Nervous System Flashcards
membrane potential
the separation of charges across the membrane or the difference in the relative number of cations (+) and anions (-) in the intracellular fluid (ICF) and extracellular fluid (ECF).
Refers to the difference in + and - charges along the thin layer of ICF and ECF membrane.
When does a membrane potential exist?
when the number of positive and negative charges on each side of the membrane are unequal. the excess of negative charges on one side are attracted to the excess of positive charges on the other so they huddle close to the membrane on their respective sides.
Resting membrane potential
the constant membrane potential of cells of non-excitable tissues and excitable cells when they are at rest (not producing electrical signals)
-70mV
Where is Na greatest in concentration, K, A-?
Na: extracellular Fluid
K: Intracellular Fluid
A-: Intracellular Fluid ONLY
How are the concentrations of NA and K maintained?
By the Na+ K+ Pump at the expense of ATP
At Resting potential describe the permeability of Na and K
The membrane allows the movement of both across the membrane but its permeability to K+ is greatly increase (50-75 x greater) due to more K+ channels being open at resting potential.
In which directions are the concentration gradients for Na and K and why?
Na gradient will ALWAYS be inward
K gradient wil ALWAYS be outward
because the Na+-K+ pump maintains a higher concentration of K+ inside the cell and a higher concentration of Na outside the cell
In which direction are the electrical gradients for Na and K?
since they are both positive ions, the gradient will ALWAYS be toward the negatively charged side of the membrane.
what is the K+ equilibrium potential? (Ek+)
the potential that exists when the concentration gradient (moving ions outside) and electrical gradient (pulling ions inside) are equal and opposite to each other.
-90mV (Inside being more negative)
What is the Na+ equilibrium potential? (Ena+)
the potential that exists when the concentration gradient (Moving ions inside) and electrical gradient (moving ions outside) are equal and opposite to each other.
+60mV (Inside being more positive)
What accounts for the difference between the K+ equilibrium potential and Na+ equilibrium potential?
The concentration gradient for Na+ is not as strong as that of the K+ gradient so the electrical gradient is smaller as a result
When the permeability of the plasma membrane increases for a given ion, what happens to the membrane potential?
The ion has a tendency to drive the membrane potential towards the ions own equilibrium potential
