Active potential is

temporary, quick changes in membrane potential

What is potential difference?

difference between two points
separation of charges

What determines electrical force?

Shorter the distance, greater force
Longer distance, less force

Force increases with

quantity of charge

Electrically, the cell is?


The difference in electrical charges is located?

at cell membrane

To keep membrane at -7omv (RMP)

Concentration Gradient
Nonstop Na/K pump
permeability of membrane

What ions is the membrane permeable to?


Reason for NA/K pump?

to keep the Resting Membrane potential at -70mv

How does NA/K pump work?

3 NA out
2 K in

What causes net movement of ions across a membrane?

Concentration Gradient
Electrical potential

What is equilibrium potential?

buildup of positive charge in one compartment produces an electrical potential that exactly offsets the other chemical's concentration gradient. (equal in magnitude but opposite in direction)

What is the equilibrium potential for K+, no net movement of this ion?


Electrical Signals are sent how?

Ion Movement
Graded Potentials
Action Potentials

Which ion has biggest factor for electrical force and why?

K+. it is closer to the resting potential at 90 MV. Concentration is higher & membrane 20x more permeable to K+ than Na+

How is does the resting membrane potential convey information?

When stimulus is applied, membrane is extremely permeable to Na (more outside than in-concentration gradient)

NA rushes in

the inside of cell becomes + charge

NA/K pump is activated by (ATPase)

What is the equilibrium potential for Na+, no net movement for this ion?


What equation predicts membrane potential for single ion of NA & K?

Nernst equation

Action potentials strength is determined by?

Greater the strength, greater the disturbance. Depends on Na+ rushing into cell body

Membrane potential is influenced by

concentration gradient of ions
membrane permeability to those ions

What is the concentration of Na+, Cl-, K+ outside cell?

Na+ 145
Cl- 100
K+ 5

What is the concentration of Na+, Cl-, K+ inside cell?

Na+ 15
Cl- 7
K+ 150

How do you do the Nernst Equation?

Eion=61/z log {ion}out/[ion}in

plug in concentration of ion

What equation combines NA, K, Cl concentrations?

GHK equation

AP are sensitive to?


What is the average threshold to trigger an AP?


AP is the

quick change in membrane permeability after threshold stimulus applied. (strong spikes over -55mv)

What happens during graded potential in a neuron?

decreemental-spread away from point of stimulus, becomes weaker as they progress

depolarization strength is proportional to stimulus

Graded potentials are important for

sending signals over short distances

AP are important for

sending signals over long distances of neuronal & muscle membranes

Depolarization is when the potential goes from

- to 0

Repolarization is when the potential goes from

+ to RMP

hyperpolarization is when the potential is

more - than RMP

subthreshold value

below threshold value

Na+ ion channel can be


Na channels can only go from inactive state to


Magnitude of stimulus doesn't matter in what potential?


What is the only thing that can open Na Voltage gated channels

When the RMP is at -70mv

What causes Na channels to become inactive?

opening K channels at peak and renentry state

Supramaximal stimulus is when the

K+ is still open
Na+ not completely closed

When supramaximal stimulus happens, what period is it said to be in?

relative refactory period

Why only AP in trigger zone?

abundant voltage gated channels

why is refractory period a limitation?

2 signals can't be summed up

Conduction of signals happen in

myelinated and unmyelinated axons

Myelinated are located in what NS? is it fast or slow conduction of signal?

PNS, fast

Unmyelinated are located in what NS? is it fast or slow conduction of signal?

CNS, slow because of ions move out & in has resistance

Myelinated conduction is called the

saltatory conduction.

What is saltatory conduction?

AP leap node to node, only needs Na+

What is mylenated made from?

lipid tissue
acts as insulation
cytoplasm cannot leave

What has faster Conduction, thin or thick Axons?

Thicker and myleinated, because has less resistance

Effect of extracellular K+ concentration of excitability of neurons

normokalemia- -70mv RMP

Hyperkalemia- -60 RMP (closer to threshold) More K outside cell-doesn't take much to get to threshold (tachycardia)

Hypokalemia--80 RMP harder to get to threshold

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