Lecture 9: General Senses (Somatic and Visceral Senses)

• What is the role of sensory information in the CNS?

  It is conveyed for further processing
• What types of sensations can animals consciously detect?

  Touch, pain, and temperature
• Why is sensory information necessary for the body?

  To maintain homeostasis
• What is the difference between sensation and perception?

  Sensation is awareness; perception is interpretation
• What are the three steps involved in all senses?

  1. A physical stimulus
  2. Transformation into a nerve impulse
  3. Response as perception or conscious experience
• Where do somatosensory signals originate from?

  Cutaneous areas, muscles, or joints
• What are viscerosensory signals?

  Signals from internal structures of the body
• Where are sensory receptors located?

  In every tissue except the nervous system
• How are sensory receptors classified?

  Based on their terminal morphology
• What are free nerve endings?

  Receptors with no special modifications
• What are encapsulated nerve endings?

  Sensory terminals ensheathed by connective tissue
• What type of receptors are all encapsulated nerve endings?

  Mechanoreceptors
• What are the five classes of sensory receptors?

  1. Mechanoreceptors
  2. Chemoreceptors
  3. Nociceptors
  4. Thermoreceptors
  5. Photoreceptors
• What do mechanoreceptors detect?

  Touch, proprioception, hearing, and balance
• What do chemoreceptors function in?

  Sensing itches, taste, and smell
• What do nociceptors detect?

  Pain
• What do thermoreceptors sense?

  Hot or cold
• What do photoreceptors sense?

  Electromagnetic energy
• How can sensory receptors be classified by location?

  1. Exteroceptors - sensitive to external stimuli
  2. Interoceptors - monitor visceral organs
  3. Proprioceptors - detect position of bones and muscles
• What do exteroceptors detect?

  Stimuli outside the body
• Where are exteroceptors located?

  Near the surface of the body
• What do interoceptors monitor?

  Visceral organs and their function
• What do proprioceptors provide information about?

  Position of bones and muscles
• What are the general senses?

  • Temperature
  • Pain
  • Touch
  • Pressure
  • Vibration
  • Proprioception
• What are the special senses?

  • Olfaction (smell)
  • Vision (sight)
  • Gustation (taste)
  • Equilibrium (balance)
  • Audition (hearing)
• Where are general sensory receptors located?

  Throughout the body
• Where are receptors for special senses located?

  In specialized structures or organs
• What do mechanoreceptors detect?

  Distortions in their cell membrane
• What are the three classes of mechanoreceptors?

  1. Tactile receptors
  2. Baroreceptors
  3. Proprioceptors
• What sensations do tactile receptors provide?

  Touch, pressure, and vibration
• What are the two principal mechanoreceptors in the superficial skin layer?

  Merkel disc and Meissner’s corpuscles
• How does Merkel disc adapt?

  It is slow adapting
• How does Meissner’s corpuscles adapt?

  It is rapidly adapting
• What do Pacinian corpuscles respond to?

  Rapid indentation of the skin
• What do Ruffini endings sense?

  Stretch of the skin
• What do baroreceptors sense?

  Change in walls of distensible organs
• What happens when baroreceptors detect increased blood pressure?

  A reflex is initiated to adjust heart rate
• What information do baroreceptors in the lungs send?

  Information regarding lung inflation
• What do proprioceptors monitor?

  Position of joints and tension in muscles
• How do proprioceptors adapt?

  They do not adapt