L5 Resting Membran Potential Flashcards
Do all living cells have some resting potential?
Yes
What’s the membrane potential present in cells of non-excitable tissues?
A constant
What’s resting potential ?
Difference that exists across the membrane of excitable cells at a steady state
What are the two excitable tissues?
Muscles and nerves
What’s the resting membrane potential of a neuron?
-70mV
What’s the resting membrane potential of a muscle cell?
-90mV
Which ion has a greater influence on RMP?
K+ because higher conductance at rest
Ohms law/Goldman equation
Estimates membrane potential knowing equilibrium potentials and conductances for each ionic species in a question
Em= (gkEk + gNaENa + gClECl + gCaECa) /(gK+gNa+gCl+gCa)
g = conductance
E depends only on conc gradient of ion out and ion in
Conductance changes as
More channels open
Short version of ohms law/ Goldman equation
Em= (gKEk+gNaENa)(gK+gNa)
If K + channels suddenly open with no concentration gradients or other property changes what happens to E memb?
gK goes up
And therefore Ememb gets more neg
Now cell is hyperpolarized
Hypokalemic means
Lower K+ in ECF than normal
Hyperkalemic means
Higher K+ in ECF than normal
What happens to a severely hypokalemic patients RMP?
Hyperpolarized RMP
gets more negative
Further away from where it needs to get to be able to activate
What happens if a muscle becomes hyperpolarized?
They can’t contract properly
Can lead to paralysis, suffocation, asystole
What happens to a severely hyperkalemic patients RMP?
Depolarized RMP
Gets more positive
Fire more often that normal
What happens if a neuron RMP becomes depolarized?
They fire more often
Tingling sensation
Muscle twitch
Bradycardia or arrhythmia
Severe hyperkalemic can lead to paralysis as the neurons and muscles enter into a state where they cannot reset or fire again
Na+-K+ATPase transfers what?
3 Na + out
2 K+ in
Contributes only 5-20mV to RMP
Diffusion of ions down conc gradient is the primary mechanism that maintains RMP
Overall the sodium potassium pump doesn’t contribute to RMP
It just maintains it
Most membrane potential is caused by the diffusion of sodium and potassium down conc gradients though backgrounders channels
Increase ECF K+ or Na+ both lead to
Depolarization of RMP
Decreased ECF K+ or Na+ lead to
Hyperpolziaton of RMP
At rest, there’s a high permeability to
Potassium
