The nervous system

• What is the primary function of the nervous system?


  To detect and react to stimuli
• Why do multicellular organisms need a nervous system?


  To communicate and coordinate responses to stimuli
• What are the main parts of the Central Nervous System (CNS)?


  • Brain
  • Spinal cord
• How is the CNS connected to the body?


  By sensory neurones and motor neurones
• What do sensory neurones do?


  They carry information as electrical impulses from receptors to the CNS
• What is the role of motor neurones?


  To carry electrical impulses from the CNS to effectors
• What are effectors in the nervous system?


  Muscles and glands that respond to nervous impulses
• What are receptors?


  Cells that detect stimuli
• Give examples of different types of receptors.

  Taste receptors on the tongue and sound receptors in the ears
• How do receptors and effectors interact in the nervous system?


  • Receptors detect stimuli
  • Effectors respond to nervous impulses
  • Muscles contract; glands secrete hormones
• What is the role of the Central Nervous System (CNS)?


  • Acts as a coordination center
  • Receives information from receptors
  • Coordinates a response
  • Sends information to effectors
• Describe the sequence of events when a bird spots a cat.

  Stimulus → Receptor → Sensory neurone → CNS → Motor neurone → Effector → Response
• What happens when the bird's eye receptors are stimulated?


  Sensory neurones carry the information to the CNS
• How does the CNS decide on a response to a stimulus?


  It processes the information received from receptors
• What is a synapse in the nervous system?


  • Connection between two neurones
  • Nerve signal transferred by chemicals
  • Chemicals diffuse across the gap to set off a new electrical signal
• What do chemicals do at a synapse?


  They diffuse across the gap to transfer the nerve signal
• What is the difference between complex and simple nervous systems?


  Complex systems are found in large animals, while simple systems are in organisms like jellyfish
• What is a reflex response?


  • An automatic response to a stimulus
  • Occurs without conscious thought
  • Common in simple organisms like jellyfish