17 The Special Senses PowerPoint Lecture Presentations prepared
17 The Special Senses PowerPoint Lecture Presentations prepared by Jason LaPres Lone Star CollegeNorth Harris 2012 Pearson Education, Inc. An Introduction to the Special Senses Five Special Senses 1. Olfaction 2. Gustation 3. Vision 4. Equilibrium 5. Hearing 2012 Pearson Education, Inc.
17-1 Smell (Olfaction) Olfactory Organs Provide sense of smell Located in nasal cavity on either side of nasal septum Made up of two layers 1. Olfactory epithelium 2. Lamina propria 2012 Pearson Education, Inc. 17-1 Smell (Olfaction) Layers of Olfactory Organs Olfactory epithelium contains: Olfactory receptors Supporting cells Basal (stem) cells
2012 Pearson Education, Inc. 17-1 Smell (Olfaction) Layers of Olfactory Organs Lamina propria contains: Areolar tissue Blood vessels Nerves Olfactory glands 2012 Pearson Education, Inc. Figure 17-1a The Olfactory Organs Olfactory Pathway to the Cerebrum Olfactory Olfactory Olfactory epithelium nerve bulb
fibers (N I) Olfactory tract Central nervous system Cribriform plate Superior nasal concha 2012 Pearson Education, Inc. The olfactory organ on the left side of the nasal
septum 17-1 Smell (Olfaction) Olfactory Glands Secretions coat surfaces of olfactory organs Olfactory Receptors Highly modified neurons Olfactory reception Involves detecting dissolved chemicals as they interact with odorant-binding proteins 2012 Pearson Education, Inc. 17-1 Smell (Olfaction) Olfactory Discrimination Can distinguish thousands of chemical stimuli CNS interprets smells by the pattern of receptor activity
Olfactory Receptor Population Considerable turnover Number of olfactory receptors declines with age 2012 Pearson Education, Inc. Figure 17-2 Olfactory and Gustatory Receptors Olfaction and gustation are special senses that provide us with vital information about our environment. Although the sensory information provided is diverse and complex, each special sense originates at receptor cells that may be neurons or specialized receptor cells that communicate with sensory neurons.
Stimulus Action removed potentials Stimulus Dendrites Specialized olfactory neuron Stimulus Threshold Generator potential 2012 Pearson Education, Inc. to CNS
Figure 17-2 Olfactory and Gustatory Receptors Olfactory reception occurs on the surface membranes of the olfactory cilia. Odorantsdissolved chemicals that stimulate olfactory receptorsinteract with receptors called odorant- binding proteins on the membrane surface. The binding of an odorant to its receptor protein leads to the activation of adenylyl cyclase, the enzyme that converts ATP to cyclic-AMP (cAMP). Odorant molecule Inactive enzyme MUCOUS LAYER
In general, odorants are small organic molecules. The strongest smells are associated with molecules of either high water or high lipid solubilities. As few as four odorant molecules can activate an olfactory receptor. The cAMP then opens sodium channels in the plasma membrane, which, as a result, begins to depolarize. Closed sodium channel Depolarized membrane Active
enzyme RECEPTOR CELL 2012 Pearson Education, Inc. If sufficient depolarization occurs, an action potential is triggered in the axon, and the information is relayed to the CNS. Sodium ions enter 17-2 Taste (Gustation) Gustation Provides information about the foods and liquids
consumed Taste Receptors (Gustatory Receptors) Are distributed on tongue and portions of pharynx and larynx Clustered into taste buds 2012 Pearson Education, Inc. 17-2 Taste (Gustation) Taste Buds Associated with epithelial projections (lingual papillae) on superior surface of tongue 2012 Pearson Education, Inc. 17-2 Taste (Gustation) Taste Buds Contain:
Basal cells Gustatory cells Extend taste hairs through taste pore Survive only 10 days before replacement Monitored by cranial nerves that synapse within solitary nucleus of medulla oblongata Then on to thalamus and primary sensory cortex 2012 Pearson Education, Inc. 17-2 Taste (Gustation) Gustatory Discrimination Four primary taste sensations 1. Sweet 2. Salty
3. Sour 4. Bitter 2012 Pearson Education, Inc. Figure 17-3a Gustatory Receptors Water receptors (pharynx) Umami Sour Bitter Salty Sweet Landmarks and receptors on the tongue 2012 Pearson Education, Inc.
