KAAP220 Lecture Notes - Cribriform Plate, Olfactory Bulb, Nasal Septum
11 May 2018
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Lecture 24
• Chapter 15 - the special senses
• For each special sense - what is it (anatomy), and how does it work (sense reception, pathway to
the brain) - from reception of the sense to interpretation of that sense in the brain
• 5 - gustation (taste), olfaction (smell), vision, hearing, equilibrium (balance)
• Olfaction
• Important for smelling foods, giving awareness of our environment and situation (baby’s diaper),
and potential dangers
• Can make you hungry
• Food and smell are very closely intertwined - smelling food being cooked; telling if a food is good
or bad (spoiled/rotten food)
• Smelling smoke - know that there’s a fire; smelling chemicals
• Nasal osteology
• Ethmoid bone - forms superior lateral wall of the nasal cavity; includes superior and middle
conchae; the roof of the cavity is formed by the cribriform plate (has lots of holes for nerves
going back to the brain) of the ethmoid bone
• Medial wall = nasal septum; perpendicular plate, vertically oriented, extended down from
cribriform plate, makes up majority of the septum
• Vomer makes up some of the septum
• CN I - olfactory nerve
• Made of olfactory bulb and olfactory tract
• Olfactory tract goes just above the cribriform plate, and nerves extend from the tract down
through the plate
• Olfaction
• Olfactory epithelium
• Distributed along cribriform plate, superior portion of the perpendicular plate, and superior
nasal conchae laterally - where the olfactory nerves extend down through the plate
• Contain olfactory receptor cells, supporting cells of the receptor cells, and basal cells (smaller
cells closest to the lamina propria; stem cells of supporting cells)
• Olfactory receptor cells - bipolar
• Olfactory receptors are dendrites of specialized neurons
• Dissolved odorants bind to olfactory receptors; dissolve in the mucus of olfactory epithelium
• Triggers depolarization = generator potential (same concept as a graded potential)
• With strong enough stimulus, generator potential triggers action potentials that go to CNS
• Odorants = dissolved chemicals that stimulate olfactory neurons
• Olfactory pathway
• Odorants being inhaled into cavity, these dissolve in the mucus, and then are received by dendrites
of bipolar cells; bipolar cells extend through cribriform plate into the olfactory bulb where they
synapse with 2nd order neuron to bring that information back to brain
• Olfactory receptor cells = dendrites
• Axons go up through cribriform plate to olfactory bulb, olfactory tract, then information is carried
to the limbic system and hypothalamus (as well as olfactory cortex)
• Gustation/taste
• Taste receptors (also chemoreceptors) that are located all along the tongue
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Document Summary
Distributed along cribriform plate, superior portion of the perpendicular plate, and superior nasal conchae laterally - where the olfactory nerves extend down through the plate. Contain olfactory receptor cells, supporting cells of the receptor cells, and basal cells (smaller cells closest to the lamina propria; stem cells of supporting cells) Dissolved odorants bind to olfactory receptors; dissolve in the mucus of olfactory epithelium. Lingual papillae - epithelial projections on tongue surface: decline in number with age, lingual papillae, chemoreceptor cells located in taste buds in some lingual papillae, vallate (surround) papillae. Relatively large - each contains up to 100 taste buds. Produces aqueous humor and changes shape of the lens. Ciliary muscle - smooth muscle ring, projects inward. Ciliary zonule sinus (canal of schlemm); diffuses through vitreous body to retinal surface (vitreol humor: vision - light enters the eye. Allows light to enter eye - transparent and clear. Dense matrix of multiple layers of collagen fibers.
