THE NERVOUS SYSTEM

• the nervous system detects and reacts to stimuli (a change in the environment)
• PARTS OF THE NERVOUS SYSTEM:

  • CENTRAL NERVOUS SYSTEM: consists of the brain, the spinal cord, sensory neurons and motor neurones.
  • SENSORY NEURONES: the neurones that carry information as electrical impulses from the receptors to CNS.
  • MOTOR NEURONES: the neurones that carry electriacl impulses from the CNS to effectors.
  • EFFECTORS: all your muscles and glands which respond to nervous impulses
• ORDER of nervous system:

  1. stimulus
  2. receptor
  3. sensory neurone
  4. CNS
  5. motor neurone
  6. effector
  7. response
• Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (CNS). The CNS is the brain and spinal cord. The CNS coordinates the response of effectors which may be muscles contracting or glands secreting hormones.
• neurons transmit information very quickly to and from the brain, and the brain quickly decides how to respond to a stimulus
• SYNAPSES CONNECT NEURONES:

  • the connection between two neurones is called a SYNAPSE
  • the nerve signal is transmitted by chemicals and diffuse (move) across the gap
• REFLEXES HELP PREVENT INJURY:

  • reflexes are rapid, automatic responses to certain stimuli that don't involve the conscious part of the brain - they can reduce the chances of being injured

  E.g.

  If someone shines a bright light into your eye, your pupils automatically get smaller so that less light gets into your eye - stops it from getting damaged
• Relay neurone

  • Impulses are sent along a sensory neurone to a relay neurone in the CNS
  • Impulses travel along the motor neurone to the effector
• Effector

  Muscle contracts or glands secrete hormones
• Sensory neurone

  Impulses are sent along a sensory neurone to a relay neurone in the CNS
• Synapse

  Impulses reaching a synapse trigger chemicals to be released
• Receptors

  Detect stimulus
• Reflex arc

  1. Neurones in reflex arc go through the spinal cord or go through an unconscious part of the brain

  2. Impulses are sent along a sensory neurone to a relay neurone in the CNS

  3. Impulses travel along the motor neurone to the effector
• Motor neurone

  Impulses travel along the motor neurone to the effector
• Stimulus

  • Painful bee sting