Lecture 6 part two (SECOND MIDTERM) Flashcards Preview

Bio 223 > Lecture 6 part two (SECOND MIDTERM) > Flashcards

Flashcards in Lecture 6 part two (SECOND MIDTERM) Deck (46):
1

If multiple sodium gates open, the sodium permeability is..

a lot higher

2

Basic concept:
When a certain channel opens, what changes?

The permeability to that certain ion

3

In graded potentials, movement of the sodium ions inside of the cytoplasm is called...

local current

4

Any shift from the resting membrane potential toward a more positive potential is called...

a depolarization
"Getting rid of the polarity (difference) of the cell" - Noriega

5

Basic concept:
In a voltage gated channel, how can it reach the next "change"?

it MUST reach the next voltage level

6

In order to depolarize again, what must happen?

It must "repolarize"

7

What is repolarization?

The process of restoring the normal resting membrane potential after depolarization

8

The directional, continued depolarization along an axon is known as...

the action potential

9

There are 2 voltage gated channels. What are they?

-Sodium voltage gated
-Potassium voltage gated

10

The sodium voltage gated channels have 2 gates to them. What are they?

-Activation (on top)
-Inactivation (on bottom)

11

At the resting potential, what is the status of the gates?

-Sodium activation gate is closed (inactivation gate is open)
-Potassium activation gate is closed

12

At threshold, what happens to the gates?

-Sodium activation gate opens (inactivation gate is the same way it was at resting potential)
-Potassium activation gate is closed

13

Now that the sodium gate is open, what happens to permeability?

The cell is more permeable to sodium; sodium floods inside

14

When sodium floods in, what happens to the inside?

It becomes more positive; reverses polarity and reaches +30 mV

15

What happens when the inside reaches +30mV?

-Sodium inactivation gate closes (activation gate doesn't change)
-Potassium activation gate OPENS

16

When the sodium gate closes, what happens to the permeability?

It is less permeable to sodium

17

When only the potassium gate is open, where does the potassium go? What happens? What is it called?

-outside
-the inside becomes more negative
-repolarization

18

In order to "reset the entire system and go back to the very beginning," what has to happen? What is it called?

-It has to go past -70mV and go all the way down to -90mV
-Hyperpolarization

19

Once -90mV is reached, what is the status of the gates?

Sodium inactivation gate opens (activation gate closes)
Potassium gate closes

20

Since the gates are closed at -90mV but the voltage is still not at -70mV, how does it get back to that resting potential?

the leak channels

21

What CANNOT happen after depolarization? And what is that period called?

-It CANNOT depolarize again until it re-establishes the resting potential
-The refractory period

22

When is it when both activation gates are open but the sodium inactivation gate closes?

The refractory phase

23

The refractory phase has two parts. What are they?

Absolute
Relative

24

Absolute refractory phase:

The membrane cannot respond to further stimulation from the moment the voltage-gated sodium channels open at threshold until sodium channel inactivation ends, because all the voltage-gated sodium channels are already open or are inactivated.

25

Relative refractory phase:

Begins when the sodium channels regain their normal resting condition, and continues until the membrane potential stabilizes at resting levels.

26

How can the speed of the conduction be increased?

Depolarization skips from node to node

27

Jumping from node to node happens when?

Saltatory proragation

28

Events of saltatory propagation:

1. An action potential occurs at initial segment
2. A local current produces a graded depolarization that brings the axolemma at the next node to threshold
3. An action potential develops at the next node
4. A local current produces a graded depolarization that brings the axolemma at the next node to threshold

29

To go from one neuron to it's target cell (or another neuron), chemical signals are needed. They are called:

neurotransmitters

30

Important functions of myelin:

1. insulates axon so it's easier to maintain differential resting potential
2. speeds up conduction
3. prevents "cross-talk" between different neurons grouped in a single nerve

31

Acetylcholine and norepinephrine are what?

neurotransmitters

32

When that depolarization travels all the way down and the action potential reaches the terminal end (telodendria) of the axon, it's going to open what kind of channels? Where?

Voltage-gated calcium channels in the cytosol of the axon terminal

33

Calcium that enters the cell causes what to happen?

It causes vesicles to bond to cell membrane and release its content (neurotransmitters)

34

What stores the neurotransmitters?

vesicles

35

The space (gap) where the neurotransmitters are released is what?

synaptic cleft

36

What happens after the neurotransmitters are released into the synaptic cleft?

They bind to receptors for chemically gated channels on the next neuron

37

The junction between 2 neurons is called:

the synapse

38

Presynaptic neuron:
Postsynaptic neuron:

Presynaptic neuron: before synapse
Postsynaptic neuron: after synapse

39

What can happen to the neurotransmitter when it gets released?

-it can be reabsorbed into the presynaptic neuron
-it can be broken down by enzymes

40

2 basic ways neurotransmitters can work:

Directly: ionotropic effects (changing ion concentrations across membrane)
Indirectly: metabotrophic effects (changing metabolism of the cell)

41

Indirect neurotransmitter action:

-metabotrophic effects
-essentially a second messenger system
-effects can last longer that direct action

42

The effect of a neurotransmitter depends on the __________, NOT the ____________!

receptor, NOT the neurotransmitter!

43

In indirect actions, what is the "link" between the first messenger and the second messenger?

a G Protein

44

The indirect action can be ________ or ________; meaning it can make things easier to reach threshold or more difficult to do so.

excitatory (easier), inhibitory (more difficult)

45

Excitation:

Influx of calcium (Ca2+); decrease passage of chloride (Cl-) and potassium (K+); metabolic changes; change in number of receptors

46

Inhibition:

Influx of chloride (Cl-); increased passage of potassium (K+); metabolic changes; change in number of receptors