1 / 77

The Special Senses

The Special Senses. Sensory Reception. Sensory reception is a great example of the diversity of neuronal function.

jaldana
Download Presentation

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. The Special Senses

  2. Sensory Reception • Sensory reception is a great example of the diversity of neuronal function. • Said another way, if we want to know how our brains work, the senses are a good place to start. They are probably simple versions of things like personality and reasoning.

  3. Taste

  4. Chemical Senses • Chemical senses – gustation (taste) and olfaction (smell) • Their chemoreceptors respond to chemicals in aqueous solution • Taste – to substances dissolved in saliva • Smell – to substances dissolved in fluids of the nasal membranes

  5. Taste Buds • Most of the 10,000 or so taste buds are found on the tongue • Taste buds are found in papillae of the tongue mucosa

  6. Taste Sensations • There are five basic taste sensations • Sweet – sugars, saccharin, alcohol, and some amino acids • Salt – metal ions • Sour – hydrogen ions • Bitter – chemicals, toxins, medicines • Umami – monosodium glutamate (MSG)

  7. Taste Transduction • Taste receptors work just like neurons. Their axon hillock has to get to -55mV. • Na+ influx in salty tastes • H+ in sour tastes (by directly entering the cell, by opening cation channels • Sweet by closing K+ leak channels) • Bitter by releasing Ca2+ from intracellular stores. • Umami by opening glutamate channels

  8. Taste Buds

  9. Taste Transduction

  10. Gustatory Pathway • Cranial Nerves VII, IX, and X carry impulses from taste buds to the medulla • These impulses then travel to the thalamus, and from there fibers branch to the: • Gustatory cortex (taste) • Hypothalamus and limbic system (appreciation of taste) Throat

  11. Think about taste • How many taste receptors have we discussed? • How many tastes do you think you can sense? • What do you think the mechanism for sensing so many tastes with 5 receptors be? Nobody really knows.

  12. Think about taste • Black vs. green olives • I hate tomatoes but I am ok with spaghetti sauce. • I am not particular about taste, I have eaten spaghetti thousands of times. • Cold pizza, hot pizza, instant cold pizza. • Wine gargle • Meat substitutes • Why do some people like salt with their food (fat) • Sugar on cottage cheese. I ask Ella and Celi to try all their foods, but I will never try this.

  13. Influence of Other Sensations on Taste • Taste is 80% smell • We also sense heat, texture, and pain. • Temperature and texture enhance or detract from taste

  14. Sense of Smell • Olfactory receptor cells are bipolar neurons with radiating olfactory cilia

  15. Physiology of Smell • Olfactory receptors respond to several different odor-causing chemicals • You can smell about 10,000 smells • When bound to ligand these proteins initiate a G protein mechanism, which uses cAMP as a second messenger • cAMP opens Na+ and Ca2+ channels, causing depolarization of the receptor membrane that then triggers an action potential

  16. Olfactory Transduction Process Na+ Odorant binding protein Odorant chemical Active Inactive Na+ influx causes depolarization ATP Adenylate cyclase cAMP Depolarization of olfactory receptor cell membrane triggers action potentials in axon of receptor Cytoplasm

  17. It must be the combination of different receptors that allows us to smell a variety of smells. Carnation Rose Skunk

  18. It must be the combination of different receptors that allows us to smell a variety of smells.

  19. Think about smell • One thing to note is that you smell and taste different types of molecules. • Taste = small ions and small molecules • Smell = usually large organic molecules • http://leonlab.bio.uci.edu/odorants.cfm • Here again, as with taste, you have more smells than you have receptors. • How? • Why do we smell?

  20. Olfactory Pathway • Olfactory receptor cells synapse with mitral cells • Glomerular mitral cells process odor signals • Mitral cells send impulses to: • The olfactory cortex • The hypothalamus, amygdala, and limbic system

  21. Vision

  22. Eye and Associated Structures • 70% of all sensory receptors are in the eye • Accessory structures include eyebrows, eyelids, conjunctiva, lacrimal apparatus, and extrinsic eye muscles

  23. Conjunctiva • Transparent membrane that: • Lines the eyelids as the palpebral conjunctiva • Covers the whites of the eyes as the ocular conjunctiva • Lubricates and protects the eye • Conjuctivitis (pink eye)

  24. Lacrimal Apparatus • Consists of the lacrimal gland and associated ducts • Lacrimal glands secrete tears • Tears • Contain mucus, antibodies, and lysozyme

  25. Extrinsic Eye Muscles • Six straplike extrinsic eye muscles • Enable the eye to follow moving objects • Maintain the shape of the eyeball • Four rectus muscles originate from the annular ring • Two oblique muscles move the eye in the vertical plane

  26. Summary of Cranial Nerves and Muscle Actions • Names, actions, and cranial nerve innervation of the extrinsic eye muscles

  27. Structure of the Eyeball • A slightly irregular hollow sphere with anterior and posterior poles • The wall is composed of three tunics – fibrous, vascular, and sensory • The internal cavity is filled with fluids called humors

  28. Structure of the Eyeball

  29. Iris • The colored part of the eye • Pupil – central opening of the iris • Regulates the amount of light entering the eye during: • Close vision and bright light – pupils constrict • Distant vision and dim light – pupils dilate • Changes in emotional state – pupils dilate when the subject matter is appealing or requires problem-solving skills • Pinhole effect

  30. Pinhole effect

  31. Retina • A delicate two-layered membrane • Pigmented layer – the outer layer that absorbs light and prevents its scattering • Neural layer, which contains: • Photoreceptors that transduce light energy • Bipolar cells and ganglion cells • Amacrine and horizontal cells

  32. Retina

  33. The Retina: Photoreceptors • The primary component of the neural layer are the… • Rods: • Respond to dim light • Are used for peripheral vision • Cones: • Respond to bright light • Have high-acuity color vision • Are concentrated in the fovea centralis We’ll come back to rods and cones when we learn physiology

  34. Blood Supply to the Retina • The neural retina receives its blood supply from two sources • The outer third receives its blood from the choroid • The inner two-thirds is served by the central artery and vein Choroid Central

  35. Macular Degeneration • Macular Degeneration is when the visual center of the retina is damaged. • There are two types; wet and dry. • Wet = blood • Dry = metabolic breakdown products of the retina

  36. Macular Degeneration

  37. Fovea Centralis and Macula Lutea

  38. Inner Chambers and Fluids • The lens separates the internal eye into anterior and posterior segments Anterior Posterior

  39. Anterior Segment Anterior Posterior • Composed of two chambers • Anterior – between the cornea and the iris • Posterior – between the iris and the lens • Aqueous humor • A plasmalike fluid that fills the anterior segment • Supports, nourishes, and removes wastes

  40. Inner Chambers and Fluids • The posterior segment is filled with a clear gel called vitreous humor that: • Transmits light • Supports the posterior surface of the lens • Holds the neural retina firmly against the pigmented layer • Contributes to intraocular pressure (glaucoma and detached retina)

  41. Anterior Segment Anterior Posterior

  42. Lens • A biconvex, transparent, flexible, avascular structure that: • Allows precise focusing of light onto the retina • Is composed of epithelium and lens fibers • Lens epithelium – anterior cells that differentiate into lens fibers • Lens fibers – cells filled with the transparent protein crystallin • With age, the lens becomes more compact and dense and loses its elasticity

  43. Light • Our eyes respond to a small portion of this spectrum called thevisible spectrum • Different cones in the retina respond to different wavelengths of the visible spectrum

  44. Refraction and Lenses • When light passes from one transparent medium to another its speed changes and it refracts (bends) • Light passing through a convex lens (as in the eye) is bent so that the rays converge to a focal point

  45. Refraction and Lenses • When a convex lens forms an image, the image is a horizontal and vertical reflection.

More Related