The Nervous System

• Nervous system


  Allows humans to react to their surroundings and coordinate their behaviour
• The Nervous System Detects and Reacts to Stimuli

  1. Organisms need to respond to stimuli (changes in the environment) in order to survive

  2. Multicellular organisms developed nervous and hormonal communication systems
• Parts of the Nervous System

  • Central Nervous System (CNS)
  • Sensory Neurones
  • Motor Neurones
  • Effectors
• Central Nervous System (CNS)


  • In vertebrates, consists of the brain and spinal cord
  • In mammals, connected to the body by sensory and motor neurones
• Sensory Neurones


  Carry information as electrical impulses from receptors to the CNS
• Motor Neurones


  Carry electrical impulses from the CNS to effectors
• Effectors


  Muscles and glands, which respond to nervous impulses
• Receptors and Effectors


  • Receptors are the cells that detect stimuli
  • There are many different types of receptors
  • Receptors can form part of larger, complex organs
  • Effectors respond to nervous impulses and bring about a change
• The Central Nervous System (CNS) Coordinates the Response

  1. Receives information from receptors

  2. Coordinates a response

  3. Response is carried out by effectors
• Example of the Nervous System Response

  • Bird spots a cat
  • Receptors in the eye are stimulated
  • Sensory neurones carry information to the CNS
  • CNS decides what to do
  • CNS sends information to muscles in the wings (effectors)
  • Muscles contract and the bird flies away
• Synapse


  • The connection between two neurones
  • Nerve signal is transferred by chemicals which diffuse across the gap
  • Chemicals then set off a new electrical signal in the next neurone