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91 Cards in this Set

  • Front
  • Back
2 Components of pain:
-Unpleasant senation
-Emotional experience
What causes pain?
Actual or potential tissue damage
What is nociception?
Activation of nociceptors and neural pathways.
Does nociception always lead to pain?
No; can be activated without the person having a conscious perception of pain
What is Pain?
A complex cognitive perception of a sensory stimulus within the context of environment, previous experience, and emotion.
lack of sensation
lack of pain
lack of thermal sensation
increased pain from a normally painful stimulus
Pain from a normally Nonpainful stimulus like light touch.
Decreased pain from a normaly painful stimulus
unpleasant, abnormal sensation - tingling, pricking, and tickling.
2 types of pain:
Which serves a function?
-Acute - serves critical function
Function of acute pain:
Warns that an injury should be avoided or treated
3 diseases that cause loss of Acute Pain sensation:
-Congenital insensitivity to pain
What is the stimulus that activates nociceptive pain?
Tissue injury or inflammation.
What type of fibers respond to the released inflammatory mediators from tissue?
Unmyelinated C-fiber nociceptors
What 2 drugs block the release of inflammatory mediators during inflammation?
What is the mechanism of NSAIDS?
Block the synthesis of prostaglandins from arachidonic acid.
What is Neuropathic pain?
Pain caused by direct damage to nerves in the PNS or CNS.
What is often the quality of the sensation from neuropathic pain?
Burning or Electrical quality
2 diseases that commonly have neuropathic pain as part:
-Post Shingles neuralgia
-Diabetic neuropathy
How does the pain Anterolateral pathway compare to the dorsal column pathway?
It is more complex
Why is the Anterolateral system more complex?
Because it involves components of emotion, environment, and memory on top of the simple nociceptive stimulus.
Where do anterolateral systems diverge?
In the pons - they are similar through the medulla.
What are the 3 types of stimuli that can stimulate nociceptors?
What are 2 types of free nerve endings on pain receptors?
Adelta (mechanonociceptors)
C fibers (nociceptors)
What type of response do both pain receptor types have?
Slow adapting
What do Adelta fibers mediate?
What is it like in quality?
First pain - immediate, short, pricking.
What do C fibers mediate?
What is it like in quality?
2nd pain: delayed, long lasting, burning.
At what sites in the body are nociceptors found?
-Internal visceral organs
In what Rexed Laminae do nociceptive afferents synapse?
(most vs some)
Laminae 1/2 - most
Laminae V/X - some
What are Lamina 1/2 called?
-Substantia gelatinosa
-Marginal zone
What neurotransmitters does the chemical synapse of pain/temp in the spinal cord involve?
-Substance P
Where do most 2nd order neurons in the spinal cord go after synapse?
Cross the central commissure to contralateral Anterolateral columns.
So what side of the spinal cord does pain and temp ascend?
So how do lesions of the spinal cord affect pain/temp sensation?
Cause loss of pain and temp on the contralateral side of body (if it was a unilateral lesion).
What is a cordotomy?
Surgical cutting of the anterolateral trats in patients suffering intractable pain.
What patients get cordotomies?
Only terminally ill
Result of cordotomy on one side:
Analgesia and Athermia on opposite side of body.
Where is complete loss of pain and temp seen when a level of the spinal cord is severed?
2-3 segments below the cut.
Why is cordotomy only performed on terminally ill patients?
Because pain often recurs within 6 months as other pathways begin to carry the information.
Do axons regrow?
So if the anterolateral tract on the left side of the spinal cord at T1-T2 is cut, where would analgesia and athermia result?
In T4 and below on the right side of body.
What is central cord syndrome?
When a hole develops in the spinal cord center.
What disease causes central cord syndrome?
What is Syringomyelia?
Formation of cysts and gliosis in the cord center, extending several inches rostral or caudally.
What does the lesion resulting from Central Cord Syndrome cut?
Crossing anterolateral axons
What segments of the spinal cord are usually affected by Central cord syndrome?
What dermatome levels are affected by central cord syndrome?
Only those in which the spina levels are affected - the lesion is not at the anterolateral TRACTS, but in the CENTER.
What are the 3 pathways carried in the Anterolateral tract?
