MT - Neuronal Function (Part 1) Flashcards
What structures make up the CNS?
The brain and spinal cord.
What structures make up the PNS?
The neurons and glia that aren’t part of the CNS.
Define depolarization, repolarization, and hyperpolarization.
Depolarization: membrane potential becomes more +ve
Repolarization: membrane potential returns to resting value
Hyperpolarization: membrane potential becomes more -ve than resting value.
What 2 components influence the membrane potential of a cell?
- Relative ion permeabilities
2. Relative ion concentrations inside and outside the cell
For the Nernst equation, what is RT/zF at 22C?
58 mV.
For the Nernst equation, what is RT/zF at 37C?
61.5 mV.
What transporter maintains the concentration gradients of Na+ and K+?
The Na+ / K+ ATPase.
For every ATP that gets hydrolyzed by the Na+ / K+ ATPase, what is the net movement of ions?
3 Na+ ions transported out and 2 K+ ions transported in
What happens to the membrane potential when Na+ channels are opened?
The membrane depolarizes.
What happens to the membrane potential when the K+ channels are opened?
The membrane hyperpolarizes.
What equation gives the conductance of a membrane?
Conductance = 1/Resistance
What equation gives the electrochemical driving force?
Driving force = conductance (charge-equilibrium potential)
Define the “electrochemical driving force”.
How far the membrane potential is from equilibrium.
What ion channels are voltage-gated?
Na+, K+, and Ca 2+ channels.
What ion channels are ligand-gated?
Glutamate receptors, GABA receptors, nicotinic acetylcholine receptors, 5-HT3, P2X
What is the equation for Ohm’s law?
Voltage = current * resistance
What is the capacitance of a membrane?
The ability of a membrane to store charge when a voltage difference occurs.
What equation gives the capacitance of a membrane?
Capacitance = charge difference / voltage difference
What are the 3 features of a capacitor that define its function?
- Material properties
- Area of the conducting surfaces
- Thickness of the insulating layer
What effect does the area of the conducting surfaces have on membrane capacitance?
Larger area = greater capacitance
What effect does the thickness of the insulating layer have on membrane capacitance?
Thicker = greater capacitance
What quality of membrane electrophysiology is described by the time constant?
The time over which the membrane potential will decay to 37% of its maximal value (how well does it hold charge).
What variables affect the time constant of a membrane?
- Resistance of the cell membrane
2. Capacitance of the cell membrane
What effect does having a low membrane resistance have on the time constant of a membrane?
The capacitor becomes full faster, depolarizes faster, and conducts faster (lower time constant).
How is the change in membrane potential in an unmyelinated axon affected by distance?
It decreases rapidly with distance.
What equation describes conduction decrement in an axon with distance?
decrement =sqrt((membrane resistance)/(internal resistance + external resistance))
What effect does increasing the resistance of intracellular/extracellular fluids have on the decrease in voltage along an axon?
Higher fluid resistance = greater decrease.
What effect does decreasing the membrane resistance have on the decrease in voltage along an axon?
Lower membrane resistance = greater decrease.
