Propagation potential and conduction velocity Flashcards
How often are leak channels open?
All the time
How often are gated channels open?
Open in response to particular events e.g. a voltage change
What are some functional elements of voltage-gated ion channels?
Selectivity filter
Voltage sensor
Activation gate
Inactivation gate
What is the selectivity filter for?
Na+ and K+
What is the voltage sensor for ?
Na and K channels
What is the activation gate for?
Na and K channels
What is the inactivation gate for?
Na channel only
What are the different states for a voltage-gated channels for Na+?
- Closed
- Open
- Inactivated
- Closed
What are the different states for a voltage-gated channels for K+?
- Closed
- Open (1ms delay)
- Closed
When do the Na+ channels close?
When the K+ channels open
What is patch clamp recording?
Electrode up against the cell measuring a patch of membrane without entering the cell
How does the electrode measure the membrane without entering the cell?
By applying suction down the membrane to pull some of the membrane against the electrode
What do you use the electrode to do?
Create a small depolarisation
During a patch clamp recording what is the state of the cell at rest?
Na channels closed
K channels closed
During a patch clamp recording what is the state of the cell at on depolarisation immediately
Na channels open (activation)
pNA increases
Em is driven down towards ENa
K channels still closed
During a patch clamp recording what is the state of the cell at depolarisation with a delay?
Na inactivation, gates close Na channels are closed K channels open pK increases Em is driven back to Ek
During a patch clamp recording what is the state of the cell has gone through the method?
Na activation gates closing
Na inactivation gates re-opening
K channels closing
What does the Na+ K+ pump act in the background to do?
Move Na and K ions back to their original places
Is the Na+/K+ essential?
No
A nerve can support about 10,000 action potentials even when the pump is poisoned
What can be seen by recording 2 points along an axon?
Than an action potential (AP) moves away from the point of electrical stimulation (stimulus electrode)
What is an electrotonic currrent/ local current?
Current flowing passively along an axon decays with distance beyond the block