Ion channels and action potential Flashcards

1
Q

Always open and allow ___ to passively diffuse down concentration gradient (out of cell)

A

K+ Leak channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Always open and allow ___ nto passively diffuse down concentration gradient (into cell )

A

Na+ leak channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

open when threshold is reached and allows Na+ influx

A

Voltage Gated Na+ Channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Open around peak of action potential and allow K+ efflux

A

delayed recitifier voltage gated K+ Channel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

RMP (-70 mV)

A

K+ makes a bigger contribution to establishing the RMP than Na+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Depolarization

A

amount of Na+ entering cell is greater than the amount of K+ leaving cell through K+ leak channel, so nerve interior becomes increasingly positive and depolarizes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

threshold

A

voltage the membrane potential must increase to in order for an action potential to occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Peak

A

Membrane potential of nerve peaks near Nernst potential of Na+. Voltage gated Na+ channels close
and Delayed Rectifier Voltage Gated K+ Channel opens. Na+ stops flowing into cell and K+ starts
flowing out of cell through leak channels and Delayed Rectifier V-Gated K+ channel. Cell interior stops
becoming increasingly positive and instead starts to become negative as K+ leaves cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Repolarization

A

Only channel open is Voltage Gated Delayed Rectifier K+ channels, so cell interior is
getting increasingly negative as amount of K+ flowing out > amount of Na+ flowing in

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Undershoot

A

Delayed Rectifier K+ channels are slow to open and close, so membrane potential dips
slightly below RMP as K+ continues to flow out of cell as gate on Delayed Rectifier K+ channel slowly
closes (Results in hyperpolarization)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

voltage clamping

A

technique that enables you to hold the membrane voltage of an excitable cell at a fixed voltage while you measure the current passing through the cell membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

current =

A

Conductance * Voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

if there is an inward and outward current, ions must be moving in and out of the ___

A

neuron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how do we know which parts of the current curves are due to the movement of Na+ or K+

A

TTX- toxin by puffer fish block Na+ channels
TEA : selectively blocks potassium channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

above the y axis corresponds to ____ ions leaving the cell

A

positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Na+ channels open __ and open ___

A

first and quickly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

K+ channels open ___ and ___

A

after and slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

hold voltage constant and measure change in current

A

Voltage clamp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

hold current constant and measure change in voltage

A

current clamp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

same principle as voltage clamp but measures the current in a single channel at fixed voltage

A

patch clamp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

depolarization

A

Depolarization, in biology, refers to a sudden change within a cell, during which the
cell undergoes a dramatic electrical change. Most cells, especially those that compose
the tissues of highly organized animals, typically maintain an internal environment
that is negatively charged compared to the cell’s surrounding environment. This difference in charge is called the cell’s membrane potential. In the process of depolarization,
the negative internal charge of the cell becomes positive for a very brief time. This shift
from a negative to a positive internal cellular environment allows for the transmission
of electrical impulses both within a cell and, in certain instances, between cells. This
communicative function of depolarization is essential to the function of many cells,
communication between cells, and the overall function of an organism.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

open and close fast (slope is greater )

A

Voltage gated Na+ Channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Time dependent because it has an inactivation gate

A

Voltage gated Na+ Channels

24
Q

(Certain amount of time (and voltage) has to pass
before it will reopen after depolarizing - inactivation
period)

A

Voltage gated Na+ Channels

25
3 conformations: Open, closed-inactivated, and closed
Voltage gated Na+ Channels
26
Responsible for depolarization
Voltage gated Na+ Channels
27
Responsible for absolute refractory period
Voltage gated Na+ Channels
28
Allows for passage of Na+ into cell
Voltage gated Na+ Channels
29
Open and close slow (Why we call them “Delayed Rectifier”)
Voltage Gated K+ Channels
30
Time independent (no inactivation period) because it does not have an inactivation gate
Voltage Gated K+ Channels
31
2 confirmations open, closed
Voltage Gated K+ Channels
32
responsible for repolarization
Voltage Gated K+ Channels
33
responsible for relative refractory period
Voltage Gated K+ Channels
34
allows for passage of K+ out of cell
Voltage Gated K+ Channels
35
___ channels can be target for local anesthetics lidocaine or drugs cocaine
Na
36
absolute refractory period
time period where another action potential cannot occur no matter how strong of a stimulus is applied
37
Na+ channels being in their close inactivated state
absolute refractory period
38
relative refractory period
another action potential can occur but the stimulus must be stronger than normal because the cell is hyperpolarized
39
"persistant activation" of the delayed recitifier V gated K+ channels
relative refractory period
40
factors that can affect threshold
number of K+ leak channels
41
local circuit
current that is produced during an action potential which triggers depolarization to spread to a nearby membrane
42
Refractory periods (Closed-inactivated state of V-Gated Na+ channels) prevent backwards propagation of an action potential.
true
43
local potential
change in membrane potential due to an applied stimulus. The change in potential is dependent on how strong the stimulus is
44
High Ca2+ levels results in decreased ____ because excess calcium binds to the ____ This causes the Na+ channels to have decreased excitability because the positive charges seem to alter the ability of the channel to sense the changes in voltage, which means a stronger ____ will be needed for these Na+ channels to open to generate an action potential
excitability voltage sensor of Na+ channels. depolarization
45
Low Ca2+ levels results in _____ because the voltage sensors are ___ shielded and perceive stimuli to be greater than they actually are. Thus, a ____ than normal depolarization will open the V-Gated Na+ channels and generate an action potential
hyperexcitability less shielded a weaker
46
Nodes of Ranvier
points along an axon with no myelination. There are also a lot of Na+ and K+ channels concentrated there, with a higher density of Na+ channels than K+ channels. The high density of Na+ channels is what enables saltatory conduction (action potentials bypassing a myelinated section of neuron and jumping from node to node). K+ channels are more highly concentrated in the paranodal axolemma (next to the node).
47
axon
long fiber-like structures responsible for sending signals in the form of action potentials to adjacent cells
48
myelination
49
What influences conduction velocity in different neurons?
Two inherent properties of the neurons: (1) the space constant and (2) the time constant
50
space constant
distance an action potential can travel before it reaches 37% of its inital strength
51
What biologically increases the space constant (and thus increases conduction velocity)?
(1) Properties of phospholipids, number of leak channels, and presence of myelin→Increase membrane resistance (2) More layers of myelin → Increases axon diameter which decreases internal resistance
52
Time Constant is
is the amount of time required to charge and discharge the membrane. It is calculated with the equation
53
Myelination increases the membrane resistance and decreases membrane capacitance. It may look like the two changes cancel each other out since we are multiplying them by each other, but the decrease in membrane capacitance outweighs the increase in membrane resistance. So, myelination overall decreases the time constant, thereby increasing conduction velocity.
T
54
1) INCREASING THE SPACE CONSTANT INCREASES
CONDUCTION VELOCITY
55
THE TIME CONSTANT INCREASES CONDUCTION VELOCITY
(2) DECREASING
56
myelin increases conduction velocity in 3 ways
increases membrane resistance (Rm) Decreases internal resistance decreases membrane capacitance
57
diseases of nervous system that involve pathologic loss of myelin
mulitple scelrosis and guillain barre syndrome