Chapter 17 - Special Senses

Chapter 17 - Special Senses -...

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Chapter 17 - An Introduction to the Special Senses Five Special Senses: Olfaction, Gustation, Vision, Equilibrium & Hearing 1. Smell (Olfaction) Olfactory Organs provide sense of smell; located in nasal cavity on either side of nasal septum Made up of two layers: Olfactory epithelium & Lamina propria  Layers of olfactory organs Olfactory epithelium contains olfactory receptors, supporting cells & basal (stem) cells Lamina propria contains areolar tissue, blood vessels, nerves & olfactory glands Olfactory Glands : secretions coat surfaces of olfactory organs Olfactory Receptors  are highly modified neurons Olfactory reception  involves detecting dissolved chemicals as they interact with odorant-binding proteins Olfactory Pathways: axons leaving olfactory epithelium collect into 20 or more bundles; penetrate the cribriform plate of  ethmoid & reach olfactory bulbs of cerebrum where first synapse occurs Axons leaving olfactory bulb : travel along olfactory tract to reach olfactory cortex, hypothalamus & portions of limbic  system Olfactory Discrimination: can distinguish thousands of chemical stimuli CNS interprets smells by the pattern of receptor activity Olfactory Receptor Population: considerable turnover; # of olfactory receptors declines with age 2. Taste (Gustation) Gustation  provides information about the foods and liquids consumed Taste receptors  (gustatory receptors) are distributed on tongue & portions of pharynx & larynx Taste buds: associated with epithelial projections (lingual papillae) on superior surface of tongue Three types of lingual papillae 1. Filiform papillae: provide friction but do not contain taste buds 2. Fungiform papillae: contain five taste buds each 3. Taste buds  contain basal (stem) cells & gustatory cells: extend  taste hairs  through taste pore & survive only 10 days before  replacement Gustatory Discrimination: primary taste sensations:  Sweet, Salty, Sour & Bitter Additional human taste sensations i. Umami: characteristic of beef/chicken broths and Parmesan cheese; receptors sensitive to amino acids, small peptides,  and nucleotides  ii. Water: detected by  water receptors  in the pharynx Taste:  dissolved chemicals contact taste hairs & bind to receptor proteins of gustatory cell iii. Salt & sour receptors: chemically gated ion channels & stimulation produces depolarization of cell iv. Sweet, bitter & umami stimuli: G proteins:  gustducins End Result of Taste Receptor   Stimulation Release of neurotransmitters by receptor cell 5. Dendrites of sensory afferents wrapped by receptor membrane 6. Neurotransmitters generate action potentials in afferent fiber Taste Sensitivity vii. Exhibits significant individual differences  viii.
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This note was uploaded on 07/13/2011 for the course BIOL 2401 taught by Professor Watson during the Summer '10 term at Richland Community College.

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Chapter 17 - Special Senses -...

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