Resting potential Flashcards
What does it mean if a neurone is at rest?
It experiences no stimulation detected by the receptors (enough to reach threshold)
What happens if a neurone is at rest?
Establishment of a resting potential by differences in charge inside to outside the neurone over the cell surface membrane
What 3 factors cause an establishment of a resting potential?
Difference in membrane permeability to diff ions
Electrochemical gradients
The movement of sodium ions and potassium ions
At rest what are the charges inside a neurone ?
Negative
At rest what are the charges outside a neurone?
Positive
How is the inside of a neurone at rest negative if potassium ions are at a higher concentration there?
Because there are other molecules eg protein in the neurone that can mean overall, the charge inside a neurone is negative
So despite molecules/ions of different charges being both inside and outside, the above effect means overall the inside is negatively charged
How is the outside of a neurone at rest positive if there are still negatively charged ions???
Because there is a high concentration of sodium ions causing area of high pos charge
So despite molecules/ions of different charges being both inside and outside, the above effect means overall the outside is positively charged
Sodium ions are at a high concentration…….
outside the neurone
Potassium ions are at a high concentration……..
inside the neurone
The first step in generating a resting potential
Na+K+ pump protein actively transports 3 Na+ ions out of the cell and 2 K+ ions into the cell (in this ratio per 1 ATP hydrolysed)
Net effect of Na+K+pump protein
Overall positive charge on outside
Negative charge inside
(more positive leaves than positive that enters neuron)
How else can we enhance the resting potential (neg inside, pos outside) in a neurone?
By differences in membrane permeability:
higher permeability to K+ ions than it does to Na+ ions
K+ ions can diffuse out of neurone to increase neg charge
But harder for Na+ ions to diffuse in to neurone so pos charge outside is maintained (and charge inside wont become more pos)
Why are neurone membranes more permeable to K+ ions than Na+ ions?
There is a higher number of potassium ion leak channel proteins and lower number of sodium ion leak channel proteins in the membrane
Allows more movement of K+ than Na+
How are Na+ and K+ ions transported to enhance the resting potential?
By facilitated diffusion using:
Na+ leak channel proteins
K+ leak channel proteins
Are ions transported in?out of the neurone membrane?
NO transported in and out of the NEURON CELL!
They are transported OVER the membrane
