Membrane Potential/Changing Flashcards
(13 cards)
What is a MP?
Potential inside the cell relative to the potential outside the cell
What is RMP set up by mostly?
Permeability to K+ channels
What is cardiac RMP compared to RBC RMP? What does this indicate about the selective permeability to K+?
-80 to -95 vs -9mV
RBCs not very selective to K+ meaning other ions contribute to the RMP
Cardiac myocytes almost totally selective to K+ as close to K+ equilibrium potential (-95mV)
What is the equilibrium potential for an ion? How can you measure this?
The MP where net flow for that ion is 0 = equilibrium
Nernst
Contribution of each ion to membrane potential is called _________
Conductance
Give an example of where you would find mechanoreceptors?
Skin, hair cells inner ear
How do mechanoreceptors in ear lead to CNS interpretation (6)
1) Sound wave - Ear hairs move
2) K+ channels close at cuticular plate
3) Cell depolarises
4) Ca2+ channels open, Ca2+ in
5) Neurotransmitter released - dopamine or dynorphin
6) Post synaptic neuron to brain
What is an EPSP give 3 examples of excitatory transmitters. What does this potential do?
Example of a an excitatory transmitter acting on a ligand gated ion channel eliciting a change in membrane potential that causes depolarisation post-synaptically. Ach, dopamine, glutamate. Makes the neuron more likely to fire an Action Potential.
What is an IPSP, give two examples of inhibitory NTs. What does this potential do?
Example of inhibitory transmitters that open ligand-gated channels post-synaptically that cause hyperpolarisation. GABA Glycine. Makes the neuron less likely to fire an Action Potential.
Talk through the stages of a cardiac myocyte action potential from phase 0-4
0 - Fast Na+ channels open, raises MP, further Na+ channels open, depolarisation, membrane potential overshoots. Fast Na+ channels close (time-dependent) L-type Ca2+ channels open
1 - Early repol Transient K+ channels open,
2 Plateau - L-type Ca2+ channels still open, K+ out through delayed rectifier channels
3 - Repolarisation - Delayed rectifier K+ channels open
L-type Ca2+ channels inactivate.
At which membrane potential can cardiac myocytes then generate a self-sustaining inward Na+ current during an action potential? At which membrane potential do L-type Ca2+ channels open?
- 70mV after fast Na+ channels have opened
- 40mV
During which phase of cardiac AP does Ca2+ ion entry trigger CICR
Mostly phase 2
Are direct-GPCR ion channels and GPCR-2nd messenger ion channels slow or fast?
Direct - quite rapid
2nd messenger systems Slower - as use other signalling molecules in cell.
