Sensory receptors

• What is a sensory receptor?

  A structure specialized to detect a stimulus
• What is a sense organ?

  A structure composed of nervous and other tissues
• How do sense organs vary in complexity?

  They can be complex like eyes or simple like dendrites
• How can receptors be classified?

  • By stimulus modality
  • By origin of the stimulus
  • By distribution in the body
• What do thermoreceptors respond to?

  Heat and cold
• What do photoreceptors respond to?

  Light
• What are nociceptors?

  Pain receptors responding to tissue injury
• What do chemoreceptors respond to?

  Chemicals, including odors and tastes
• What do mechanoreceptors respond to?

  Physical deformation of cells or tissues
• What do exteroceptors sense?

  Stimuli external to the body
• What do interoceptors detect?

  Stimuli in internal organs
• What do proprioceptors sense?

  Position and movements of the body
• What are the two broad classes of senses?

  • General senses: widely distributed receptors
  • Special senses: limited to the head
• What do general senses include?

  Touch, pressure, stretch, heat, cold, pain
• What are special senses?

  Senses limited to the head and cranial nerves
• What is sensory transduction?

  Converting a sensory signal into an electrical signal
• How does stimulus intensity affect action potentials?

  Higher intensity generates higher frequency of action potentials
• What are tonic receptors?

  Slow adapting receptors responding continuously
• What are phasic receptors?

  Rapidly adapting receptors that stop responding
• What are the properties of sensory systems?

  • Stimulus: energy source
  • Receptors: specialized structures
  • Transducers: convert energy into action potentials
  • Conduction: nerve impulses to the CNS
  • Translation: CNS integration and processing
• What are touch receptors?

  Free or encapsulated nerve endings
• What are temperature receptors also known as?

  Thermoreceptors
• What is the function of cold receptors?

  Detect temperatures below body temperature
• What activates nociceptors?

  Signals from damaged tissue or strong stimuli
• What are the three categories of nociceptors?

  Mechanical, thermal, and chemical
• What are the pathways activated by inflammatory pain?

  • Reflexive protective pathway integrated in spinal cord
  • Ascending pathway to cortex for pain perception
• What does the olfactory epithelium contain?

  More than 1,000 different odorant receptors
• How does the brain discriminate odors?

  Using population coding from olfactory receptors
• Where are olfactory receptor cells located?

  In a mucous membrane at the top of the nose
• What happens when an odor molecule binds to a receptor?

  Chemical changes result in signals sent to the olfactory bulb
• Where do olfactory signals travel after the olfactory bulb?

  To the limbic system and primary olfactory cortex
• What is the primary taste sensation?

  Salty, sweet, sour, bitter, and umami
• What must happen for a chemical to be tasted?

  It must dissolve in saliva and contact gustatory hairs
• What is the life cycle of taste buds?

  They last ten days to two weeks
• How is taste information transmitted to the brain?

  Via different nerves depending on receptor location
• Which nerve collects information from the anterior tongue?

  The facial nerve
• Which nerve collects information from the posterior tongue?

  The glossopharyngeal nerve
• What are the optical components of the eye?

  Cornea, aqueous humor, lens, vitreous body
• What is vision?

  The perception of objects by light
• What percentage of sensory receptors are in the eyes?

  About 70%