PAIN

Question 1

what is pain?

Answer 1

it is an unpleasant, sensory/emotional experience.

Question 2

what is nociception

Answer 2

activation of neural pathways by stimuli that damage or threaten tissues

Question 3

what is a noxious stimuli

Answer 3

potentially damaging stimulus

Question 4

what is a nociceptive stimulus

Answer 4

stimulus that activates the neural pathway

Question 5

a nerve is a poor insulator and conductor! what does it need?

Answer 5

it needs PROPAGATED by an ACTION POTENTIAL!

Question 6

what is the resting membrane potential?

Answer 6

-70mV (all cells) , excitable cells like nerve and muscle cells cause a rapid change in membrane potential

Question 7

what is the resting membrane potential driven by?

Answer 7

it is driven by ions with the greatest membrane permeability

Question 8

how is the RMP dervied?

Answer 8

permeability of ions, conc gradient of ions, active transporters

Question 9

where is Na located in the cell membrane

Answer 9

OUT of the cell

Question 10

where is K located in the cell membrane

Answer 10

IN the cell

Question 11

what is the ratio of Na to K to transport in and out of the cell

Answer 11

3 to 2 , we also need ATP (energy)

Question 12

what is the K equilibrium potential

Answer 12

-90mV (drives RMP of -70mV which is closer to -90)

Question 13

what is the Na equilibrium potential

Answer 13

+60mV

Question 14

describe what happens during an action potential

Answer 14

the MP depolarises to -50 (threshold), sodium channels open, sodium flows in down the CG meaning that the membrane is more permeable to sodium at this point.
this results in RAPID depolarisation to +30mV - closer to na +60 as drives MP as now more peremable.

due to the rapid depolarisation it then means that the sodium channels inactivate, then the K channels open and k flows in causing rapid depolarisation (slight delay). the membrane is now driven by k+ toward -90mv. the k channels close and na channels rest back to the rmp of -70mv

Question 15

what is the hodgkins cycle

Answer 15

positive feedback loop, AP propagates along a nerve like the domino effect. this results in depolarisation and NA is open.

Question 16

what does LA do to sodium channels

Answer 16

it blocks it, meaning there is no AP along the nerve and therefore no PAIN signal.

Question 17

describe the features of an action potential

Answer 17

it is an all or nothing event , it moves in one direction

Question 18

describe the absolute refractory period

Answer 18

Na channels do not get reset therefore the AP cant occur

Question 19

describe the relative refractive period

Answer 19

k channels open, AP can occur with a large stimulus

Question 20

what happens when we increase the width of an axon

Answer 20

conduction will be faster

Question 21

what is myelination

Answer 21

basically insulator of the nerve, making it faster as it jumps from node to node.

Question 22

class of nerves, identify them.

Answer 22

C (NOTE THAT C FIBRES ARE NOT MYELINATED!!!) , A DELTA, A BETA, A ALPHA (order from slowest to fastest and thinnest to thickest) increase in width means faster nerve

Question 23

what makes up the PNS

Answer 23

cranial nerves and spinal nerves

Question 24

what makes up the CNS

Answer 24

brain stem and spinal chord

Question 25

what makes up the sensory root

Answer 25

the trigeminal nerve! - opthalmic, maxillary, mandibular (this exhibits efferent muscles of mastication), motor root (exhibits afferent) - 3 DIVISIONS, 2 ROOTS, 1 GANGLION

Question 26

what makes up the brainstem

Answer 26

pons at the top then the medulla then the spinal chord going off the pons

Question 27

what is the SENSORY order of pathway in the brainstem

Answer 27

main sensory nucleus, nucleus oralis, nucleus interpolaris, nucleus caudalis

Question 28

what are nociceptors

Answer 28

nociceptors are AFFERENT and are found at nerve endings, they are absent in the brain liver and lung

Question 29

what 2 types of pain do we get?

Answer 29

FAST - A delta fibres, wider diameter than C fibres SLOW - fine, unmyelinated, smallest diameter

Question 30

what is a graded potential

Answer 30

a local change, triggering event needs to occur for it to happen eg a stimulus (it is also post synaptic)

Question 31

what is transduction

Answer 31

it is a SENSORY STIMULUS (electrical) - it MUST have an adequate stimulus to reach (-50mv) in order to cause an action potential/a response

Question 32

describe what happens with nociceptor transduction

Answer 32

we have DIRECT and INDIRECT DIRECT - can be chemical, mechanical, or thermal ie TRVP1 (capsican) INDIRECT - tissue injury response, inflammation, it is generally the effect of substances released from nerve endings - this makes sense as it is a nociceptor transduction!!!

Question 33

what do NSAIDS do?

Answer 33

they block sensation of nerves!

Question 34

what is substance P

Answer 34

A NEUROTRANSMITTER AND A MODULATOR OF PAIN PERCEPTION. It is released as a result of the axon reflex - it increases sensitisation of neighbouring nociceptors and also increases vascular permeability

Question 35

explain the different types of pain in the teeth

Answer 35

enamel and dentine - short and sharp pain pulp - dull and long

Question 36

describe what makes up pulp nerves

Answer 36

they are AFFERENT (meaning its coming from the outside world to IN) - c and delta fibres are to do with pain then we have b fibres which are to do with mechanoreception.

Question 37

what zone is the plexus of nerves found within pulp?

Answer 37

the plexus of nerves are found in the cell free zone - under odontoblast layer.

Question 38

what 3 theories are there for dentinal sensitivity?

Answer 38

dentine innervation theory, odontoblast receptor theory, hydrodynamic theory (most likely one)