MR 3 Flashcards
What units is the resting membrane potential measured in, and how is it expressed?
In millivolts - mV.
Expressed as the potential inside the cell, relative to that outside the cell.
What is the RMP of:
- nerves
- skeletal muscles
- cardiac muscle
Nerves
From-50mV to -75mV
Cardiac and skeletal
From -80mV to -90mV
Explain what selective permeability of a membrane is, and what this confers for the RMP?
Membranes contain proteins that can alter permeability to ions.
In their open state, they will allow flow of ions down their respective concentration gradients.
Depending on which protein channels are open, the RMP is set accordingly.
Eg, at rest the voltage insensitive K+ channel is open and K+ flows out. However there are other proteins in the membrane that are slightly permeable to other ions so the RMP does not set to the Ek of potassium (see later sessions).
Explain the term equilibrium potential for an ion.
This is the membrane potential at which there is no net movement of ions as there is no electrical or diffusion gradient.
What is meant by depolarisation?
An event that leads to the membrane potential of a cell becoming less negative. This means it moves closer or above 0mV.
- this occurs when there is an influx of Na+ or Ca2+
Explain what is meant by the term hyperpolarisation
An event that leads to the membrane potential becoming more negative than it should be. Eg, it moves more negative than its RMP.
- seen when there is opening of Cl- and K+ channels.
What exactly sets the RMP of a cell?
This is set by the relative permeability to ions.
Give an example sample of a fast transmission receptor.
The NAChR at the NMJ.
- the receptor for acetylcholine is itself an ion channel too. The ion channel is intrinsic in the receptor.
What is meant by slow transmission receptors?
When the receptor and the ion channel are separate.
An example of this are the G protein coupled receptors.
How may the resting membrane potential of a cell be measured?
Using a micro electrode. This can pierce the membrane and read the membrane potential.
The tip is less than 1micrometre thick.
