Sensory Physiology PAIN pp Flashcards
Nociception
The sensory response to a noxious stimulus
Pain
Perception of nociceptive sensory info
Sensory discrimination
Perception of exteroreceptive or enteroreceptive noxious localization
Motivation affective
emotional and sympathetic responses & associated behaviors
Physical pain
transient
localized
minimal tissue damage
Inflammatory pain
Acute & Chronic
Tissue damage
Mediated by the inflammatory process
Hypersensitivity (protective promotes healing)
Neuropathic pain
Damage/alteration to the nervous system
chronic maldaptive
Types of pain
Somatic - superficial, visceral
Superficial pain
Discrete localization
Initial sharp Ad
Delayed burning C
Deep diffuse localization
Visceral pain
primarily conveyed by C type fibers
Poorly localized
Pain is referred
Free nerve endings
Elaborate a variety of receptors responsive to chemical, mechanical and/or thermal modalities
TRP Family
TRPV1 - Capsaicin TRPV2 - Capsaicin TRPV3 - Camphor TRPV4 - Camphor TRPV8 - Menthol TRPA 1 - Mustard oi
Chemical Activators
Potassium
Hydrogen down ASIC
Substance P tachykinin
Bradykinin B1
Chemical sensitizers
Prostaglandins
Leukotrienes
ATP
Other inflammators
Silent nocicecptors
Unresponsive to non noxious until it is sensitized
Responsive to inflammation then pressure and temp
Pain receptor Characteristic
Slowly adapting
High threshold
Sensitization
Primary hyperalgesia
Sensitization
An alteration of membrane that brings the resting potential closer to treshold
Primary Hyperalgesia
Increase sensitivity to noxious and non noxious stimuli in the area and immediately surround
Dorsal Horn Afferent fibers
Travel several segments above & below in Lissauer tract to allow innervation over several adjacent segments
Spinothalamic neurons w/ cell bodies in lamina V
Receive non noxious sensory information conveyed by Aa & Ab fibers
Spinothalamic neurons Other
Ad - Received by Lamina 1 & V
C - Lamina 2 & 3
Nociceptive specific
from lamina I, II, III
Wide Dynamic Range
Both noxious and non noxious input
Physiologic Pain
Acute, critical for survival, bodies own warning signal, 0.1 sec. Very adaptive
Ad mech or thermal
Pathologic Pain
Chronic, begins after 1 sec after stimulus, usually associated w/ tissue injury. Maladaptive, persistant & slow conducting
Dull, throbbing,aching, nauseaus, emotional
Nociceptive Pain
Physiologic pain, transient, localized, no real or minimal tissue
WARNING
Inflammatory Pain
Acute & Chronic Tissue damage Inflammatory process Hypersensitivity Protective, promotes healing
Dysfunctional Pain
No understanding lesion found, disproportionate to tissue injury
IBS, Fibromyalgia
Neuropathic Pain
Damage to CNS or PNS
Disproportionate to intensity of nocicepter activation
Pathologic pain, maladaptive
No protective fx
Physio pain processing
Transduction
Transmission
Modulation
Perception
Inflammatory soup 1
Tissue injury causes release of Bradykinin, 5HT, prostaglandins, K+ stimulate C fibers
Inflammatory soup 2
Active C fiber release CGRP and Substance P, stimulates mast cells -> histamine
Inflammatory soup 3
CGRP & substance P released by C fiber cause the dilation of blood vessels
Primary Hyperalgesia
Peripheral process Spreading of action potentials Up sensitivity Up receptive field Inflammatory mediators & Substance P Activate SILENT Nociceptors
Allodynia
Pain resulting from non noxious stimulus
Axon Reflex
sympathetic sensory coupling Flare response Coupling Triple response Redness, edema & wheal flare
Cutaneous fibers
Ad mech + heat
C fiber polymodal
Muscle fibers
Similar to joint
Respond to mech, thermal, chem & ischemia
Articular fibers
2x unmye/mye
Ad small, C
respond to mech & inflammation
Viscera
Predominately C fibers
Respond to mech distention & chemical
Central Sensitization
Wind up
2ndary Prolonged & increased activation
Recruitment of adjacent neurons
Changing pharmacology
Neuroplasticity
Modulation of intracellular signaling & changes in gene expression
Dorsal column Medial lemniscus
Discriminative touch
Proprioception
Anterolateral System
Temp
Pain
Crude touch
Neospinothalamic Tract
Fast Ad, mech & acute temp
Lamina 1,4+5
VPL Thalamus
Primary sensory cortex
Paleospinothalamic tract
Slow C fiber, Lamina 2,3 + 4 DM Thalamus Limbic system Medial affect motivation Emotional & visceral Release stress hormones
Spinoreticular tract
Reticular formation
Motor response to pain
Descending path control
Spinomesencephalic tract
Midbrain PAG
Regulation & modulation of Pain
Descending pain control
Superior colliculus - gaze to injury
Anterior Cingulate Cortex
Perception of pain Imagining pain Observation of pain Attention to pain Initiation of behavioral rxn's
Insula
Relay station to the limbic system
Learning & pain
to hypothalamus
Pain modulation
Gate Control Theory
Ab fibers can reactivate and fire faster than C
PAG
Activates encephalin to neurons that project to Raphe nuclei in brainstem
Rostral Ventral Medulla
Nucleus Raphe Magnus
5HT projections to the dorsal horn of the spinal cord
Locus Coeruleus pon
NE projections to the dorsal horn of the spinal cord
PAG Pain modulation
Ventrolateral - Sympathetic inhibition
Dorsal - Sympathetic excitation
Pain therapies
Relief Delay Opioid NSAIDs Glucocorticoids DMARDS