B3.1

• what are the 2 parts of the human nervous system?

  the central and peripheral nervous system
• what is a bundle of neurones called?

  nerve
• how is information sent through the nervous system?

  as electrical impulses along neurones
• stimulus

  a detectable change in the internal or external environment of an organism
• examples of stimulus

  light, sound or temperature
• receptor

  a cell or organ which detects a stimulus
• neurone

  a nerve cell that is adapted to carry electrical charges (nerve impulses) from one part of the body to another
• sensory neurone

  carries nerve impulses from receptors to the CNS
• motor neurone

  carries nerve impulses from CNS to effectors
• relay neurone

  carries nerve impulses from sensory neurone to motor neurone in the spinal cord
• effector

  a cell, tissue, organ or organ system that responds to a stimulus
• gap between 2 neurones

  synapse
• how do voluntary responses move?

  through the nervous system via the brain
• how do automatic/reflex responses move?

  through the unconscious part of the brain or the spinal cord
• what is the pathway of an electrical impulse?

  1. sensory receptor detects a stimulus
  2. receptor transmits information as an electrical impulse along the sensory neurone to the relay neurones in the CNS
  3. CNS coordinates the response and sends impulse along a motor neurone to the effector
  4. effector initiates a response
• examples of responses from an effector?

  a muscle contraction or the secretion of a hormone from a gland
• how are axons adapted to ensure fast transmission of electrical impulses?

  1. fatty layer called myelin sheath --> provides insulation --> increases speed of impulse
  2. long in length --> reduces number of synapses --> speeds up transmission
  3. branched endings/dendrites --> create links between neurones
• what do synapses ensure?

  impulses travel in one direction
• what chemical transmits the impulse from one neurone to the next>?

  neurotransmitters
• why are neurotransmitters destroyed/recycled after the electrical impulse is sent?

  prevents continued stimulation of the 2nd neurone, preventing repeated impulses to be sent