Crash Course Taste and Smell

• Anosmia

  Partial or complete loss of the sense of smell (and with it, most of the ability to taste)
• Anosmia is caused by things as diverse as head trauma, respiratory infections, even plain old aging
• Transduction


  The process where sensory cells translate chemical, electromagnetic, and mechanical stimuli into action potentials that the nervous system can make sense of
• Major special senses

  • Vision
  • Touch
  • Hearing
  • Balance
  • Taste
  • Smell
• Chemoreceptors


  Receptors in taste buds and nasal passages that detect molecules in food and air
• Volatile


  In a gaseous state, allowing odorant molecules to be sucked up into the nostrils
• Olfactory epithelium


  The main organ of the olfactory system, a small yellowish patch of tissue on the roof of the nasal cavity containing millions of olfactory sensory neurons
• Olfactory sensory neurons


  Bowling pin-shaped neurons with receptors for just one kind of smell
• Glomerulus


  A tangle of fibers where olfactory axons meet up with the dendrites of mitral cells, relaying the smell signal to the brain
• Olfactory tract


  The pathway that sends smell signals from the glomerulus to the olfactory cortex and the limbic system
• Taste buds


  Specialized epithelial cells, not nervous tissue, that register and respond to different taste molecules
• Gustatory cells


  The taste receptor epithelial cells that actually do the tasting
• Basal cells


  The stem cells that replace the gustatory cells after they are damaged
• Gustatory hairs


  Thread-like protrusions of the gustatory cell membrane that run down to taste pores
• Tastants


  Food chemicals that must dissolve in saliva to diffuse through taste pores and bind to receptors on gustatory cells
• Graded potential


  The type of potential generated when salty tastants open sodium channels in gustatory cells
• Action potential


  The signal relayed through neurons to the taste area of the cerebral cortex
• The brain releases digestive enzymes in saliva and gastric juices to help break down the food once taste is detected