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