Dr Mitcheson lecture 3 Flashcards
Define the equilibrium potential
The potential when the electrical forces are equally opposed by the concentration gradient.
What equation is used to determine the Equilibrium potential?
Nerst Equation
Does the resting potentials for many different Ek concentrations equal the line provided using the Nerst equation?
No. It is slightly more positive at the start of the line due to the small movement of Na.
What equation can be used to calculate the relative permeability of the membrane?
Goldmann-Hodgkin-Katz equation
What causes the rising phase of the Action potential?
Na+ ions entering through Na+ channels
What can be used to measure ion fluxes during an AP?
Radioactive isotopes
What technique can be used to measure the movement of charged molecules?
Voltage clamp
What provides current in a voltage clamp set up?
FBA - it takes readings from voltage command (uses the experimental voltage required) and compares this to the actual membrane potential. If there is a difference, the electrode injects current to compensate for the difference and this current is then measured.
Which channels are first to open during an action potential?
Na+ channels.
From Na+ current how can you measure Na+ current?
Take the K+ current from the current of the two put together.
How can you measure K+ current?
- Use pharmacological agents (tetrotodoxin) to block Na channels;
- Use a Na+ replacement
- Change ENa to 0mV so there is no net movement of Na+.
What is the symbol and units of conductance?
G and Siemens (S)
What does conductance change with?
Membrane potential. The larger the depolarisation the larger and faster the change in conductance (governed by the number of Na and K channels).
