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Physiology Pt. 1 - Coggle Diagram
Physiology Pt. 1
Pain
Definition
An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage
Homeostatic Emotion, Effective learning stimulus, Withdrawl reflexes, Immbolizes parts to allow for healing
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Nocioceptors
Mechanical, Chemical, and Thermal free nerve endings of Ad and C fibers
C Fibers = dull, aching, burning pain (small, unmyelinated)
Aδ fibers = sharp, pricking (thin, myelinated)
Agents
Activators (Potassium, Serotonin, Bradykinin, HIstamine)
Sensitizers (Prostaglandins, Leukotienes)
Nocioceptive Pain
noxious stimulus transduced into electrical acitivity at periperal termonals of Ad and C fiber afferents
Other types
Inflammatory Pain
Damaged tissue, inflammation release chemical mediators that activate/sensitise nocioceptors
Neuropathic pain
lesions in the CNS or dysfunction in the PNS can activate central pain pathways and rive LT neuropalstic changes
Innervation of Teeth
Noicoceptors respond to mechanical, chemical and thermal stimuli
Hydrodynamic theory - movement of dentinal fluid exctes mechanoreceptive receptors in the subodonto plexus
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PDL mechanoreceptor afferts can innerrvate mor ethan one tooth and make it difficult to localise pain
mu receptors have been found in pulpal tissues, possible MoA
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Referred pain
The convergence of visceral and somatic pain fibers onto the same neurons in the dorsal horn (dermatome) can result in phantom pain
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Nueralgia
Usually pressure on a nerve, can cuase the peripheral area of stimulation to be felt as pain, due to the afferent signals along that nerve being activated
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Central sensitization
Neuroplastic changes occur due to frequent stimulation, this can result in sensitization (allodynia) where non noxious stimuli/inputs cause pain
Pain modification
Ascending Pathways
Gate-control mechanism = large diameter A alpha and beta fibers activate interneruons to inhibit transmission of pain
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Descending pathways
Stimulation of the grain at several sites aids in analgesia by releasing there on N.T and descinding them to inhibit the afferent signals
Homeostasis
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Receptors detect the change, send an afferent signal to the control center (hypothalamus) and compare against a setpoint, send out an efferent signal to the body for a compensatory response to return the to normal
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Feedforward = a response in the absence of feedback, anticipates change
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Error signal - when negative feedback cannot return to normal, error is the sustained deviation from the set point
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Feedback gain - is the amount of correction/amount of abnormality still required (ie number..)
Hypothalamus
Vegetative control: CVS, Temp, Water regulation
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Behavioral: Thirst (water reg), Huger/Satiety (feeding)
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Anterior Pituitary Gland
Release of tropic hormones (e.g., TSH, ACTH, GH, LH, FSH, Prl)
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LA
Physiological Action
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Cells can depolarise, but cannot produce an action potential
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Structure
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Amide
E.g lignocaine, prilocaine, articaine, mepivicaine
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They have to penetrate lipid membranes when they are un-ionized to have their effect on Vg Na+ channels
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LA is affected by inflammaed tissues as there is a lower pH, this reduces the no. un-ionized forms of LA
Vasoconstrictor
Reduce rate of removal, reduce bleeding at site, reduce unwanted systemtic effects at site
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Eg. Vasopression (synthetic analouge) for when cardiac stimulation is an issue, but these are contraindicated in pregnant woman
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Analgesia
Psychological Methods
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Conselling, eductaion, stress managemenr
Physical methods
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Physcial therapy, massage, acupuncture (jaw exercises, oral splints)
Pharmological Methods
NSAIDS
Cyclooxygenase (COX) inhbitors an dprevent production of prostaglandin tehrfore reducing nociceptor senseitization
Cox's
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Cox 2 = Induced with tissue injruy (pain, vasodilatation, fever)
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Opioids
Opioids bind mu receptors and inhibit substance P release from nociceptors at primary CNS afferbet synapses and also reduce their excitablity for new signals
Ex. Codeine, DHC, Sevredol
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Pre-Emptive Analgesia
Hypersensitivity can occur due to tissue injury (chemo/cytokines) and central hyperexcitability causing plastic changes
Pre-surgical NSAID (paracoxib) & preincisional long-acting LA (bupivicaine) can reduce post-operative pain
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Oral Sensation
Peripheral Nuerons
A(alpha) - mylenated, Largest and fastest
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A(delta) - mylenated, thin and slower
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C fibers - unmyelinated, smaller and slowest
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Sensory Receptors
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Coding
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Intensity
SIze of the stimulus, frequency of coding
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Location
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Receptive fields, discrimination
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A(beta) - mylenated, large and fast
Skin mechanorecptors, PDLs
Mechanorecptors
Skin of the face and TMJ
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(Slow adapting) Ruffini's Corpucle, Merkel's receptors, tactile
(Rapid adapting) Meissner's corpuscle, hair follicle receptor
PDLs
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Which teeth are in contact, direction, amount of force
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Muscle Spindles
Primary - middle part of the intrafusla fibers (Type 1, fast sensory afferents)
Secondary - peripheral - Type II, slower afferent fibers
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Joints Receptors
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Include: Ruffini, Pascini, Golgi, Free Nerve endings
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Taste
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Taste Receptors
Papillae
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Fungiform papillae
Lateral sepct of the tongue, numerous (~250)
Taste Buds
Modified epithelial cells, with Special Visceral Afferent
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Five primary tastes
Sweet, Salt, Sour, Bitter and Umami
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