The action potential

Question 1

what are muscle spindles

Answer 1

stretch receptors of skeletal muscle

Question 2

what happens when stretch the mechanoreceptors

Answer 2

opening of Na channels causing receptor potential

Question 3

what type of potential are receptor potentials

Answer 3

graded - good for strength coding

Question 4

what happens to receptor potentials over space

Answer 4

decremental - decrease

Question 5

what does action potential begin

Answer 5

spike initiation zone

Question 6

how is info coded in action potential

Answer 6

frequency and pattern of AP

Question 7

5 phases of an AP

Answer 7

1. resting
2. rising
3. overshoot
4. falling (repolarizing)
5. hyperpolarization

Question 8

what is AP threshold

Answer 8

minimum voltage that must be reached to initiate - 55mV

Question 9

what happens with more depolarization

Answer 9

more frequent AP

Question 10

what limits AP frequency

Answer 10

refractory period (absolute or relative)

Question 11

what opens with AP

Answer 11

Na and K channels

Question 12

which channel opens faster

Answer 12

Na, and K sustains over depolarization

Question 13

what are 3 states of Na channel

Answer 13

1. resting
2. activated
3. inactivated

Question 14

what reverses inactivation of Na channel

Answer 14

regaining -70

Question 15

what happens during threshold phase

Answer 15

inward Na> outward L

Question 16

what happens during rising phase

Answer 16

rapid opening of Na channels

Question 17

what happen in overshoot

Answer 17

Na inactivation and delayed opening of VG K channels

Question 18

what happens in falling phase

Answer 18

Na inactivation and K

Question 19

what happens in hyperpolarization

Answer 19

residuale VG K and IL

Question 20

what happens in absolute refractory period

Answer 20

Na channel inactivation prevents AP generation

Question 21

what is direction of Na channel propagation of channel

Answer 21

orthodromic

Question 22

what determines speed of conduction

Answer 22

length of membrane

Question 23

what happens with larger diameter axon

Answer 23

less axial resisitance- faster conduction

Question 24

what forms myelin in PNS and CNS

Answer 24

PNS - schwann cells

CNS - oligodendricites

Question 25

what are interuptions in myelin

Answer 25

nodes of ranvier

Question 26

what is conduction that jumps along nodes

Answer 26

saltatoy conduction

Question 27

what are diseases that demylenate PNS and CNS

Answer 27

PNS - guillain-barre | CNS- MS

Question 28

how does local anasthetic work

Answer 28

blocks Na channels of pain fibers so can't give signal