Neurophysiology Flashcards
what maintains the resting potential? ( MEMBRANE)
- Cell membrane (phospholipid bilayer): around all of neuron
Define the resting mem.potential? ( Electrochem. Gradient)
electrochemical gradient (ie intracellular ION concentration: different from extracellular ION concentration).
So: has the POTENTIAL to change
Which - Ions important for neurophysiology? ( Na=, K+, Ca2+, CL-)
Cations = Na+, K+, Ca2+ and Anion = Cl-
See diagnosis P 10
What is the usual resting pot?
-70mV
What impacts the movement of ions across the plasma membrane?
Channels!
The difference in electric charge b/n ICF and ECF means that some ions will easily move across the plasma membrane if their channels are open
Diagnosis P 11
Describe the function of Ion channels? ( FLOW of ions)
Ions cross the plasma membrane via proteins called ion channels: K+ channels are open: K+ flows in and out
Resting mem. potential (RMP) AGAIN!
- Electrical gradient: the difference in electrical charge between two adjacent areas. If an area is negative: what flows into it?
positive ions will flow to it.
- Positive K+ ions will flow from the outside of the cell to the inside (-)
- RMP is restored by “Na+/K+ pump” and open K+ channels
What is the concentration Gradient?
FLOW to less
difference in concentration of a particular ion between two adjacent areas.
If an area has many K+ ions, the K+ ions will flow to an area with LESS ! K+ ions.
Why aren’t the levels of K+ the same between inside & outside at rest??
- K+ ions move into cell due to electrical gradient and move out due to the concentration gradient..
(Na+/K+) pump in the cell membrane: brings in 2 K+ and removes 3 Na+ ions.
More K+ ions inside and more Na+ ions are outside of the cell.
what is (Adenosine Triphosphate - ATP) ?
Gives E
Gives Energy to the pump above
ATP : required as sodium is being transported out of the cell and K+ is being transported into the cell - both travelling against their concentration gradient
see p 13- 14
How do we measure Action potentials?
Electrodes +
IC and EC pot. measured by recording electrodes and an oscilloscope .
Action potentials produce a rapid reveal in potential
P 15-19: Look at these !!!
An action potential only occurs when?
AXON HILLOCK
if enough positive charge reaches the axon hillock to go above the threshold potential of the neuron
The threshold potential (threshold of excitability) is commonly?
-50mV
around -50mV in neurons
What happens when the threshold is reached?
Depolarisation !
Na+ channels open and heaps of Na+ comes into the cell - depolarisation (more positive).
When is the peak of an act.pot?
+ 30mV
(+30mV) ….Na+ channels close and voltage-gated K+ channels open: K+ leaves the cell - repolarisation (more negative). At this stage the neuron is in the absolute refractory period - it cannot fire.
