BMS2011 Lecture Notes - Lecture 15: Taste, Stratum Basale, Ciliary Body
30 May 2018
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Week 7. CNS and Special Senses
• 5 traditional senses:
o Sight
o Hearing
o Smell
o Taste
o Touch (somatosensory)
o Others (eg. balance, pain, echolation-bats, electroreception-fish, magnetoreception-
birds)
• Taste is innervated by CN VII, IX, and X (facial, glossopharyngeal, vagus)
• Smell is innervated by CN I (olfactory)
• OLFACTORY/SMELL:
o Chemosensation
o Olfactory neurons live in epithelium and detect odours (chemicals)
o Converts chemical signal to nerve impulse
o Multiple neuron pathways
o Olfactory bulb is part of brain
o Transduction in olfactory nerves (PNS), axons pierce bone (cribriform plate) and enter
olfactory bulb where 2nd order neurons (mitral cells) live
o Mitral cells send axons to a number of brain areas, including anterior olfactory nucleus
(identify smell), piriform cortex, medial amygdala (mating-pheromones), and the
entorhinal cortex (olfactory memory).
o Anosmia: loss of smell (can just be a cold or more sinister eg. brain tumor)
o Glia: allow potential new neuron growth -> transplant into damaged spinal cord (grow
spinal cord)
o Olfactory nerves can be damaged in trauma -> cribiform plate -> CSF -> if you get cracks
can have CSF drip through nose
find more resources at oneclass.com
find more resources at oneclass.com
o Epithelium includes 3 cell types:
Olfactory receptor cells (odour detection)
Supporting cells (sustain and maintain receptors)
Basal cells (stem cells)
o Olfactory bulb is extremely small in humans (can barely see in cadavers)
o Testing smell is very complex, must use substances which are distinctive and do not
excite taste buds or irritate epithelium (eg. vinegar) -> false positive
o Taste or flavour is a combination of olfaction, texture and excitation of taste buds
-a lot of taste is through smell
• TONGUE/TASTE:
o Taste buds:
Circumvallate Papillae: form v shape, complex, a lot of taste buds, innervated by
CNIX
Foliate papillae: ridges and grooves towards the posterior part of tongue found
at lateral borders, innervated by CNVII and IX
Filiform papillae: not actually taste buds just surface of tongue -> rough, not
involved in gustation
Fungiform: mushroom shaped, mostly at the dorsal surface of tongue
-innervated by CN VII
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
A lot of taste is through smell: tongue/taste, taste buds: Circumvallate papillae: form v shape, complex, a lot of taste buds, innervated by. Foliate papillae: ridges and grooves towards the posterior part of tongue found at lateral borders, innervated by cnvii and ix. Filiform papillae: not actually taste buds just surface of tongue -> rough, not involved in gustation. Fungiform: mushroom shaped, mostly at the dorsal surface of tongue. Corneoscleral envelope firm white and cornea of eye. One type of protein -> crystalline that keeps transparent (if not transparent = cataracs) Tethered to ciliary body which is attached by zonals. Sympathetic ns: sphincter pupillae muscle: constrictor pupillae, smooth muscle. Inner neural layer: retina: eyeshine = reflective (see in animals at night, use fovea the most -> peak, binocular vision: Cones dominant in fovea (high colour discriminative vision) > whether fruits are ripe -> trichromatic vision. Rods are more frequent in peripheral retina.
