action potentials

Question 1

depolarization

Answer 1

the cell becomes less negative

Question 2

hyperpolarization

Answer 2

the eletrical force becomes stronger as the cell gets more negative, potassium starts to flow in and equalise again

Question 3

action potential

Answer 3

small change in the membrane potential due to a stimulation through electrical currents or chemical messengers, resulting in a less negative cell

Question 4

action potential threshold

Answer 4

when the neuronal cell is stimulated above -60mv and voltage gated channels open

Question 5

process of an action potential

Answer 5

• neuron is stimulated above a threshold
• voltage gated channels for na and k open up
• sodium starts to flow into the cell (both concentration and electrical gradient)
• cell starts to depolarize
• potassium starts to flow out of the cell (concentration gradient)
• membrane potential rises until it reaches 20mv and voltage gated channels close again
• sodium influx stops immediately but potassium continues to flow through leaky channels
  -electrical and concentration gradient push potassium out
• continues until eletcrical and concentration force are in equilibrium again (-70mv)
• sodium/potassium pump, pump sodium out and potassium into the cell to restore chemical balance

Question 6

what causes the increase in positivity in the cell

Answer 6

sodium flows back into the cell much stronger than potassium flowing out

Question 7

what causes hyperpolarization

Answer 7

the potassium outflux is stronger than sodium influx so the cell becomes negative

Question 8

why do we need protein pumps

Answer 8

to pump the sodium from a low concentration to a high concentration

Question 9

protein pumps

Answer 9

actively moves sodium out and potassium in

Question 10

how do protein pumps work

Answer 10

binds two potassium on the outside, flips around to put the two potassium inside the cell and binds three soidum, then flips again to move the sodium outside the cell

Question 11

all or none response

Answer 11

you cant have a little action potential. cells only differentiate by how many actions they produce, not by size

Question 12

action potential propogation

Answer 12

how electrical activity moves down the axon to the terminal region

Question 13

axon hillock

Answer 13

where the initial sodium ion channels start

Question 14

steps of an action potential propogating

Answer 14

• as the area of the neuron thats activated depolarizes, that part of the membrane reaches -60mv
• at -60mv, the ion channel next to it opens up
• as sodium flows in the cell depolarizes
• this spreads to the next sodium channel that reaches the thresh hold and so on
• once one ion channel has opened up, the area on the membrane close by opens up, all along the axon

Question 15

what is propogation

Answer 15

-once the action potential has been generated it moves along by activating the next ion channel like dominoes in a row, until it moves so far that the membrane reaches 20mv and the channels close again

Question 16

what state to sodium ion channels go into when they close

Answer 16

the refractory state

Question 17

types of refractory state

Answer 17

absoloute, relative

Question 18

absoloute refractory state

Answer 18

not response at all, about 1ms

Question 19

relative refractory state

Answer 19

only responsive to strong stimuli (2-4ms)

Question 20

what is the purpose of the refractory state

Answer 20

allows the membrane potential to go back to -70mv, so the cell doesnt continue firing

Question 21

why is the refractory state important

Answer 21

stops information from moving from the axon to the terminal and and back to the axon

Question 22

myelinated neurons

Answer 22

neurons with a myelin sheet wrapped around the axon to insulate them

Question 23

nodes of ranvier

Answer 23

gaps in mylein sheets on myelinated neruons that action potentials jump between when propogated

Question 24

why are myelinated neurons good

Answer 24

propogate action potentials about 10x faster, helps communicate over a long distance faster

Question 25

saltatory conduction

Answer 25

the way an electrical impulse skips from node to node down the full length of an axon