Action Potentials Part 3

Question 1

channelopathy

Answer 1

broken ion channel
genetic disease
malformed channel

Question 2

febrile seizures

Answer 2

channels take longer to close
keep firing action potentials
example of channelopathy

Question 3

ttx

Answer 3

from puffer fish
tetrodoxin
clogs na+ permeable pore by binding to channel
blocks action potential
fatal

Question 4

red tide

Answer 4

saxitoxin
blocks na+ channel
consume oysters/clams
causes nausea, dizziness, tingling in extremities

Question 5

black mamba

Answer 5

dendrotoxin
k+ channel blocker
death

Question 6

how does action potential continue down axon

Answer 6

positive na+ ions rush in, flow down axon, causing membrane just ahead to depolarize to threshold
k+ pumped out of each area in sequence
wave of depolarizations and depolarizations with sodium potassium pump reestablishing gradient along the way

Question 7

spike initiation zone

Answer 7

location where action potentials are generated
has many voltage gated sodium channels concentrated
sensory nerve endings
axon hillock

Question 8

axon potentials direction

Answer 8

only travel in one direction
bc na+ channels behind go into refractory period when inactivated
can generate from either end but typically only one direction bc structure of neuron causes threshold at spike initiation zone

Question 9

factors influencing action potential conduction velocity

Answer 9

temperature
axon diameter
path of positive charge
degree of myelination

Question 10

temperature

Answer 10

higher temperature = faster speed

warm blooded animals faster responses than cold blooded animals

Question 11

axon diameter

Answer 11

larger diameter, faster conduction
larger axons less resistance to flow of ions, easier to reach threshold
ex giant squid v fast

Question 12

path of positive charge

Answer 12

if stay inside axon, faster
if leak out across axonal membrane, slower
more ion channels = slower

Question 13

degree of myelination

Answer 13

more myelinated = faster

unmyelinateud conduction = slow

Question 14

saltatory conduction

Answer 14

myelinated conduction fast bc of this
electrical signal jumps from node to node
myelin sheath = insulator, currents flow only at nodes of ranvier
30 times faster than continuous conduction

Question 15

nodes of ranvier

Answer 15

high concentration of voltage gated ion channels
makes conduction faster
breaks in myelin sheath