Neurobiology IIII ( Lecture 24-28) Flashcards
What is equilibrium potential.
membrane potential that exactly opposes the concentration gradient.
– charge of the plasma membrane that is equal but opposite to the concentration gradient.
In a cell permeable to only one ion, the _____ equation can be used to calculate the equilibrium potential.
Nernst Equation
The constant 61 in the _____ equation represents what three things
1) Faraday’s constant for electrical forces
2) physiological temperature for 37 degrees
3) universal gas content
The resting potential of a neuron is _____ mV
-70
The greater the ________ to an ion species, the greater the ion species will make to the membrane potential
permeability
Membrane potential for Na+, K+ and Cl- can be calculated through the _________ equation.
GHK
Goldman-Hodgkin-Katz
The resting membrane potential is largely due to the movement of ______ out of the cell.
K+
(T/F) the resting membrane potential is equal to the K+ equilibrium potential
False, there are still small channels of Na+ open in the resting state that may cancel out the effect of some K+ moving out
The Na+ / K+ ATPase pumps pumps ______ out of each cell for every ______ pumped in. This unequal transport results in the inside of the cell to be more ______.
3 Na+
2 K+
negative
The contribution of the Na+/ K+ pump is …
create a small electrical gradient in order for concentration gradients to remain down allowing ions to diffuse to produce charge separation
Transient changes in membrane potential from the resting level produce electrical signals and can occur in the form of ______ and ________
graded potentials
action potentials
Talk about the steps from being polarized to hyperpolarization
- Polarization — Resting membrane potentials starts at -70mV, which means that is is polarized.
- Depolarization– The membrane is depolarized, meaning charges go towards 0.
- Overshoot – This refers to the reversal of the membrane potential. The inside is not more positive compared to the outside
- Repolarizing– When depolarized membrane returns to its resting value
- Hyperpolarized – when potential is more negative than the resting potential
Graded potentials in neurons are depolarizations or hyperpolarizations that generally occur in _____ and ______
cell bodies / dendrites
What are graded potentials?
Graded potentials refer to changes in the membrane potential that are limited to a small area of the plasma membrane. Charges flow from the origin to adjacent regions of the plasma membrane, which are still at resting potential.
Define the steps of graded potential ( 3 steps)
- A region of the membrane has been depolarized by a small chemical signal. The opening of cation channels result in the potential to be less negative than adjacent areas.
- Positive charges ( K+) flow away from the depolarized area toward regions that are more negative
- Outside the cell, positive charge will from more positive membrane regions to less positive regions.
Graded potentials are called “graded” because _____________
magnitude change in potential can vary
In addition to the movement of ions on the inside and outside of cell, charge is ________ because _______
lost across membranes
the membrane is permeable to ions through open membrane channels
Local current is ________, ______ as the distance from the site of the origin of the graded potential increases.
This is also unique to graded potentials
decremental, decreasing
What is Summation ? (unique to graded potentials)
If additional stimuli occurs before the graded potential dies away, they can be added to the depolarization of the first stimulus
________ allow excitable membranes to conduct large, rapid changes in membrane potential called ______.
Voltage-gated ion channels
Action Potentials
When the membrane is at resting potential ( negative) , both K+ and Na+ channels tend to be _____. _______ tends to open them.
Closed.
Depolarization
2 key differences between Na+ and K+ channels.
- K+ channels tend to be slower / more sluggish than Na+ channels. Na+ channels respond rapidly to depolariziation. During repolarization, K+ channels are also slower to close.
- Na+ channels have a state of being inactive that limits the Na+ flux by blocking the channels shortly after depolarization. When the membrane repolorizes, Na+ channels go back to being in a closed state
The resting membrane potential is close to the _____ equilibrium potential because there are more open ____ channels than _____ channels. (these are leak channels)
K+
K+/ Na+
