PHYS20008 Lecture Notes - Lecture 3: Resting Potential, Membrane Potential, Axon Hillock
21 Jun 2018
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Lecture 3: Membrane potential
Anatomy of a nerve cell:
Nerve cells carry information via electrical signals. Neurons generate electrical signals
through brief, controlled changes in the permeability of their cell membrane to particular
ions (such as Na+ and K+)
Important parts of the nerve cell include:
Input zone: Cell body
Trigger zone: Axon hillock
Conducting zone: Axon
Output zone: Axon terminals
The most important ions involved within a nerve cell are:
1) Na+: More concentrate outside the cell than inside with an equilibrium potential at
37oC of +60mV
2) K+: More concentrated inside the cell than outside with an equilibrium potential at
37oC of -90mV
Resting membrane potential (RMP):
This refers the membrane potential of non-excitable cells and excitable cells at ‘rest’. It is
measured at -70mV. Most of RMP (>90%) is due to passive diffusion of K+ and Na+ down
their concentration gradient rather than being due to the Na+/K+ pump (active transport).
This is because the Na+/K+ pup maintains Na+ and K+ gradients which has indirect
effect in maintaining RMP. Ions will move/diffuse in or out the cell due to relative
permeability of membrane to get to the resting membrane potential.
*Unbalanced changes create membrane potential
A relatively large net diffusion of K+ outwards establishes an Equilibrium potential of -90mV,
and a relatively small net diffusion of Na+ inwards neutralises some of the potential created
by K+ alone. As there is no diffusion of large intracellular anionic proteins, a resting
membrane potential of -70mV is easily achieved- maintains negativity.
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Document Summary
Neurons generate electrical signals through brief, controlled changes in the permeability of their cell membrane to particular ions (such as na+ and k+) The most important ions involved within a nerve cell are: na+: more concentrate outside the cell than inside with an equilibrium potential at. 37oc of +60mv: k+: more concentrated inside the cell than outside with an equilibrium potential at. This refers the membrane potential of non-excitable cells and excitable cells at rest". Most of rmp (>90%) is due to passive diffusion of k+ and na+ down their concentration gradient rather than being due to the na+/k+ pump (active transport). This is because the na+/k+ pup maintains na+ and k+ gradients which has indirect effect in maintaining rmp. Ions will move/diffuse in or out the cell due to relative permeability of membrane to get to the resting membrane potential.
