block 5 lecture 8 action potentials

Question 1

what is an action potential?

Answer 1

rapid change in electrical charge across a plasma membrane

Question 2

where do action potentials occur?

Answer 2

neurons muscle fibers and endocrine cells

Question 3

what is the cell body of a neuron also called?

Answer 3

soma

Question 4

what is the main input structure on a neuron?

Answer 4

dendrites

Question 5

what is the output structure of a neuron

Answer 5

axon

Question 6

what does myelination do?

Answer 6

provides insulation

Question 7

what is the region between soma and axon called?

Answer 7

axon hilock

Question 8

what may the signals be arriving at the synapse?

Answer 8

excitory or inhibitory

Question 9

what are the signals called travelling in dendrites?

Answer 9

electrotonic potentials

Question 10

when travelling in dendrites what is the response called and what does this mean?

Answer 10

graded response, response is proportional to the stimulus

Question 11

what happens to the negative and positive electrotonic potential

Answer 11

they are summed in the soma

Question 12

what does the excitation have to be above to get an action potential?

Answer 12

threshold

Question 13

what kind of spread of action potential do you get down the axon?

Answer 13

non decramental

Question 14

what is the membrane potential?

Answer 14

difference of electrical potential between the inside and outside of the cell

Question 15

what voltage is the resting potential?

Answer 15

-70

Question 16

what is the threshold potential? (value)

Answer 16

-55

Question 17

what do ion channels do?

Answer 17

selectively transfer ions

Question 18

what are the 3 types of ion channels in maintaining resting potential?

Answer 18

leak ion channels, voltage gated ion channels, ligand gates ion channels

Question 19

what is the active tranport in an action potential?

Answer 19

sodium potassium pump

Question 20

how does the sodium potassium pump work?

Answer 20

3 sodium and ATP binds to pump
hydrolysis of ATP phosphrylates the pump causing it to change in shape
this releases sodium ions and allows two potassium ions to bind
release of the phosphryl group releases potassium into the cystol

Question 21

what are the three factors of resting potential?

Answer 21

low protein permeability
sodium potassium pump
high potassium permeability through leak channels

Question 22

limitations of the nerst equation?

Answer 22

one ion
only considers valance and conc gradient
dosent consider permeability

Question 23

what are the 4 stages of an action potential?

Answer 23

resting state
depolarizing phase
repolarising phase
undershoot

Question 24

during the resting state what is happening?

Answer 24

-70mv, all voltage gated sodium and potassium channels closed

Question 25

during the depolarization phase what is happening?

Answer 25

-55 threshold is reached, voltage gated sodium ion channels open

Question 26

during the repolarization phase what is happening?

Answer 26

+40mv, voltage gated potassium ion channels open, sodium voltage gated channels close

Question 27

during the undershoot what is happening?

Answer 27

-80mv, potassium channels slowly close

Question 28

after the threshold what is the strength of the stimulus encoded by?

Answer 28

frequency of action potential

Question 29

how is the action potential conducted in an unmyelinated axon?

Answer 29

sodium entry at axon hiloclk locally depolarises axon, adjacent axon depolarised

Question 30

how is one way conduction of an action potential ensured?

Answer 30

sodium channels are inactivated due to the refractory period

Question 31

how are action potentials conducted in a myelinated axon?

Answer 31

the myelin sheath prevents leakage, sodium and potassium channels are concentrated at the nodes of ranvier, saltatory conduction

Question 32

what does the speed of conduction depend on?

Answer 32

diameter and myelination

Question 33

what does the diameter change during action potential conduction?

Answer 33

larger axon faster conduction

Question 34

what are C axons?

Answer 34

smaller than a micron and unmyelinated

Question 35

what is MS?

Answer 35

autoimmune, T cells attack the myelin sheath

Question 36

what is tetrodotoxin?

Answer 36

toxin produced by symbiotic bacteria in pufferfish that block s sodium channels

Question 37

what do local anesthetic do?

Answer 37

block voltage gated sodium ion channels, prevent Adelta and C fibers which transmit pain

Question 38

what are the types of local anesthetics?

Answer 38

esters: cocain amides: lidocain

Question 39

what can prolong local anesthetics?

Answer 39

vasoconstrictors