2 Action Potentials

Question 1

capacitance

Answer 1

whenever two conducting materials are separated by an insulating membrane

passive membrane properties

Question 2

capacitance is ___ proportional to thickness of a capacitor

Answer 2

inversely

passive membrane properties

Question 3

current

Answer 3

the net movement of electrical charge

passive membrane properties

Question 4

capacitive current

Answer 4

before ions flowing across a cell membrane can cause a change a change in voltage, they need to strip ions away from the inner cell membrane

passive membrane properties

Question 5

capacitive current (stimulates/ inhbits) action potentials

Answer 5

inhibits: it represents a charge sink that must be “filled” before there is a net flow of ions across the membrane

Question 6

membrane time constant (tau)

Answer 6

time it takes for 63% of a total membrane potential to change

Question 7

temporal summation

Answer 7

favored by a longer time constant or more frequent stimuli

Question 8

cable properties

Answer 8

consider the axon a series of membrane segments, each with its own membrane resistance and membrane capacitance to current flow into the cytoplasm

Question 9

length constant

Answer 9

the distance at which 37% of the original change in membrane potential still occurs

Question 10

speed of propagation

Answer 10

large diameter axons are faster

passive membrane properties

Question 11

Ri

Answer 11

internal resistance, 1/diameter squared)

passive membrane properties

Question 12

Rm

Answer 12

1/ Diameter

Question 13

Gullian-Barre Syndrome

Answer 13

loss of myelin in PNS only

diseases

Question 14

Multiple Sclerosis

Answer 14

loss of myelin in CNS only: T cell immune infiltrates cause activation of microglia and macrophages

diseases

Question 15

Charcot-Marie-Tooth Disease

Answer 15

a peripheraland sensory neuropathy caused by loss of myelin due to gap junction mutation

demyelinating disease

Question 16

tetrodioxin (TTX)

Answer 16

puffer fish toxin, blocks Na+ channel

Toxin: Na+ Channel

Question 17

Saxitoxin (STX)

Answer 17

red algae toxin; plugs Na+ channels

Toxin: Na+ Channel

Question 18

Conus Toxin

Answer 18

blocks Calcium gated channels

Question 19

myelin plaque

Answer 19

the accumulation of debris, microglia, and macrophages at the focal sites of myelin destruction

Diseases

Question 20

axon diameter- speed?

Answer 20

1. largest: golgia tendon bodies
2. mechanoreceptors of skin
3. pain, temperature
4. smallest temperature, itch, pain

myelin

Question 21

what percent of Schwann cells form a sheath around a single axon?

Answer 21

30%, most form loops around multiple axons

Question 22

Neuregulin (NRG)

Answer 22

regulates the thickness of the myelin sheath (number of layers)

Question 23

channelopathies

Answer 23

diseases caused by mutations in channels, often associated with epilepsy

Question 24

lidocaine

Answer 24

binds to Na+ and promotes inactivation

Question 25

rising phase

Answer 25

voltage-gated Na+ channels open, K+ activation is slow

Question 26

falling phase

Answer 26

Na channel inactivation and K channel activation | dominate

Question 27

absolute refractory period

Answer 27

too much Na+ inactivation

Question 28

relative refractory period

Answer 28

residual K+ activity still occuring and counteracting depolarization

Question 29

3 common parts of a voltage-gated ion channel

Answer 29

1. pore loop (P) 2. Voltage sensor (S4 region) 3. inactivation loop

Question 30

selectivity filter

Answer 30

1. ion size | 2. hydration energy

Question 31

pore loops

Answer 31

ion selectivity, charges at the tip of the loop can significantly alter the ion that is selected for

Question 32

S4 Region

Answer 32

voltage sensitivity, an OUTWARD TWIST due to positive charges repeating every 3 amino acids respond to changes in membrane potential

Question 33

K+ inactivation

Answer 33

ball and chain model ball: positive charge chain: flexible AAs

Question 34

sodium channel inactivation

Answer 34

a plug between domains 3 and 4

Question 35

Ca Channels: T-type

Answer 35

located at the end of synapses

Question 36

Ca Channels: L-type

Answer 36

the cell body of neurons

Question 37

which channels activate fastest: Na, K, Ca

Answer 37

Na> Ca> K Fast>Medium> Slow inactivation is slower than Na

Question 38

Ca shoulder

Answer 38

Ca delays the repolarization of the membrane an epinephrine-enhanced

Question 39

norepinephrine effec ton Ca2+

Answer 39

NE can inhibit Ca influx in the Pre-Synaptic neurons via Beta/ Gamma units

Question 40

delayed rectified K channels

Answer 40

do not inactviate, rather remain open as long as the membrane is depolarized

Question 41

role: TASK K channel

Answer 41

resting membrane potential

Question 42

Voltage-Gated Na Channels

Answer 42

action potentials

Question 43

Voltage-Gated K Channels

Answer 43

delayed rectified, non-inactivating action potentials

Question 44

Voltage Gated Ca channels

Answer 44

action potentials, neurotransmitter release

Question 45

Voltage Gated K Channels, A current, rapidly inactivating

Answer 45

firing rate

Question 46

Hyperpolarizing-activated cation channels

Answer 46

Ih, HCN channels firing rates, pacemaking, rhythmic activity