Lecture 6 part two (SECOND MIDTERM)

Question 1

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

Answer 1

a lot higher

Question 2

Basic concept:

When a certain channel opens, what changes?

Answer 2

The permeability to that certain ion

Question 3

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

Answer 3

local current

Question 4

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

Answer 4

a depolarization

“Getting rid of the polarity (difference) of the cell” - Noriega

Question 5

Basic concept:

In a voltage gated channel, how can it reach the next “change”?

Answer 5

it MUST reach the next voltage level

Question 6

In order to depolarize again, what must happen?

Answer 6

It must “repolarize”

Question 7

What is repolarization?

Answer 7

The process of restoring the normal resting membrane potential after depolarization

Question 8

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

Answer 8

the action potential

Question 9

There are 2 voltage gated channels. What are they?

Answer 9

• Sodium voltage gated

- Potassium voltage gated

Question 10

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

Answer 10

• Activation (on top)

- Inactivation (on bottom)

Question 11

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

Answer 11

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

Question 12

At threshold, what happens to the gates?

Answer 12

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

Question 13

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

Answer 13

The cell is more permeable to sodium; sodium floods inside

Question 14

When sodium floods in, what happens to the inside?

Answer 14

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

Question 15

What happens when the inside reaches +30mV?

Answer 15

• Sodium inactivation gate closes (activation gate doesn’t change)
• Potassium activation gate OPENS

Question 16

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

Answer 16

It is less permeable to sodium

Question 17

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

Answer 17

• outside
• the inside becomes more negative
• repolarization

Question 18

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

Answer 18

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

- Hyperpolarization

Question 19

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

Answer 19

Sodium inactivation gate opens (activation gate closes)

Potassium gate closes

Question 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?

Answer 20

the leak channels

Question 21

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

Answer 21

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

Question 22

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

Answer 22

The refractory phase

Question 23

The refractory phase has two parts. What are they?

Answer 23

Absolute

Relative

Question 24

Absolute refractory phase:

Answer 24

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.

Question 25

Relative refractory phase:

Answer 25

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

Question 26

How can the speed of the conduction be increased?

Answer 26

Depolarization skips from node to node

Question 27

Jumping from node to node happens when?

Answer 27

Saltatory proragation

Question 28

Events of saltatory propagation:

Answer 28

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

Question 29

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

Answer 29

neurotransmitters

Question 30

Important functions of myelin:

Answer 30

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

Question 31

Acetylcholine and norepinephrine are what?

Answer 31

neurotransmitters

Question 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?

Answer 32

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

Question 33

Calcium that enters the cell causes what to happen?

Answer 33

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

Question 34

What stores the neurotransmitters?

Answer 34

vesicles

Question 35

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

Answer 35

synaptic cleft

Question 36

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

Answer 36

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

Question 37

The junction between 2 neurons is called:

Answer 37

the synapse

Question 38

Presynaptic neuron:

Postsynaptic neuron:

Answer 38

Presynaptic neuron: before synapse

Postsynaptic neuron: after synapse

Question 39

What can happen to the neurotransmitter when it gets released?

Answer 39

• it can be reabsorbed into the presynaptic neuron

- it can be broken down by enzymes

Question 40

2 basic ways neurotransmitters can work:

Answer 40

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

Question 41

Indirect neurotransmitter action:

Answer 41

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

Question 42

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

Answer 42

receptor, NOT the neurotransmitter!

Question 43

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

Answer 43

a G Protein

Question 44

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

Answer 44

excitatory (easier), inhibitory (more difficult)

Question 45

Excitation:

Answer 45

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

Question 46

Inhibition:

Answer 46

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