17-2 Taste (Gustation) Additional Human Taste Sensations Umami Characteristic of beef/chicken broths and Parmesan cheese Receptors sensitive to amino acids, small peptides, and nucleotides Water Detected by water receptors in the pharynx 2012 Pearson Education, Inc. 17-2 Taste (Gustation) Gustatory Discrimination Dissolved chemicals contact taste hairs Bind to receptor proteins of gustatory cell Salt and sour receptors Chemically gated ion channels
Stimulation produces depolarization of cell Sweet, bitter, and umami stimuli G proteins Gustducins 2012 Pearson Education, Inc. 17-2 Taste (Gustation) End Result of Taste Receptor Stimulation Release of neurotransmitters by receptor cell Dendrites of sensory afferents wrapped by receptor membrane Neurotransmitters generate action potentials in afferent fiber 2012 Pearson Education, Inc. 17-2 Taste (Gustation) Taste Sensitivity
Exhibits significant individual differences Some conditions are inherited For example, phenylthiocarbamide (PTC) 70% of Caucasians taste it but 30% do not Number of taste buds Begins declining rapidly by age 50 2012 Pearson Education, Inc. Figure 17-2 Olfactory and Gustatory Receptors Salt and Sour Receptors Sweet, Bitter, and Umami Receptors Salt receptors and sour receptors are chemically gated ion channels whose stimulation produces depolarization
of the cell. Receptors responding to stimuli that produce sweet, bitter, and umami sensations are linked to G proteins called gustducins (GUST-doos- inz)protein complexes that use second messengers to produce their effects. Sour, salt Gated ion channel Sweet, bitter, or umami
Membrane receptor Resting plasma membrane Inactive G protein Active G protein Channel opens Depolarized membrane Active G protein Active 2nd messenger
Depolarization of membrane stimulates release of chemical neurotransmitters. 2012 Pearson Education, Inc. Inactive 2nd messenger Activation of second messengers stimulates release of chemical neurotransmitters. 17-3 Accessory Structures of the Eye Accessory Structures of the Eye Provide protection, lubrication, and support Include: The palpebrae (eyelids) The superficial epithelium of eye The lacrimal apparatus
2012 Pearson Education, Inc. 17-3 Accessory Structures of the Eye Eyelids (Palpebrae) Continuation of skin Blinking keeps surface of eye lubricated, free of dust and debris Eyelashes Robust hairs that prevent foreign matter from reaching surface of eye 2012 Pearson Education, Inc. 17-3 Accessory Structures of the Eye Eyelids (Palpebrae) Tarsal glands Secrete lipid-rich product that helps keep eyelids from sticking together
2012 Pearson Education, Inc. 17-3 Accessory Structures of the Eye Superficial Epithelium of Eye Lacrimal caruncle Mass of soft tissue Contains glands producing thick secretions Contributes to gritty deposits that appear after good nights sleep Conjunctiva Epithelium covering inner surfaces of eyelids (palpebral conjunctiva) and outer surface of eye (ocular conjunctiva) 2012 Pearson Education, Inc. Figure 17-4a External Features and Accessory Structures of the Eye
Eyelashes Pupil Lateral canthus Palpebra Palpebral fissure Sclera Medial canthus Lacrimal caruncle Corneal limbus Gross and superficial anatomy of the accessory structures 2012 Pearson Education, Inc.
