Senses

• Sensing


  Sensory cells translating stimuli (chemical, electromagnetic, mechanical) into action potentials that our nervous system can integrate
• General sensory receptors


  Modified nerve endings of sensory neurons
• Touch


  A general (somatic) sense that relates to our ability to detect pressure, pain, temperature, and tension through a variety of general sensory receptors
• Special senses


  Vision, smell, taste, hearing, and equilibrium
• Special sensory receptor cells

  In sensory organs (like your ear and eye) and/or epithelial structures (like your taste buds and olfactory epithelium) in your head
• Vision


  The dominant sense of humans
• Light


  Electromagnetic waves
• Vision


  Photoreceptors in our eyes convert light energy to electrical energy (APs) that then travel to the brain
• Eye


  • Surrounded by protective fat and the bony orbits in the skull
  • Accessory structures: Eyebrows, Eyelids and Eyelashes, Lacrimal apparatus
  • Extrinsic eye muscles: 6 on each eyeball control the eye's movement

  
• Eye


  • Internally hollow with fluids (humors) that hold its shape
  • Wall of the eyeball is made of 3 layers: Fibrous layer, Vascular layer, Inner layer (retina)

  
• Retina


  2 layers: Outer pigmented layer, Inner neural layer with photoreceptors (rods and cones) that convert light energy to APs
• Lens


  The convex transparent disc that focuses the light that is allowed in and projects it onto the retina in the inner layer
• Vitreous humor


  The clear gel that fills the posterior segment of the eye behind the lens
• Aqueous humor


  The clear fluid that fills the anterior segment in front of the lens
• Smell (olfaction)


  Use chemoreceptors to detect molecules in the air (dissolved in fluids from our nasal membranes)
• Odor


  The gaseous molecules we smell
• Smell (olfaction)


  Molecules bind to receptors, APs down the olfactory nerve into the ethmoid bone, and eventually to the olfactory bulb that connects to our brain
• Taste (gustation)


  Use chemoreceptors to detect molecules in our food (dissolved in saliva)
• Taste buds


  The sensory organ of taste, mainly inside of papillae (the bumps on your tongue)
• Taste (gustation)


  Sensory receptor cells, APs, signal to the gustatory cortex of brain, release of digestive enzymes to break down the food, ENERGY!
• Hearing and balance


  The ear is the sensory organ
• Hearing


  Sound creates vibrations in the air that hit our eardrums and cause tiny bones (auditory ossicles) to move internal fluid against a membrane, triggering tiny "hair" cells to stimulate neurons, APs to the brain
• Ear


  • 3 parts: (1) outer/external, (2) middle ear for hearing, (3) inner ear for hearing and maintaining equilibrium
• External (outer) ear


  Pinna (auricle), External acoustic meatus (auditory canal), Function: Catch sound waves and pass them deeper into the ear through the auditory canal
• Middle ear


  Tympanic cavity, 3 tiny bones (auditory ossicles: malleus, incus, and stapes), Function: Amplify sound waves to make stronger for when they get to inner ear
• Inner ear


  Labyrinth (bony and membranous), Function: Turn physical vibrations into electrical impulses (APs) to travel to brain
• Inner ear


  • Semicircular canals: aid in maintaining balance when head rotates
  • Cochlea: contains hair cells that vibrate at different frequencies stimulating the organ of Corti to send AP through cochlear nerve to the auditory cortex in the brain
  • Vestibule: key structure for maintaining balance, Head movements cause fluid to stimulate hair cells, send AP through the vestibular nerve