Sensory & Pain Flashcards
3 Neuron Pathways
1st: sensory receptor to SC or BS
2nd: SC or BS to thalamus
3rd: Thalamus to cerebral cortex
Stimulus
-when applied to a receptor, triggers graded membrane potential
-determines type of receptors activated
Receptor
-converts stimulus into AP
-specialized and responds only to specific stimulus type and intensity
Conduction
AP travels to CNS
Translation
CNS receives, integrates info, prepares response
Receptor Morphology
-different shapes/functions of receptors
Simple Receptors: unmyelinated, free nerve endings
Complex Neural receptors: myelinated, nerve endings enclosed in connective tissue
Special Senses Receptors: Myelinated, release neurotransmitters onto sensory neurons
Special Senses Receptors
-somatic: tactile, thermal, pain, proprioceptive
-Visceral: internal organs
Specialized Senses Receptors
Smell, taste, vision, hearing, balance
Exteroceptors
-near body surface
-external stimuli
Interoceptors
-deep
- comes from body
-BP, blood pH, proprioception
Nociceptors
-occur in all receptors that are sensitive to stimuli that either damage or have damage potential
-can take a scenic route instead of going to the brain
Proprioceptors
-muscles, tendons, ligaments, tendons
-position and kinesthetic sense
Photoreceptors
-vision
Tonic Receptors
-respond continuously if stimulus remains
-slow adapting
-detect object pressure (static)
Book laying on hand
Phasic Receptors
-adapt to continuous stimulus and then stop responding even with stimulus
-fast adapting
-motion, vibration, rate of change
Wearing glasses, clothing on body
Afferent Axon diameter decreasing diameter
Ia, Ib, II, III, IV
AB, ADelta, C
Sensory neuron receptive field
-area of skin innervated by 1 afferent nerve
-smaller fields with greater densiy distally, more sensitivity
-larger fields proximally, less sensitivity
Cutaneous Receptors
Superficial, subcutaneous, mechanoreceptors (AB), Free nerve endings (Adelta & C)
-all go to the same peripheral nerve bundle
Superficial Cutaneous Receptors
-small receptive field, epidermis and dermal palpalae
-Meisner’s Corpuscles: light touch, vibration (superficial)
-Merkel’s Discs: pressure (deeper)
Subcutaneous Cutaneous Receptors
-large receptive field, dermis
-Pacinian Corpuscle: touch, vibration (deeper)
-Ruffini’s ending: stretch (more superficial)
Mechanoreceptors
-light touch, vibration, stretch, pressure
- AB fibers
Free nerve endings
-ADelta & C fibers
-course touch, pain, temperature
Conduction
-3rd step of sensory system
Determinants:
-Modality: specialized stimulation
-Location
-Intensity: # and frequency of activated receptors
-Duration
Signal Integration
3 Levels
-Receptor Level: normal receptor/stimulus interaction; more stimulus more reaction
-Circuit level
-Perceptual Level
Circuit Level of Sensory Integration
-Divergence: synapses spread AP to several areas of CNS
-Convergence: synapses can focus action potentials from several sensory neurons on narrowed area
Perceptual Level of Sensory Integration
-sensory tract caries impulse to respective region of the brain
-testing comes in to determine what level of integration is faulty
Nerve Conduction Velocity Tresting
Electrical stimulation to peripheral nerves (NCV)
Looks at
-Distal latency: time from stimulation to distal recording sight (testing myelination)
-Amplitude: # of axons conducting
-Conduction Velocity: indication of myelin
Somatosensory evoked potentials (SSEP)
-tests peripheral and central pathways
stimulation at distal sight recording proximally
Clinical Implications : Peripheral Nerve Lesions
-neuropathy
-Nerve compression: large first then small
Order of sensory loss
-proprioception and light tough
-cold
-fast pain
-heat
-slow pain
Clinical Implications : Sensory Ataxia
-injury to dorsal column, roots, or nerves
-EC vs EO testing
Cerebellar: cannot adapt, same with EC/EO, intact proprioception
Sensory: can adapt with EO/EC, impaired proprioception
Clinical Implications : Varicella Roster
-Shingles
-painful rash in dermatome pattern
-chicken pox remains dormant in sensory ganglia then travel to nerve endings
Nociceptive Pain
-acute or chronic tissue injury stimulates nociceptors to become perception of pain
Non-Nociceptive pain
-malfunction of neural pain without the presence of injury
-neuropathic pain, central sensitivity, pain syndromes
Pain Control
Central Processing:
-cingulate and insula during perception of pain
Endogenous Opioids:
-endorphins bind to opiate receptors
Spinal Cord:
-inhibitory neurons
-enkephalin and dynorphin
Segmental Level of Control:
-Gate control theory
-non nociceptive fibers closes a gate for nociceptive fibers
Pain inhibition
Periphery: decreases prostaglandins
Dorsal Horn: release enkephalin or dynorphin
Brainstem: descending system
Hormonal System: pituitary gland and periaqueductal grey
Cortical Level: prefrontal, insular, and cingulate lobes
-spinolimbic, spinomesencephslic, and spinoreticular tracts
Referred Pain
-visceral tissues to skin
-convergence of nociceptive and somatic info
Chronic Pain
Disease (Primary pain):
-no biological function or tissue damage
Ex: fibromyalgia, migraines
Symptom (secondary pain):
-symptom of another condition
-continuous stimulation of nociceptors from tissue injury
-even after healing
-damage to somatosensory system
Central Sensitization
-CNS responds excessively to continuing nociceptive input
-cause changes to cells reactiveness
-pain top-down regulation disturbed
Paresthesia
-abnormal sensation
-dysfunction of neurons
Neuropathic Pain
-pain from direct lesion or disease
-Dysesthesias
Dysesthesias
- abnormal sensation that can occur on it’s own or from stimulation
Allodynia, hyperalgesia, spontaneous pain, temporal summation
Allodynia
pain caused by something that normally doesn’t cause pain
Hyperalgesia
-Primary: excessive sensitivity to normal pain
-Secondary: pain spreads to uninjured areas
Spontaneous Pain
pain unrelated to external stimulus
Temporal Summation
-increased pain due to repeated stimulus
Fibromyalgia
-tenderness and stiffness of muscles and tissues
-widespread pain
-increased pain without stimuli
Complex Regional Pain Syndrome
-not related to nerve or nerve root distribution
-affects distal limb
-abnormal response to trauma
-central sensitization with functional changes in brain
Sx: red or pale skin, edema, stiff joints, muscle atrophy, tremors
Nonspecific Low Back Pain
-no specific injury
-muscle guarding and abnormal movements
Ectopic Foci
-cause pain
-outside of nociceptors and become unmyelinated, increasing sensitivity to stimuli
Ephaptic Transmission
-Cross Talk
-lack of insulation due to demyelination that allows 1 action potential to affect more than 1 neuron
-cause for allodynia
Structural Reorganization
-long term central sensitization causes CNS rewiring
-new synapses carry more nociceptive information
Small Fiber Neuropathy
Partial central sensitization cause by :
-post-herpetic neuralgia: shingles
-diabetes
-gulliain barre syndrome (polyneuropathies)
Phantom Limb Sensations
-sensations related to posture, length, and movement of missing limb
Residual Limb Pain:
-easier to treat then Phantom limb pain
Phantom Limb Pain:
-absence of sensory inputs causing nociceptors to be overactive
PT Clinical Implication
-considered psychosocial aspects of chronic pain
-Consider: distress, disuse, and disability
