Neurons Flashcards
Where is the negative and positive charge in a cell membranes resting potential?
Outside the cell is positive
Inside the cell is negative
What is the term for an electrically charged cell, it is said to be….
Polarized
If positive charges flow into a cell, the potential inside the cell becomes? Which is called?
Less negative
Depolarization
If positive charges flow out of a cell, the potential becomes? What is this called?
More negative
Repolarization
If positive charges flow out of a resting cell or negative charges flow in, what happens to the cells potential? What is this called?
Becomes more negative
Hyperpolarization
Movement of what to the inside of a cell causes depolarization?
Na+ ions
Movement of what to the outside of a cell causes repolarization?
K+
What establishes the resting membrane potential?
The asymmetric distribution on Na+ and K+ ions.
The membrane is selectively permeable to K+ (it’s allowed to leave), but impermeable to Na+
SHE SAYS IT’S K+ LEAKINESS
After a cell repolarizes by K+ ions leaving through the channels, what activates to establish the RMP?
The Na/K pump
How much of each ion does the Na/K pump move?
3 Na+ out for every 2 K+ in
What allows the small amount of K+ to leave the cell and create the RMP?
Non-gated channels are always open and allow “leaking”
What is the difference between the ion movement that occurs with depolarization/repolarization vs the Na/K pump?
During depolarization and repolarization (even RMP) ions are moving down their concentration gradient. The Na/K pump moves ions against their concentration gradient which requires energy (active transport).
Name the 3 states of the gated Na+ channels
Resting state (she also calls this potentially active or closed)
Active state
Inactive state
Describe the resting state of the gated Na+ channel
She also calls this potentially active and closed
The Na channel is closed, and can be stimulated
Describe the active state of the Na+ gated channel
Threshold potential has been reached, the Na+ channel opens and allows Na+ to flow into the cell (depolarization)
Describe the inactive state of the gated Na+ channel
The inactivation plug closes and remains that way until RMP is reached. This state can not be stimulated no matter the stimulus.
Where is the inactivation gate in the gated Na+ channel?
It is the intracellular gate
What is an absolute refractory period and when does it occur?
Period of time when no matter the stimulus, a second action potential can not occur. It occurs during the time when Na+ channels are inactivated.
What is a relative refractory period and when does it occur?
Represents a time period in which a second action potential can occur, but only with a Supra threshold stimulus. This occurs immediately following absolute refractory period (RMP -> hyperpolarization).
On an action potential graph, at what point does the inactivation gate close?
At the peak
When is the Na/K pump activated?
At the completion of repolarization
What conducts the impulse away from the cell body of a neuron?
The axon
How many axons does each cell have?
Only one
Where are sodium channels principally located on the neuron?
On the axon
