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51 terms

Resting , graded & action potentials

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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?
neutral
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?
NA+
K+
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?
-90mV
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?
+60mV
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

z=1
plug in concentration of ion
What equation combines NA, K, Cl concentrations?
GHK equation
AP are sensitive to?
voltage
What is the average threshold to trigger an AP?
-55mv
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
open
closed
inactivated
Na channels can only go from inactive state to
closed
Magnitude of stimulus doesn't matter in what potential?
active
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