HL 2 Biology

E.1 Reflexes


reflex: a rapid, unconscious response to a stimulus

  • stimulus: a change in either the internal/external environment that is detected by a receptor & elicits a response
  • response: a change in an organism, produced by a stimulus

<<Reflexes and reflex arcs>>

  • reflex arc: a series of neurons involved in the animals response to a stimuli

Neurons involved in the response of animals to stimuli

  • receptors (e.g. pain) – nerve endings of sensory neurons
  • sensory neurons- carries impulse to CNS
  • relay neurons – message from sensory neurons taken in by synaptic transmission
  • motor neurons – impulse from relay neuron passed to motor neurons through synapses; in to animal’s muscle
  • effectors – movement/response to stimulus
  • **co-ordination: connections between sensory, relay and motor neurons for response to stimulus

pain withdrawal reflex: involves another reflex arc used to co-ordinate response to pain stimulus by the spinal cord

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