Neurones: resting potential 5.3.3 Flashcards
What is a resting axon?
One that is not transmitting impulses
What is the resting potential
When the inside of the axon always has a negative electrical potential compared to the outside of the axon
What is the potential difference of the resting potential?
-70mv
The inside of the axon is about 70mv lower than the outside
What are the two factors that contribute to establishing and maintaining the resting potential?
- Active transport of sodium ions and potassium ions
- Differential membrane permeability
Where are carrier proteins known as sodium potassium pumps located?
In the membrane of neurones
What do these sodium potassium pumps require?
ATP for active transport
How are sodium and potassium transported in/out the membrane at rest?
Active transport
Describe the actions of the sodium/potassium pump
Actively transport 3 sodium ions out of the axon for every 2 potassium ions that are actively transported in.
Meaning there are more ions outside of the axon than inside - making the inside more negative
What is an electrochemical gradient?
The difference between the ions located inside and outside of the membrane
What ion are the protein channels in the membranes of the axon more permeable to?
Potassium
What occurs as a result of the protein channels in the axon membrane being less permeable to sodium?
It means potassium ions can diffuse back down their concentration gradient, out of the axon, at a faster rate than sodium ions
What does the cell surface membrane of neurones contain (other than the pump)
Selective protein channels that allow sodium and potassium ions to move across, by facilitated diffusion.
These are less permeable to sodium ions
How is the resting potential maintained?
By the net movement of positively charged ions out of the axon - by the sodium potassium pump
