Please enable JavaScript.

Coggle requires JavaScript to display documents.

Somatic Sensations (Tactile Sensation (Stimulated by mechanoreceptors in…

- - - - 50% act rapidly - touch, vibration, movement
      - some are slow adaptation - sensation of pressure
      - Fingertips
        
        Small and well-defined receptive field
        
        Discriminative touch: provides precise contour and location information
      - Large fields: skin stretch and palm movement
- - - - Spinal injury
      - eg. ulceration on butt from sitting too long due to ischemia
    - - Surface of skin and internal surfaces (joint surfaces, periosteum, arterial surface)
      - Deep parts of tissue - lack nociceptors, but can be summated if tissue damage is extensive - slow pain
      - Exception - brain
    - - Mechanical
      - Thermal
      - Chemical
        
        ONLY for slow pain
        
        Substances which stimulate nociceptors
        
        Histamines
        
        Serotonin
        
        Bradykinins
        
        ACh
        
        K+
        
        Acids
        
        Proteolytic enzymes
        
        Prostaglandin - sensitises nociceptors to pain
        
        Important for the slow, suffering pain experience
    - - Important that individual is aware of pain as long as pain stimuli persists
      - Hyperalgesia - hypersensitivity to pain
        
        Increased pain with constant stimuli
  - - - Occurs at 0.1 second after pain stimuli inflicted
      - Transmits via A-delta fibres
      - Not felt in the deeper tissues of the body
      - Needle prick, knife cut - electric, sharp, pricking, acute pain
    - - Occurs after 1 second but increases slowly over seconds and minutes
      - Usually associated with tissue destruction
        
        Excruciating and leads to often unbearable, prolonged pain
      - Occurs in both skin and deeper tissues and organs
      - Burning, chronic, throbbing, nauseus, aching
      - Transmitted by the C fibres
  - - - Pain is perceived above 45 degrees Celcius
      - Permanent damage if such temperature is maintained indefinitely
    - - Extracts from damaged tissue cause intense pain when injected under normal skin
      - Bradykinin causes the most pain - possibly the single most important nociceptive transmitter
      - Increased K - increased intensity
      - Proteolytic enzymes
        
        Directly damage nerve endings
        
        Increased permeability to ions
        
        Excite pain
      - Greatly decreases threshold stimulation for mechano and thermosensitive nociceptors, while exciting chemosensitive nociceptors
        
        Increased pain from touch and heat stimuli following sunburn
    - - Decreased blood flow
        
        Accumulation of lactic acid and chemical substances
        
        Due to anaerobic respiration
        
        Tissue damage
        
        Sensation within few minutes
      - Increases with metabolism
        
        Exercising arm with blood cuff preventing arterial flow - pain within seconds rather than minutes
    - - Involuntary movement of muscle - occurs and resolves quickly, but often painful
      - Common cause of pain and clinical pain syndromes
        
        Due to
        
        Activation of mechanosensitive nociceptors
        
        Tissue ischemia
        
        Compression of blood vessels
        
        Increased blood tissue stimulation
- - - - Tactile:touch, vibration, pressure, itch, tickle
      - Pain: acute and slow
      - Thermal: cold and hot
      - Propioception: musccle, joint, tendon position (movement and position)
- - - - Involves three neurons
        
        1 sensory
        
        2 interneurons
      - Both pathways converge partially at thalamus
      - Each pathway crossovers to the opposite side of the body at some point
    - - Anterolateral system pathway
        
        CNS signals originates from the dorsal root of the spinal gray matter
        
        1st synapse and crossover occurs in the dorsal root of the spinal cord
        
        Travels up to the brain via the anterior and lateral white column of the spinal cord
        
        Low spatial orientation but slow transmission
        
        Sensations
        
        Pain and thermal
        
        Crude touch and pressure
        
        Itch and tickle
      - Dorsal column lemniscus pathway
        
        Signal originates from the original sensory neuron from the spinal cord
        
        Signal ascends via the dorsal lemniscus white column
        
        1st synapse and crossover occurs in the medulla
        
        High spatial orientation but rapid transmission
        
        Sensation
        
        Discriminative touch (High degree of localisation)
        
        Phasic receptors (Vibration)
        
        Propioception (position)
        
        Weight discrimination (pressure intensity)