Biology Sylvia S. Mader Michael Windelspecht Chapter 38 Sense Organs Lecture Outline See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. 1 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1

Biology, 9th ed, Sylvia Mader Chapter 40 Outline Sense Organs 38.1 Sensory Receptors 38.2 Chemical Senses 38.3 Sense of Vision 38.4 Senses of Hearing and Balance 38.5 Somatic Senses

Biology, 9th ed, Sylvia Mader Chapter 40 38.1 Sensory Receptors Sense Organs Sensory receptors Specialized cells capable of detecting changes in internal or external conditions, and of communicating that information to the central nervous system Capable of facilitating sensory transduction Conversion of an event (stimulus) occurring in the environment into a nerve impulse There is no difference between the nerve impulses carried by different types of sensory nerves Perceptions – Any sensory stimuli of which humans, and perhaps other animals, become conscious

Biology, 9th ed, Sylvia Mader Chapter 40 Sensory Receptors Sense Organs Sensory receptors (continued) Chemoreceptors Sensory receptors responsible for taste and smell Photoreceptors Sensory receptors responsible for responding to light Mechanoreceptors Sensory receptors stimulated by mechanical forces, such as pressure Thermoreceptors Sensory receptors stimulated by changes in temperature

Biology, 9th ed, Sylvia Mader Chapter 40 38.2 Chemical Senses Sense Organs Chemoreception is found almost universally in all animals Thought to be the most primitive sense Allow organisms to locate food, find a mate, detect dangerous environmental chemicals, etc.

Biology, 9th ed, Sylvia Mader Chapter 40 Chemical Senses Sense Organs Sense of Taste in Humans In humans, taste buds are located primarily on the tongue Taste buds open at a taste pore Taste buds have supporting cells and elongated taste cells that end in microvilli Five primary tastes Sweet, sour, salty, bitter, and umami (savory) Taste buds for each are located throughout the tongue, although certain regions may be more sensitive to particular tastes

Biology, 9th ed, Sylvia Mader Chapter 40 Taste Buds in Humans Sense Organs 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.

Biology, 9th ed, Sylvia Mader Chapter 40 Chemical Senses Sense Organs Sense of Smell in Humans Dependent on olfactory cells Located within olfactory epithelium in the roof of the nasal cavity Nerve fibers from olfactory cells lead to the same neuron in the olfactory bulb Sense of taste and smell Work together to create a combined effect Interpreted by the cerebral cortex

Olfactory Cell Location and Anatomy Biology, 9th ed, Sylvia Mader Chapter 40 Olfactory Cell Location and Anatomy Sense Organs 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

Biology, 9th ed, Sylvia Mader Chapter 40 38.3 Sense of Vision Sense Organs How Animals Detect Light Photoreceptors are sensory receptors that are sensitive to light Arthropods Contain compound eyes composed of many independent ommatidia Photoreceptors generate nerve impulses which pass to the brain by way of optic nerve fibers Insects have limited color vision

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

Biology, 9th ed, Sylvia Mader Chapter 40 Nectar Guides Sense Organs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. nectar guides (Both): © Heather Angel/Natural Visions

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs The Human Eye Three Layers Sclera - Opaque outer layer Fibrous layer covering most of the eye In front of the eye, the sclera becomes the transparent cornea Conjunctiva – covers surface of the sclera and keeps the eyes moist

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs The Human Eye Three Layers Choroid - Thin middle layer Contains blood vessels In front of the eye, the choroid thickens to form the ciliary body and the iris The iris regulates the size of the pupil The lens helps form images Retina - Inner layer Contains photoreceptors called rod cells and cone cells Contains the fovea centralis Region of densely packed cone cells where light is focused

Anatomy of the Human Eye Biology, 9th ed, Sylvia Mader Chapter 40 Anatomy of the Human Eye Sense Organs 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

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs Focusing of the Eye 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, which provides visual accommodation Shape of lens is controlled by the ciliary muscle Distant object – ciliary muscle is relaxed Near object – ciliary muscle is contracted

Focusing of the Human Eye Biology, 9th ed, Sylvia Mader Chapter 40 Focusing of the Human Eye Sense Organs 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

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs Photoreceptors of the Eye Both rods and cones have an outer segment joined to an inner segment by a stalk Pigment molecules are embedded in membrane of the disks in the outer segment Rhodopsin - pigment composed of opsin and retinal, a derivative of vitamin A Rods permit vision in low light Peripheral vision and motion Cones permit vision in bright light Fine detail and color

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs Photoreceptors of the Eye (continued) Rods permit vision in low light Peripheral vision and motion Cones permit vision in bright light Fine detail and color Three different types of cones, each containing a different type of photopigment B (blue) G (green) R (red)

Photoreceptors in the Eye Biology, 9th ed, Sylvia Mader Chapter 40 Photoreceptors in the Eye Sense Organs 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

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs Integration of Visual Signals in the Retina The retina has three layers of neuronsa Layer closest to choroid contains rod and cone cells Middle layer contains bipolar cells Innermost layer contains ganglion cells Rod and cone cells synapse with the bipolar cells, which in turn synapse with ganglion cells responsible for initiating nerve impulses

Biology, 9th ed, Sylvia Mader Chapter 40 Sense of Vision Sense Organs Integration of Visual Signals in the Retina Human retina has approximately 150 million rod cells 6 million cone cells 1 million ganglion cells Since more rod cells synapse on a ganglion cell than cone cells, cone cells provide sharper more detailed images of an object than rod cells

Common Abnormalities of the Eye with Possible Corrective Lenses Biology, 9th ed, Sylvia Mader Chapter 40 Common Abnormalities of the Eye with Possible Corrective Lenses Sense Organs 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

38.4 Senses of Hearing and Balance Biology, 9th ed, Sylvia Mader Chapter 40 38.4 Senses of Hearing and Balance Sense Organs How Animals Detect Sound Waves Insects Tympanum – a membrane stimulated to vibrate by sound waves that directly activates nerve impulses in attached receptor cells Fish Lateral line system – detects water currents and pressure waves from nearby objects, helping the organism guide their movement and locate other fish

Senses of Hearing and Balance Biology, 9th ed, Sylvia Mader Chapter 40 Senses of Hearing and Balance Sense Organs The Human Ear Outer ear - Pinna and auditory canal Middle ear begins at tympanic membrane and ends at oval and round windows The ossicles (three small bones) are found between the tympanic membrane and the windows Malleus (hammer), incus (anvil), and stapes (stirrup) Auditory tube (eustachian tube) extends from the middle ear to the nasopharynx Inner ear has three areas Semicircular canals - associated with equilibrium Vestibule - associated with equilibrium Cochlea – associated with hearing

Anatomy of the Human Ear Biology, 9th ed, Sylvia Mader Chapter 40 Anatomy of the Human Ear Sense Organs 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

Senses of Hearing and Balance Biology, 9th ed, Sylvia Mader Chapter 40 Senses of Hearing and Balance Sense Organs The Auditory Canal and Middle Ear Sound waves enter the auditory canal Sound waves strike the tympanic membrane, causing it to vibrate Malleus takes pressure from inner surface of tympanic membrane Passes it via the incus to the stapes, multiplying the pressure along the way Stapes strikes the membrane of oval window, passing pressure to fluid within the cochlea

Senses of Hearing and Balance Biology, 9th ed, Sylvia Mader Chapter 40 Senses of Hearing and Balance Sense Organs Inner Ear Spiral organ (organ of Corti) contains hair cells that synapse with nerve fibers of the cochlear nerve Mechanoreceptors for sound are the hair cells of the cochlear canal Sound causes the basilar membrane to vibrate The stereocilia of the hair cells bend Nerve impulses begin in the cochlear nerve and travel to the brain stem, then to the auditory center of the cerebral cortex

Mechanoreceptors for Equilibrium Biology, 9th ed, Sylvia Mader Chapter 40 Mechanoreceptors for Equilibrium Sense Organs 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

Biology, 9th ed, Sylvia Mader Chapter 40 38.5 Somatic Senses Sense Organs Somatic senses Senses whose receptors are associated with the skin, muscles, joints, and viscera Proprioceptors Mechanoreceptors involved in reflex actions that maintain muscle tone Muscle spindles, Golgi tendon organs Cutaneous receptors Make the skin sensitive to touch, pressure, pain, and temperature Meissner corpuscles Krause end builds Merkel disks Pacinian corpuscles Ruffini endings

Muscle Spindles and Golgi Tendon Organs Biology, 9th ed, Sylvia Mader Chapter 40 Muscle Spindles and Golgi Tendon Organs Sense Organs Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 1 muscle spindle 2 2 muscle fiber 1 quadriceps muscle bundle of muscle fibers 3 sensory neuron to spinal cord Golgi tendon organ tendon

Biology, 9th ed, Sylvia Mader Chapter 40 Somatic Senses Sense Organs Somatic senses (continued) Pain Receptors Also termed free nerve endings or nociceptors Damaged cells release chemicals causing nociceptors to generate nerve impulses that are interpreted by the brain as pain.