Coordination and response

• Nervous system


  Coordinates the various organs and systems of the body so that the organism as a whole can function correctly
• Nervous system


  A Communications Network whereby signals in the form of electrical impulses are sent along nerve cells called neurons
• Receptor cells

  • Detect stimuli in both the internal and external environment
  • Send electrical impulses to the central nervous system
• Central nervous system


  • Consists of the brain and spinal cord
  • Processes and assesses the information received
  • Sends impulses to the muscles and glands (effectors) which respond accordingly
• Peripheral nervous system


  Consists of the nerves outside of the central nervous system that connect the brain and spinal cord to the rest of the body
• Types of neurons


  • Sensory neurons
  • Motor neurons
  • Relay neurons
• Neuron


  • Cell body containing a nucleus
  • Fibers called dendrites that Branch outwards to make contact with other neurons
  • A long nerve fiber called an axon
• Sensory neurons


  Carry impulses from the sense organs to the central nervous system
• Motor neurons


  Carry impulses from the central nervous system to effectors
• Relay neurons


  Found inside the central nervous system and connect sensory and motor neurons
• Synapse


  Junctions between neurons where the impulse is passed from one neuron to another
• Reflex action


  1. Stimulus detected by receptor cells

  2. Electrical impulse transmitted by sensory neuron to spinal cord

  3. Relay neuron passes impulse to motor neuron

  4. Motor neuron carries impulse to effector (muscle)

  5. Muscle contracts and response occurs
• Reflex action


  • Automatically and rapidly integrates and coordinates stimuli with the responses of effectors
  • Extremely quick response to a change in the environment that doesn't involve conscious thought
• Reflex actions


  • Coughing or sneezing due to irritant particles in the nasal passages
  • Blinking automatically when something comes into contact with the eye
• Reflex arc


  Neural pathway in the nervous system that a reflex follows
• Synapse


  • Electrical impulses are passed across synapses from one neuron to another in One Direction only
  • When an Impulse arrives at the synapse, membrane-bound structures called vesicles release chemical Messengers called neurotransmitters
  • The neurotransmitter molecules diffuse across the synaptic gap from the pre-synaptic neuron and then bind with receptor proteins on the other side, stimulating a new impulse in the postsynaptic neuron