Chapter 3 - The Neuronal Membrane at Rest Flashcards
Excitable Membrane
A membrane which is capable of conducting action potentials
Cytosol and Extracellular Fluid
Contains water, which has an uneven charge (polar). Ions dissolved in these fluids enable membrane potentials
Action Potentials (four parts).
After the membrane is depolarized by opened sodium channels, the rising phase begins. Then the membrane is depolarized past threshold and overshoots before befinning the falling phase. The membrane potential hyperpolarizes until it undershoots the resting potential. It then slowly depolarizes back to resting.
Absolute Refractory period
‘Spike’ in action potential
Relative refractory period
Undershoot and gradual depolarization back to resting potential
Receptor Potential (PSP)
As intense and long as stimulus (with exceptions).
Potential Degradation
An potential usually degrades 2/3 its height for ever mm travelled
Axon Hillock
Region of axon very rich in voltage gated sodium channels.
Sodium Channels
Voltage and concentration gradient. Open immediately for 1 ms
Potassium channels
Open about 1 ms after Na channels and close a while later (why it undershoots). Then Na/K pump brings potential back to rest after undershoot
Universal Properties of Neurons
All neurons have action potentials, resting potentials, receptor potentials etc. And these potentials are all the same size across different neurons
Dendrites and Action Potentials
Dendrites don’t have action potentials
Axon Speed and Thickness
Wide axons transmit potentials more quickly because of less leaking.
Nodes of Ranvier
Rich in voltage gated sodium channels, because there is no leakage where there is myelin, no need for heavy Na inflow where there is no leakage.
Saltatory Movement
Jumping of potential from node of ranvier to node of ranvier
