5. Equilibrium Potential Flashcards
Most areas have a _ charge inside and _ charge outside
Negative, Positive
What channels are involved with graded potentials and respond to neurotransmitters?
ligand-gated
What channels are involved with changes in electrical charge (membrane potential) and action potentials?
voltage-gated
Where do voltage gated channels start to open up?
Initial segment of the axon hillock
The 2 glial cells in the PNS are _
Satellite cells
Schwann cells
the 4 glial cells in the CNS are _
oligodendrocytes
astrocytes
microglia
ependymal cells
ACh receptor is a _ channel
ligand gated
T/F Gap junctions are involved with electrical synapse
True
T/F Membrane potential involves single ions
False (multiple)
_ ions have a higher concentration outside
Na+, Cl-
_ ions have a higher concentration inside
K+
K+ is driven out of the cell due to _ and also driven into cell by _
the concentration gradient, electrical attraction (to A-)
The _ equation solves for equilibrium potential and is _
Nernst
Ex= + or - 60log(Xo/Xi)
The equilibrium potentials for: K+ Na+ Cl- Ca 2+
-90 mV
+60 mV
-70 mV
+90 mV
_ is the threshold of a typical neuron
-55 mV
At rest, membrane potential is driven by _
leak channels
T/F membrane potential is due to K+ and Na+ channels and the Na-K ATPase pump
True
_ equation is used to calculate membrane potential and is _
Goldman’s equation
Vm= 60 log(P[K]out + P[Na]out + P[Cl-]in)
(P[K]in + P[Na]in + P[Cl-]out)
Permeability of K:Na:Cl at rest
1 : .01 : .45
What drug shuts down the Na/K pump and does it affect AP or MP?
Oubane
No, leak channels are still open
Typical resting membrane potential is _
-70 mV
Graded potential are also known as _ potentials
local
Where are ligand gated channels located on neurons?
Cell bodies and dendrites
For graded potentials, as you move further from the point of origin the strength or amplitude _
decreases
Time constant is defined as _
the time required for voltage in cell to drop 63%
Time constant is dependent on _
Resistance x capacitance (size of membrane)
The _ the time constant, the _ the drop in voltage
larger, slower
Longer time constants allow graded potentials to undergo _, increasing the likelihood of an action potential to fire
temporal summation
When ligand gated channels open, _ flows in causing _
Na, depolarization
T/F Stimulus strength effects amplitude of action potential
False (once threshold hits, it is all or none)
After depolarization, most of the inactivation gates are _, stopping entry of Na+
closed
At resting membrane potential, the activation gate is _, waiting for depolarizing stimulus to arrive due to ligand gated channels
closed
Conductance (g) is defined as _
the ease at which ions flow through voltage gated channels
_ period is where it is impossible to initiate another action potential, because inactivation gates are _
Absolute refractory period
closed
_ period is where a 2nd action potential can be activated but requires a _ stimulus to reach threshhold
Relative refractory period
higher
Ohm’s law states voltage=
I X R
H-Huxley model states current=
g(Vm-E)
Driving force for ions is _
(Vm-E)
For cations, when the driving force is +, ions flow _
outward
For cations, when the driving force is -, ions flow _
inward
For anions, when the driving force is +, ions flow _
inward
For anions, when the driving force is -, ions flow _
outward
Tetraethylammonium (TEA) blocks _ resulting in no _ flow
K+ current
outward
Tetrododoxin (TTX) blocks _ resulting in reduced _ flow
Na+ current
inward
Pronase keeps Na+ channels open by _
cleaving off inactivation gate from VG Na+ channels
Permeability of K : Na : Cl after threshold
1 : 20 : .45
Length constant is when _
the voltage decreases over distance by 63% (graded potentials)
Longer length constants have a greater chance to cause an AP due to _
spatial summation
Length constant equation is _
square root of rm/ri
The larger the diameter of a neuron, the _ the resistance
smaller
The speed of AP=
length constant/time constant
or
(rm/ri)/ (rm x capacitance)
Bigger axons transport signals _ due to a decrease in _
Faster
internal resistance
For bigger axons, _and _ decrease
membrane and internal resistance
For bigger axons, _ increases
capacitance
Myelinated axons transport signals _ _ faster, due to an increase in _ and decrease in _
much, much
membrane resistance
capacitance
What is the type of conduction where the AP jumps from node to node?
saltutory
Defects in Ca channels cause _ and _
paralysis (hypokalemic)
malignant hyperthermia
Defects in Na channels cause _ and _
Paralysis (hyperkalemic)
Atypical myotonia
Defects in Cl channels cause _ and _
Myotonia
cystic fibrosis
