Module 7 - Action Potentials Flashcards
Key defining factor of excitable cells
Use action potentials
Typical durations of action potential
2 and 5 ms on nerve and skeltelal muscle
200 hundred ms in heart
If all action potential intensities are the same, how does body distinguish stimulus intensity
By changes of frequency of action potentials
Threshold value
-55mV
In terms of probability, what switches when threshold is reached
Probability of Na channels opening GREATER than probability of closing
Causes positive feedback loop
Why overshoot past RMP during action potential
During this phase, permeability to K is higher than it usually is at rest, meaning more get out and we get overshoot
Where is voltage sensor located in NaV
in 4th TM domain
What will stop positive feedback loop in NaV
NaV inactivation gate closing
What feedback system to Kv havw
negative feedback
Membrane repolarises causing K channels to slowly close, fear and fewer remain open until it just self terminates
When is absolute refractory period
during spike
CNt produce another AP when one is already happening
Relative refractory period when
After the spike
Cell is less excitable
AP can still be fired if the stimulus is large enough (threshold is raised)
What happens to ion conc during AP
remains constant
What type of disease is dravet syndrome
epileptic seizures in young children
What causes dravet syndrome
mutation in SCN1A => mutated NaV1.1 channel
Prevents APs in inhibitory neurons
Too much action in brain
What can help relive symptoms of dravet syndrome
CBD - non psychoactive
or THC - psychoactive
