Action Potential Flashcards
What is the resting potential of a neuron?
The difference in electrical charge between the inside of a neutron and the outside of a neutron
When at rest, the cell membrane of a neuron maintains what kind of gradient?
An electrical gradient, also known as polarization
What is a neuron’s membrane composed of?
2 layers of phospholipid molecules + embedded cylindrical proteins that allow certain chemicals to pass through
What is polarization in a neuron’s membrane?
(AKA electrical gradient) the difference in electrical charge between the inside and outside of a cell
The inside of a membrane has what kind of a charge?
The inside has a slight negative charge compared to the outside (due to negatively charged proteins)
What is resting potential?
The difference in voltage between the inside and outside of a cell
How do researchers measure the resting potential of a cell?
By inserting a microelectrode into the cell body
What is the average electrical charge of the inside of a neuron?
-70 millivolts (mV)
What is the concentration gradient?
The difference in distribution of ions across the cell membrane
What are action potentials?
Messages sent by the axons
When does hyperpolarization occur?
Increased polarization as a product of using an electrode to increase a membrane’s negative charge
What does it mean to depolarize a neuron?
To reduce a neuron’s polarization to zero
Any depolarization that reaches/passes the threshold of the membrane produces what?
Action potential
What does the all-or-none law state?
The amplitude and velocity of an action potential are independent from the intensity of the stimulus that initiated it, as long as the stimulus reaches the threshold
What are the 3 principles of the chemicals events behind action potential?
- At the start, sodium ions are mostly outside the neuron, and potassium ions are mostly inside.
- Depolarizing the membrane opens the sodium and potassium channels.
- At the peak of the action potential, the sodium channels close.
When do voltage-gated sodium and potassium channels typically open, and what happens to sodium channels at the peak of the action potential?
Voltage-gated sodium and potassium channels open when the membrane is depolarized, and sodium channels snap shut at the peak of the action potential
What is the absolute refractory period?
The period of time after the peak of the action potential, in which the sodium channels shut tightly and remain tightly shut for approximately the next millisecond. During this time, the membrane cannot produce an action potential, regardless of the stimulation
What is the relative refractory period?
After the absolute refractory period, sodium channels relax a bit, while the rapid departure of potassium ions has driven the membrane potential farther into negative territory than usual, and a stronger-than-usual stimulus is necessary to initiate an action potential. (2-4 ms)
What are the 2 variables that the refractory period depends on?
Closed sodium channels and potassium flowing out of the cell
Suppose researchers find that Axon A can produce up to 1,000 action potentials per second (at least briefly, with maximum stimulation), but Axon B can never produce more than 100 per second (regardless of the strength of the stimulus). What could we conclude about the refractory periods of the two axons?
Axon A has a shorter refractory period than Axon B and can recover more quickly to fire more action potentials
