Sensory System

OT Dude Academy’s Free NBCOT® Exam Prep Course Medical Terminology, Anatomy, and Physiology Sensory System
Contents Hide
1 Introduction
2 Gustation (Taste)
3 Olfaction (Smell)
4 Audition (Hearing)
5 Equilibrium (Balance)
6 Somatosensation (Touch)
7 Vision (Sight)

Source 1  licensed under Creative Commons Attribution 4.0 International License.

Introduction

The sensory system consists of the following senses:

  • Taste
  • Smell
  • Touch (pressure, vibration, stretch, hair-follicle position)
  • Hearing
  • Sight
  • Balance
  • Temperature (thermoreceptors)
  • Pain (nociceptors)
  • Proprioception
  • Kinesthetic
  • Visceral

Gustation (Taste)

  • Gustation is the sense associated with the tongue.
  • The tongue is lined with stratified squamous epithelium.
  • Raised bumps called papillae contain the structures for taste transduction.
  • Within the structure of the papillae are taste buds that contain specialized gustatory receptor cells for the transduction of taste stimuli.
  • These receptor cells are sensitive to the chemicals contained within foods that are ingested, and they release neurotransmitters based on the amount of the chemical in the food.
  • Neurotransmitters from the gustatory cells can activate sensory neurons in the facial, glossopharyngeal, and vagus cranial nerves.
  • Tastes: sweet, salty, sour, bitter, umami, fats.

Olfaction (Smell)

  • Responsive to chemical stimuli.
  • Scent receptor messages travel to the cerebrum, specifically to the primary olfactory cortex that is located in the inferior and medial areas of the temporal lobe and additionally to the hypothalamus, where smells become associated with long-term memory and emotional response.

Audition (Hearing)

  • The transduction of sound waves into a neural signal is made possible by the structures of the ear.
  • Anatomy: external ear, middle ear, inner ear.
    • Auditory canal, temporal bone, tympanic membrane, ossicles, oval window, bony labyrinth, cochlea.
  • Cochlea is responsible for hearing.
  • Vestibule is responsible for balance.
  • Sound is transduced into neural signals within the cochlear region of the inner ear, which contains the sensory neurons of the spiral ganglia.
  • Cochlea encodes auditory stimuli for frequencies between 20 and 20,000 Hz, which is the range of sound that human ears can detect.

Equilibrium (Balance)

  • The inner ear is responsible for encoding information about equilibrium.
  • Cells that sense head position, head movement, and body motion are located within the vestibule of the inner ear.
  • Head position is sensed by otolith organs.
  • Head movement is sensed by the semicircular canals.
  • The neural signals generated in the vestibular ganglion are transmitted through the vestibulocochlear nerve to the brain stem and cerebellum.

Somatosensation (Touch)

  • The group of sensory modalities that are associated with touch, proprioception, and interoception.
  • Modalities include pressure, vibration, light touch, tickle, itch, temperature, pain, proprioception, and kinesthesia.
  • Many of the somatosensory receptors are located in the skin, but receptors are also found in muscles, tendons, joint capsules, ligaments, and in the walls of visceral organs.
  • Nociception is the sensation of potentially damaging stimuli.

Vision (Sight)

  • Based on the transduction of light stimuli received through the eyes.
  • Lashes help to protect the eye from abrasions by blocking particles that may land on the surface of the eye.
  • Tears are produced by the lacrimal gland, located beneath the lateral edges of the nose. Tears flow over the conjunctiva to wash away foreign particles.
  • Movement of the eye within the orbit is accomplished by the contraction of six extraocular muscles.
  • The retina is composed of several layers and contains specialized cells for the initial processing of visual stimuli.
  • The photoreceptors (rods and cones) change their membrane potential when stimulated by light energy.
  • There are no photoreceptors at the very back of the eye, where the optic nerve begins. This creates a “blind spot” in the retina and a corresponding blind spot in our visual field.
  • At the fovea, the retina lacks the supporting cells and blood vessels, and only contains photoreceptors.
  • Visual acuity is greatest at the fovea.
  • 3 types of cone opsins that are sensitive to different wavelengths of light and provide us with color vision.
  • Low-light vision is in grayscale.
  1. Betts, J.G., Young, K.A., Wise, J.A., Johson, E., Poe, B., Kruse, D. H., Korol, O., Johnson, J.E., Womble, M. & DeSaix, P. (2013). Anatomy and Physiology. OpenStax. http://cnx.org/content/col11496/latest/[↩]
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