Exam 1 Flashcards Chapter 3 &4
(30 cards)
Cell is ____ times more permeable to K+ than to Na
25-30
When the membrane is more permeable to potassium ions than it is to sodium ions, the inside of the cell is _______
negatively charged
When the membrane is more permeable to sodium ions than it is to potassium ions, the inside of the cell is _________
positively charged
The membrane potential of the cell is determined by
the permeability of the membrane to potassium ions with respect to sodium ions.
In general, nerve and muscle cells change their permeability between Na+ and K+ not by changing the number of channels, but by ______
opening or closing pores through the channels.
The potassium and sodium ion gradients across the membrane are also important. They determine the magnitude of the ________
Equilibrium potential for each ion
if cell is permeable to potassium only the equilibrium potential for potassium Ek is
-94 mV
if cell is permeable to sodium only the equilibrium potential will be Ena
Ena = +60 mV
The resting cell is much more permeable to ____ than to ____
The resting cell is much more permeable to K+ than to Na+.
resting membrane potential for cell is usually ____
-70
Polarization
Unequal distribution of positive and negative charges across a molecule, or in this case, a membrane)
Permeability of the plasma membrane at rest is much greater for ______ than for any other ion.
Permeability of the plasma membrane at rest is much greater for potassium than for any other ion.
(for right now in this class)
The sodium-potassium ATPase pump maintains ion gradients (low sodium, high potassium _____ the cell & vice-versa ____ the cell).
The sodium-potassium ATPase pump maintains ion gradients (low sodium, high potassium inside the cell & vice-versa outside the cell).
the concentration gradient for K+ will always be ___
outward
the concentration gradient for Na+ will always be ______
inward
the membrane potential is due to differences in the concentration and the permeability of key ions, especially ________
K+ and Na+
Note, however, that there are anions in the ECF (primarily Cl-) and in the ICF (primarily proteins) that also contribute to the _______
Note, however, that there are anions in the ECF (primarily Cl-) and in the ICF (primarily proteins) that also contribute to the resting membrane potential.
all cell types possess a _____
membrane potential
2 of the most excitable cell types are
neurons and muscle cell
depolarization
decrease in potential membrane less negative
repolarization
return to resting potential after depolarization
hyperpolarization
increase in potential membrane more negative
The size of the change in membrane potential diminishes with distance traveled (graded potentials are _______) because of “current” loss.
The size of the change in membrane potential diminishes with distance traveled (graded potentials are decremental) because of “current” loss.
local current flow
causes the change in membrane potential (depolarized area in the previous slide) to spread from the site of initiation
