6.1 Membrane Potentials Flashcards
All cells have membrane potential which is
The difference in charge across a membrane
Sodium, Potassium ATPase moves
Three Sodium 2+ ions out and
two Potassium + ions in
examples of negatively charged ions in the cell
DNA, proteins
Difference in charge across a membrane can be measured using a
Voltmeter
More positive charge found _____ and less positive (more negative) charge found ______.
Outside, inside
Inverting the membrane potential is known as creating
Action potential
Action potential is known as
Work being done
Which cells can create action potential (converting membrane potential)
Excitable tissues (nervous and muscle)
RMP
Resting membrane potential
A neurons RMP is around
-70 mv
Depolarization is when
The cell becomes less negative (more positive)
Hyper-polarization is when
The cell becomes more negative (less positive)
Voltage gated Na+ channel
- open at approx -55mv
- allow sodium in
- quick to respond
Voltage gated K+ channel
- open at approx 30mv
- potassium will go out
- slower to respond
After -55mv threshold is reached what happens
Depolarization: Charge jumps to 30mv (positive) because sodium channels opened.
Then, when the sodium channels close, the potassium channels open causing potassium to flow out (Less positive in the cell aka hyper polarization). Drops to -70 - -90 mv.
After the depolarization and hyper polarization, what happens
The -70 mv gradient is re-established by the sodium potassium atpase pump
Steps of action potential
- RMP -70mv
- Excitable stimulus
- Threshold reached -55mv
- Voltage gated Na+ channel opens
- Depolarization
- Na+ channels close (+30mv)
- K+ channels open, re-polarization
- Hyper polarization (goes beyond -70)
- K+ channels close
- Na+/K+ ATPase returns RMP
Absolute refractory period is
When you cannot have another action potential occur (channels already open can’t open again or further)
From the threshold point to the RMP (before hyperpolarization)
Relative refractory period
From after the absolute refractory period to when RMP is re-established (all of the hyper polarization bit) Hard to stimulate but you can.
