refers to the difference in the electrical charges (a voltage) between the interior and the exterior of the cell membrane
Membrane Potential
the voltage that is present when the cell is in an unstimulated state (but does not suggest that it is not metabolically active)
Resting Membrane Potential
(also known as Equilibrium Potential)
Na+ Ion Concentration in Cytoplasm & ECF, Ratio, and Equilibrium Potential
Cytoplasm: 15 mM
ECF: 150 mM
Ratio: 10:1
Equilibrium Potential: +60 mV
K+ Ion Concentration in Cytoplasm & ECF, Ratio, and Equilibrium Potential
Cytoplasm: 150 mM
ECF: 5 mM
Ratio: 1:30
Equilibrium Potential: -90 mV
Cl- Ion Concentration in Cytoplasm & ECF, Ratio, and Equilibrium Potential
Cytoplasm: 7 mM
ECF: 110mM
Ratio: 15:1
Equilibrium Potential: -70 mV
There would always be a negative charge inside the cell because K+ ions are smaller and have K+ channels, therefore they can exit the cell easily unlike the _______ _______
Large anions (A-)
(Given the difference in the rate of movement of the ions through the SPM, especially given that there are biomolecules that carry a charge that cannot pass through the SPM, there would always naturally be a difference in charges across the SPM – which is the RMP.
Also known as the leak channel
K+ channel
(it will always leak whether or not there is a stimulus. although, rate is slow)
Na+ flowing into the cell _________ it
depolarizes
(in depolarization, the interior of the cell membrane has more positive charges than the exterior)
Cl- flowing into the cell _________ it
hyperpolarizes
(in hyperpolarization, the interior of the cell membrane has more negative charges than the exterior)
The change in the voltage must reach the ________ before it reaches the action potential
threshold
(gradual depolarization until the threshold; once threshold is reached, very rapid depolarization would occur)
Very rapid change in the voltage of a membrane when a stimulus is presented and it is above the threshold
Action Potential
(also known as Spike Potential)
Phases in the Action Potential
- Resting potential
- Threshold
- Depolarization
- Action potential
- Repolarization → Hyperpolarization
- Resting
[Phase in the Action Potential]
K+ channel, the leak channel, is open while the Na+ channel is closed because there is no stimulus yet
Resting Potential
[Phase in the Action Potential]
Gradual rise; Na+ channels start to open
Threshold
[Phase in the Action Potential]
After threshold is reached, all Na+ channels open therefore Na+ flows in
Depolarization
[Phase in the Action Potential]
The peak reached due to the flow of Na+
Action Potential
[Phase in the Action Potential]
Na+ channels, the fast-opening/fast-closing channel, close. K+ voltage gated channels open, together with the K+ leak channels, causing K+ to flow out
Repolarization
[Phase in the Action Potential]
In Hyperpolarization, why is there an undershoot (voltage below resting potential)?
gated K+ channels are slow to close
[Phase in the Action Potential]
all K+ voltage-gated channels close
Resting
The action potential can be ________ directionally along the surface of the cell membrane
propagated
(action potential propagated is the nerve impulse)
Small gaps of the axon not covered with myelin sheath
Nodes of Ranvier
(due to the myelin sheath and the nodes of ranvier, the nerve impulse transmission or the action potential propagation is faster)
Name of the transmission of the nerve impulse
Node to Node Transmission
the rapid “leap” or “jump” of electrical impulses along a myelinated axon from one node of Ranvier to the next, rather than traveling continuously along the entire length of the axon
Saltatory conduction
Where is the stimulus presented? Presynaptic neuron or Postsynaptic cell?
Presynaptic neuron
