Pain And Hyperalgesia

Question 1

Mention areas with NO nociceptors

Answer 1

Brain, bone, liver parenchyma, lung alveoli,

Question 2

Describe mechanism of stimulation of nociceptors

Answer 2

Tissue damage leads to accumulation of pain producing substances (kinin, potassium, histamine, substance P), which stimulate chemo-sensitive pain receptors & lower the threshold for stimulation of thermosensitive and mechanosensitive pain receptors.

Question 3

Higher nervous perception site of pain is ….& its adaptability is …..

Answer 3

Thalamus & sensory cortex
Non-adapting (tonic receptors)

Question 4

Causes of cutaneous pain

Answer 4

Injury/inflammation of skin
Irritation of dorsal roots
Referred pain to skin other diseased deep or visceral structure

Question 5

Compare fast & slow cutaneous with respect to:
1.. summation
2. Receptors
3. Perception

Answer 5

F, no sum, mechano-&thero-sensitive pain receptors, sensory cortex
S, sum, all esp chemo, reticular formation, specific thalamic nuclei & tectum of midbrain

Question 6

Fast pain fibers terminate on ….. in spinal cord, & in ….. in thalamus

Answer 6

Lamina marginalis
VPLN

Question 7

Slow pain fibers ends on …. In spinal cord

Answer 7

Lamina II & III

Question 8

Enumerate structures on which Most neurons of the paleospinothalamic pathway end

Answer 8

1. Reticular nuclei of brain stem
2. Tectal area of midbrain
3. Periaqueductal gray region

Question 9

Causes of deep pain

Answer 9

1. Injury/inflammation of deep structures
2. Ischemia/spasm of muscles

Question 10

Causes of visceral pain

Answer 10

1. Inflammation of peritoneal covering of viscera
2. Irritation/ischemia of viscera
3. Spasm/overdistention of viscera

Question 11

Describe characters of visceral pain

Answer 11

The same characters of slow cutaneous pain
May lead to: depressor autonomic effects, rigidity of overlying skeletal muscle, referred to other structures.

Question 12

Compare slow & fast pain with resoect to somatic, autonomic & emotional reactions

Answer 12

Fast: flexor withdrawal reflex occurs, symp activity, crying, restlessless & anxiety
Slow: rigidity of overlying muscle with deep & visceral pain, para, emotional depression & sadness

Question 13

2ry hyperalgesia frequently results from ……

Answer 13

Lesions in the spinal cord or the thalamus

Question 14

Compare primary & secondary hyperalgesia

Answer 14

1ry: inflamed skin around injury, facilitation of pain receptors by chemicals (substance P), non-painful stimulus becomes painful.
2ry: healthy skin, convergence-facilitation theory, painful stimulus becomes more painful

Question 15

CP of Zoster

Answer 15

Severe pain followed within few days by a rash similar to that of varicellabut is unilateral and limited in distribution to the skin innervated by a DRG

Question 16

Tic douloureux is ….

Answer 16

Trigeminal neuralgia (5th cranial nerve)

Question 17

Examples of referred pain

Answer 17

Gall bladder to epigastrium & tip of the rt scapula
Appendix to skin around umbilicus
Renal to skin of back, inguinal region & testis
Cardiac pain to inner aspect of left arm

Question 18

Mention the dermatomal rule with examples

Answer 18

The pain is referred to dermatomes that share the same embryonic segment as the structure in which the pain originates.
Heart & arm has same embryonic origin, testicle migrate with supply from primitive urogenital ridge.

Question 19

Compare convergence-projection & facilitation theories

Answer 19

P , afferents that carry visceral pain coverge on the same second order neuron that recives pain signals from the skin, the brain projects these sensations to the skin as it is always informed about it not the viscrea.
F, the afferents that carry visceral pain convege on the same spinal cord segment as the one for skin , but both have sepearate 2nd order neurons. They facilitate and even activate the nearby skin pathway.

Question 20

Mention extra-cranial causes of headache

Answer 20

1. Spasm of musckes of head & neck
2. Irritation of nasal structures
3. Ear disorders
4. Eye disorders & errors of refraction
5. Tooth disorders

Question 21

Mention intracranial pain-sensitive structures

Answer 21

Venous sinuses, tentorium & dura at base of the brain, blood vessels of the meninges esp middle meningeal arteries.

Question 22

Headache due to intracranial cause is referred to …..&…..

Answer 22

Frontal half of head (stimulation above tentorium)
Post part of head (occipital headache) (stimulation beneath tentorium)

Question 23

List intracranial causes of headache

Answer 23

1. Meningeal irritation
2. Low CSF pressure
3. Alcohol
4. HTN
5. Migraine (abnormal vascular phenomenon)

Question 24

Describe steps of pain analgesia system in brain & spinal cord

Answer 24

Periventricular area of hypothalamus secretes b-endorphins which stimulate periaqueductal grey area that secretes enkephalin which stimulate magnus raphe nucleus that secrete serotonin which stimukate the pain inhibitiry complex of interneurons in the dorsal horns of the spinal cord that secrete enkephalins which cause pre & postsynaptic inhibition of pain fibers where they synapse on the dorsal horns

Question 25

Mention components of brain opiate system & their sites

Answer 25

1. B-endorphin: in hypothalamus & pituitary
2. Met-&leu-enkephalin: brain stem & spinal cord
3. Dynorphin: same areas as enkephalins

Question 26

Explain “Gate theory”

Answer 26

The substantia gelatinosa is considered the gate for pain sensations. Inhibition of pain at this spinal pain gate occurs by lateral inhibition. Inhibition of pain afferents occurs by interneurons in spinal cord which release GABA or enkephalin or serotonin.

Question 27

Mention sites for opioid receptors

Answer 27

Periventricular area of hypothalamus
Periaqueductal area
Raphe magnus nucleus

Question 28

Mention sites where electrical stimulation can cause analgesia

Answer 28

Periaqueductal gray area, raphe magnus nucleus, periventricular nuclei, selected areas which stimulate large sensory neurons

Question 29

Mention mechanisms of of surgical pain control

Answer 29

Cordotomy (interruption of spinothalamic pathway)
Cauterization of specific pain areas in intralaminar nuclei in the thalamus