Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Human Senses
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Special Senses Taste, smell, sight, hearing, and balance Special sensory receptors Localized – confined to the head region Receptors are not free endings of sensory neurons Special receptor cells
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Chemical Senses: Taste and Smell Taste – gustation Smell – olfaction Receptors – classified as chemoreceptors Respond to chemicals
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Taste – Gustation Taste receptors Occur in taste buds Most are found on the surface of the tongue Located within tongue papillae
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Taste Buds Figure 16.1a, b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Taste Sensation and the Gustatory Pathway Four basic qualities of taste Sweet, sour, salty, and bitter A fifth taste – umami – “deliciousness” No structural difference among taste buds
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Smell (Olfaction) Receptors are part of the olfactory epithelium Olfactory epithelium composed of: Cell bodies of olfactory receptor cells Supporting cells – columnar cells Basal cells – form new olfactory receptor cells Axons of the olfactory epithelium pass through the bones of the skull before making their way to the olfactory bulb of the brain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Olfactory Receptors Figure 16.3a, b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Eye and Vision Visual organ – the eye 70% of all sensory receptors are in the eyes 40% of the cerebral cortex is involved in processing visual information
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 16.5b Accessory Structures of the Eye Lacrimal apparatus – keeps the surface of the eye moist (produces tears)
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Fibrous Tunic Most external layer of the eyeball Composed of two regions of connective tissue Sclera – posterior five-sixths of the tunic White, opaque region Provides shape and an anchor for eye muscles Cornea – anterior one-sixth of the fibrous tunic Limbus – junction between sclera and cornea Scleral venous sinus – allows aqueous humor to drain
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Medial View of the Eye Figure 16.7a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Posterior View of the Anterior Half of the Eye Figure 16.9a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Vascular Tunic Figure 16.8
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Iris Visible colored part of the eye Composed of smooth muscle Pupil – the round, central opening Sphincter pupillae muscle (constrictor or circular) Dilator pupillae muscle (dilator or radial) Act to vary the size of the pupil
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Pupillary dilation and constriction
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Retina Figure 16.10a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Photoreceptors The retina contains the light detecting rods Two main types Rod cells – more sensitive to light Allow vision in dim light Cone cells – operate best in bright light Enable high-acuity, color vision Considered neurons
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Photoreceptors Figure 16.11
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Medial View of the Eye Figure 16.7a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure 16.10c Blood Supply of the Retina Retina receives blood from two sources Outer third of the retina – supplied by capillaries in the choroid Inner two-thirds of the retina – supplied by central artery and vein of the retina
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Internal Chambers and Fluids Figure 16.8
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Lens A thick, transparent, biconvex disc Held in place by its ciliary zonule
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Visual Pathways to the Brain and Visual Fields Figure 16.15a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Normal Opthalmoscopic View of Eye
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Eye and Vision: Macular Degeneration Age-related macular degeneration (AMD) Involves the buildup of visual pigments in the retina Dry Wet
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Macular Degeneration Simulation
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Eye and Vision: Retinopathy Retinopathy in diabetes Vessels have weak walls – causes hemorrhaging and blindness
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of the Eye and Vision: Trachoma Trachoma – contagious infection of the conjunctiva
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Ear: Hearing and Equilibrium The ear – receptor organ for hearing and equilibrium Composed of three main regions Outer ear – functions in hearing Middle ear – functions in hearing Inner ear – functions in both hearing and equilibrium
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Outer (External) Ear Composed of: The auricle (pinna) Helps direct sounds External acoustic meatus Lined with skin Contains hairs, sebaceous glands, and ceruminous glands Tympanic membrane Forms the boundary between the external and middle ear
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Outer (External) Ear Figure 16.17a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear The tympanic cavity A small, air-filled space Located within the petrous portion of the temporal bone Medial wall is penetrated by: Oval window Round window Pharyngotympanic tube (auditory or eustachian tube) Links the middle ear and pharynx
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Structures of the Middle Ear Figure 16.17b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Figure The Middle Ear Ear ossicles – smallest bones in the body Malleus – attaches to the eardrum Incus – between the malleus and stapes Stapes – vibrates against the oval window
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Inner (Internal) Ear Inner ear – also called the labyrinth Lies within the petrous portion of the temporal bone Bony labyrinth – a cavity consisting of three parts Semicircular canals Vestibule Cochlea
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Inner (Internal) Ear Figure 16.17b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Membranous Labyrinth Figure 16.20
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy and Function of the Maculae Figure 16.21a
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy and Function of the Maculae Figure 16.21b
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Semicircular Canals Figure 16.20
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Structure and Function of the Crista Ampullaris Figure 16.22
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings The Cochlea A spiraling chamber in the bony labyrinth
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Equilibrium and Hearing: Meniere’s Syndrome Meniere’s syndrome – equilibrium is greatly disturbed Excessive amounts of endolymph in the membranous labyrinth Normal Meniere’s
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Equilibrium and Hearing: Conduction Deafness Deafness Conduction deafness Sound vibrations cannot be conducted to the inner ear Ruptured tympanic membrane, otitis media, otosclerosis Normal tympanic membrane Otitis mediaRuptured tympanic membrane
Copyright © 2005 Pearson Education, Inc., publishing as Benjamin Cummings Disorders of Equilibrium and Hearing: Sensorineural Deafness Deafness Sensorineural deafness Results from damage to any part of the auditory pathway mild severe