T8L2 nerve impulses Flashcards
Explain how the resting potential is established
Sodium-Potassium pump, pumps 3Na+ out and 2K+ in
More K+ inside than outside axon and membrane is about 10 times more permeable to K+ so K+ leak out of closed gated channels
More positive outside than inside
pd of -70mv
What role do organic anions play in estabishing the resting membrane potential
Organic anions are too big to pass out of axon so this contributes to inside being negatively charged
Explain how depolarisation occurs
Sodium ion channels open which allows sodiums to diffuse from outside of the cell to the inside of the cell and this forms a pd of 40mv
How does repolarisation occur
K+ channels and K+ diffuse out of axon to lead to inside being more negative than outside
how does hyperpolarisation occur
Potassium ion channels stay open and potassium ions continue to diffuse out of axon - reaching a pd of -90mv
why does hyperoplarisation occur
- regulates frequency of impulses
- prevents impulse going backwards
How is the resting potential reestablished after hyperpolarisation occurs
Na+/K+ pump
Explain the all or nothing response
If insufficient sodium channels open
Full depolarisation does not occur
So stimulus is below the threshold value
And no impulse is propagated
Action potential generated is always of the same size regardless of the size of the stimulus as long as it is above the critical value
Explain the refractory period
Period of time after an impulse where axon excitability is low to allow the axon to return to its resting state
This controls the frequency of impulses sent
Name the two types of summation
Temporal and spatial
Explain temporal summation
When multiple action potentials along one neurone signal the intensity
Explain spatial summation
When action potentials have to be generated in more than one presynaptic neurone to generate an action potential in the post synaptic neurone
