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pain sensation - Coggle Diagram

- - - - Visceral pain initiates reflex spasm
        (contraction) of skeletal muscle in
        the abdominal wall and makes it rigid.
        It is most marked when inflammation of the viscera involves the peritoneum.
- - - - Pain is usually referred to a structure
        that developed from the
        same segment during
        the embryonic development.
        
        This principle is called the
        Dermatomal Rule.
        
        eg:
        
        the heart and the arm have the
        same segmental origin;
        similarly,
        
        the testicles and kidney
        developed from the same
        primitive urogenital ridge.
  - - - eg:
        
        Phantom limb pain.
        
        Pain of stone in the gall bladder referred to the tip of the right
        shoulder.
        
        Pain in the testicles due to stone in the ureter.
        
        During a heart attack, pain is often experienced at the tip of left
        shoulder and tends to spread in the inner aspect of left arm.
- - - - Primary hyperalgesia,
        
        It occurs within an area of tissue damage
        
        particularly caused due to a bum or bacterial infection.
        
        The condition is characterized by decrease in pain threshold, inflammation and flare.
        
        This is due to release of chemical substances like histamine, SHT, plasma kinin and prostaglandins from damaged tissues
        -which sensitize the unmyelinated ‘C’ afferent endings.
      - Secondary hyperalgesia.
        
        It occurs in undamaged tissue adjacent to
        the site of injury.
        
        There is no lowering of pain threshold
        
        but with a given noxious stimulus, the pain produced is unpleasant, prolonged and
        more severe.
        
        It is probably due to spread of excitation impulse within the CNS from the injured area
        -and occurs when central excitatory
        state is marked.
    - - Selective damage to large sensory fiber
        allows light tactile stimuli
        to produce severe pain
        even in the absence of peripheral tissue damage.
      - Tabes Dorsalis
        
        In this condition
        degeneration of dorsal (sensory)
        nerve roots occurs;
        affecting specially
        
        fibers in dorsal columns
        
        and fibers which convey pain.
        
        The disease is usually caused by syphilis.
        
        Characteristic features
        
        Lightning pain of varying intensity
        which come in attacks with pain free intervals in between.
        
        It is due to stimulation of pain fibers in dorsal
        nerve roots.
        
        Loss of deep sensibility i.e.
        -loss of position sense,
        -passive movement
        -n vibration sense.
        
        Reflexes. Deep tendon reflexes like knee, ankle, bicep, tricep jerks
        -which depend on the intactness of the reflex arc are lost.
        
        Marked disturbance of voluntary movements.
        
        Loss or decrease in pain sensibility produces:
        -trophic disturbances such as perforating ulcers at pressure points;
        -anaesthesia around the anus,
        over legs, upper chest and inner
        border of hands
        due to involvement of dorsal nerve roots in
        lumbosacral and cervicothoracic regions of the spinal cord;
        -anaesthesia of central part of the face due to involvement of Vth cranial nerve;
        -Charcot Joints occurs due to
        repeated trauma to joints,
        finally leading to damage to the articular surface.
- - - - thermal stimulation
        
        mechanical stimulation
        
        chemical stimulation
- - - - Neurons in the reticular formation & thalamus are activated by the pain pathways n
        connected with the hypothalamus
        n other brain areas,
        such as limbic system that integrate autonomic n endocrine stress responses.
        It also generates the behavioural patterns of aggression & defence.
- - - - However, recovery occurs within few seconds
        after restoration of circulation
        and pain disappears.
        
        Lewis P-factor may consist of more than one substance, for example:
        
        K+,
        
        adenine nucleotides
        
        and lactic acid.