M10

• Mydriasis


  Pupil dilation
• Miosis


  Pupil constriction
• Sensation

  Process initiated by stimulating sensory receptors

  
• Perception


  Conscious awareness of stimuli received by sensory neurons

  
• Senses


  The means by which the brain receives information about the environment and the body
• Sensory Receptors


  Nerve endings or specialized cells capable of responding to stimuli by developing action potentials

  
• Types of Sensory Receptors

  • Mechanoreceptors
  • Chemoreceptors
  • Photoreceptors
  • Thermoreceptors
  • Nociceptors

  
• Free Nerve Endings


  Simplest and most common type of sensory receptors
• Temperature Receptors


  Can only respond to temperature between 12°C (54°F) and 47°C (117°F) and only the pain receptors are stimulated in temperatures beyond
• Temperature Receptors

  • Cold Receptors
  • Warm Receptors
• Touch Receptors


  • Merkel Disks
  • Hair Follicle Receptors
  • Meissner Corpuscles
  • Ruffini Corpuscles
  • Pacinian Corpuscles
• Pain


  Group of unpleasant perceptual and emotional experience
• Types of Pain Sensation

  • Localized, sharp, pricking, or cutting pain
  • Diffuse, burning, or aching pain
• Referred Pain


  Originates in region that is not source of pain stimulus; sensory neurons from superficial area & neurons from source of pain converge onto same ascending neurons of spinal cord

  
• Local Anesthesia


  Injection of chemical anesthetics near sensory receptor or nerve in local areas of the body which suppresses the action potentials from pain receptors
• General Anesthesia


  A treatment where chemical anesthetics that affect the reticular activating system are administered resulting to loss of consciousness
• Gate Control Theory


  An inherent control system which may explain the physiological basis for several techniques that have been used to reduce the intensity of pain; key element is the concept of a gate that allows pain signals to reach the brain when it is open, and blocks the signals when it is closed
• Special Senses


  • Smell & taste
  • Vision
  • Hearing & balance

  
• Olfaction


  Sense of smell
• Olfactory Neurons


  Bipolar neurons within the olfactory epithelium which lines the superior part of nasal cavity

  
• There are at least 400 functional olfactory receptors in humans & can detect an estimated 10,000 different smells
• Olfactory Cortex


  Involved in both conscious perception of smell & visceral & emotional reactions linked to odors

  
• Adaptation


  Feedback loops; inhibit transmission of action potentials due to prolonged exposure to a given odorant
• Taste Buds


  Oval, sensory structures located on papillae of tongue, hard palate, & epiglottis that detect taste stimuli
• Taste Bud Cells


  • Specialized Epithelial Cells
  • Taste Cells
• All taste buds are able to detect all basic taste sensations (sweet, sour, salty, bitter, and umami); however, each can be most sensitive to one class of taste stimuli
• Many taste sensations are strongly influenced by olfactory sensations
• Accessory Structures of the Eye

  • Eyebrows
  • Eyelids & Eyelashes
  • Conjunctiva
  • Lacrimal Apparatus
  • Extrinsic Eye Muscles

  
• Tunics of the Eyeball

  • Fibrous Tunic
  • Vascular Tunic
  • Nervous Tunic
• Sclera


  Firm, white, outer layer that helps maintain eye shape, protects internal structures, and provides attachment sites for extrinsic eye muscles

  
• Cornea


  Transparent; permits entry of light & also bends or refracts it
• Choroid


  Consists of vascular network & many melanin-containing pigment cells (appears black)
• Ciliary Body

  Contains ciliary muscles which attached to perimeter of the lens by suspensory ligaments
• Lens


  A flexible, biconvex, transparent disc
• Iris

  Colored part of eye; a contractile structure that surrounds & regulates the diameter of pupil (an opening where the light pass through); control the amount of light entering the eye

  
• Iris Muscles


  • Circular smooth muscles (constrict pupil)
  • Radial smooth muscles (dilate pupil)
• Layers of the Retina

  • Pigmented Retina
  • Sensory Retina
• Rods


  Sensitive to light & can function in dim light; contain a photosensitive pigment called rhodopsin, which consists of opsin (colorless protein) loosely bound to retinal (yellow pigment; requires vitamin A to be manufactured)
• Cones

  Require much more light & provide color vision; has 3 types, each sensitive to a color: blue, green, or red
• Retinal Interneurons


  • Bipolar Cells
  • Horizontal Cells
  • Ganglion Cells