action potentials

Question 1

is ICF or ECF more negative

Answer 1

ICF

Question 2

what causes ICF to be more negative

Answer 2

‘leaky’ diffusion of K+ ions out of the cell , also impact of Na/K pump which generates a +1 charge outside of the cell

Question 3

3 different forms of Na channels

Answer 3

• m gate closed , h gate open , seen at RMP , no flow
• m gate and h gate open, threshold has been reached, Na influx allowed
• m gate open , h gate closed , refractory period, no more APs can pass

Question 4

how many gates to Na and K channels have

Answer 4

K = 1 
Na = 2

Question 5

describe the process of an action potential

Answer 5

1 - stimulus reaches threshold
2 - Na channels start to open and influx begins (positive feedback)
3 - MP reaches peak and Na channels ‘h’ gate closes and K channels open
4 - K efflux restores RMP and Na channels h gate opens and m gate closes ready for next AP

Question 6

what can increase conduction speed

Answer 6

axon diameter and myelin sheath

Question 7

saltatory conduction

Answer 7

propagation of APs along myelinated axons e.g between the nodes of ranvier

Question 8

endoneurium

Answer 8

surrounds single axons

Question 9

perineurium

Answer 9

surrounds groups of axons

Question 10

epineurium

Answer 10

surrounds peripheral nerves - contains bundes of axons, bvs , fat etc

Question 11

A- alpha axons

Answer 11

myelinated, proprioceptors

Question 12

A-beta axons

Answer 12

myelinated , mechanoreceptors

Question 13

A - delta axons

Answer 13

myelinated , mechano, thermo (cold) , nociception and chemoceptors (taste)

Question 14

C axons

Answer 14

non-myelinated, mechano, thermo (hot) and nociception

Question 15

what is the order of axon susceptibility to LA

Answer 15

most susceptible = a - delta then c then a - beta then a - alpha
some senses are blocked before others

Question 16

what are the 3 components of LAs

Answer 16

they are organic molecules
aromatic region (hydrophobic)
amide or ester bond
amide side chain (hydrophillic)

Question 17

why are LA bases presented as hydrochlorides

Answer 17

to increase their solubility in aqueous solutions

Question 18

when is LA active

Answer 18

when it is partly dissosciated

B.H+ + Cl-

Question 19

in what form can LA pass through the membrane

Answer 19

unionised form
B.
must be ionised again to block the channel

Question 20

why are smaller diameter axons more susceptible to LA

Answer 20

they have less Na channels

Question 21

where are Na channels blocked in myelinated axons

Answer 21

concentrated at nodes of ranvier

Question 22

what is contained in LA solutions

Answer 22

base - present as a hydrochloride
reducing agent
preservative
vasoconstrictor*

Question 23

alpha adrenoreceptor

Answer 23

vasoconstriction

Question 24

beta 1 adrenoreceptor

Answer 24

increase HR

Question 25

beta 2 adrenoreceptor

Answer 25

vasodilation

Question 26

why is adrenaline used over noradrenaline

Answer 26

adrenaline at local level affects alpha receptors more than beta but systemically beta more which has little to no effect on arterial BP
noradrenaline both locally and systemically affects alpha receptors more which increases TPR, CO and arterial BP

Question 27

by what methods are ester and amide LAs broken down

Answer 27

ester - tissue esterases

amide - liver amidases

Question 28

felypressin

Answer 28

synthetic vasopressin
vasoconstrictor
not to be given to pregnant women

Question 29

lignocaine max dose

Answer 29

4.4mg/kg

Question 30

hyperpolarisation vs repolarisation

Answer 30

hyper - makes MP more -ve

repolarisation - restores RMP

Question 31

cations

Answer 31

+ve

Question 32

anions

Answer 32

-ve

Question 33

symptoms of an allergic reaction

Answer 33

red itchy rash, red itchy eyes, sneezing, runny nose, coughing/wheezing

Question 34

symptoms of anaphylaxis

Answer 34

breathing difficulties, faint, collapse, tachycardia , confusion