Neurons and Action Potentials

What is equilibrium potential

Membrane voltage where there is no net ion movement

Equilibrium potential is determined by what 2 things, which one is variable

Concentration and electrical valence; concentration is most variable

What equation is used for equilibrium potentail

Nernst equation

At resting membrane potential, what is the driving force for potassium to enter

Electrical gradient

At resting membrane potential what is the driving force for potassium to exit cells

Concentration gradient

At resting membrane potential, what is the driving force for sodium to enter cells

Concentration gradient and electrical gradient

At resting membrane potential, what is the driving force for sodium to ext cells

None

What is the equilibrium potential for potassium

-90

What is the equilibrium potential for sodium

+60

What is the resting membrane potential and which ion equilibrium potential is it close to

-70; potassium

What ion has more leak channels

Potassium

What equation is used for membrane potential

Goldman-hodgkin-katz

What three things determine membrane potential

Concentration, charge, permeability

What is net movement of ions if equilibrium and membrane potential are equal

No net movement

What is net ion movement if equilibrium and membrane potential are not equal

Net ion movement shifts membrane potential closer to ions equilibrium potential

What is net movement of ions if the equilibrium and membrane potential are of opposite signs

Concentration and electrical gradients going in same direction; ions move down gradients

What is the net movement of an ion if membrane potential is greater than equilibrium potential and both are negative

Potassium moves down concentration gradient and membrane potential becomes more negative

What is net movement of an ion if the membrane potential is less than equilibrium potential and both are negative

Potassium moves down electrical gradients and membrane potential becomes more positive

What is net movement of an ion if membrane potential is less than equilibrium potential and both are positive

Sodium moves down concentration gradient and membrane potential becomes more positive

What is net movement of ions if the membrane potential is greater than equilibrium potential and both are positive

Sodium moves down electrical gradient and membrane potential becomes less positive

What is the movement of ions if within normal range of membrane potential

Downs their concentration gradient

When do voltage gated channels close

When membrane potential returns to resting

When do voltage gated channels open

Attainment of threshold potential

What determines inactivation of voltage gated channels

Time

What determines the threshold potential is reached

Summation of all graded potentials at given time

What is temporal summation

High frequency stimulation by single neuron

What is spatial summation

Simultaneous stimulation by several neurons

Where does summation occur

Axon hillock and transmitted down axon

What is happening at resting membrane potential

Sodium gates closed

Potassium gates closed

Potassium leak channels open

What is happening at depolarization

Voltage gated sodium - open; both gradients favor movement into cell

Voltage gated potassium - closed

Potassium leak - open; both gradients favor movement tout of the cells

What it is important to keep in mind about depolarization and repolarization

weather VMware is positive or negative

What is happening at repolarization

Voltage gated sodium channels - inactive

Voltage gated potassium channels - open; both gradients favor movement out of cell

Potassium leak - open; both gradients favor movement out of cell

What is happening during hyperpolarization

Voltage gated sodium - closed

Voltage gated potassium - open; concentration gradient drives movement out of cell

Potassium leak - open; drives movement out of the cell

What is happening during return to resting potential

Voltage gated sodium - closed

Voltage gated potassium - closing but slowly

Potassium leak - open; drive net movement out of cell

What happens if sodium and potassium are unregulated in plasma

Neurological problems

What is hypoatremia

Low plasma sodium

What is hypokalemia

Low plasma potassium

What is hypermatermia

High sodium in plasma

What is hyperkalemia

High potassium in plasma

How do VGSC inhibitors work

Inhibit voltage gated sodium channel opening which affects sensation of pain by blocking AP

What is tetrodotoxin

Lethal neurotoxin from puffer fish which results in respiratory paralysis

What types of clinical signs might occur with demyelination of neurons

Slowed signals within both sensory and motor neurons.