Sense Organs

• Sense


  Ability to perceive stimuli
• Sensation


  Conscious awareness of stimuli received by sensory neurons
• Sensory receptors


  Sensory nerve endings that respond to stimuli by developing action potentials
• Classification of Senses


  • General senses
  • Special senses

  
• General senses


  • Receptors over large part of body that sense touch, pressure, pain, temperature, and itch
  • Somatic provide information about body and environment
  • Visceral provide information about internal organs

  
• Special senses


  • Smell, taste, sight, hearing, and balance
• Types of Receptors


  • Mechanoreceptors
  • Chemoreceptors
  • Photoreceptors
  • Thermoreceptors
  • Nociceptors
• Mechanoreceptors


  Detect movement
• Mechanoreceptors


  • Touch, pressure, vibration
• Chemoreceptors


  Detect chemicals
• Chemoreceptors


  • Odors
• Photoreceptors


  Detect light
• Thermoreceptors


  Detect temperature changes
• Nociceptors


  Detect pain
• Types of Touch Receptors


  • Merkel's disk
  • Hair follicle receptors
  • Meissner corpuscle
  • Ruffini corpuscle
  • Pacinian corpuscle
• Merkel's disk


  Detect light touch and pressure
• Hair follicle receptors


  Detect light touch
• Meissner corpuscle


  Deep in epidermis, localizing tactile sensations
• Ruffini corpuscle


  Deep tactile receptors, detect continuous pressure in skin
• Pacinian corpuscle


  Deepest receptors, associated with tendons and joints, detect deep pressure, vibration, position
• Pain is an unpleasant perceptual and emotional experience
• Localized pain


  Sharp, pricking, cutting pain, rapid action potential
• Diffuse pain


  Burning, aching pain, slower action potentials
• Local anesthesia


  Action potentials suppressed from pain, receptors in local areas, chemicals are injected near sensory nerve
• General anesthesia


  Loss of consciousness, chemicals affect reticular formation
• Referred pain


  Originates in a region that is not source of pain stimulus, felt when internal organs are damaged or inflamed, sensory neurons from superficial area and neurons of source pain converge onto same ascending neurons of spinal cord
• Olfaction is the sense of smell, occurs in response to odorants, receptors are located in nasal cavity and hard palate, we can detected 10,000 different smells
• Olfaction process


  1. Nasal cavity contains a thin film of mucous where odors become dissolved

  2. Olfactory neurons are located in mucous, dendrites pick up odor, depolarize, and carry odor to axons in olfactory bulb (cranial nerve I)

  3. Frontal and temporal lobes process odor

  
• Taste buds


  Sensory structures that detect taste, located on papillae on tongue, hard palate, throat, each contains 40 taste cells with taste hairs that extend into taste pores

  
• Taste process


  1. Taste buds pick up taste and send it to taste cells

  2. Taste cells send taste to taste hairs

  3. Taste hairs contain receptors that initiate an action potential which is carried to parietal lobe

  4. Brain processes taste

  
• Types of tastes


  • Sweet
  • Sour
  • Salty
  • Bitter
  • Umami
• Certain taste buds are more sensitive to certain tastes, taste is also linked to smell
• Accessory structures of the eye


  • Eyebrow, eyelid/eyelashes, conjunctiva, lacrimal apparatus, extrinsic eye muscles

  
• Eyebrow


  Protects from sweat, shade from sun
• Eyelid/Eyelashes


  Protect from foreign objects, lubricates by blinking
• Conjunctiva


  Thin membrane that covers inner surface of eyelid

  
• Lacrimal apparatus


  Produces tears
• Extrinsic eye muscles


  Help move eyeball
• Anatomy of the eye

  • Hollow, fluid filled sphere, composed of 3 layers (tunics), divided into chambers
• Sclera


  Firm, white outer part, helps maintain eye shape, provides attachment sites, protects internal structures