ET : N - Membrane Potentials

Question 1

what are the building blocks and instruments of communication in the brain

Answer 1

neurons or nerve cells

Question 2

which direction do synaptic potentials travel

Answer 2

from dendrites in towards cell body

Question 3

which direction do action potentials travel

Answer 3

out towards axon and axon terminals

Question 4

what happens to action potentials when they reach the axon terminal

Answer 4

info transferred to other cells through synapses

Question 5

what two components does communication consist of

Answer 5

electrical signals (dendrites, cell body, axon) and chemical signals (synapses)

Question 6

resting membrane potential of cytoplasm in comparison to extracellular space

Answer 6

more negative/lower than RMP of extracellular space

Question 7

almost all cells in the body have a _______ RMP

Answer 7

negative

Question 8

what two things can suddenly respond with a transient change of the potential (with an action potential) in response to a stimulus

Answer 8

neurons and muscle fibres

Question 9

what happens to RMP when stimulus is added and what is this known as

Answer 9

suddenly changes and becomes positive, this is transient and goes back to negative. this is known as an action potential

Question 10

what does a typical neuron consist of

Answer 10

soma (cell body), dendrites and a single axon

Question 11

what is membrane potential

Answer 11

voltage across the cell membrane

Question 12

what is RMP

Answer 12

membrane potential at rest

Question 13

typical value of RMP

Answer 13

between -50 and -70 mV

Question 14

what two techniques are used to measure intracellular potentials

Answer 14

the microelectrode recording technique and the patch-clamp technique

Question 15

describe patch clamp technique (how does it work and what does it need)

Answer 15

larger tip that does not penetrate the membrane, seals to membrane (between bilipid layer and glass of clamp) creating contact between inside of cell and electronic device allowing to measure current. patch clamp needs an electrolyte otherwise current doesn’t transmit

Question 16

the rmp: electrical potential difference (50 to 70 mV) across the cell membrane from _______ ___ ______. There is more ________ charges inside the cell in comparison to the extracellular fluid

Answer 16

separation of charge

negative

Question 17

by convention, what is the potential outside the cell defined as

Answer 17

zero

Question 18

if potential outside cell is defined as zero, intracellular potential is therefore usually _______ _____.

Answer 18

below zero

Question 19

what three things cause rmp (very important to remember)

Answer 19

1) unequal concentrations of Na+ and K+ inside and outside the cell
2) unequal permeability of the cell membrane to these ions
3) electrogenic action of the Na-K pump

Question 20

relative concentrations of K+ and Na+ inside and outside the cell?

Answer 20

concentration of potassium is much higher inside the cell than outside

concentration of sodium is much higher outside the cell than inside

Question 21

how are the concentration gradients for K+ and Na+ maintained

Answer 21

by the Na+/K+ pump

Question 22

what would happen if cells had membranes permeable to ions

Answer 22

the gradient would dissipate due to diffusion

Question 23

the cell membrane is a little permeable to __________ and these ions will try to ____ __ the cell, the cell membrane is highly permeable to __________ and these ions will try to _______

Answer 23

sodium
get in
potassium
escape

Question 24

what does the sodium potassium pump do that maintains conc gradients

Answer 24

removes the sodium that entered the cell and inserts back in the potassium that left the cell

Question 25

what is the ratio of this pump

Answer 25

3:2 (sodium:potassium)

Question 26

since it is not a 1:1 ratio, (more sodium out than potassium in) the pump removes more…

Answer 26

positive charges than it introduces which adds negativity to the cell in comparison to outside

Question 27

what are ion channels

Answer 27

channels that have selective permeability to ions

Question 28

what two components cause unequal permeability of the cell membrane

Answer 28

non-gated (leak) channels and gated channels

Question 29

non-gated leak channels are ______ at rest

Answer 29

open

Question 30

gated channels are ________ at rest

Answer 30

closed

Question 31

in the cell membrane of neurons, there are many _______ ____ channels and very few ________ ___ channels

Answer 31

many leak K+ channels

very few leak Na+ channels

Question 32

At rest, PK+/PNa+ =

Answer 32

40/1

Question 33

what is the determinig factor of the resting membrane potential

Answer 33

the leak channels

Question 34

at rest, cell membrane is much more permeable to which ion?

Answer 34

potassium (compared to sodium)

Question 35

what does net flow of zero mean

Answer 35

the flow of one ion is identical to the flow of another ion in the opposite direction

Question 36

what does is the equilibrium potential

Answer 36

an intracellular potential at which the net flow of ions is zero, in spite of a conc gradient and permeability

Question 37

what can be used to calculate the equilibrium potential for each ion

Answer 37

the nernst equation

Question 38

explain how conc gradient and electrostatic gradient is set up using potassium as an example

Answer 38

there is more potassium inside the cell than outside, so conc gradient is present. due to many leak channels for potassium, potassium can move from inside to outside. but when it moves outside it leaves a negative charge inside which attracts the positive potassium back into the cell - so there are two forces chemical gradient and an electrostatic force. At some point, the amount leaving will be equal to the amount entering and will create a net flow of zero

Question 39

what does the equilibrium potential prevent

Answer 39

shifts of ions (there are shifts but net flow remains zero) and this also maintains the cons gradient

Question 40

the nernst equation only applies to a situation in which …

Answer 40

a cell membrane is permeable to only one ion (i.e. has leak channels only for one specific ion)

Question 41

glia cells have leak channels for which ion and what does this make the RMP in glia cells

Answer 41

potassium only and thus RMP = Ek = (-80mV)

Question 42

what is the equilibrium potential for Na

Answer 42

~+60

Question 43

what is the equlibrium potential for K

Answer 43

~-80

Question 44

in neurons, which channels affect the RMP

Answer 44

both K+ and Na+

Question 45

(important) The higher the permeability of the cell membrane to a particular ion… (relative to RMP)

Answer 45

the greater the ability of this ion to shift the RMP towards its equilibrium potential

Question 46

at rest, which ion is permeability of membrane higher to (which ion is equilibrium potential closest to)

Answer 46

K+

Question 47

in comparison to glia cells, ther RMP in neurons is… (and why)

Answer 47

less negative due to a small contribution of leak Na+ channels

Question 48

what do you use to calulate the value of the RMP taking into account both the cons grads and the permeability of RMP to K+ and Na+ ions

Answer 48

the goldman equation

Question 49

how many mV outside the cell

Answer 49

0mV

Question 50

how many mV inside the cell

Answer 50

~-65mV