Science S1 YR9 (BIO + PHI)

• Stimulus response model


  1. Stimulus detected

  2. Impulse sent to central nervous system

  3. Response generated
• An object moving with a speed of 98 m/s and has a kinetic energy of 700 J, calculate the mass of the object
• Central nervous system


  Brain and spinal cord
• Peripheral nervous system


  The nerves that connect the central nervous system to the rest of the body
• Neurons


  Nerve cells
• Nerves


  Axons of neurons grouped together
• Copy the diagram of a nerve cell into your notebooks
• Sensory neurons


  Carry the impulse generated by the stimulus to the central nervous system
• Interneurons


  Carry the impulse through the central nervous system
• Motor neurons


  Take the impulse to effectors such as muscles or glands
• Cell body


  • Highly sensitive branching extensions called dendrites
  • Possess numerous receptors that can receive messages from other cells
• Axon


  Long structure that the electrical impulse travels through
• Myelin


  White insulating substance that covers the axon and helps speed up the conduction of the message
• Watch the video: https://www.youtube.com/watch?v=qPix_X-9t7E and be prepared to share 3 things that you learnt from the information
• Write down two ways in which the structure of the neuron matches its function. Share your ideas with the person next to you
• Synapse


  The gap between neurons
• Vesicles


  Tiny containers that transport chemicals called neurotransmitters to the cell membrane
• Neurotransmitters


  Chemicals released into the synapse
• Reflex actions


  1. Stimulus detected by receptor

  2. Message sent via sensory neuron to interneuron in spinal cord

  3. Message sent from motor neuron to effector

  4. Response generated
• Reflex arc


  Pathway involving only a few neurons and travelling only to and from the spinal cord
• Electrical and chemical signals