inside

Charge of -70mV

Depolarization

Stimulus causes Na+ channels to open allowing sodium to rush into the cell

Causes charge inside cell to increase

If stimulus is strong enough an action potential is generated

Repolarization

When the charge inside the cell reaches 40 mV causing the Na+ channels to open

K+ rushes out of the cell causing charge inside cell to decrease

Hyperpolarization

So much K+ leaves the cell that the charge inside the cell drops to -80mV

Threshold Potential

Stimulus needs to be strong enough to keep Na+ channels open long enough to reach -55mV

If not immediately returns to resting potential but if so, the charge will go to +40mV

Impulse Propagation

An action potential in one set of membrane proteins provides the stimulus for an action potential in another allowing action potentials to travel down the neuron

Salutary Conduction

Transmission of impulse through a myelinated axon

Faster and more efficient

Action potentials only need to occur at Nodes