17-3 Accessory Structures of the Eye Lacrimal Apparatus Produces, distributes, and removes tears Lacrimal gland (tear gland) Secretions contain lysozyme, an antibacterial enzyme 2012 Pearson Education, Inc. Figure 17-4b External Features and Accessory Structures of the Eye Superior Tendon of superior rectus muscle oblique muscle Lacrimal gland ducts Lacrimal punctum Lacrimal gland Lacrimal caruncle
Inferior nasal concha Opening of nasolacrimal duct The organization of the lacrimal apparatus. 2012 Pearson Education, Inc. 17-3 The Eye Eyeball Is hollow
Is divided into two cavities 1. Large posterior cavity 2. Smaller anterior cavity 2012 Pearson Education, Inc. Figure 17-5b The Sectional Anatomy of the Eye Fibrous layer Cornea Sclera Anterior cavity Vascular layer (uvea)
Iris Ciliary body Choroid Neural layer (retina) Posterior cavity Neural part Pigmented part Horizontal section of right eye 2012 Pearson Education, Inc. Figure 17-5a The Sectional Anatomy of the Eye Fornix
Sagittal section of left eye 2012 Pearson Education, Inc. 17-3 The Eye The Fibrous Layer Sclera (white of the eye) Cornea Corneal limbus (border between cornea and sclera) 2012 Pearson Education, Inc. 17-3 The Eye Vascular Layer (Uvea) Functions 1. Provides route for blood vessels and lymphatics that supply tissues of eye 2. Regulates amount of light entering eye
3. Secretes and reabsorbs aqueous humor that circulates within chambers of eye 4. Controls shape of lens, which is essential to focusing 2012 Pearson Education, Inc. Figure 17-5c The Sectional Anatomy of the Eye Visual axis Anterior cavity Posterior Anterior chamber chamber Cornea Edge of pupil Iris Suspensory ligament of lens
Ciliary body Ora serrata Sclera Choroid Retina Posterior cavity Ethmoidal labyrinth Lateral rectus muscle Medial rectus muscle Optic disc
Fovea Optic nerve Central artery and vein Orbital fat Horizontal dissection of right eye 2012 Pearson Education, Inc. 17-3 The Eye The Vascular Layer Iris Contains papillary muscles Change diameter of pupil Color of the eye
2012 Pearson Education, Inc. Figure 17-6 The Pupillary Muscles Pupillary constrictor (sphincter) Pupil 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 2012 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 17-3 The Eye The Vascular Layer Ciliary Body Extends posteriorly to level of ora serrata
Serrated anterior edge of thick, inner portion of neural tunic Contains ciliary processes, and ciliary muscle that attaches to suspensory ligaments of lens The ciliary body of the eye changes the shape of the lens for far and near vision 2012 Pearson Education, Inc. 17-3 The Eye The Vascular Layer The choroid Vascular layer that separates fibrous and inner layers posterior to ora serrata Delivers oxygen and nutrients to retina 2012 Pearson Education, Inc. 17-3 The Eye
The Inner Layer Outer layer called pigmented part Inner called neural part (retina) Contains visual receptors and associated neurons Rods and cones are types of photoreceptors Rods Do not discriminate light colors Highly sensitive to light Cones Provide color vision Densely clustered in fovea, at center of macula 2012 Pearson Education, Inc. Figure 17-5c The Sectional Anatomy of the Eye Visual axis Anterior cavity Posterior Anterior chamber chamber
Cornea Edge of pupil Iris Suspensory ligament of lens Nose Corneal limbus Conjunctiva Lacrimal punctum Lacrimal caruncle Lower eyelid Medial canthus
Ciliary processes Lateral canthus Lens Ciliary body Ora serrata Sclera Choroid Retina Posterior cavity Ethmoidal labyrinth
Lateral rectus muscle Medial rectus muscle Optic disc Fovea Optic nerve Central artery and vein Orbital fat Horizontal dissection of right eye 2012 Pearson Education, Inc.
