neurons

• Neurons


  The basic building blocks of the nervous system, nerve cells that process and transmit messages through electrical and chemical signals
• 80% of neurons are located in the brain (there are about 200 billion in total)
• Structure of neurons


  • Cell body
  • Dendrites
  • Axon
• Dendrites


  Receive signals from other neurons or from sensory receptors and carry information towards the cell body
• Cell body


  Includes a nucleus that contains the genetic code
• Axon


  Carries the impulse away from the cell body, covered in a fatty layer of myelin sheath which protects the axon, stops 'messages' being from getting muddled with each other and speeds up the electrical impulse as it segmented at the Nodes of Ranvier leaving the axon exposed
• Terminal buttons


  At the end of the axon, communicate with the next neuron in the chain across a gap known as the synapse
• Function of a neuron

  Receive, respond to and send messages. Messages sent by axons are called action potentials.
• Resting state of a neuron

  Inside of the neuron is negatively charged
• Action potential


  When an impulse is sent from the cell body, this electrical charge sends the signal down the axon (away from the cell body)
• Sensory neurons


  • Carry messages from sensory receptors to the CNS, have long dendrites and short axons
• Relay (inter) neurons


  • Connect the sensory neurons to the motor or other relay neurons, allow sensory and motor neurons to communicate with each other, found in the CNS, have short dendrites and short axons
• Motor neurons


  • Connect the CNS to the muscles and glands, located in the CNS and project their axons outside the CNS to directly or indirectly control muscles, when stimulated release neurotransmitters that bind to receptors on the muscle and trigger a response leading to muscle movement, have short dendrites and long axons
• Sensory neuron example


  • If you touch a hot stove, the sensory neurons pick up the heat, this information is passed to relay neurons which pass it to motor neurons, instructing the hand to move away from the heat
• Sensory neuron example


  • If you get asked a question, sensory neurons pick up the sound, this information is processed in the auditory cortex, relay neurons associated with memory are activated to recall the answer, then neurons associated with language formulate the answer, motor neurons in the tongue and mouth produce the speech required
• on


  5 mar
• Sensory, relay and motor neurons


  Structure and function
• Neurons are the basic building blocks of the nervous system, they are nerve cells the process and traremit messages through electrical and chemical signals
• 80% of neurons are located in the brain (there are about 100 billion in total)
• Structure of neurons


  • Cell body
  • Dendrites
  • Axon
• Dendrites


  Receive signals from other neurons or from sensory receptors and carry information towards the cell body
• Cell body


  Includes a nucleus that contains the genetic code
• Axon


  • Impulse is carried away from the cell body
  • Covered in a fatty layer of myelin sheath
  • Protects the axon
  • Stops 'messages' being from getting muddled with each other
  • Speeds up the electrical impulse as it segmented at the Nodes of Ranvier leaving the axon exposed
• Terminal buttons


  • At the end of the axon
  • Communicate with the next neuron in the chain across a gap known as the synapse
• Function of a neuron

  • Receive, respond to and send messages
  • Messages sent by axons are called action potentials
  • When resting, the inside of a neuron is negatively charged
  • When an impulse is sent from the cell body, this electrical charge sends the signal down the axon (away from the cell body) - an action potential
• Sensory neurons


  • Carry messages from sensory receptors to the CNS (central nervous system)
  • Sensory receptors can be found in the eyes, ears, tongue and skin
  • Sensory neurons convert information from these sensory receptors (from external stimuli such as light) into neural impulses that are passed on to the brain or spinal cord (for reflex actions)
  • They have long dendrites and short axons
• Relay (inter) neurons


  • Connect the sensory neurons to the motor or other relay neurons
  • Allow sensory and motor neurons to communicate with each other
  • Found in the CNS
  • About 97% of the neurons in the CNS are relay neurons
  • They have short dendrites and short axons
• Motor neurons


  • Connect the CNS to the muscles and glands
  • Located in the CNS and project their axons outside the CNS and directly or indirectly control muscles
  • When stimulated, the motor neuron releases neurotransmitters that bind to the receptors on the muscle and trigger a response that leads to muscle movement
  • They have short dendrites and long axons