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Lecture

BIOB34H3 Lecture Notes - Lingual Papilla, Palpebral Fissure, Lacrimal Sac


Department
Biological Sciences
Course Code
BIOB34H3
Professor
Ted Petit

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Chapter 16 Special Senses
Olfactory Sensations: Smell
- Types of cells
1. receptors lie in nasal epithelium of superior portion of nasal cavity
a. bipolar neurons
1) distal end is a dendrite with olfactory cilia (hairs), which generate impulses in
response to odor molecules
2) axon synapses with another neuron in the olfactory bulb
2. supporting cells
a. columnar epithelial cells, secrete mucus
3. basal cells
a. between supporting cells
b. stem cells that replace old receptor cells about every month
4. olfactory (Bowman's) glands
a. produce mucus that empties onto the olfactory epithelium by ducts (odor molecules must
dissolve in mucus to be sensed)
- Olfactory pathway
1. olfactory bulb neurons receive signals from receptors
a. sends signals along olfactory tract to olfactory area on medial surface of temporal lobe,
limbic system and part of frontal lobe
Gustatory Sensations: Taste
- Taste buds
1. mostly on tongue, some on soft palate, cheeks and pharynx
2. in papillae (elevations on tongue)
a. vallate papillae are on back of tongue
b. fungiform papillae are scattered over tongue surface
c. filiform papillae cover the surface of the tongue but do not have taste buds
3. three kinds of epithelial cells
a. gustatory cells are the receptor cells (have microvilli with receptors, substance to be
tasted must be dissolved in saliva in a taste pore); they synapse with sensory nerve fibers
b. supporting cells
c. basal cells, which can differentiate into other cell types
4. five primary taste sensations
a. sweet, sour, salty, bitter, umami
b. each tends to be sensed on certain areas of tongue, but an individual receptor may
respond to more than one kind of taste
- Gustatory pathways
1. fibers leading from taste buds are in...
a. facial nerves (from anterior 2/3 of tongue)
b. glossopharyngeal nerves (from posterior 1/3)
c. vagus (from throat and epiglottis)
d. The three cranial nerves end in the medulla, from there fibers project to gustatory area in
parietal lobe via the thalamus
Visual Sensations and the Eye
- Accessory structures of the eye
1. eyebrows
a. shade eyes from sunlight, protect from perspiration
2. eyelashes
a. protective, when disturbed trigger reflex blinking
3. eyelids (palpebrae)
a. upper and lower lids separated by palpebral fissure, they meet at medial and lateral canthi
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