Lecture Notes: Special Senses

Overview

Cranial Nerve I: Olfactory nerve
Pathway:
- Smell travels through nasal cavity
- Passes through cribriform plate to olfactory bulb
- Travels via olfactory tract to olfactory cortex (mainly in temporal lobe)
Unique Feature: Does not pass through thalamus
Clinical Relevance: Impairment can indicate conditions like Parkinson’s Disease

Taste Buds: Chemoreceptors for different tastes (salt, sweet, bitter, sour, umami)
Cranial Nerves:
- Posterior 1/3: Glossopharyngeal nerve (CN IX)
- Anterior 2/3: Facial nerve (CN VII), specifically chorda tympani

Pathway:
- External/Outer Ear → Middle Ear → Internal/Inner Ear
- Conductive Hearing: Due to sound wave vibrations
- Neural Hearing: Cochlea converts sound to neural impulses
Ear Anatomy:
- Outer Ear: Auricle/Pinna, Helix, Antihelix, Tragus
- Middle Ear: Tympanic membrane, Ossicles (Malleus, Incus, Stapes), Eustachian tube
- Inner Ear: Cochlea, Vestibule, Semicircular canals
Balance and Disorders:
- Vestibular system key for balance
- Disorders like vertigo and treatment methods

Eye Anatomy:
- Layers: Cornea, Sclera, Choroid, Retina
- Chambers: Anterior cavity (Aqueous humor), Posterior cavity (Vitreous humor)
- Structures: Iris (pupil dilator and constrictor), Ciliary bodies (control lens), Lens
Visual Processing:
- Refraction in cornea and lens flips image upside down
- Retina processes image, fibers transmit to brain for orientation correction
Retina Specifics:
- Photoreceptors: Cones (color vision), Rods (black and white)
- Fovea Centralis: Area of clearest vision
Visual Fields:
- Right and left visual fields processed across eyes and brain
- Optic Chiasm: Crossing point, critical in diagnosing lesions
- Lesions in optic nerve, chiasm, or tracts affect vision differently

Tear Production and Drainage:
- Lacrimal gland → Puncta → Lacrimal sac → Nasolacrimal duct
- Explains why nose runs when crying

Covered the senses: touch, smell, taste, hearing, sight, detailing their anatomy, pathways, and clinical relevance.