1. Spinothalamic
2. Spinoreticular
3. Spinomesencephalic
What components of pain are mediated by the Spinothalamic tract?
-Discriminative aspect of pain - location and intensity.
-Emotional suffering
Where does the Spinothalamic 2nd order neuron terminate?
In 2 places in the thalamus:
-VPL (discriminative)
-CLN (central lat) (emotional)
Where do the 3rd order axons of the Spinothalamic tract project?
To the S1 cortex areas 3b, 1, and 2
What part of the S1 somatosensory cortex does not recieve pain and temp?
The S1 cortex areas (3b, 1, 2) tell you what about pain/temp?
VPL recieves what somatosensory input?
-Dorsal columns (medial lemnisc)
but they terminate on different neurons obviously
Where do the 3rd order neurons from the Central Lateral nucleus synapse in thalamus project?
To MANY areas of cortex, particularly the LIMBIC cortex.
What component of pain is mediated by the CLN?
Emotional suffering
Which nuclei in the thalamus that recieve pain and temp info are somatotopically organized?
Only VPL - not CLN
How do the 3rd order neurons from the VPL get to the cortex?
-Posterior limb of internal capsule
-Corona radiata
Where do the 2nd order neurons in the Spinoreticular tract synapse?
In the Reticular formation in the medulla and pons.
Where do 3rd order axons from the Reticular Formation project?
To diffuse areas in the cortex and thalamus.
3 components of paint that are mediated by the Spinoreticular tract:
-Attention to pain
-Affective response
Where do Spinomesencephalic 2nd order neurons terminate?
What regions of the midbrain receive spinomesencephalic input?
1. PAG - periaqueductal gray
2. Superior colliculus
What is the Periaqueductal gray?
The region of gray matter that surrounds the cerebral aqueduct
What component of pain is carried by the Spinomesencephalic tract?
Central modulation of pain - the control of descending pathways
What information is carried in the anterolateral columns along with Pain and Temp?
Crude touch from dorsal columns - just a little bit.
Mnemonic for pain and temp:
-Ahh that feels better
So what are the 3 thalamic projections of pain/temp in the cortex?
1. Somatosensory (S1 - 3b, 1, 2; also SII)
2. Cingulate gyrus (limbic)
3. Insula
Function of SI projection?
Function of Limbic/cingulate projection?
Function of Insular projection?
Appropriate response
How do lesions of the insula affect pain/temp sensation?
The patient can still feel pain and temp, but does not appropriately respond to it.
What pathway carries pain and temp info from the face?
Trigeminothalamic tract
Peripheral nerves that carry pain/temp from face to CNS:
Trigeminal nerves
Where does CN V enter the CNS?
At the pons
Where do the primary afferents (unsynapsed) of CN V go after entering at the pons?
Immediately descend in ipsilateral side to Spinal Trigeminal Nucleus
Where do 2nd order neurons from the trigeminal nucleus in the spine project?
To contralateral spine, then ascend w/ Anterolateral tracts to the VPM
Do the pain/temp afferents from the face do anything at the Chief Principle nucleus of V?
No; that's in the pons, and they bypass it in preference for the SPINAL nucleus of V
Where do the 3rd order neurons from the VPM project?
To the LATERAL SI cortex and some to the reticular formation and midbrain.
What is Trigeminal Neuralgia?
Severe pain episodes that last seconds to minutes and are brought on by chewing or shaving or touching trigger points.
What is the cause of trigeminal neuralgia?
What is TMJ disorder?
Chronic pain in the TMJ or chewing muscles - has recurrent headaches.
What structure in the brain plays a prominent role in INHIBITING pain pathways?
The reticular formation.
What specific area in the brain initiates pain suppression?
PAG - the periaqueductal gray in the midbrain
What does the PAG project to in its pain suppression pathway?
-Locus ceruleus in pons
-Raphe nuclei in medulla
How are neurons in the Locus ceruleus and Raphe nuclei involved in pain suppression?
They send axons down spinal cord to synapse on inhibitory interneurons or directly onto spinothalamic projections to suppress ascending pain/temp.
What is referred pain?
Visceral pain that is perceived as somatic pain at the dermatome levels where visceral afferents enter.