in Neural Control and Coordination (Nervous System) by

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Best and Tailor defined reflex action as “A quick, automatic involuntary and often unconscious action brought when the receptor are stimulated by external or internal stimuli”. Example- hammering by hand at the site of mosquito bite. CNS controls reflex actions.

Mechanism of Reflex action: The reflex action is completed in a series of events. For example, when the hand is pricked with a needle, immediately hand is withdrawn from the source. The events that occur are,

  1. Pricking of needle stimulates skin receptors by receiving stimulus,
  2. Sensory impulse is formed and is carried by dendrites innervating the skin.
  3. Impulse is carried to the association neuron by axon of sensory neuron,
  4. The association neuron receives sensory impulse, interprets, analyses and generates motor impulse
  5. Motor impulse again travels through synapse between association neuron and motor neuron
  6. Impulse travels through motor neuron and reaches effector organ like skeletal muscles or the gland,
  7. The effector organ gives a proper response like contraction of the muscles or secretion by the gland.

Types of reflex action:

The reflex action may be cerebral (controlled by the brain) or spinal (controlled by the spinal cord). In man most of the reflex actions are controlled by spinal cord. Reflexes are of two types:

1. Unconditional or Inborn reflexes:

  • These are inborn or hereditary
  • They are permanent, never disappear and need no previous experience.
  • Example- blinking eyes with strong light; withdrawal of hand when pricked; suckling of milk by baby; swallowing, knee jerk; sneezing; coughing etc.

2. Conditional or acquired reflexes:

  • These are acquired during life by experience or learning.
  • These are individual one which require proper training
  • Long experience and proper training makes perfection,
  • These are noninherited
  • These are temporary and may disappear or reappear,
  • Example- driving motorcar, cycling, playing water polo, cricket or any game etc.

Significance of Reflex action:

  1. Reflex action helps the animals to adjust quickly to the changing environment.
  2. The life may have been in danger in the absence of reflex action. Thus reflexes have survival value.
  3. Most of the reflexes are controlled by spinal cord without involving brain and prevents over loading of the brain and brain fatigue.