Special Senses

Functions and Special Senses

  • Sensing stimuli and processing information

  • Coordinating movements

Protective Accessory Structures of the Eye

  • Eyebrows & Eyelashes: Protect against foreign objects

  • Eyelids: Protect and prevent drying out

  • Lacrimal Apparatus: Secretes tears (lacrimal fluid) containing salts, mucus, and lysozyme

  • Muscles of the Eye: Control eye movement (Superior/Inferior Rectus, Medial/Lateral Rectus, Superior/Inferior Oblique)

Layers of the Eyeball

  • Fibrous Tunic: Outer coat (cornea and sclera)

  • Vascular Tunic: Supplies blood and secretes fluids

  • Neural Tunic/Retina: Transduces light into nerve impulses

Chambers of the Eye

  • Anterior Cavity: Contains aqueous humor (maintains shape, nourishes lens/cornea)

  • Posterior Cavity: Contains vitreous body (prevents collapse of eyeball)

Structure of the Retina

  • Photoreceptors

    • Rods: Detects shades of gray in dim light

    • Cones: Detects color in bright light

  • Fovea Centralis: Area of highest visual acuity

Imaging in the Eye

  • Refraction: Bending of light (majority by cornea)

  • Accommodation: Adjusting lens shape for focus

  • Rhodopsin: Photopigment involved in light detection

Visual Pathway: Eye to Brain

  • Action potentials travel via optic nerve to visual cortex

  • Information is processed to create visual representation

Regions of the Ear

  • Outer Ear: Receives sound waves

  • Middle Ear: Conveys vibrations (contains tympanic membrane and ossicles)

  • Inner Ear: Houses receptors for hearing and balance (contains cochlea and vestibular apparatus)

Sound Perception Process

  1. Sound waves directed through outer ear to tympanic membrane.

  2. Vibrations transmitted by ossicles to the oval window.

  3. Fluid pressure waves created in cochlea stimulate hair cells, producing action potentials.

  4. Impulses travel via vestibulocochlear nerve to auditory cortex.

Equilibrium

  • Static Equilibrium: Maintains head position relative to gravity (utricle/saccule)

  • Dynamic Equilibrium: Maintains head position during movement (semicircular canals)

  • Hair cells generate action potentials in response to position changes.

Gustation

  • Gustatory Receptors: Detect primary tastes (Sour, Sweet, Bitter, Salty, Umami)

  • Taste perception involves integration of tastes and smells to create flavor experiences.