1. Journal #1: List the 5 special senses
Fun fact: Humans have five to six million odor detecting cells, but that is nothing compared to the animal kingdom. Rabbits have 100 million and a dog 220 million
Objective #1: Describe the sensory organs of smell (olfaction) and taste (gustation) and trace their sensory pathways to the brain.

2. Ch. 17 An Introduction to Special Senses
Olfaction- SMELL
Gustation- TASTE
*Interactive: pgs

3. Olfaction Olfactory Organs
Location: Nasal Cavity (on either side of septum)
Two Layers
Olfactory Epithelium
Olfactory Receptor Cells
Basal Cells (regenerative stem cells)
Lamina Propria (underneath)
Areolar tissue, blood vessels, & nerves
Olfactory Glands (Bowman’s Glands): form mucus

4. Olfactory Receptors Specialized neurons Knob projects to epithelium
Up to 20 cilia on each knob
Provide surface area for interaction with water and lipid soluble compound interaction
Olfactory reception occurs when these chemicals interact with odorant-binding proteins

6. Olfactory Pathways
Axons from olfactory epithelium group into 20 or more bundles
Move through the cribriform plate of ethmoid bone
Reach Olfactory bulbs of cerebrum, then efferent fibers travel to hypothalamus and limbic system
*Olfactory receptors do not adapt well to continued stimulus, which is why you eventually lose your sensitivity to persistent smells
*Only sense to directly reach cerebral cortex

8. Gustation Taste Receptors (Gustatory Receptors)
Superior tongue, and adjacent pharynx and larynx
Receptors and epithelium for specialized structures called taste buds (about 3000 in adults)
Lingual Papillae (3 types on the Tongue)
Filiform: provide friction, but have no taste buds
Fungiform: about 5 taste buds each
Cirumvallate: as many as 100 taste buds each

9. Taste Receptors
Each taste bud contains about 40 slender spindle shaped cells
Basal cells: stem cells
Gustatory cells: taste receptors
have microvilli surrounded by openings filled with fluid called taste pores
Replaced every 10 days

11. Gustatory Pathway
Taste buds innervate the facial, glossopharyngeal, and vagus nerves
Sensory information then carried to medulla, thalamus, and sensory cortex
Sense of texture and heat is carried by trigeminal nerve
*sense of taste increased by olfactory receptors

12. Vagus Nerve

13. Gustatory Discrimination
Primary Taste Sensation
Sweet, salty, sour, and bitter
Less know taste sensations
Umami: pleasant taste receptive to presence of amino acids, small peptides, and nucleuotides (cirumvallate papillae)
Water: receptors in pharynx processed in hypothalamus and affect water balance & blood volume