Chapter 4

Question 1

Action potential is also called…

Answer 1

• Spike
• Nerve impulse
• Discharge

Question 2

Action potential is a rapid…

Answer 2

Reversal of membrane potential where the inside becomes positively charged with respect to the outside

Question 3

What is synaptic transmission?

Answer 3

Synaptic transmission is the transfer of information from neuron to neuron

Question 4

How do action potentials affect information transfer?

Answer 4

The frequency and pattern of action potentials constitute the code used by neurons to transfer information from one location to another

Question 5

Action potential is responsible for

Answer 5

Conveying information over long distances

Question 6

What is depolarization?

Answer 6

Depolarization is when the membrane voltage becomes more positive

Question 7

What is hyperpolarization?

Answer 7

Hyperpolarization is when the membrane voltage becomes more negative

Question 8

Positive ion influx results in…

Answer 8

Depolarization

Question 9

Positive ion efflux results in…

Answer 9

Hyperpolarization

Question 10

Negative ion influx results in…

Answer 10

Hyperpolarization

Question 11

Negative ion efflux results in…

Answer 11

Depolarization

Question 12

How is action potential generated?

Answer 12

Action potential is generated through a depolarizing current of membrane beyond threshold
- Occurs naturally via excitatory synaptic transmission
- Occurs artificially via current injection into a neuron with a microelectrode

Question 13

If injected current does not depolarize the membrane to threshold…

Answer 13

No action potentials will be generated

Question 14

If injected current depolarizes the membrane beyond threshold…

Answer 14

Action potentials will be generated

Question 15

The action potential firing rate ____ as the depolarizing rate ____

Answer 15

Increases; increases

Question 16

Neurons are electrically ___

Answer 16

Active

Question 17

Glia are electrically ____

Answer 17

Silent

Question 18

Explain the process of a chain reaction of action potential with a foot puncture:

Answer 18

Foot puncture, stretch membrane of nerve fibers
- Opens Na+ permeable channels-> Na+ influx-> depolarized membrane->reaches threshold-> action potential

Question 19

Action potential graph

Answer 19

*Undershoot occurs after hyperpolarization

Question 20

Characteristics of action potentials

Answer 20

1. Have a threshold for initiation
2. All or nothing (below threshold = none, above threshold = all)
3. Always depolarizing
4. Constant amplitude
5. Constant duration
6. Propagate without decrement
7. Have a two part refractory period (absolute: during falling phase, relative: during undershoot)

Question 21

What is membrane current?

Answer 21

Net movement of K+ across membrane

Question 22

Potassium channel number is ____ to electrical conductance

Answer 22

Proportional

Question 23

Membrane potassium current consists of…

Answer 23

Flow and driving force

Question 24

What is the rising phase?

Answer 24

Inward sodium current, influx of Na+ ions

Question 25

What is the falling phase?

Answer 25

Outward potassium current, efflux of K+ ions

Question 26

What are Hodgkin and Huxley known for?

Answer 26

Use of patch-clamp electrophysiology to demonstrate properties of AP

Question 27

What is the purpose of a voltage clamp?

Answer 27

"Clamp" membrane potential at any chosen value

Question 28

What does the voltage gated sodium channel consist of?

Answer 28

Transmembrane domains and ion-selective pore

Question 29

What are the 3 states of voltage gated sodium potentials?

Answer 29

Closed, open, inactivated

Question 30

Channel closing and reactivation require...

Answer 30

Negative Vm reset

Question 31

What occurs in the absolute refractory period?

Answer 31

Channels are inactivated

Question 32

What is the extracellular concentration of Na+?

Answer 32

150 mM

Question 33

What is the intracellular concentration of Na+?

Answer 33

15 mM

Question 34

What is the extracellular concentration of K+?

Answer 34

5 mM

Question 35

What is the intracellular concentration of K+?

Answer 35

100 mM

Question 36

What are some toxins that target voltage gated sodium channels (VGSC)?

Answer 36

1. Puffer fish tetrodotoxin 2. Red tide saxitoxin 3. Batrachotoxin

Question 37

What happens with puffer fish tetrodotoxin (TTX)?

Answer 37

Clogs Na+ permeable pore

Question 38

What happens with red tide saxitoxin?

Answer 38

Na+ channel is blocked

Question 39

What happens with batrachotoxin?

Answer 39

Inactivation so channels remain open

Question 40

What is channelopathies?

Answer 40

Generalized epilepsy, febrile seizures

Question 41

Potassium gates open ___ than sodium gates

Answer 41

Later

Question 42

Potassium conductance serves to ____ membrane potential

Answer 42

Rectify or reset

Question 43

What is the structure of VGKC's?

Answer 43

Four separate polypeptide subunits join to form a pore

Question 44

Do voltage-gated K+ channels activate?

Answer 44

No

Question 45

What occurs at T1?

Answer 45

Voltage-gated Na+ channels open

Question 46

What occurs at T2?

Answer 46

The voltage-gated Na+ channels inactivate and K+ channels are opening

Question 47

What occurs at T3?

Answer 47

The voltage-gated K+ channels are closing, stopping K+ efflux

Question 48

What occurs during the absolute refractory period?

Answer 48

Voltage gated Na+ channels are inactivated

Question 49

What occurs during the relative refractory period?

Answer 49

It occurs during after-hyperpolarization. Voltage gated Na+ channels become reactivated, but membrane potential is below resting and would require greater depolarization current to fire another action potential than at rest

Question 50

What does the spike-initiation zone consist of?

Answer 50

Sensory nerve endings and axon hillock

Question 51

What factors influence conduction velocity?

Answer 51

- Spread of action potential along membrane (dependent on axon structure) - Path of positive charge (inside axon = faster), across the axonal membrane = slower) - Axonal excitability (axonal diameter: bigger=faster) - Number of voltage gated channels - Myelination

Question 52

What does orthodromic mean?

Answer 52

Action potential travels in one direction (down the axon to the axon terminal)

Question 53

What does antidromic (experimental) mean?

Answer 53

Backward propagation

Question 54

What is the typical conduction velocity of propagation of action potential?

Answer 54

10 m/sec

Question 55

What is the typical length of action potential?

Answer 55

~2 msec

Question 56

Layers of myelin sheath facilitate....

Answer 56

Current flow (in conduction velocity)

Question 57

What type of conduction occurs at Nodes of Ranvier?

Answer 57

Saltatory conduction; here voltage gated sodium channels are concentrated

Question 58

What id Optogenetics?

Answer 58

- Introduction of foreign genes: express membrane ion channels, open in response to light Ex: In the mouse brain, neurons firing controlled by light delivered by optic fiber

Question 59

What is the flow of neuronal signal transmition due to puncture in the skin?

Answer 59

Puncture the skin-> nerves stretch-> Na+ open-> Ap initiated and propagated->information "communicated" to the next neuron across the membrane (synaptic transmission)