Generation & Propagation of Action Potentials

Question 1

What acts as a capacitor in the cell?

Where are the - charges?

Answer 1

Cell membranes

Negative charges on the intracellular ide

Question 2

What effect does capacitance have on action potential?

Answer 2

Slows the time course because capacitance must first be disipated for depolarization & hyperpolarization.
Rapid

Question 3

Membrane Time Constant

Answer 3

Time it takes for a 63% change in membrane potential

1-10 milliseconds

Question 4

Temporal summation and effect of time constant

Answer 4

Longer time constant = action potentials can overlap

Also refers to small stimuli that can only generate an AP if fired closely after each other

Question 5

Speed of propagation

Answer 5

1/sqrt((rmXri) X Cm)

Question 6

Length Constant

Answer 6

sqrt(rm/ri)

Question 7

Name 4 passive membrane properties

Answer 7

1. Capacitance
2. Membrane time constant
3. Speed of propagation
4. Length constant

Question 8

Name 1 organism that relies solely on passive properties for membrane AP

Answer 8

C. elegans

Question 9

Absolute refractory period

Answer 9

No AP can be generated

Na channels open & become inactivated

Question 10

Refractory period

Answer 10

Greater stimulus required to generate an AP

K + channels open but overshoot hyperpolization

Question 11

Role of pore loops

Answer 11

Ion selectivity based on size + hyrdophobicity

Question 12

Role of S4 membrane

Answer 12

Every 3rd amino acid + charged

AP results in confirmation change, twists ad moves up, opens channel

Question 13

K channel inactivation method

Answer 13

Ball and chain

Question 14

Na channel inactivation method

Answer 14

Loop between 3rd and 4th domains stays “plugged in” until membrane is repolarized

Question 15

Rank activation speed

NA K Ca

Answer 15

1. Na
2. Ca
3. K

Question 16

Rank Inactivation speed

Na and Ca

Answer 16

Na faster than Ca

Question 17

Role of CA on AP

Answer 17

Depolaization

Question 18

Role of K on AP

Answer 18

Repolarization

Delays reaching threshhol

Question 19

Role of Ca on AP

Answer 19

Delays repolirization

Sometimes see Ca shoulder

Question 20

What are “A current” channels

Answer 20

Special K channels that prolong the interspike interval

Question 21

What are Nucleotide gated channels

Answer 21

• Important in pacemaker cells
• Open only in hyperpolarized state
• Encourage depolarization towards threshold
• Cation influx

Question 22

Name 3 Na channel blockers

Answer 22

Tetrodotoxin
Saxitoxin
Lidocaine

Question 23

Name 1 K channel blocker

Answer 23

Tetrathyamonium (TEA)

Question 24

Name 1 Ca channel blocker

Answer 24

Conus toxin

Question 25

What channel is overactive in pain

Answer 25

Na

Question 26

What channels are responsible for hyperactivity in epilepsy

Answer 26

Na | - Fail to inactivate, prolonged deolarization, abnormal excitability

Question 27

Define channelopathies

Answer 27

Genetic disorders in channel functioning

Question 28

Dysmylinating vs Demylinating disease

Answer 28

``` Dys = abnormal myelin De = No myelin ```

Question 29

Gullian Barre Syndrome

Answer 29

PNS myelin is lost

Question 30

Multiple sclerosis

Answer 30

CNS myelin is lost

Question 31

Charcot-Mari-Toot Syndrome

Answer 31

Gap junctions are abnormal, no nutrient transfer to outer layers = death

Question 32

Proagation is usally uni-directional but what channels can cuse bidirectional propagation?

Answer 32

Na

Question 33

``` Effect of diametr on the following Capaciatance Membrane Resistance Speed Internal resistance ```

Answer 33

Inc. capacitance Dec. membrane resistance Inc. speed Dec. internal resistance (inverse square of diameter)

Question 34

Benefits of mylination

Answer 34

Less ATP Decrease capacitance Increases speed, length constant, membrane resistance

Question 35

Support neurons of PNS

Answer 35

Schawn cells

Question 36

Support neurons of the CNS

Answer 36

Glial cells

Question 37

What cells interact in order to trigger myelination

Answer 37

Glia and axons

Question 38

What molecule determines the number of "wraps" of myelin

Answer 38

neuroglin

Question 39

Role of Myelin Associated Protein in myelination | PNS or CNS

Answer 39

Initial glial-axon interaction | PNS & CNS

Question 40

Po | PNS or CNS

Answer 40

Myelin compaction | PNS

Question 41

Proteolipid Protein | PNS or CNS

Answer 41

Mylin compaction | CNS

Question 42

Myelin Basic Protein | PNS or CNS

Answer 42

Myelin compaction | CNS & PNS