Chapter 3 - The Neuronal Membrane at Rest Flashcards Preview

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Flashcards in Chapter 3 - The Neuronal Membrane at Rest Deck (16):

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


4 Ways to Clean up Cleft Transmitter

1. It diffuses away
2. Protein on presynapic membrane called transporters transports transmitter back to vesicle or for breakdown
3. Glial cells uptake extra transmitter
4. Enzymes in cleft on post-synaptic side (especially) can break down transmitters very fast