central pain

Question 1

what is the role of the central trigeminal pathway in central pain?

Answer 1

• representation of pain
• pain processing
• referred pain

Question 2

how many layers are there in the medullary dorsal horn? what layers do Nociceptive specific fibers terminate on?

Answer 2

medullary dorsal horn- 10 layers

Nociceptive specific terminate mostly in superficial layers I and 2

Question 3

Non-nocioceptive fibers terminate on what layers of the medullary dorsal horn?

Answer 3

terminate mostly in deeper layers III, IV,V

Question 4

T/F: nociceptive and non-nociceptive terminate in separate/distinct layers of the medullary dorsal horn

Answer 4

False- Overlap in layers II & V

Question 5

what 2 types of neurons are found in the medullary dorsal horn?

Answer 5

• Nociceptive specific neurons

- Wide dynamic range neurons

Question 6

In the MDH, there can be Convergence of peripheral afferents with different __________

Answer 6

receptive fields

Question 7

Referred pain partially explained by ___________ in MDH

Answer 7

convergence

Question 8

what causes referred pain?

Answer 8

Pain & non-pain afferents converge on “pain-signaling” neuron

Question 9

what occurs during central sensitization?

Answer 9

a low-threshold mechanoreceptor that usually signals for touch will signal for pain—- Allodynia

a low-threshold mechanoreceptor will work in conjunction with a nocioceptor to lower the threshold for pain reception- hyperalgesia

Question 10

what are the steps to create central sensitization through C fiber activity?

Answer 10

A) C-fiber afferent barrage

B) MDH neuron response

C) Previously ineffective A-fiber now effective

Question 11

What changes in the MDH neurons during central sensitization?

Answer 11

Depolarization by Substance P (tachykinin)

Modification of NMDA receptor ( structural change to remove Mg++ block)

Increase in conductance of NMDA receptor

Question 12

what are the effects of A-fibers causing activation of the MDH pain centers?

Answer 12

A) A-fibers have a larger receptive field

B) A response to normally innocuous stimuli induces pain: A-beta fibers

Question 13

Following pulpitis (inflammation of the tooth pulp), Inflamed teeth are “sensitizing” central neurons with input from the healthy __________ to make them more sensitive

Answer 13

contralateral side

end result: contralateral/healthy teeth are more sensitive

Question 14

T/F: Trigeminal Tractotomy leads to the loss of sensation to the tooth pulp

Answer 14

False

Pulpal pain intact

Question 15

what are the effects of a central lesion to the pons? (in the oral cavity)

Answer 15

Intraoral touch, thermal sensitivity and pain are all diminished

Question 16

Following a Trigeminal Tractotomy, the ____________ and ________ still shows pain sensation

Answer 16

intraoral mucosa

tooth pulp

Question 17

A lesion to the ______________ will Diminish intraoral and perioral pain

Answer 17

Pons (subnucleus oralis)

Question 18

what is the response in Ventral Posterior Medial Thalamus to a noxious stimuli?

Answer 18

1. small receptive field
2. tracks the onset/offset of stimulus
3. stimulus - response linear

Question 19

what type of pain response is seen in the n. Submedius?

Answer 19

1. large receptive field
2. response outlasts stimulus
3. neural representation of negative emotion: outlasts stimulus.

Question 20

A MRI will visualize ____ tissue, while a PET scan will show ______ active tissue

Answer 20

MRI: visualize soft tissue
PET: metabolically active tissue

Question 21

what is the role of the N. submedius & cingulate cortex in the processing of pain?

Answer 21

emotional component of pain

neural response outlasts stimulus (poor localization)

activity associated with anxiety

Question 22

what is the role of the Thalamus (VPL) and somatosensory cortex in the central processing of pain?

Answer 22

localization of pain

neural response track pain stimulus

small receptive fields

Question 23

how do Forebrain pathways modulate pain perception?

Answer 23

Anxiety can increase pain perception

The placebo effect suppresses pain perception

Question 24

how is High anxiety induced when testing for it’s effects on pain perception?

Answer 24

High anxiety induced by not knowing If Low or High pain stimulus coming

Question 25

there is an increased activity in the __________________ Following Induction of Anxiety

Answer 25

Anterior Cingulate Cortex

Question 26

what 3 regions of the CNS can modulate pain (in the descending pain pathway)

Answer 26

1. forebrain: ACC: anterior cingulate cortex
2. midbrain: PAG” periaquaductal (central) grey
3. rostral ventromedial medulla

Question 27

Many of the descending pain control sites contain ___________ to suppress pain

Answer 27

endogenous opioids

example— enkephalin

Question 28

descending pathways from the medulla contain both _______ and ________ fibers

(in regards to the pain control pathways)

Answer 28

Inhibitory and excitatory

Question 29

presynaptic inhibition of pain is caused by what 2 sources?

Answer 29

medullary or local enkephalin input

endogenous opoid input locally or from the medulla

Question 30

how could the reorganization of afferent fibers explain mechanical allodynia?

Answer 30

Loss of c-fibers following nerve injury,
e.g. postherpetic neuralgia

Sprouting of non-injured A-beta fibers into superficial layers (where nocioceptive C-fibers use to terminate)

Question 31

the Anterior Cingulate Cortex is involved in what effect?

Answer 31

the placebo effect