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Membrane Potentials
Wacker lecture 1/19/11
29
Physiology
Undergraduate 4
01/24/2011

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Term
-60(smooth muscle) - -90 mV(neurons)
Definition
normal cell electrical potential difference
Term
the membrane potential that balances the ionic concentration gradient
Definition
what is the equilibrium potential for an ion
Term
~ -94mV
Definition
what potential must the cell have to keep K+ from moving out?
Term
~61mV
Definition
what potential must the cell have to keep sodium from flowing in?
Term
-80mV
Definition
what is the eq potential for K+
Term
+62 mV
Definition
what is the eq potential for Na+
Term
+123mV
Definition
what is the eq potential for Ca2+
Term
-65mV
Definition
what is the eq potential for Cl-
Term
E ion = (61.54/z) log ([ion o/ion i])
z is charge of the ion
Definition
what is the simplified nernst equation assuming 37 degrees celcius?
Term
eq potential for multiple ions
Definition
what does the goldman equation tell you?
Term
Vm = 61.54 mV log (Pk[k+]o + Pna[Na+]o + Pcl[Cl-]i ////// Pk[K+]i + Pna[Na+]i + Pcl [Cl-]o
Definition
what is the goldman eqn?
Term
K+
Definition
at rest, which ion has greater permeability? K+ or Na+
Term
K+ establishes resting membrane potential between -60 and -90 mV
Definition
if the cell is at rest, what ion eq potential is closest?
Term
action potential
Definition
rapid change in potential from - to + to - again, combination of excitatory and inhibitory signals
Term
dendrites
Definition
where is the graded potential?
Term
axons
Definition
where is the action potential?
Term
excitatory post synaptic potential
Definition
what does EPSP stand for
Term
neurotransmitters
Definition
what opens ion channels on dendrites?
Term
-62mV
Definition
if a sodium channel is opened, to what potential will the ions flow in as long as the channel is not voltage gated?
Term
sodium
Definition
what ion does depolarization depend on?
Term
voltage gated potassium channels
Definition
what ion does repolarization depend on?
Term
conductances
Definition
how fast particular ions can move
Term
rapid closing of sodium channels does not allow this
Definition
why don't action potentials move backwards?
Term
absolute refractory period
Definition
inactivation gates of Na+ closed, neuron cannot be stimulated
Term
relative refractory period
Definition
need a stronger stimulus to initiate a response
Term
once threshold of excitation is met,

1. na open, na enters cell
2. K channels open, k begins to leave the cell
3. na channels become refractory(inactivation gate closed) no more na flows in
4. k continues to leave the cell causing membrane potential to return to resting level
5. k+ channels close, Na channels reset
6. extra K+ outside diffuses away
Definition
describe the Na/and K channels throughout the action potential
Term
saltatory conduction
Definition
faster way to travel down an axon than without myelin "to leap", signals travel node to node
Term
Lidocaine and Tetrodotoxin
Definition
VGNa channel blocker
Term
Hypercalcemia
Definition
can stabilize Na current, or cause increase excitability
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