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Flashcards in 2 Action Potentials Deck (46):
1

capacitance

whenever two conducting materials are separated by an insulating membrane

passive membrane properties

2

capacitance is ___ proportional to thickness of a capacitor

inversely

passive membrane properties

3

current

the net movement of electrical charge

passive membrane properties

4

capacitive current

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

5

capacitive current (stimulates/ inhbits) action potentials

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

6

membrane time constant (tau)

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

7

temporal summation

favored by a longer time constant or more frequent stimuli

8

cable properties

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

9

length constant

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

10

speed of propagation

large diameter axons are faster

passive membrane properties

11

Ri

internal resistance, 1/diameter squared)

passive membrane properties

12

Rm

1/ Diameter

13

Gullian-Barre Syndrome

loss of myelin in PNS only

diseases

14

Multiple Sclerosis

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

diseases

15

Charcot-Marie-Tooth Disease

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

demyelinating disease

16

tetrodioxin (TTX)

puffer fish toxin, blocks Na+ channel

Toxin: Na+ Channel

17

Saxitoxin (STX)

red algae toxin; plugs Na+ channels


Toxin: Na+ Channel

18

Conus Toxin

blocks Calcium gated channels

19

myelin plaque

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

Diseases

20

axon diameter- speed?

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

myelin

21

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

30%, most form loops around multiple axons

22

Neuregulin (NRG)

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

23

channelopathies

diseases caused by mutations in channels, often associated with epilepsy

24

lidocaine

binds to Na+ and promotes inactivation

25

rising phase

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

26

falling phase

Na channel inactivation and K channel activation
dominate

27

absolute refractory period

too much Na+ inactivation

28

relative refractory period

residual K+ activity still occuring and counteracting depolarization

29

3 common parts of a voltage-gated ion channel

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

30

selectivity filter

1. ion size
2. hydration energy

31

pore loops

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

32

S4 Region

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

33

K+ inactivation

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

34

sodium channel inactivation

a plug between domains 3 and 4

35

Ca Channels: T-type

located at the end of synapses

36

Ca Channels: L-type

the cell body of neurons

37

which channels activate fastest: Na, K, Ca

Na> Ca> K
Fast>Medium> Slow

inactivation is slower than Na

38

Ca shoulder

Ca delays the repolarization of the membrane

an epinephrine-enhanced

39

norepinephrine effec ton Ca2+

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

40

delayed rectified K channels

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

41

role: TASK K channel

resting membrane potential

42

Voltage-Gated Na Channels

action potentials

43

Voltage-Gated K Channels

delayed rectified, non-inactivating

action potentials

44

Voltage Gated Ca channels

action potentials, neurotransmitter release

45

Voltage Gated K Channels, A current, rapidly inactivating

firing rate

46

Hyperpolarizing-activated cation channels

Ih, HCN channels

firing rates, pacemaking, rhythmic activity