Membrane Potentials

Question 1

what determines the resting membrane potential?

Answer 1

ion concentration differences, ion permeability (ion channels), Na/K and other pumps, negatively charged proteins (anions) inside the cell

Question 2

True/False: the resting membrane potential is negative.

Answer 2

TRUE

Question 3

the electrical potential difference that balances an ionic concentration gradient

Answer 3

equilibrium potential (E)

Question 4

what is the Nernst equation for a single ion?

Answer 4

E= (61/z) log ([ion]o/[ion]in) OR
E= (-61/z) log ([ion]in/[ion]out)

Question 5

When do you use the Goldman equation?

Answer 5

for MULTIPLE ions (it is the equilibrium potential for multiple ions)

Question 6

What is the Goldman equation?

Answer 6

Vm= 61.54 log (Pk[K+]o + Pna[Na+]o+ Pcl-{Cl-]i/ Pk[K+]i+ Pna[Na+]i + Pcl[Cl-]o

Question 7

how is an action potential triggered in a neuron?

Answer 7

graded potentials generated on dendrites of cell body . have to reach a threshold potential at the axon hillock to stimulate an action potential

Question 8

When the membrane is permeable to several different ions, the diffusion potential depends on what three factors?

Answer 8

1. ) polarity of the electrical charge on each ion
2. ) the permeability of the membrane (P) to each ion
3. ) the concentrations of the ions inside and outside of the membrane

Question 9

which two channels undergo permeability changes during transmission of a nerve impulse?

Answer 9

sodium and potassium

Question 10

What is the resting potential for nerve fibers?

Answer 10

-90 milivolts; the potential on the INSIDE the fiber is 90 more negative than the potential on the outside in the extracellular fluid

Question 11

what stage of an action potential is the resting membrane potential polarized and is before an action potential begins?

Answer 11

resting stage

Question 12

this stage occurs when the membrane becomes suddenly permeable to sodium ions and the potential becoming positive

Answer 12

depolarization stage

Question 13

this stage occurs when the sodium channels begin to close and potassium channels are open and diffusion of potassium to the exterior goes back to the normal resting negative potential

Answer 13

repolarization stage

Question 14

How is the voltage gated activation gate opened?

Answer 14

when the potential becomes less negative from -90 to -70- -50

Question 15

True/false: the inactivation gate of the sodium channel will not reopen again until the membrane potential has reached resting or more negative membrane potential.

Answer 15

TRUE; nerve fiber needs to be repolarized before channel opens again

Question 16

what is the threshold potential for an action potential to be generated?

Answer 16

-65 milivolts

Question 17

the period where a second action potential cannot be regenerated

Answer 17

absolute refractory period

Question 18

how do local anesthetics affect membrane excitability?

Answer 18

they directly affect the activation gates of sodium channels making it difficult for the gates to open and REDUCING membrane excitability

Question 19

what affect do neurotransmitters have on the synapse?

Answer 19

they can open ion channels on the dendrites, cell body and create graded potential on the axon hillock