Electricity
This can be defined as the amount of potential electrical energy stored in a system.
Voltage
This part of a neuron conducts the action potential and releases neurotransmitters at its terminals.
Axon
This value represents the membrane voltage at which an ion will be at electrochemical equilibrium in a given system.
Equilibrium potential (Eion)
For measurement of membrane voltage, one electrode is placed inside the cell, and the other "reference" (or "bath" or "ground") electrode is placed outside of the cell. Both electrodes are attached to this device, which measures the difference in voltage between the two electrodes.
Voltmeter
What stops the Hodgkins Huxley cycle at the peak of the AP and brings the membrane back to resting potential?
Inactivation of voltage-gated Na+ channels.
This measures the amount of charge moving from point A to point B per unit of time.
Current
If the axon of neuron A synapses on the soma of neuron B, neuron B is considered ____ to neuron A.
post-synaptic
EK at 25oC when [Kin] = 100mM and [Kout]=10mM
Bonus 50 points: If resting potential is -50mV, which direction is K pumped to maintain resting potential given that the membrane is permeable to K?
-59.8mV
Bonus: K is pumped into the cell.
The dependent variable in a voltage-clamp setup.
Bonus 50 points: What is the independent variable?
Current being passed into the cell to maintain command voltage (amount + direction)
Bonus: Membrane voltage ("command voltage")
Two components determine the generation of the resting membrane potential.
Bonus 100 points: What establishes the concentration gradient for the resting membrane potential?
1. Equilibrium Potential
2. Relative Permeability
...of the ions in the system.
Bonus: Na+/K+ ATP-ase (Sodium-Potassium Pump)
Opening ion channels will decrease this electrical property of the cell.
Bonus 100 points: what electrical property of the cell would increase under these conditions?
Resistance
Bonus: Conductance
This is the part of a neuron where all graded potentials are spatially and temporally summed, and an action potential is initiated if a threshold voltage is reached.
Axon hillock
During the rising (depolarizing) phase of the AP, voltage-gated Na+ channels are regulated by this sort of feedback loop.
Bonus 100 points: During the falling (repolarizing) phase of AP, voltage-gated KDR are regulated by this sort of feedback loop.
Positive
Bonus: Negative
Inward current into a cell will ____ the membrane voltage.
Depolarize (increase)
When the membrane potential (Vm) is at an ion's equilibrium potential (Eion), what is the driving force on the ion?
Vm = Eion, then driving force [Vm - Eion] = 0
There's no driving force on that ion.
This electrical property of a cell describes the relationship between charge separation across the membrane and the membrane voltage.
Capacitance
This process will cause voltage-gated Na+ channels to close after a certain amount of time, even if membrane voltage remains unchanged.
Inactivation
The equilibrium potential for this ion primarily determines the peak voltage observed during an AP.
Na+ (membrane becomes very permeable so Na+).
*Remember Goldman equation!
Lambda (length constant) is dependent on the ratio of what two factors?
Rm (membrane resistance)/Ra (axial resistance)
During the repolarization phase of the AP, what breaks the feedback loop of the slow negative cycle?
Voltage-dependent gK
When modeling a neuron as an RC circuit, this part of the neuron represents the resistor.
Bonus 200 points: What parts of a neuron are the capacitor and battery?
Ion channels (Rm)
Bonus: The cell membrane (no ion channels) and ion electrochemical gradients.
This refers to the time period during which a cell can initiate another action potential, but the threshold voltage is higher.
Bonus 100 points: What determines the length of this period?
Relative refractory period
Bonus: Inactivation kinetics of voltage-gated Na+ channels.
This rule states that our bodies (as a whole system) have no net charge separation (equal amounts of positive and negative charge overall).
Macroscopic electroneutrality
Tau (time constant) is dependent on the product of which two factors?
Membrane capacitance (Cm) and membrane resistance (Rm)
Synaptic signals that typically originate in the dendrites or soma and decay with time and distance
Synaptic/graded potentials