html5-img
1 / 30

Chapter 17: The Special Senses

Chapter 17: The Special Senses. Muse Bio 2440 Lecture #4 5/21/13. Comparison of General and Special Senses. General Senses. Special Senses. Include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations. Scattered throughout the body. Simple structures. .

bette
Download Presentation

Chapter 17: The Special Senses

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 17: The Special Senses Muse Bio 2440 Lecture #4 5/21/13

  2. Comparison of General and Special Senses General Senses Special Senses Include somatic sensations (tactile, thermal, pain, and proprioceptive) and visceral sensations. Scattered throughout the body. Simple structures. Include smell, taste, vision, hearing and equilibrium. Concentrated in specific locations in the head. Anatomically distinct structures. Complex neural pathway.

  3. Olfaction: Sense of Smell Olfactory epithelium contains 10-100 million receptors. Olfactory receptor- a bipolar neuron with cilia called olfactory hairs. - Respond to chemical stimulation of an odorant molecule. Supporting cells- provide support and nourishment. Basal cells- replace olfactory receptors.

  4. Olfactory Epithelium and Olfactory Receptors

  5. Olfactory Epithelium and Olfactory Receptors continued…

  6. Smell (Olfaction) • Olfactory Pathways • Arriving information reaches information centers without first synapsing in thalamus

  7. Olfactory epithelium Olfactory tract Olfactory bulb Nasal conchae Route of inhaled air (a) Figure 15.21a

  8. Mitral cell (output cell) Olfactory tract Glomeruli Olfactory bulb Cribriform plate of ethmoid bone Filaments of olfactory nerve Lamina propria connective tissue Olfactory gland Axon Basal cell Olfactory receptor cell Olfactory epithelium Supporting cell Dendrite Olfactory cilia Mucus Route of inhaled air containing odor molecules (b) Figure 15.21a

  9. Physiology of Olfaction Can detect about 10,000 different odors. Odorant binds to the receptor of an olfactory hair→ G-protein activation→ activation of adenylate cyclase→ production of cAMP→ opening of Na+ channels→ inflow of Na+ →generator potential→ nerve impulse through olfactory nerves→ olfactory bulbs→ olfactory tract→ primary olfactory area of the cerebral cortex.

  10. Olfactory transduction

  11. Figure 17-2 Olfactory and Gustatory Receptors Olfaction and gustation are specialsenses that provide us with vitalinformation about our environment. Although the sensory information provided is diverse and complex, each special sense originates at receptor cells that may be neurons or specialized receptor cells that communicate with sensory neurons. Stimulus Dendrites Specializedolfactoryneuron Stimulusremoved Actionpotentials Stimulus Threshold Generator potential to CNS

  12. Summary of sense of smell Odorant molecule binds one of 10-100 million receptors. Conformational change in receptor interacts with G protein G protein activates adenylate cyclase to generate cAMP cAMP opens Na+ channels to initiate depolarization. Information on number of action potentials decoded by olfactory bulbs. Animals have greater numbers of receptors thus better sense of smell Usually 10,000 times greater.

  13. Sense of Taste • Receptor organs are taste buds • Found on the tongue • On the tops of fungiform papillae • On the side walls of foliate papillae and circumvallate (vallate) papillae

  14. Circumvallate papilla Taste bud (b) Enlarged section of a circumvallate papilla. Figure 15.23b

  15. Epiglottis Palatine tonsil Lingual tonsil Foliate papillae Fungiform papillae (a) Taste buds are associated with fungiform, foliate, and circumvallate (vallate) papillae. Figure 15.23a

  16. Gustation: Sense of Taste Taste bud

  17. Structure of a Taste Bud • Flask shaped • 50–100 epithelial cells: • Basal cells—dynamic stem cells • Gustatory cells—taste cells • Microvilli (gustatory hairs) project through a taste pore to the surface of the epithelium

  18. Figure 17-3b Gustatory Receptors Tastebuds Circumvallate papilla Fungiform papilla Filiform papillae The structure and representative locationsof the three types of lingual papillae. Tastereceptors are located in taste buds, whichform pockets in the epithelium of fungiform or circumvillate papillae.

  19. Connective tissue Gustatory hair Taste fibers of cranial nerve Stratified squamous epithelium of tongue Basal cells Gustatory (taste) cells Taste pore (c) Enlarged view of a taste bud. Figure 15.23c

  20. Taste (Gustation) • Gustatory Discrimination • Primary taste sensations • Sweet (sugars) • Salty • Sour (acids) • Bitter (alkali) • umami - savory (fat)

  21. Taste Sensations - chemical triggers • There are five basic taste sensations • Sweet—sugars, saccharin, alcohol, and some amino acids • Sour—hydrogen ions • Salt—metal ions • Bitter—alkaloids such as quinine and nicotine • Umami—amino acids glutamate and aspartate

  22. Taste (Gustation) • Gustatory Discrimination • Dissolved chemicals contact taste hairs • Bind to receptor proteins of gustatory cell • Salt and sour receptors • Chemically gated ion channels • Stimulation produces depolarization of cell • Sweet, bitter, and umami stimuli • G proteins: (proteins that bind GTP- secondary messengers) • gustducins

  23. Figure 17-2 Olfactory and Gustatory Receptors Receptor cell Stimulus Stimulusremoved Stimulus Receptorcell Threshold Receptor depolarization Synapse Axon ofsensoryneuron Axon Actionpotentials Stimulus Synapticdelay to CNS Generator potential

  24. Figure 17-2 Olfactory and Gustatory Receptors Sweet, Bitter, and Umami Receptors Salt and Sour Receptors Receptors responding to stimuli that produce sweet, bitter, and umami sensations are linked to G proteins called gustducins (GUST-doos- inz)protein complexes that use second messengers to produce their effects. Salt receptors and sour receptors are chemically gated ion channels whose stimulation produces depolarization of the cell. Sweet,bitter, orumami Sour,salt Membranereceptor Gated ionchannel Resting plasmamembrane InactiveG protein ActiveG protein Channel opens Depolarizedmembrane ActiveG protein Active2nd messenger Inactive2nd messenger Activation of second messengers stimulates release of chemical neurotransmitters. Depolarization of membranestimulates release of chemicalneurotransmitters.

  25. Anatomy of Taste Buds and Papillae Taste bud- made of three types of epithelial cells: supporting cells, gustatory receptor cells and basal cells. About 50 gustatory cells per taste bud. Each one has a gustatory hair that projects through the taste pore. Taste buds are found in the papillae. Three types of papillae: vallate (circumvallate), fungiform and foliate.

  26. Physiology of Gustation • Five types of taste: sour, sweet, bitter, salty and umami. • Tastant dissolves in saliva → plasma membrane of gustatory hair→ receptor potential→ nerve impulse via cranial nerves VII, IX and X→ medulla→ thalamus→ primary gustatory area of the cerebral cortex.

  27. Influence of Other Sensations on Taste • Taste is 80% smell • Thermoreceptors, mechanoreceptors, nociceptors in the mouth also influence tastes • Temperature and texture enhance or detract from taste

  28. Gustatory Pathway

  29. Specialist taste buds map to certain regions of tongue Maps differ somewhat , but generally

  30. Actions of the Major Tastants 15-30

More Related