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PowerPoint® Lecture Slides prepared by Betsy C. Brantley Valencia College CHAPTER 9 The Senses © 2013 Pearson Education, Inc. Chapter 9 Learning Outcomes • Section 1: The General Senses • 9.1 • List the types of sensory receptors found in the skin, and specify the functions of each. • 9.2 • Explain the roles of baroreceptors and chemoreceptors in homeostasis. • Section 2: The Special Senses • 9.3 • Describe the sensory organs of smell and trace the olfactory pathways to their destination in the cerebrum, and describe the sensory organs and cranial nerves involved with gustation. © 2013 Pearson Education, Inc. Chapter 9 Learning Outcomes • 9.4 • Describe the structures of the external, middle, and internal ear, and explain how they function. • 9.5 • Describe the structures and functions of the bony labyrinth and membranous labyrinth. • 9.6 • Describe the functions of hair cells in the semicircular ducts, utricle, and saccule, and explain their role in responding to gravity and linear acceleration. • 9.7 • Describe the cochlear duct and spiral organ, and describe the structure and functions of the spiral organ. © 2013 Pearson Education, Inc. Chapter 9 Learning Outcomes • 9.8 • Describe the anatomical and physiological basis for the sensations of pitch and volume related to hearing. • 9.9 • Identify the accessory structures of the eye and explain their functions, and define conjunctivitis. • 9.10 • Describe the layers of the eye wall and the anterior and posterior eye cavities, and state the names and functions of the extrinsic eye muscles. • 9.11 • Explain how light is directed to the fovea of the retina. • 9.12 • Describe the process by which images are focused on the retina. © 2013 Pearson Education, Inc. Chapter 9 Learning Outcomes • 9.13 • Explain the structure and function of the retina's layers, describe the distribution of rods and cones, and discuss the role of photoreceptors in visual acuity. • 9.14 • Explain photoreception, describe the structure of photoreceptors, explain how visual pigments are activated, and describe how we are able to distinguish colors. • 9.15 • Explain how the visual pathways distribute information to their destinations in the brain. • 9.16 • CLINICAL MODULE Describe various accommodation problems associated with the cornea, lens, or shape of the eye. © 2013 Pearson Education, Inc. Chapter 9 Learning Outcomes • 9.17 • CLINICAL MODULE Describe age-related disorders of olfaction, gustation, vision, equilibrium, and hearing. © 2013 Pearson Education, Inc. General Senses (Section 1) • Sensitivity to temperature, pain, touch, pressure, vibration, and proprioception • Picked up by sensory receptors • Specialized cells or cell processes • Simplest – dendrites of sensory neurons (free nerve endings) • Stimulated by many different stimuli (chemical, pressure, temperature) • Little receptor specificity © 2013 Pearson Education, Inc. Sensory receptors Free nerve endings © 2013 Pearson Education, Inc. Figure 9 Section 1 1 1 General Sensory Receptors – Classification (Section 1) • Classified according to nature of primary stimulus • Nociceptors • Pain receptors • Large receptive fields and broad sensitivity • Type A and type C fibers (axons) carry pain sensation • Thermoreceptors (temperature receptors) • Located in dermis, skeletal muscles, liver, hypothalamus • Cold receptors 3–4 times more numerous than warm receptors © 2013 Pearson Education, Inc. General Sensory Receptors – Classification (Section 1) • Mechanoreceptors • Sensitive to plasma membrane change (stretching, compression, twisting, or other mechanical distortion) • Proprioceptors – monitor positions of joints and muscles • Baroreceptors – detect pressure changes in walls of blood vessels and portions of system tracts • Tactile receptors – provide touch, pressure, vibration sensation • Chemoreceptors • Respond to substances dissolved in body fluids © 2013 Pearson Education, Inc. Functional classification of general sensory receptors A Functional Classification of General Sensory Receptors Nociceptors Thermoreceptors Mechanoreceptors Proprioceptors © 2013 Pearson Education, Inc. Baroreceptors Chemoreceptors Tactile receptors Figure 9 Section 1 1 2 General Sensory Receptors in Skin (9.1) • Greatest diversity of general sensory receptors • Tactile sensitivity can be altered by infection, disease, or damage to sensory neurons or pathways • Tactile responses used for diagnosis • Sensory loss along dermatome boundary can help identify affected spinal nerve or nerves © 2013 Pearson Education, Inc. Tactile Corpuscles General sensory receptors in the skin Hair Free Nerve Endings Capsule Dendrites Tactile corpuscle Dermis Afferent fiber Lamellated Corpuscles Layers of collagen fibers separated by fluid Free nerve endings Sensory nerve Dendrite Dermis Root Hair Plexus Hair shaft Root hair plexus Ruffini Corpuscles Sensory nerves Capsule Dendrites Afferent fiber Tactile Discs Specialized epithelial cells Tactile disc © 2013 Pearson Education, Inc. Figure 9.1 Skin Receptors – Free Nerve Endings (9.1) • Branching tips of sensory neurons • Not protected; nonspecific • Respond to tactile, pain, and temperature stimuli • Most common receptors in skin © 2013 Pearson Education, Inc. Free nerve endings Hair Free Nerve Endings Free nerve endings Sensory nerve Sensory nerves © 2013 Pearson Education, Inc. Figure 9.1 Skin Receptors – Root Hair Plexus (9.1) • Monitor distortions and movements across body surface • Hair displaced, movement of follicle distorts sensory dendrites • Produces action potentials (messages) © 2013 Pearson Education, Inc. Root hair plexus Hair Root Hair Plexus Hair shaft Root hair plexus © 2013 Pearson Education, Inc. Sensory nerves Figure 9.1 Skin Receptors – Tactile Discs (9.1) • Fine touch and pressure receptors • Dendrites of afferent fiber in contact with specialized epithelial cells in epidermis © 2013 Pearson Education, Inc. Tactile discs Hair Sensory nerves Tactile Discs Specialized epithelial cells Tactile disc © 2013 Pearson Education, Inc. Figure 9.1 Skin Receptors - Tactile Corpuscles (9.1) • Also called Meissner corpuscles • Provide sensations of fine touch and pressure and lowfrequency vibration • Adapt to stimulation within a second • Most abundant in eyelids, lips, fingertips, nipples, external genitalia • Coiled and interwoven dendrites surrounded by modified Schwann cell • Fibrous capsule around entire complex anchors within dermis © 2013 Pearson Education, Inc. Tactile corpuscles Hair Tactile Corpuscles Capsule Dendrites Tactile corpuscle Dermis Afferent fiber Sensory nerves © 2013 Pearson Education, Inc. Figure 9.1 Skin Receptors - Lamellated Corpuscles (9.1) • Also called pacinian corpuscles • Sensitive to deep pressure • Most sensitive to pulsing or high-frequency vibration • Single dendrite wrapped in concentric layers of collagen fibers and specialized fibroblasts • Located in dermis, mammary glands, external genitalia • Also found in mesenteries, pancreas, walls of urethra and urinary bladder © 2013 Pearson Education, Inc. Lamellated corpuscles Hair Lamellated Corpuscles Layers of collagen fibers separated by fluid Dendrite Dermis Sensory nerves © 2013 Pearson Education, Inc. Figure 9.1 Skin Receptors – Ruffini Corpuscles (9.1) • Sensitive to pressure and distortion of reticular (deep) dermis • Little, if any, adaptation (reduction in sensitivity to constant stimulus) • Network of dendrites intertwined with collagen fibers • Surrounded by capsule • Distortion of surrounding dermis tugs/twists capsule fibers • Dendrites in turn stretched or compressed • Sends message along afferent fiber © 2013 Pearson Education, Inc. Ruffini corpuscles Hair Sensory nerves Ruffini Corpuscles Capsule Dendrites Afferent fiber © 2013 Pearson Education, Inc. Figure 9.1 Module 9.1 Review a. Identify the six types of tactile receptors located in the skin, and describe their sensitivities. b. Which types of tactile receptors are located only in the dermis? c. Which is likely to be more sensitive to continuous deep pressure: a lamellated corpuscle or a Ruffini corpuscle? © 2013 Pearson Education, Inc. Baroreceptors (9.2) • Stretch receptors that monitor changes in pressure • Free nerve endings branching within elastic tissues • Pressure changes cause stretch or recoil of elastic tissues • Change in tissue distorts receptor's branches • Structural distortion alters rate of action-potential generation © 2013 Pearson Education, Inc. Baroreceptor Locations (9.2) • Carotid sinus and aortic sinus – monitor blood pressure • Information sent plays role in regulating cardiac function and adjusting blood flow • Lungs – monitor degree of lung expansion • Information sent to respiratory centers to control breathing rate/rhythm • Colon – monitor fecal matter volume; trigger defecation • Digestive tract – monitor volume; trigger reflex movement • Urinary bladder wall – monitor volume; trigger urination © 2013 Pearson Education, Inc. Locations of baroreceptors in the body Baroreceptors of Carotid Sinus and Aortic Sinus Baroreceptors of Digestive Tract Baroreceptors of Bladder Wall © 2013 Pearson Education, Inc. Baroreceptors of Lungs Baroreceptors of Colon Figure 9.2 1 1 Chemoreceptors (9.2) • Detect small changes in concentrations of specific chemicals or compounds • Play role in reflexive control of respiration and cardiovascular function 1. Within medulla oblongata • Monitor pH and carbon dioxide levels in cerebrospinal fluid 2. In carotid bodies • Monitor pH, carbon dioxide, and oxygen levels in blood 3. In aortic bodies • Monitor pH, carbon dioxide, and oxygen levels in blood © 2013 Pearson Education, Inc. Chemoreceptors in Respiratory Centers in the Medulla Oblongata Locations of chemoreceptors Chemoreceptors of Carotid Bodies Chemoreceptors of Aortic Bodies Trigger reflexive adjustments in depth and rate of respiration Cranial nerve IX Cranial nerve X Trigger reflexive adjustments in respiratory and cardiovascular activity Branch of cranial nerve IX Internal carotid External carotid Carotid body Carotid sinus Common carotid © 2013 Pearson Education, Inc. Figure 9.2 1 2 – 3 Module 9.2 Review a. Define baroreceptor and chemoreceptor. b. Which type of receptor is sensitive to changes in blood pH? c. Where are baroreceptors located within the body? © 2013 Pearson Education, Inc. Special Senses (Section 2) • Receptors more structurally complex than receptors for general senses • Located in sense organs with protective surrounding tissue • Information distributed to specific areas in cerebral cortex • Five special senses 1. Olfaction (smell) 2. Vision (sight) 3. Gustation (taste) 4. Equilibrium (balance) 5. Hearing © 2013 Pearson Education, Inc. Olfaction and Taste Receptors (Section 2) • Olfaction sensory receptors • Modified neurons • Gustation sensory receptors • Specialized receptor cells communicating with sensory neurons • Both olfaction and gustation • Sensory receptors in epithelia • Exposed to environment • Information routed directly to CNS for processing © 2013 Pearson Education, Inc. Olfactory and gustatory sensory receptors Taste receptor Olfactory receptor © 2013 Pearson Education, Inc. Figure 9 Section 2 1 1 Hearing and Equilibrium Receptors (Section 2) • Sensory receptors protected from external environment in internal ear • Sensory information integrated and organized before forwarded to CNS • Receptors called hair cells • Free surfaces are covered with processes similar to microvilli • Mechanoreceptors are surrounded by supporting cells and monitored by dendrites of sensory neurons • External force distorts hair cell plasma membrane, altering rate of chemical transmitter release to sensory neuron © 2013 Pearson Education, Inc. Receptors for hearing and equilibrium Internal ear Displacement in this direction stimulates hair cell Displacement in this direction inhibits hair cell Hair cell Dendrite of sensory neuron Supporting cell © 2013 Pearson Education, Inc. Figure 9 Section 2 1 2 – 3 Sense of Smell (9.3) • Olfaction (sense of smell) • Provided by paired olfactory organs • Located in nasal cavity • Cover inferior surface of cribriform plate, superior portion perpendicular plate, superior nasal conchae • Odorants • Dissolved chemicals that stimulate olfactory receptors • Small, organic molecules • As few as four molecules can activate olfactory receptor © 2013 Pearson Education, Inc. Olfactory Pathway (9.3) 1. Sensory neurons stimulated by chemicals in the air 2. Axons leaving olfactory epithelium collect into 20 or more bundles; penetrate cribriform plate of ethmoid bone 3. These axons communicate with next neurons in olfactory bulb (superior to cribriform plate) 4. Axons leaving olfactory bulb form olfactory tract 5. Information distributed to olfactory cortex, limbic system, and hypothalamus 6. Strong emotional response and memories associated with smell © 2013 Pearson Education, Inc. Olfactory pathway to the cerebrum Olfactory Pathway to the Cerebrum Olfactory Olfactory nerve Olfactory epithelium fibers (NI) bulb Olfactory tract Central nervous system Stem cell Supporting cell Olfactory receptor Cribriform plate of ethmoid Olfactory epithelium of the right olfactory organ Superior nasal concha Odorants © 2013 Pearson Education, Inc. Figure 9.3 2 1 Sense of Taste (9.3) • Gustation • Provides information about foods and liquids we consume • Taste receptors located on superior surface of tongue, adjacent portions of pharynx and larynx • Lingual papillae – epithelial projections on tongue 1. Circumvallate papillae – large, shaped like pencil eraser tip, surrounded by deep epithelial folds; each papilla contains up to 100 taste buds 2. Fungiform papillae – also contain taste buds 3. Filiform papillae © 2013 Pearson Education, Inc. Cranial Nerves and Taste (9.3) • Taste information carried on cranial nerves • Vagus nerve (X) – from taste buds on surface of epiglottis • Glossopharyngeal nerve (IX) – from posterior 1/3 of tongue • Facial nerve (VII) – from anterior 2/3 of tongue • Taste sensations • Four primary – sweet, salty, sour, bitter • Umami – detected by receptors sensitive to amino acids, small peptides, nucleotides; taste of beef broth or Parmesan cheese • Water receptors – concentrated in pharynx, provide information to hypothalamus for water balance regulation © 2013 Pearson Education, Inc. Taste receptors Circumvallate Papillae Cranial Nerves Carrying Taste Information Circumvallate papillae Epiglottis Water receptors (pharynx) Vagus nerve Glossopharyngeal nerve Taste buds Umami Facial nerve Sour Bitter Salty Sweet Supporting cell Taste cell Stem cell Diagrammatic view of a taste bud Filiform Papillae © 2013 Pearson Education, Inc. Fungiform Papillae Figure 9.3 2 2 Module 9.3 Review a. Describe olfaction and its receptors. b. Describe gustation and its receptors. c. Trace the olfactory pathway, beginning at the olfactory epithelium. © 2013 Pearson Education, Inc. External Ear (9.4) • Visible portion of ear • Collects and directs sound waves toward middle ear • Elastic cartilage gives auricle flexibility • External acoustic meatus • Passageway within temporal bone • Lined with small hairs and ceruminous glands that secrete cerumen (earwax) • Cerumen slows microorganism growth, reducing chances for external ear infection • Cerumen and hairs prevent foreign objects and insects from reaching internal structures © 2013 Pearson Education, Inc. Middle Ear (9.4) • Also called tympanic cavity • Air-filled chamber • Separated from external acoustic meatus by tympanic membrane or eardrum • Thin, semitransparent sheet • Connected to pharynx by auditory tube or Eustachian tube • Permits pressure equalization on either side of tympanic membrane • Also allows microorganisms to travel from nasopharynx to middle ear, potentially causing infection called otitis media • Contains auditory ossicles © 2013 Pearson Education, Inc. Internal Ear (9.4) • Contains sensory organs for hearing and equilibrium • Receives amplified sound waves from middle ear • Superficial contours formed by layer of dense bone called bony labyrinth © 2013 Pearson Education, Inc. Structures in the ear External Ear Middle Ear Auricle Auditory ossicles Auricle Internal Ear Semicircular canals Temporal bone Facial nerve ( VII) Vestibulocochlear nerve ( VIII) Bony labyrinth Tympanic cavity Tympanic membrane External acoustic meatus © 2013 Pearson Education, Inc. To nasopharynx Auditory tube Figure 9.4 1 1 Auditory Ossicles (9.4) • Three auditory ossicles conduct and amplify vibrations to internal ear 1. Malleus – attaches to tympanic membrane 2. Incus – attaches malleus to stapes 3. Stapes – attaches incus to oval window, an opening in bone surrounding internal ear • Located in middle ear • Articulations between are smallest synovial joints in body • Small skeletal muscles that insert on malleus and stapes contract to reduce amount of vibration to protect tympanic membrane © 2013 Pearson Education, Inc. Auditory ossicles location Auditory Ossicles Malleus Incus Stapes Temporal bone (petrous part) Connections to mastoid air cells Oval window Stabilizing ligament Branch of facial nerve VII (cut) Muscles of the Middle Ear External acoustic meatus Tympanic cavity (middle ear) Auditory tube Round window Tympanic membrane © 2013 Pearson Education, Inc. Figure 9.4 2 2 Module 9.4 Review a. Name the three tiny bones located in the middle ear. b. What is the function of the auditory tube? c. Why are external ear infections relatively uncommon? © 2013 Pearson Education, Inc. Bony Labyrinth (9.5) • Internal ear divided into bony and membranous labyrinths • Bony labyrinth • Shell of dense bone • Surrounds and protects membranous labyrinth • Composed of three parts 1. Semicircular canals 2. Vestibule 3. Cochlea • Perilymph – flows between bony and membranous labyrinths © 2013 Pearson Education, Inc. Internal ear structures Bony Labyrinth Semicircular canals Vestibule Cochlea Membranous Labyrinth Receptor areas Semicircular ducts Utricle and saccule Cochlear duct Bony labyrinth Perilymph Membranous labyrinth Endolymph © 2013 Pearson Education, Inc. KEY Membranous labyrinth Bony labyrinth Figure 9.5 1 – 2 Membranous Labyrinth (9.5) • Collection of fluid-filled tubes and chambers • Houses receptors for equilibrium and hearing • Filled with endolymph; surrounded by perilymph • Composed of: 1. Vestibular complex • Semicircular ducts – within semicircular canals, monitor rotational movements in three different planes • Vestibule containing utricle and saccule – contain receptors sensitive to gravity and linear acceleration 2. Cochlear duct – contained within cochlea, forms spiral-like snail shell, involved in hearing © 2013 Pearson Education, Inc. Concept map for membranous labyrinth with illustration Membranous Labyrinth Vestibular Complex (equilibrium) Semicircular Ducts © 2013 Pearson Education, Inc. Cochlear Duct (hearing) Utricle and Saccule Figure 9.5 3 3 Module 9.5 Review a. Identify the components of the bony labyrinth. b. What separates the membranous labyrinth from the bony labyrinth? c. Explain the regional differences in the sensitivities of the various receptor complexes in the membranous labyrinth. © 2013 Pearson Education, Inc. Semicircular Ducts (9.6) • Contains hair cells that respond to rotation • Three ducts 1. Anterior 2. Posterior 3. Lateral • Each duct has an ampulla (expanded region) • Receptors in specific region of ampulla called crista ampullaris • Processes of hair cells embedded in cupula (flexible, elastic, gelatinous structure) © 2013 Pearson Education, Inc. Crista ampullaris location Semicircular Ducts Anterior Posterior Lateral Ampulla Utricle Cupula Ampulla filled with endolymph Hair cells Crista ampullaris Supporting cells Sensory nerve © 2013 Pearson Education, Inc. Figure 9.6 1 1 Endolymph Movement (9.6) • Cupula floats in endolymph above crista ampullaris • Rotation of head causes: • Movement of endolymph • Movement of cupula to side • Distortion of receptor processes • Movement in one direction stimulates hair cells • Movement in opposite direction inhibits hair cells • Stopping rotational movement stops endolymph movement and cupula returns to normal position © 2013 Pearson Education, Inc. Change in endolymph movement with head rotation Direction of duct rotation Direction of relative endolymph movement Direction of duct rotation Semicircular duct Ampulla © 2013 Pearson Education, Inc. At rest Figure 9.6 2 2 Rotational Planes (9.6) • Three semicircular ducts lie in three rotational planes • Each responds to one rotational movement • Horizontal rotation (shaking head "no") stimulates receptors in lateral semicircular duct • Vertical rotation (nodding "yes") stimulates receptors in anterior semicircular duct • Tilting head side to side stimulates receptors in posterior semicircular duct © 2013 Pearson Education, Inc. Rotational planes of semicircular canals Anterior semicircular duct for "yes" Posterior semicircular duct for tilting head to the side © 2013 Pearson Education, Inc. Figure 9.6 3 3 Utricle and Saccule Equilibrium Sensation (9.6) • Sensory structure in utricle and saccule is a macula • Hair cell processes embedded in gelatinous otolithic membrane • Surface of membrane packed with calcium carbonate crystals called otoliths (ear stones) • Utricle sensitive to changes in horizontal movement • Saccule sensitive to changes in vertical movement © 2013 Pearson Education, Inc. Structures in the macula Utricle Endolymphatic sac Endolymphatic duct Saccule Gelatinous layer forming otolithic membrane Otoliths Nerve fibers Hair cells © 2013 Pearson Education, Inc. Figure 9.6 4 – 5 Changing Head Position (9.6) • Head upright • Otoliths on top of otolithic membrane • Weight presses on macular surface, pushing hair cell processes down • Head tilted • Gravity pulls on otoliths, shifting to side • Otolith movement distorts hair cell processes stimulating receptors • Perception of linear acceleration – otoliths lag behind, giving effect of tilting head © 2013 Pearson Education, Inc. Otolithic membrane movement with change in position Gravity Gravity Receptor output increases © 2013 Pearson Education, Inc. Otolith moves “downhill,” distorting hair cell processes Figure 9.6 6 6 Module 9.6 Review a. Define otoliths. b. Cite the function of receptors in the saccule and utricle. c. Damage to the cupula of the lateral semicircular duct would interfere with what perception? © 2013 Pearson Education, Inc. Cochlear Duct (9.7) • Long, coiled tube suspended between two chambers filled with perilymph 1. Scala vestibuli 2. Scala tympani • Bony labyrinth encases all three ducts except at oval window (base of scala vestibuli) and round window (base of scala tympani) • Hair cells of cochlear duct in structure called spiral organ, or organ of Corti, which runs length of cochlea © 2013 Pearson Education, Inc. Cochlear structures Scala vestibuli Round window Stapes at oval window Cochlear duct Scala tympani From oval window Cochlear Vestibular branch branch Vestibulocochlear nerve (VIII) Vestibular membrane Basilar membrane Scala vestibuli Spiral organ Cochlear duct Scala tympani Temporal bone (petrous part) To round window © 2013 Pearson Education, Inc. Cochlear nerve Vestibulocochlear nerve (VIII) Semicircular canals KEY From oval window to tip of spiral From tip of spiral to round window Figure 9.7 11 – 22 Sectional view of cochlear spiral Sectional view of the cochler spiral © 2013 Pearson Education, Inc. LM x 200 Figure 9.7 22 Spiral Organ (9.7) • Cochlear duct separated: • From scala vestibuli by vestibular membrane • From scala tympani by basilar membrane • Spiral organ located in cochlear duct on basilar membrane • Processes of spiral organ hair cells in contact with overlying tectorial membrane • Sensory neurons monitor hair cell movement • Axons of these sensory neurons form cochlear branch of vestibulocochlear nerve (VIII) © 2013 Pearson Education, Inc. Details of cochlear structures Bony cochlear wall Scala vestibuli Vestibular membrane Cochlear duct Basilar membrane Cell bodies of sensory neurons Scala tympani Cochlear branch of vestibulocochlearnerve Spiral organ Tectorial membrane Outer hair cell Basilar membrane © 2013 Pearson Education, Inc. Inner hair cell Nerve fibers Figure 9.7 33 – 44 Pressure Wave (9.7) • Sound waves at tympanic membrane trigger pressure changes in perilymph in cochlea • Basilar membrane bounces up and down in response to pressure changes • Hair cell processes pushed against tectorial membrane and distorted • More movement means more hair cells and more rows of hair cells stimulated © 2013 Pearson Education, Inc. Changes in hair cell movement with pressure wave Distortion of hair cell processes At rest © 2013 Pearson Education, Inc. Pressure wave in perilymph Figure 9.7 44 Module 9.7 Review a. Where is the spiral organ located? b. Name the fluids found within the scala vestibuli, scala tympani, and cochlear duct. c. Identify the structures visible in the light microscope of the cochlear spiral in sectional view. © 2013 Pearson Education, Inc. Hearing (9.8) • Perception of sound • Sound • Waves of pressure conducted through a medium • In each wave, area of compressed molecules and area of molecules farther apart • Distance between adjacent wave crests (or troughs) is wavelength © 2013 Pearson Education, Inc. Sound waves are waves of pressure conducted through a medium Wavelength Air molecules Tuning fork © 2013 Pearson Education, Inc. Tympanic membrane Figure 9.8 1 1 Sound Frequency (9.8) • Frequency • Number of waves (cycles) passing a fixed point in a given time • Frequency of sound measured in cycles per second (cps) or hertz (Hz) • Pitch of sound is really frequency • Sound travels at same speed, so higher frequency means shorter wavelengths • High frequency sound = high pitch; 15,000 Hz or more • Very low frequency sound = low pitch; 100 Hz or less © 2013 Pearson Education, Inc. Frequency and amplitude of sound waves Sound energy arriving at tympanic membrane Wavelength Amplitude 1 wavelength 0 © 2013 Pearson Education, Inc. Time (sec) Figure 9.8 2 2 Volume or Intensity (9.8) • Amplitude of sound wave determined by amount of energy carried • Amount of energy in sound waves is intensity • Louder sounds have greater energy so higher amplitudes • Measured in decibels (dB) © 2013 Pearson Education, Inc. © 2013 Pearson Education, Inc. Figure 9.8 3 3 Pitch Determination (9.8) • Sound waves striking a flexible object make it vibrate • Vibration to same frequency of sound waves is resonance • Tympanic membrane resonates to sound waves • Movement of tympanic membrane causes pressure waves in cochlea • Basilar membrane more flexible in some regions, resonates to different frequencies at different locations • Location of vibration interpreted as pitch • Number of stimulated hair cells interpreted as volume © 2013 Pearson Education, Inc. Location of movement produced by sound of different frequencies Cochlea Stapes at oval window 16,000 Hz Round window Less flexible 6000 Hz Basilar membrane 1000 Hz More flexible This diagram shows the location where movement of the basilar membrane is produced by sound waves of different frequencies © 2013 Pearson Education, Inc. Figure 9.8 4 4 Events involved in hearing Events Involved in Hearing Sound waves arrive at the tympanic membrane. Movement of the tympanic membrane causes displacement of the auditory ossicles. 1 2 Movement of the stapes at the oval window establishes pressure waves in the perilymph of the scala vestibuli. 3 The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. 4 Vibration of the basilar membrane causes vibration of hair cells against the tectorialmembrane. 5 Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII. 6 Tympanic duct Basilar membrane Cochlear duct Vestibular membrane Movement of sound waves Vestibular duct Tympanic membrane © 2013 Pearson Education, Inc. Round window Figure 9.8 5 5 Module 9.8 Review a. Define decibel. b. Beginning at the external acoustic meatus, list the events in hearing. c. How would sound perception be affected if the round window could not bulge out as a result of increased perilymph pressure? © 2013 Pearson Education, Inc. Eyelids and Eyelashes (9.9) • Eyelash • Helps prevent foreign matter from reaching eye surface • Eyelid or palpebra • Continuation of skin • Blinking of eyelids keeps eye surface lubricated and removes dust and debris, protects eye surface • Palpebral fissure is gap separating upper and lower eyelids • Connected by medial and lateral canthus • Lacrimal caruncle • Location of glands producing thick secretions © 2013 Pearson Education, Inc. Accessory structures of the eye Eyelids and Eyelashes Eyelashes Cornea Eyelid or palpebra Medial canthus Lateral canthus Palpebral fissure Pupil Lacrimal caruncle © 2013 Pearson Education, Inc. Figure 9.9 1 1 Conjunctiva (9.9) • Epithelium covering inner surfaces of eyelids and outer surface of eye • Mucous membrane covered by specialized stratified squamous epithelium • Continuous with epithelium covering surface of cornea (transparent area on anterior surface) • Tarsal glands or Meibomian glands • Modified sebaceous glands on inner margin of each eyelid • Secrete lipid-rich product keeping eyelids from sticking together © 2013 Pearson Education, Inc. Conjunctiva of the eye Tarsal glands Conjunctiva Conjunctiva © 2013 Pearson Education, Inc. Figure 9.9 2 2 Tears (9.9) • Produced by lacrimal gland • Reduce friction • Remove debris • Prevent bacterial infection (contain antibacterial enzyme lysozyme and antibodies) • Provide nutrients and oxygen to conjunctival epithelium © 2013 Pearson Education, Inc. Lacrimal Apparatus (9.9) 1. Produces, distributes, and removes tears 2. Lacrimal gland or tear gland with associated ducts • Almond-shaped gland produces 1 mL tears per day • Tear ducts deliver tears from lacrimal gland to space behind upper eyelid • Lacrimal puncta – small pores drain lacrimal lake (where tears collect) 3. Paired lacrimal canaliculi – small canals connect lacrimal puncta to lacrimal sac 4. Lacrimal sac – nestles in lacrimal sulcus of orbit 5. Nasolacrimal duct – carries tears from lacrimal sac to inferior meatus in nasal cavity © 2013 Pearson Education, Inc. Lacrimal apparatus Components of the Lacrimal Apparatus Lacrimal gland Superior rectus muscle Tear ducts Lacrimal puncta Upper eyelid Lower eyelid Orbital fat layer Lacrimal canaliculi Lacrimal sac Nasolacrimal duct Inferior rectus muscle Inferior oblique muscle © 2013 Pearson Education, Inc. Inferior meatus Figure 9.9 3 3 Conjunctivitis (9.9) • Also called pinkeye • From damage to and irritation of conjunctival surface • Redness from dilated blood vessels deep to conjunctival epithelium • Caused by: • Pathogenic infection • Physical, allergic, or chemical irritation © 2013 Pearson Education, Inc. Conjunctivitis © 2013 Pearson Education, Inc. Figure 9.9 4 4 Module 9.9 Review a. List the accessory structures associated with the eye. b. Explain conjunctivitis. c. Which layer of the eye would be the first affected by inadequate tear production? © 2013 Pearson Education, Inc. Wall of the Eye – Fibrous Layer (9.10) • Three layers of eye wall (fibrous, vascular, neural) • Fibrous layer – outermost layer • Consists of continuous components cornea and sclera • Border between is corneal limbus • Functions: 1. Provides mechanical support and physical protection 2. Attachment site for extrinsic eye muscles 3. Contains cornea, which allows passage of light and aids in focusing process © 2013 Pearson Education, Inc. Wall of Eye – Vascular Layer (9.10) 1. Provides route for blood vessels and lymphatics to eye • Choroid – contains extensive capillary networks 2. Regulates amount of light entering eye • Iris – contains blood vessels, pigment cells, smooth muscle; controls pupil diameter and amount of light entering eye 3. Secretes and reabsorbs aqueous humor 4. Controls shape of lens, part of focusing process • Ciliary body – ring of smooth muscle connected to ligaments that hold lens in place and epithelial cells that secrete aqueous humor © 2013 Pearson Education, Inc. Wall of Eye – Neural Layer (9.10) • Neural layer, or retina • Innermost layer of eye • Consists of: • Thin outer layer (pigmented layer) that absorbs light • Thick inner layer (neural layer) containing photoreceptors, cells sensitive to light © 2013 Pearson Education, Inc. Layers of the eye wall Fibrous Layer Corneal Cornea Sclera limbus Vascular Layer Iris Lens Optic nerve Ciliary body Choroid Neural Layer Retina containing photoreceptors © 2013 Pearson Education, Inc. Figure 9.10 1 1 Eye Cavities (9.10) • Ciliary body and lens divide eye into: • Small anterior cavity • Anterior chamber from cornea to iris • Posterior chamber from iris to ciliary body and lens • Large posterior cavity • Taken up mostly by vitreous body or vitreous humor, gelatinous substance © 2013 Pearson Education, Inc. Anterior and posterior cavities of the eye Anterior Cavity Cornea Anterior chamber Iris Ciliary body Lens Posterior chamber Posterior Cavity Optic nerve © 2013 Pearson Education, Inc. Figure 9.10 2 2 Extrinsic Eye Muscles (9.10) • Six extrinsic eye muscles position the eye 1. Superior oblique – controlled by cranial nerve IV 2. Superior rectus – controlled by cranial nerve III 3. Lateral rectus – controlled by cranial nerve VI 4. Inferior oblique – controlled by cranial nerve III 5. Inferior rectus – controlled by cranial nerve III 6. Medial rectus – controlled by cranial nerve III © 2013 Pearson Education, Inc. Lateral view of right eye showing extrinsic eye muscles Superior oblique Superior rectus Levator palpebrae superioris Optic nerve Lateral rectus Inferior oblique Maxilla Inferior rectus © 2013 Pearson Education, Inc. Figure 9.10 3 3 Medial view of right eye showing extrinsic eye muscles Trochlea (ligamentous sling) Superior rectus Levator palpebrae superioris Superior oblique Optic nerve Medial rectus Inferior rectus Inferior oblique © 2013 Pearson Education, Inc. Figure 9.10 4 4 Eye Movements (9.10) • Each extrinsic muscle, when contracted, produces different eye movements 1. Superior oblique – rolls eye; looks down and laterally 2. Superior rectus – eye looks up 3. Lateral rectus – eye looks laterally 4. Inferior oblique – rolls eye; looks up and laterally 5. Inferior rectus – eye looks down 6. Medial rectus – eye looks medially © 2013 Pearson Education, Inc. Anterior view of right eye showing movement of eye in response to extrinsic muscle contraction Superior rectus Lateral rectus Trochlea Superior oblique Medial rectus Inferior oblique Inferior rectus © 2013 Pearson Education, Inc. Figure 9.10 55 Module 9.10 Review a. Name the three layers of the eye. b. What gives the eyes their characteristic color? c. Name the extrinsic eye muscles and describe the way in which each moves the eye. © 2013 Pearson Education, Inc. Eye Anatomy Organization (9.11) • Cornea – allows light entry into eye • Dense matrix of multiple layers of collagen fibers • No blood vessels, obtains nutrients from tears • Lens • Held in place by suspensory ligaments connected to ciliary body • Tension on ligaments keeps lens less than spherical • Retina – contains photoreceptors, supporting cells, neurons • Choroid – contains nutrient-carrying blood vessels • Sclera – dense, fibrous connective tissue • Stabilizes shape of eye • Insertion point for extrinsic eye muscles © 2013 Pearson Education, Inc. Visual Axis of the Eye (9.11) • Light passes through center of cornea and center of lens to specific location on retina • Imaginary line from center of object seen through center of cornea and lens to retina is visual axis • Highest concentration of photoreceptors at center (fovea) of an area (macula) • Fovea is site of sharpest vision • Optic nerve (CN II) • Carries visual information to the brain © 2013 Pearson Education, Inc. Sectional view of both eyes Transparent cornea Lens Suspensory ligaments Ciliary body Retina with photoreceptors Vascular choroid layer Sclera Iris Visual axis of the eye Lens Choroid Photoreceptors in inner, neural portion of retina Nose Sclera Macula fovea Optic nerve (N II) © 2013 Pearson Education, Inc. Orbital fat Figure 9.11 11 Pupil Constriction and Dilation (9.11) • Amount of light entering the eye controlled by two layers of smooth muscles, located in iris • Controlled by autonomic nervous system • Pupillary dilator muscles • Activated by sympathetic system and dim light • Increase pupil diameter • Pupillary constrictor muscles • Activated by parasympathetic system and bright light • Decrease pupil diameter © 2013 Pearson Education, Inc. Pupillary muscles of the iris respond to amount of light Pupillary constrictor (sphincter) The pupillary dilator muscles extend radially away from the edge of the pupil. Contraction of these muscles enlarges the pupil. Pupillary dilator (radial) Decreased light intensity Increased sympathetic stimulation © 2013 Pearson Education, Inc. The pupillary constrictor muscles form a series of concentric circles around the pupil. When these sphincter muscles contract, the diameter of the pupil decreases. Increased light intensity Increased parasympathetic stimulation Figure 9.11 22 Module 9.11 Review a. Which eye structure does not contain blood vessels? b. List the structures and fluids that light passes through from the cornea to the retina. c. What happens to the pupils when light intensity decreases? © 2013 Pearson Education, Inc. Light Refraction (9.12) • Light refracted or bent when it passes from one medium to another with different density • For example, air to cornea • Light rays refracted by cornea • Additional refraction when light passes through lens • Lens provides refraction to focus light rays toward focal point on retina • Distance between lens and focal point is focal distance © 2013 Pearson Education, Inc. Light rays are refracted to a focal point Focal distance Light from distant source (object) Focal distance Close source Focal point Lens The closer the light source, the longer the focal distance Focal distance © 2013 Pearson Education, Inc. The rounder the lens, the shorter the focal distance Figure 9.12 11 Accommodation (9.12) • Human lens can't move, but it can change shape, called accommodation • Close vision • Ciliary muscles contract, moving ciliary body closer to lens • Reduced tension on suspensory ligaments • Elastic capsule of lens pulls lens into more spherical shape • Thicker lens bends light rays more, so can focus on close objects • Distance vision • Ciliary muscles relax, moving ciliary body away from lens • Suspensory ligaments increase pull on lens • Lens flattens © 2013 Pearson Education, Inc. Ciliary muscles control the shape of the lens For Close Vision: Ciliary Muscle Contracted, Lens Rounded For Distant Vision: Ciliary Muscle Relaxed, Lens Flattened Focal point on fovea © 2013 Pearson Education, Inc. Figure 9.12 22 Inverted and Reversed Images (9.12) • Light from each point in an object focused on retina • Image on retina is inverted and reversed • Brain compensates, so perception is of original orientation © 2013 Pearson Education, Inc. Refraction makes images appear upside down and reversed on the retina © 2013 Pearson Education, Inc. Figure 9.12 33 Inner Limit of Clear Vision (9.12) • To view closer objects requires greater thickening of lens (more refraction) • Limit to how close clear vision occurs (near point) determined by elasticity of lens • Children can focus 7–9 cm from eye • With age, lens stiffens • Young adult can focus 15–20 cm from eye • Distance increases to 83 cm at age 60 © 2013 Pearson Education, Inc. Module 9.12 Review a. Define focal point. b. When the ciliary muscles are relaxed, are you viewing something close up or something in the distance? c. Why does the near point of vision typically increase with age? © 2013 Pearson Education, Inc. Parts of the Retina (9.13) • Pigmented part of retina • Absorbs light that passes through neural part • Prevents visual "echoes" • Cells have biochemical reactions with retina's light receptors • Neural part of retina • Photoreceptors – in outermost layer, closest to pigmented part • Ganglion cells – form innermost layer of cells • Optic disc – where axons of ganglion cells converge to form optic nerve • No photoreceptors, also called blind spot © 2013 Pearson Education, Inc. Parts of the retina Pigmented Part of the Retina Neural Part of the Retina The outermost layer, closest to the pigmented part of the retina, contains the photoreceptors. Ganglion cells form the innermost layer of cells in the neural part of the retina. The axons of the ganglion cells converge at the optic disc to form the optic nerve, which carries visual information to the brain. The optic disc has no photoreceptors; because an image falling on this portion of the retina cannot be detected, it is called the blind spot. Central retinal vein Central retinal artery Optic nerve Sclera Choroid © 2013 Pearson Education, Inc. Blood vessels enter and leave the interior of the eye within the optic nerve. They radiate across the inner surface of the eye, servicing the inner layers of cells in the neural part of the retina. Figure 9.13 1 1 Photograph of retina in right eye Optic disc (blind spot) Fovea (dense area at the center of the lighter macula) Macula Central retinal artery and vein emerging from center of optic disc © 2013 Pearson Education, Inc. Figure 9.13 2 2 Photoreceptors of the Retina (9.13) • Rods – black and white vision • Highly sensitive, enable us to see in dim light • About 125 million in each eye • Highest density at periphery of retina • Cones – color vision • Sharper, clearer vision than rods but require more light • About 6 million in each eye • Highest density at fovea of macula • Bipolar cells – not photoreceptors, but are connection between rods and cones and ganglion cells © 2013 Pearson Education, Inc. Photoreceptors of the retina Pigmented part of retina Photoreceptors of the Retina Rods Cones Other retinal cells can facilitate or inhibit communication between photoreceptors and ganglion cells Bipolar cells Ganglion cells LIGHT © 2013 Pearson Education, Inc. Figure 9.13 3 3 Module 9.13 Review a. Define rods and cones and briefly state their functions. b. If you enter a dimly lit room, will you be able to see clearly? Why or why not? c. If you had been born without cones in your eyes, explain why you would or would not be able to see. © 2013 Pearson Education, Inc. Photoreceptor Structures (9.14) • Rods and cones have two segments 1. Outer segment – contains flattened membranous plates, discs • Discs contain special organic compounds, visual pigments • Pigments derivatives of rhodopsin, pigment found in rods • Rhodopsin composed of opsin and retinal (synthesized from vitamin A) • Type of opsin determines wavelengths absorbed by retinal 2. Inner segment – contains major organelles • Responsible for cell functions other than photoreception (responding to photons) © 2013 Pearson Education, Inc. Rods and cones structure Structure of Cones Structure of Rods Pigment Epithelium In a cone, the discs are infoldings of the plasma membrane, and the outer segment tapers to a blunt point. In a rod, each disc is an independent entity, and the outer segment forms an elongated cylinder. Melanin granules Outer Segment Discs Connecting stalks Inner Segment Mitochondria Golgi apparatus Nuclei Cone Rhodopsin molecule Retinal Opsin Rods Each photoreceptor synapses with a bipolar cell. Bipolar cell LIGHT © 2013 Pearson Education, Inc. Figure 9.14 1 1 – 22 Light Energy to Nerve Impulse (9.14) • Light strikes visual pigment • Retinal molecule changes shape • Changes permeability of outer segment • Converts light energy into nerve impulse © 2013 Pearson Education, Inc. Changes in visual pigments with exposure to light 1 When light is absorbed, retinal changes to a more linear shape. This change activates the opsin molecule. 2 Opsin activation changes the rate of neurotransmitter release by the inner segment at its synapse with a bipolar cell. Photon 6 Once the retinal has returned to its original shape, it can recombine with opsin. The rhodopsin molecule is now ready to repeat the cycle. The regeneration process takes time; after exposure to very bright light, photoreceptors are inactivated while pigment regeneration is under way. 3 enzyme Opsin Opsin Changes in bipolar cell activity are detected by one or more ganglion cells. Neurotransmitter release Bipolar cell 4 5 The retinal is converted to its original shape. This conversion requires energy in the form of ATP. © 2013 Pearson Education, Inc. After absorbing a photon, the rhodopsin molecule begins to break down into retinal and opsin, a process known as bleaching. Ganglion cell Figure 9.14 33 Wavelengths of Light (9.14) • Three types of cones, each with different type of opsin sensitive to different wavelengths of light • Can be stimulated in various combinations to perceive colors, stimulation of all three equally is perceived as white 1. Blue cones – 16 percent of cones 2. Green cones – 10 percent of cones 3. Red cones – 74 percent of cones • Color blindness comes from lacking one or more cone pigments • 2 percent of males lack either red or green pigments © 2013 Pearson Education, Inc. Wavelengths of light to which types of cones respond Light absorption (percent of maximum) 100 75 Blue cones Rods Red cones 50 25 0 Green cones WAVELENGTH (nm) 650 500 550 600 400 450 Violet Blue Green Yellow Orange © 2013 Pearson Education, Inc. 700 Red Figure 9.14 44 Module 9.14 Review a. Identify the three types of cones. b. Explain why your vision is momentarily impaired after viewing a camera's flash. c. How could a diet deficient in vitamin A affect vision? © 2013 Pearson Education, Inc. Depth Perception (9.15) • Images from left and right eyes overlap • Visual cortex of each cerebral hemisphere receives information from both eyes • Depth perception is interpretation of threedimensional relationships among objects • Brain does this by comparing relative positions of objects in images received by two eyes © 2013 Pearson Education, Inc. Visual pathways and depth perception Combined Visual Field Left side Right side Left eye Binocular vision Right eye only only The Visual Pathways Photoreceptors in the retina Retina Optic disc Optic nerve (N II) Optic chiasm Optic tract Optic tract Lateral geniculate nucleus Lateral geniculate nucleus (thalamus) Visual cortex of cerebral hemispheres Optic radiation Left cerebral hemisphere © 2013 Pearson Education, Inc. Right cerebral hemisphere Figure 9.15 11 Module 9.15 Review a. Define optic radiation. b. Where are visual images perceived? c. Trace the visual pathway, beginning at the photoreceptors in the retina. © 2013 Pearson Education, Inc. Accommodation Problems (9.16) • Emmetropia or normal vision • Distant objects focused clearly when ciliary muscles relaxed and lens flattened • Myopia or nearsighted (can see close objects most clearly) • Eyeball too deep or curvature of lens too great • Image of distant object focused in front of retina • Corrected with diverging lens to spread light rays apart © 2013 Pearson Education, Inc. Accommodation Problems (9.16) • Hyperopia or farsighted (can see distant objects most clearly) • Eyeball too shallow or lens too flat • Ciliary muscles have to contract to focus on distant object • Close range, lens cannot refract enough • Corrected with converging lens for additional refraction © 2013 Pearson Education, Inc. Accommodation issues with the eye Emmetropia Myopia Diverging lens Hyperopia Converging lens © 2013 Pearson Education, Inc. Figure 9.16 11 Reshaping the Cornea (9.16) • One way to correct myopia and hyperopia is by surgery reshaping cornea • Photorefractive keratectomy (PRK) • Uses computer-guided laser to remove 10–20 µm of cornea from outer surface • Laser-assisted in-situ keratomileusis (LASIK) • Reshapes interior layers of cornea, covers with flap of normal cornea • 70 percent LASIK patients achieve normal vision • Corneal scarring rare in either procedure © 2013 Pearson Education, Inc. Surgical reshaping of cornea © 2013 Pearson Education, Inc. Figure 9.16 11 Module 9.16 Review a. Define emmetropia. b. Discuss two surgical procedures for correcting myopia and hyperopia. c. Which type of lens would correct hyperopia? © 2013 Pearson Education, Inc. Disorders of Olfaction (9.17) • Disorders of olfaction (sense of smell) result from: • Head injury that damages olfactory nerve • Normal age-related changes • Olfactory receptors regularly replaced by stem cell division • But total number declines with age and receptors become less sensitive © 2013 Pearson Education, Inc. Disorders of Gustation (9.17) • Disorders of gustation (sense of taste) result from: • Problems with olfactory receptors • Sense of smell and taste closely related • Common cold affects both • Damage to taste buds – by inflammation or infections • Damage to cranial nerves (VII, IX, X) • Age-related changes © 2013 Pearson Education, Inc. Disorders of Vision (9.17) • Cataract • Condition in which lens loses transparency • Can result from injury, radiation, reaction to drugs • Most common form is senile cataracts • Natural consequence of aging • Damaged or nonfunctional lens can be replaced by artificial substitute © 2013 Pearson Education, Inc. Cataracts Normal eye Eye with cataract © 2013 Pearson Education, Inc. Figure 9.17 33 Equilibrium Disorders (9.17) • Vertigo – illusion of movement • Caused by conditions altering function of: • Internal ear receptor complex • Examples: • Anything that disturbs endolymph, like flushing external acoustic meatus with cold water • Excessive consumption of alcohol or certain drugs • Vestibular branch of vestibulocochlear nerve • Sensory nuclei and pathways in central nervous system • Motion sickness – headache, sweating, nausea, vomiting • Motion sickness drugs depress activity in brain stem © 2013 Pearson Education, Inc. Hearing Disorders (9.17) • Conductive deafness • From interference with normal transfer of vibrations from tympanic membrane to oval window • Caused by excess wax, trapped water, scarring of tympanic membrane, immobilization of auditory ossicles • Nerve deafness • Problem with cochlea or along auditory pathway • Can be caused by very loud noises damaging sensory cilia on receptor cells • Bacterial or viral infections can also kill receptor cells © 2013 Pearson Education, Inc. Hearing Loss (9.17) • Occurs with age from: • Accumulated damage from loud noises and other injuries • Decreasing flexibility of tympanic membrane • Stiffness of auditory ossicle joints and ossification of round window © 2013 Pearson Education, Inc. Changes in hearing with age © 2013 Pearson Education, Inc. Figure 9.17 55 Module 9.17 Review a. Which cranial nerves provide taste sensations from the tongue? b. Identify two common classes of hearing-related disorders. c. What causes vertigo? © 2013 Pearson Education, Inc.