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Special Senses
Chapter 17
The Special Senses
• Smell, taste, vision, hearing and equilibrium
• Housed in complex sensory organs
• Ophthalmology is science of the eye
• Otolaryngology is science of the ear
Olfactory Epithelium and Receptors
Physiology of Olfaction
Many different combinations of receptors produces the possibility for thousands of different odor sensations.
Low threshold, only few molecules needed.
Adaptation - rapid
Physiology of Olfaction
Olfactory Pathway
Olfactory receptors
Olfactory (I) nerves
Olfactory tract
Temporal lobe (primary olfactory area)
Tongue
4 major classes:
bitter
sour
salty
sweet
Gustation
Anatomy of Taste Buds and Papillae• Taste bud- made of three types of epithelial
cells: supporting cells, gustatory receptor cells and basal cells.
• About 50 gustatory cells per taste bud. Each one has a gustatory hair that projects through the taste pore.
• Taste buds are found in the papillae.
• Three types of papillae: vallate (circumvallate), fungiform and foliate.
Physiology of Gustation
• Five types of taste: sour, sweet, bitter, salty and umami.
• Tastant dissolves in saliva → plasma membrane of gustatory hair→ receptor potential→ nerve impulse via cranial nerves VII, IX and X→ medulla→ thalamus→ primary gustatory area of the cerebral cortex.
Vision
Accessory Structures of Eye
Lacrimal Apparatus
Anatomy of Eye
Wall of the Eyeball• Three layers:
– Fibrous tunic- outer layer• Sclera “white” of the eye
• Cornea-transparent coat
– Vascular tunic or uvea- middle layer• Choroid
• Ciliary body consists of ciliary processes and ciliary muscle
• Iris
– Retina- inner layer• Optic disc
• Macula lutea- fovea centralis
Muscles of Iris
Retina
View with Ophthalmoscope
Retina
Interior of the Eyeball• Lens
– lack blood vessels, consists of a capsule with proteins (crystallins) in layers; transparent.
– divides the eyeball into two cavities: anterior and posterior.
- Anterior cavity- further divided into anterior and posterior chambers. Both are filled with aqueous humor.
- Posterior cavity (vitreous chamber)-filled with vitreous body.
Chambers of the Eye
Cavities of the Interior of Eyeball• Anterior cavity (anterior to lens)
– filled with aqueous humor• produced by ciliary body• continually drained• replaced every 90 minutes
– 2 chambers• anterior chamber between cornea and iris• posterior chamber between iris and lens
• Posterior cavity (posterior to lens)– filled with vitreous body (jellylike)– formed once during embryonic life– floaters are debris in vitreous
Eye Structure Summary
• Refraction: Bending of light as it passes from one substance (air) into a 2nd substance with a different density (cornea)
• In the eye, light is refracted by the anterior & posterior surfaces of the cornea and the lens
Image Formation
Vision Correction
Photoreceptors
Rods
Cones
Photopigments
Neurotransmitters of Vision
Visual Pathway
Anatomy of Ear
Middle Ear
Inner Ear
Cochlea and
Cranial Nerve VIII
One Turn of
Cochlea and
Organ of Corti
Physiology of Hearing
Auditory Pathway
Balance and Position
Crista and Rotational Movement
Ear Structure Summary