Biology

SPINAL CORD

  • The spinal cord is located within the vertebral column and consist of the following:
  • The grey matter forms the central part of the spinal cord.
  • It consists of nerve¬cell bodies and intermediate nerve fibres.
  • The white matter of the spinal cord carries sensory nerve fibers while the ventral root carries motor nerve fibers.

Simple and Conditioned Reflex Actions

Simple Reflex Action

  • A simple reflex action is an automatic response to a stimulus.
  • The route that is followed by impulses during a reflex action is called a reflex arc.
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A reflex action follows the following sequence:

  • A receptor is stimulated and an impulse is transmitted along a sensory nerve fibre to the spinal cord.
  • The impulse is picked up by an intermediate neurone within the CNS.
  • The intermediate nerve fibre transmits the impulse to a motor nerve fibre which is connected to an effector.
  • The effector responds.

Examples of reflex action include:

  • Pulling the hand away from a hot object.
  • The knee jerk.
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Conditioned Reflexes

  • These are learned responses.
  • When two or more stimuli are presented to an animal at the same time and repeatedly, the animal eventually responds to either stimulus.
  • For example, if a hungry animal is presented with food, it will respond by salivating.
  • If a bell is rung at the same time as the food is presented to the animal, the animal will learn to associate the sound of the bell with food.
  • Eventually, the animal can be made to salivate at the sound of the bell alone.
  • This response is called conditioned reflex and is one of the ways by which animals learn.
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See also:

FUNCTIONS OF MAJOR PARTS OF THE HUMAN BRAIN

NERVOUS SYSTEM

PRODUCTION OF AUXINS AND THEIR EFFECTS ON PLANT GROWTH

RECEPTION, RESPONSE AND CO-ORDINATION IN PLANTS

BIOLOGY PRACTICAL ACTIVITIES

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