pain

Question 1

what spinal cord tract carries pain and temperature sensation?

Answer 1

The lateral spinothalamic tract.

Question 2

where does the spinothalamic tract cross?

Answer 2

INSIDE the spinal cord, at the anterior white comissure.

Question 3

The spinothalamic tract is somatotopically arranged. How?

Answer 3

cervical section medial, sacral segments lateral.

Question 4

how many neurons are involved in the spinothalamic utilisation of sensory info from skin to sensorimotor cortex?

Answer 4

3

Question 5

Where are the psudounipolar neurons located ?

Answer 5

cellbodies in the dorsal root ganglion.

Question 6

Where do the pseudounipolar neurons enter the dorsal horn?

Answer 6

At the same segmental level as their cellbodies are in the dorsal root ganglion.

Question 7

what two types of fibers transmit pain?

Answer 7

A-delta fibers
C fibers

Question 8

what type of pain does the A-delta fibers transmit?

Answer 8

Fast and immediate pain.

Question 9

How does A-delta fibers look?

Answer 9

They have a large diameter and transmit as fast as 6 milliseconds.

Question 10

What type of fibers transmit slow aching pain (dermatome wise) that comes from inflammation?

Answer 10

C fibers.

Question 11

C fibers make several connections in the dorsal horn before ascending. WHy?

Question 12

WHat happen in the Lissauer tract and where is it localized?

Answer 12

Its a collection of descending or ascending collaterals of the primary pain-neuron.

Question 13

What happens with the primary pain neuron after travelling up or down in the lissauer tract?

Answer 13

They synapse to a secondary neuron, wither in substantia gelatinosa or in nucleus proprius.
both localised in the apex of the posterior grey matter horn. - they are usually 1-2 levels higher than the point of entry of the 1st nerve.

Question 14

What does the 2nd level pain neurons do after synapsing with the primary neuron in the nucleus gelatinousa or nucleus proprius in the posterior horn apex?

Answer 14

The AXONS of the 2nd order neuron travel anteriorly and cross in the anterior white comissure.

Question 15

Where are the 2nd level neurons of pain travelling after crossing in the anterior white commissure?

Answer 15

Through the lateral spinothalamic tract, up in between the inferior olivary nucleus and the trigeminal nerve spinal tract nucleus in medulla oblongata where it aligns with the anterior spinothalamic tract and form the “spinal lemniscus”

Question 16

What is “the spinal lemniscus”?

Answer 16

Its the anterior and lateral spinothalamic tract forming a common lemniscus at the level of the inferior olivary nucleus/trigeminal spinal nucleus in medulla oblongata.

Question 17

Where in pons does the spinal lemniscus travel?

Answer 17

In the dorsal pons.

Question 18

What happen with the spinal lemniscus in the midbrain?

Answer 18

They synapse with 3rd order neurons in Thalamus.

Question 19

What nuclei of Thalamus are synpasing with 2nd order neurons from the spinal lemniscus?

Answer 19

• ventral posterior lateral
• ventral medial posterior
• medial dorsal.
  *

Question 21

In what thalmic nucleus does most of the lateral spinothalamic tract 2nd order neurons synapse?

Answer 21

In the ventral posterolateral nucleus of thalamus..

Question 21

What will be “arranged” through synapses of crude pain and temperature 2nd order fibers in the ventral posterolateral nucleus of Thalamus?

Answer 21

Initiation of emotional reactions.

Question 22

HOw do the 3rd order neurons from the spinothalamic tract get from Thalamus to the primary sensory cortex in the postcentral gyrus?

Answer 22

Through the posterior limb of the internal capsule then through corona radiata and then reach the target.

Question 23

What more targets except for the primary sensory cortex is 3rd order neurons from the spinal lemniscus synapsing to?

Answer 23

• insular cortex
• primary somatosensory cortex (postcentral gyrus)
• cingulate cortex.

Question 24

what is “affective sensation”

Answer 24

its a cause of the spinothalamic tract initiating eg withdrwal from hot or sharp objects and itching from a scratch etc.

Question 25

what is the role of the spino-mesencephalic-limbic pathway?

Answer 25

its one of two indirect systems in the spinothalamic tract. Its main role is to cause the pain to have an impact and cause a reaction to it.

Question 26

there is a specific condition in which fine touch and proprioception is lost ipsilateral and pain and temperature perception is lost contralaterally to the hemisection. What is it called?

Answer 26

Brown-Sequard syndrome.

Question 27

what may cause chronic pain?

Answer 27

• injury to nerve endings
• scar formation in nerves
• abberrant reinnervation following nerve damage, causing the person to interpret touch as pain - Allodynia.
• inflammation
• cancer

Question 28

What is a “winding up” effect?

Answer 28

repeated stimulation of C-fibers by eg inflammation; will cause repeated release of glutamate. This causes a winding up phenomenon where the individual is more prone to that pain.

Question 29

another name for glutamate

Answer 29

NMDA

Question 30

What drugs can reduce and even abolish wind-up?

Answer 30

NSAIDs and Opioids. They do it by reducing excitability of spinal cord neurones.

Question 31

What is central sensitisation?

Answer 31

A combination of:
* enhancement in function of neurons and circuits in the nociceptive pathways caused by increases in membrane excitability and synaptic efficiacy.
* Reduced inhibition

• A manifestation of plasticity of the somatosensory NS in response to activity, inflammation and neural injury.

Question 32

What is hyperalgesia?

Question 33

WHat is central sensitisation?

Question 34

What is “wind up” of pain?

Answer 34

A frequency dependent upregulation of excitability of spinal cord neurones evoked by stimulation of C-fibers. Glutamate/NMDA seems to have a part in this. (eg. repeat provocation of inflammed joint)

Question 35

What drugs may reduce or even abolish wind up and how?

Answer 35

NSAID and Opioids. By reducing exitability of spinal cord neurones.

Question 36

Central sensitisation is not the same as wind up. What is it?

Answer 36

Its a patophysiologic process in which the CNS undergo changes that alter its processing of pain.

Question 37

What is the difference between the two “central sensitisation” types - allodynia and hyperalgesia?

Answer 37

Allodynia - normally not painful stimuli create a painful reaction
Hyperalgesia - painful stimuli become out of proportion painful.

Question 38

What might cause chronic pain?

Answer 38

Chronic pain can be caused by a variety of factors, such as:

injury to the nerve endings
scar formation in the nerves
aberrant reinnervation following nerve damage, causing the person to interpret touch as pain (allodynia)
Inflammation
cancer

Question 39

Manifestation of central sensitization

Answer 39

Central sensitization manifests as pain hypersensitivity, particularly dynamic tactile allodynia, secondary punctate or pressure hyperalgesia, aftersensations, and enhanced temporal summation.

It can be readily and rapidly elicited in human volunteers by diverse experimental noxious conditioning stimuli to skin, muscles or viscera, and in addition to producing pain hypersensitivity, results in secondary changes in brain activity that can be detected by electrophysiological or imaging techniques.

Question 40

What are deschending pain control pathways?

Answer 40

There are facilitatory and inhibitory nociceptive pain control pathways that alters the respons to pain stimuli in the spinal cord.

Question 41

What is the descending antinociceptive pathway?

Answer 41

The descending antinociceptive pathways begin at the supraspinal level and project to neurons in the dorsal horn of the spinal cord. The periaqueductal gray matter (midbrain), locus ceruleus (pons), and nucleus raphemagnus (medulla) are important structures in the modulation of nociceptive input.

Question 42

Which are the main neurotransmittors imlicated in descending pain control?

Answer 42

5-HT, NA and endogenous opioids.