Sensory Systems: Vestibular, Auditory, and Visual

Vestibular Sensory System

• Damage to the vestibular system can result in:
  • Nystagmus (involuntary eye movement).
  • Vertigo (sensation of dizziness).
  • Unsteadiness.
• The vestibular system is crucial for:
  • Balance.
  • Sensing body movement through space.
  • Maintaining head and body posture.
  • Determining direction and speed.

Hearing & Equilibrium: Anatomy and Functions of the Ear

• Outer Ear
  • Parts: Auricle/pinna & auditory canal.
  • Function: Funnels sound to the tympanic membrane (eardrum).
• Middle Ear
  • Parts:
    • Tympanic membrane (eardrum): Vibrates when sound hits it.
    • Ear ossicles: Amplify sound vibrations and pass them through the oval window.
    • Eustachian tube: Equalizes pressure.
• Inner Ear
  • Parts:
    • Bony labyrinth:
      • Cochlea (spiral organ): Detects sound vibrations (Hearing).
      • Vestibule: Contains the saccule & utricle which detect gravity, linear acceleration, head movement, and position.
      • Semicircular canals: Ampulla detects rotation of the head.
    • Vestibulocochlear nerve (CN VIII): Transmits hearing and equilibrium information.

Vision and Refractive Errors

• Visual Acuity Chart
  • The chart displays lines of text with decreasing font sizes, used to assess visual acuity.
  • Distances are indicated in feet (FT) and meters (M).
    • 50 FT = 15.2 M
    • 40 FT = 12.2 M
    • 30 FT = 9.4 M
    • 25 FT = 7.62 M
    • 20 FT = 6.10 M
    • 15 FT = 4.57 M
    • 13 FT = 3.96 M
    • 10 FT = 3.04 M
• Emmetropia: Normal vision.
• Myopia: Nearsightedness.
• Hyperopia: Farsightedness.

Myopia (Nearsightedness)

• Cause: Eyeball is too long.
• Correction: Corrected with concave (minus) lenses.

Hyperopia (Farsightedness)

• Cause: Eyeball is too short.
• Correction: Corrected with convex (plus) lenses.

Astigmatism

• (Information about astigmatism is not provided in the transcript.)