Nerve cells (Neurons)

• Sensory Input

  Sensory receptors (e.g. eyes, nose) gather information from the environment and send it to the brain
• Integration

  The brain processes and understands the sensory input and decides what should be done in response
• Motor Output

  Messages are sent from the brain to the muscles or glands to cause a response
• Nervous System

  A communication network that controls what you do and what other body systems do

  • Made up of the Central Nervous System and Peripheral Nervous System
• Central Nervous System (CNS)


  • Made up of the brain and spinal cord
  • Receives information from the body, processes it and decides what to do
• Peripheral Nervous System (PNS)


  • Nerves that branch off the brain and spinal cord
  • Receives information from the environment (using senses) and sends it to the CNS (brain) branch
  • It also passes signals from the CNS and sends them to parts of the body such as muscles (effectors)
• Nerve cells

  • Are called neurons
  • Send electrical messages (impulses) to your brain and from your brain
  • Impulses control the movements and senses in our bodies

  Examples:

  • Making our muscles contract when we run
  • Our heart rate increases in a stressful situation
  • Our bodies shiver when we are cold
• Impulsive neurons


  • Each neuron is connected to other neurons
  • Each neuron receives an impulse (message) from the previous neuron and sends the same message to the next neuron

  They send two types of messages:

  1. Sensory messages using sensory neurons
  2. Motor messages using motor neurons
• Sensory Messages

  • Go from your sensory organs to your brain (CNS), telling your brain about the outside environment

  Example:

  • When it's cold
  • When something smells bad
• Motor Messages


  • Go from the brain (CNS) to your muscles, causing your muscles to contract

  Examples:

  • When you raise your hand to ask a question
  • When you blink your eye
• Signals sent between neurons

  • Neurons transmit electrochemical messages
  • They pass an electric signal along the length of the neuron
  • They pass chemicals from one neuron to the next
  • The messages that the neurons send to each other travel very fast
  • The chemicals that are passed between neurons are called neurotransmitters
  • These are packages of chemicals that can have effects on the next neuron.

  Example:

  • It could slow down the message being sent or speed it up
  • Neurotransmitters pass from one neuron to the next. This gap between neurons is called a synapse.
• Parts of a Neuron

  1. Dendrites
  2. Cell Body
  3. Axon
  4. Axon Terminal
  5. Synapse
  6. Myelin/Myelin Sheath
  7. Nodes of Ranvier
• Dendrites


  • The extensions of cytoplasm from the cell body
  • They receive messages from other neurons and pass them to the cell body
• Cell Body


  • Receives signals from the dendrites and decide whether they should be passed on
  • Contains the nucleus
• Axon


  • The one long extension of cytoplasm that transmits the message away from the cell body, towards the end/axon terminal
• Axon Terminal


  • The end of the axon
  • Where the electrical message stops and the neurotransmitters are released
• Synapse


  • The gaps between the axon terminal and the next neuron ( usually at a dendrite)
  • Neurotransmitters pass across the synapse to bind to the next neuron, passing the message on
• Myelin/Myelin Sheath


  • The fatty substance that surrounds an axon in segments
  • Helps to protect the axon from damage as well as speed up the message (it stops the voltage from 'leaking' out)
• Node of Ranvier


  • The gaps between the Myelin
• Dendrite Location 


  Diagram:

  
• Cell Body Location

  Diagram:

  
• Axon Location


  Diagram:

  
• Axon Terminal Location


  Diagram:

  
• Synapse Location

  Diagram:

  
• Myelin and Nodes of Ranvier location


  Diagram: