Biology, 9th ed, Sylvia Mader Chapter 40 Sense Organs

Outline Chemical Senses Sense of Vision Sense of Hearing Taste Smell Sense of Vision Human Eye Focusing Photoreceptors Sense of Hearing Sense of Balance Outline

Sensory receptors responsible for taste and smell are termed chemoreceptors Chemoreception is found almost universally in animals Thought to be most primitive sense Chemical Senses

In humans, taste buds are located primarily on the tongue Taste buds open at a taste pore Have supporting cells and elongated taste cells that end in microvilli Four primary tastes Bitter, sour, salty, sweet Taste buds for each are concentrated on the tongue in particular regions Sense of Taste

b(All): © Omikron/SPL/Photo Researchers, Inc. Taste Buds in Humans Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. tonsils epiglottis sensory nerve fiber supporting cell taste pore 10 µm papillae taste bud connective tissue taste cell microvilli a. Tongue b. Papillae c. Taste buds d. One taste bud b(All): © Omikron/SPL/Photo Researchers, Inc.

Sense of Smell Sense of taste and smell Dependent on olfactory cells Work together to create a combined effect Interpreted by the cerebral cortex Dependent on olfactory cells Located within olfactory epithelium In the roof of the nasal cavity Nerve fibers from olfactory cells lead to neuron in the olfactory bulb Sense of Smell

Olfactory Cell Location and Anatomy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. olfactory bulb neuron olfactory tract frontal lobe of cerebral hemisphere olfactory bulb olfactory epithelium nasal cavity odor molecules sensory nerve fibers olfactory epithelium a. supporting cell olfactory cell olfactory cilia of olfactory cell b. odor molecules

Sense of Vision Photoreceptors are light sensory receptors Arthropods Photoreceptors generate nerve impulses which pass to the brain by way of optic nerve fibers Arthropods Eyes are compound Insects have limited color vision Sense of Vision

Compound Eye Compound eye cornea crystalline cone photoreceptor cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Compound eye cornea crystalline cone photoreceptor cells pigment cells optic nerve fibers Fly head Ommatidium © Farley Bridges

(Both): © Heather Angel/Natural Visions Nectar Guides Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. nectar guides (Both): © Heather Angel/Natural Visions

Vertebrates and certain molluscs have a camera-type eye Single lens focuses an image of the visual field on closely-packed photoreceptors Sense of Vision

The Human Eye Three Layers Sclera - Opaque outer layer Fibrous layer Choroid - Thin middle layer Iris regulates size of pupil Retina - Inner layer Contains rod cells and cone cells The Human Eye

Anatomy of the Human Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sclera choroid retina ciliary body retinal blood vessels lens iris optic nerve pupil fovea centralis cornea posterior compartment filled with vitreous humor anterior compartment filled with aqueous humor retina suspensory ligament choroid sclera

Light rays pass through the pupil and are focused on the retina Focusing starts at the cornea and continues as rays pass through the lens and humor Shape of lens is controlled by ciliary muscles Distant Object - Muscles Relaxed Near Object - Muscles Contracted Focusing the Eye

With normal aging, the lens loses its ability to accommodate for near objects Also may make lens subject to cataracts Nearsighted Elongated eyeball - Wear concave lenses Farsighted Shortened eyeball - Wear convex lenses Focusing the Eye

Functions of the Parts of the Eye

Focusing of the Human Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ciliary muscle relaxed lens flattened light rays suspensory ligament taut a. Focusing on distant object ciliary body ciliary muscle contracted lens rounded b. Focusing on near object suspensory ligament relaxed

Common Abnormalities of the Eye with Possible Corrective Lenses Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. normal eyeball Long eyeball; rays focus in front of retina when viewing distant objects. Concave lens allows subject to see distant objects. a. Nearsightedness normal eyeball Short eyeball; rays focus behind retina when viewing close objects. Convex lens allows subject to see close objects. b. Farsightedness Uneven cornea; rays do not focus evenly. Uneven lens allows subject to see objects clearly. c. Astigmatism

Photoreceptors of the Eye Both rods and cones have an outer segment joined to an inner segment Pigment molecules are embedded in membrane of disks in the outer segment Rhodopsin Rods permit vision in low light Peripheral vision and motion Cones permit vision in bright light Fine detail and color Photoreceptors of the Eye

Photoreceptors in the Eye Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. ion channels close membrane of disk cascade of reactions rod cell light rays outer segment cone cell ion channels in plasma membrane retinal inner segment cell body opsin nucleus synaptic vesicles membrane of disk Rhodopsin molecule (opsin + retinal) synaptic endings 20 µm © Lennart Nilsson, from The Incredible Machine

Integration of Visual Signals in the Retina Retina has three layers of neurons Layer closest to choroid contains rod and cone cells Middle layer contains bipolar cells Innermost layer contains ganglion cells Synaptic integration and processing Begin in the retina Then impulses are sent to the brain

Structure and Function of the Retina Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. sclera choroid rod cell and cone cell layer choroid bipolar cell layer retina optic nerve ganglion cell layer axons of ganglion cells b. Micrograph of retina blind spot to optic nerve light rays a. Location of retina b: © Biophoto Associates/Photo Researchers, Inc.

Sense of Hearing and Balance Anatomy of the Ear Outer ear - Pinna and auditory canal Middle ear begins at tympanic membrane and ends at oval and round windows Ossicles found between tympanic membrane and the windows Auditory tube (eustachian tube) extends from middle ear to nasopharynx Inner ear has three areas Semicircular canals Vestibule Cochlea Sense of Hearing and Balance

Anatomy of the Human Ear Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Outer ear Middle ear Inner ear stapes semicircular canals incus malleus vestibule vestibular nerve pinna cochlear nerve tympanic membrane cochlea auditory canal round window auditory tube earlobe

Process of Hearing Sound waves enter the auditory canal Strike tympanic membrane, causing it to vibrate Malleus takes pressure from inner surface of tympanic membrane Passes it to the stapes, multiplying the pressure along the way Stapes strikes membrane of oval window, passing pressure to fluid within cochlea Process of Hearing

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Spiral Organ, hair cells of cochlear canal, synapse with nerve fibers of cochlear nerve Mechanoreceptors for sound are the hair cells of cochlear canal Sound causes basilar membrane to vibrate The stereocilia of the hair cells bend Stimulates nerve cells leading to the auditory center Process of Hearing

Mechanoreceptors for Hearing Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. semicircular canals cochlea stapes oval window round window vestibular canal cochlear canal tympanic canal cochlear nerve Cochlea cross section tectorial membrane stereocilia basilar membrane hair cell tympanic canal cochlear nerve Organ of Corti Stereocilia 2 µm

Mechanoreceptors of rotational equilibrium are in semicircular canals Detect rotational and/or angular movements of the head Maintain rotational equilibrium Cupula Mechanoreceptors of gravitational equilibrium are in the utricle and saccule Detect straight-line movements of the head in any direction Maintain gravitational equilibrium Otolithic Membrane Sense of Balance

Mechanoreceptors for Equilibrium Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. receptor in ampulla endolymph semicircular canals vestibular nerve ampullae cochlea utricle saccule endolymph cupula stereocilia otoliths hair cell otolithic membrane hair cell supporting cell supporting cell vestibular nerve vestibular nerve flow of endolymph flow of otolithic membrane kinocilium stereocilia a. Rotational equilibrium: receptors in ampullae of semicircular canal b.Gravitational equilibrium: receptors in utricle and saccule of vestibule

Sensory Receptors in Other Animals Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. skin water scale external opening hair cells cilia hair cell cupula lateral line nerve lateral line canal a. dendrites of sensory neurons statolith b.

Review Chemical Senses Sense of Vision Sense of Hearing Taste Smell Sense of Vision Human Eye Focusing Photoreceptors Sense of Hearing Sense of Balance Review

Biology, 9th ed, Sylvia Mader Chapter 40 Sense Organs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (Both): Courtesy of The Virginia Bloodhound Search and Rescue Association