lecture 7

• Neurons


  Communication with other neurons, receive, integrate and transmit electrochemical signals
• Types of neurons


  • Motor neurons
  • Sensory neurons

  
• Glia cells


  Provide structural support and insulation for neurons
• Types of glia cells

  • Astrocytes
  • Microglia
  • Oligodendrocytes

  
• Somatosensory system


  Body's communication network: information processing and transportation
• Neuron


  • Soma: cell body, with a nucleus which provides energy
  • Dendrites: feeler-like structures to receive information
  • Axon: long, thin fibre that transmits signals away from soma
  • Axon terminal: transmits signals to dendrites of another cell
• Basic flow of information in a neuron

  Dendrite -> soma -> axon -> to dendrites of another neuron / to effector site

  
• Structures on the axon

  • Myelin sheath: wrapped around axon, speeds up firing of neuron
  • Nodes of Ranvier: small gaps on axon with no myelin sheath

  
• Motor neurons


  • Soma are in spinal cord, receives signals from other neurons, conducts impulses along axon to axon terminals to a muscle (effector site)

  
• Sensory neurons


  • Specialized to be highly sensitive to a particular type of stimulation, dendrites attached to a sensory ending, example: skin

  
• Reflex arc is a neural pathway
• Glia cells


  • Cells that support neurons, found in CNS and PNS

  
• Astrocytes


  • Create blood-brain barrier, can help heal brain damage
• Neurons in the brain generally do not regenerate, so the blood-brain barrier has to block incoming viruses, bacteria, or other harmful material from entering the brain
• Microglia


  • Functions: clean up dead cells and prevent infection in the brain, immune defence in the nervous system, can become damaged by HIV

  
• Oligodendrocytes


  • Provide myelin to speed up transmission of neurons, process is myelination, also involved in maintenance and repair of myelin, only in CNS (in PNS: Schwann Cells)

  
• Somatosensory system


  Relays information from skin, limbs, joints and processes it in the brain, contains cutaneous mechanoreceptors that translate mechanical pressure from skin into neural signals

  
• Structures on nerve endings that allow us to sense the world (mechanoreceptors)


  • Meissner's corpuscles
  • Pacinian corpuscles
  • Merkel's discs

  
• Meissner's corpuscles


  • Sensitive to touch, located near surface of skin, concentrated in sensitive areas like fingers and hairless skin
• Pacinian corpuscles


  • Sensitive to vibration and pressure, located deep in skin, joints, ligaments, made up of layers of tissue around a free nerve ending
• Merkel's discs


  • Sensitive to pressure, position of touch, light touch, sustained response to pressure, "slowly adapting", located near surface of skin