Flashcards in L4: Action Potentials Deck (7):
What are the three characteristics of an action potential?
All-or-none: it either happens or it doesn't
Self propagating: each region of depolarization serves to generate action potentials on either side
Non-decremental: doesn't decrease in strength
What are the types of ion channels with regard to what they respond to?
-Slow leak channels - always open
-Ligand gated: require attachment of neurotransmitter or hormone to receptor
-Voltage gated: require a change in membrane potential
Describe and Compare sodium ion channels and potassium ion channels.
-have two gates: activation and inactivation
-Has four domains - which have 6 hydrophobic transmembrane segments
-Have a single gate
What are the voltages associated with the opening and closing of the channel gates during the propagation of an action potential?
-Both opened between -90 and +35
-Activation gate opens around -70 to -50 (top)
-Inactivation closed between +35 and -90 (bottom)
-Closed at -90mV
-Slow activation opens the gate from +35 to -90
Resting stage: -90mv
Depolarization: becomes permeable to sodium
Repolarization: sodium channels close and potassium channels open more than normal
Explain two ways that axons might increase the speed of conduction of an action potential.
Myelination - increases membrane resistance
Larger fiber diameter - offers large cross sectional area to internal flow of current
What is absolute refractory period?
A second action potential can not be elicited no matter how strong the stimulus is
Most fast sodium ion channels are open or in the inact state