Reflex activity

• Properties of reflex

  1. One way conduction
  2. Reaction time
  3. Summation
  4. Occlusion
  5. Subliminal fringe
  6. Recruitment
  7. After discharge
  8. Rebound phenomenon
  9. Fatigue
• 1. One way conduction: Bell-mangendie law:

  Impulses transmitted in only one direction.
• 2. Reaction time is time interval between application of stimulus and onset of reflex.

  Depends upon :

  i) length of afferent and efferent nerve fibres

  ii) velocity of impulse

  iii) Central delay
• 3. Summation :

  Muscle contracts when both nerve fibres are stimulated together with same strength of stimulus... Spatial Summation

  One nerve fibres is stimulated repeatedly with subliminal stimulus, they sum up to give response in muscle... Temporal Summation
• 4. Occlusion :

  When both nerve fibres are stimulated simultaneously, tension developed by muscle is less than sum of tension developed when each nerve is stimulated separately.

  Occlusion is due to overlapping of nerve fibres during distribution.
• 5. Subliminal fringe :

  Tension developed by simultaneous stimulation of two nerves is greater than sum of tension produced by stimulation of these nerves separately.

  Due to effect of spatial Summation
• 6. Recruitment:

  Successive activation of additional motor units with progressive increase in force of muscular contraction.

  There is a limit to number of motor neurons which are recruited. Recruitment is similar to temporal Summation
• 7. After discharge:

  Persistence or continuation of response for some time even after cessation of stimulus.

  Internuncial neurons are responsible for after discharge
• 8. Rebound phenomenon:

  When inhibition is suddenly removed, reflex activity becomes more forceful than before inhibition.
• 9. Fatigue: failure to give response to stimulus.

  Center or the synapse of reflex arc is first seat of fatigue.