Neuronal Signal Propagation Flashcards
Action potential firing is produced by ________ ion channels.
voltage-gated
The ______property of a neuron describes the likelihood that a neuron will fire an Action Potential depending upon the strength of the input signal
Excitability
________ uses an intracellular electrode to inject current commands across the surface membrane and record the neuronal electrical response (It is like a programmable charge pump)
Current clamp
Rheobase
Minimum current to reach threshold
Chronaxie
Time to fire at a current that is 2x Rheobase
By keeping _____ constant, the ________is kept constant, so all changes in current are due to change in the probability of the channel being open
membrane potential, driving force
Leak current
Linear changes in Current as expected
from Ohm’s Law
How do you isolate a Na+ ion specific component of a current?
Remove K+ from the media or add a drug (TEA) that selectively eliminates the K+ ion dependent current
How do you isolate a K+ ion specific component of a current?
Remove Na+ from the media or add a drug (TTX) that selectively eliminates the Na+ ion dependent current
Name the 3 axonal membrane ionic current components determined through H&H’s experimentation.
- Linear Leak Current (Looks Ohmic)
- A depolarization activated Na+ current that shuts down in a time dependent manner
- A depolarization activated K+ current that remains active
H&H suggested that ____ could be accurately modeled by assuming multiple switches whereas _____ only required a single switch model
activation, inactivation
What positively charged residues are found in transmembrane segment of voltage-gated K+ channel?
Arg, Lys
The ______ structure of Voltage-gated channels suggested that each S4 transmembrane segment was acting like a separate gating switch as predicted by H&H
tetrameric
_____ is a “autoinhibitory” state analogous to receptor desensitization
Inactivation
A ______exists, where the Neuron cannot fire another action potential until the Na+ channels recover from Inactivation
Refractory period
What exists close to the membrane and exists on many lipids proteins, glycosylations? Why can these be problematic?
Fixed charges - ions can bind them, so ion concentration changes can produce surface charge effects that change stability of gating charges - appears as a change in membrane potential
When are surface charge effects particularly large?
With divalent cations like Ca2+
What symptoms result from hypercalcemia?
Decreased excitability of neurons - fatigue, depression, confusion, cardiac arrhythmias, coma
What symptoms result from hypocalcemia? (often due to hypoparathyroidism)
Increased excitability - cardiac arrhythmias, cramps, tingling, bronchospasms, seizures
Higher Ca2+ outside cell (increases/decreases) surface binding, (destabilizing/stabilizing) Na+ channel gating charges in the open state, making it (harder/easier) to fire an action potential.
Increases, destabilizing, harder
Lower Ca2+ outside cell (increases/decreases) surface binding, (destabilizing/stabilizing) Na+ channel gating charges in the open state, making it (harder/easier) to fire an action potential.
Decreases, stabilizing, easier
____ are locations where + charges are entering the cell, driving a depolarization
Sinks
______ are peripheral locations that are being depolarized due to the + charges flowing in at the sink
Sources
A current loop between nearby parts of the same cell that are at different potentials is called a ____
Local circuit current