Figure 17-7a The Organization of the Retina Horizontal cell Cone Rod Pigmented part of retina Rods and cones Amacrine cell Bipolar cells Ganglion cells LIGHT
The cellular organization of the retina. The photoreceptors are closest to the choroid, rather than near the posterior cavity (vitreous chamber). 2012 Pearson Education, Inc. Figure 17-7a The Organization of the Retina Choroid Pigmented part of retina Rods and cones Bipolar cells Ganglion cells Retina LM 350
Nuclei of Nuclei of rodsNuclei of ganglion cells and conesbipolar cells The cellular organization of the retina. The photoreceptors are closest to the choroid, rather than near the posterior cavity (vitreous chamber). 2012 Pearson Education, Inc. Figure 17-7b The Organization of the Retina Pigmented part of retina Neural part of retina Central retinal vein Optic disc
Central retinal artery Sclera Optic nerve 2012 Pearson Education, Inc. Choroid The optic disc in diagrammatic sagittal section. Figure 17-7c The Organization of the Retina Fovea Macula Optic disc (blind spot)
Central retinal artery and vein emerging from center of optic disc A photograph of the retina as seen through the pupil. 2012 Pearson Education, Inc. 17-3 The Eye Optic Disc Circular region just medial to fovea Origin of optic nerve Blind spot 2012 Pearson Education, Inc. Figure 17-8 A Demonstration of the Presence of a Blind Spot 2012 Pearson Education, Inc.
17-3 The Eye Aqueous Humor Fluid circulates within eye Diffuses through walls of anterior chamber into scleral venous sinus (canal of Schlemm) Re-enters circulation Intraocular Pressure Fluid pressure in aqueous humor Helps retain eye shape 2012 Pearson Education, Inc. Figure 17-9 The Circulation of Aqueous Humor Cornea Anterior cavity
Pupil Anterior chamber Scleral venous sinus Posterior chamber Body of iris Ciliary process Lens Suspensory ligaments Pigmented epithelium Conjunctiva Ciliary body
Sclera Posterior cavity (vitreous chamber) Choroid Retina 2012 Pearson Education, Inc. 17-3 The Eye Large Posterior Cavity (Vitreous Chamber) Vitreous body Gelatinous mass Helps stabilize eye shape and supports retina 2012 Pearson Education, Inc. 17-3 The Eye
The Lens Lens fibers Cells in interior of lens No nuclei or organelles Filled with crystallins, which provide clarity and focusing power to lens Cataract Condition in which lens has lost its transparency 2012 Pearson Education, Inc. 17-3 The Eye Light Refraction of Lens Accommodation Shape of lens changes to focus image on retina The human lens focuses light on the photoreceptor cells by changing shape. The shape of the lens is controlled by the ciliary muscles.
Astigmatism Condition where light passing through cornea and lens is not refracted properly 2012 Pearson Education, Inc. Figure 17-11 Accommodation For Close Vision: Ciliary Muscle Contracted, Lens Rounded Lens rounded Focal point on fovea Ciliary muscle contracted For Distant Vision: Ciliary Muscle Relaxed, Lens Flattened Lens flattened
Ciliary muscle relaxed 2012 Pearson Education, Inc. Figure 17-13 Accommodation Problems Surgical Correction Variable success at correcting myopia and hyperopia has been achieved by surgery that reshapes the cornea. In Photorefractive keratectomy (PRK) a computer-guided laser shapes the cornea to exact specifications. The entire procedure can be done in less than a minute. A variation on PRK is called LASIK (Laser-Assisted in-Situ Keratomileusis). In this procedure the interior layers of the cornea are reshaped and then re-covered by the flap of original outer corneal
epithelium. Roughly 70 percent of LASIK patients achieve normal vision, and LASIK has become the most common form of refractive surgery. Even after surgery, many patients still need reading glasses, and both immediate and long-term visual problems can occur. 2012 Pearson Education, Inc. 17-4 Visual Physiology Anatomy of Rods and Cones Visual pigments Is where light absorption occurs 2012 Pearson Education, Inc. 17-4 Visual Physiology Color Vision Integration of information from red, green,
and blue cones Color blindness Inability to detect certain colors 2012 Pearson Education, Inc. Figure 17-15 Cone Types and Sensitivity to Color Light absorption (percent of maximum) Blue cones Rods Red Green cones cones
W A V E L E N G T H (nm) Violet 2012 Pearson Education, Inc. Blue Green Yellow Orange Red Figure 17-16 A Standard Test for Color Vision
2012 Pearson Education, Inc. A ray of light entering the eye will encounter these structures in this order: conjunctiva cornea aqueous humor lens vitreous body retina choroid 2012 Pearson Education, Inc. Photoreceptor cells (rods and cones) form synapses with other nerve cells. When stimulated by light, rods and cones pass graded potentials to bipolar cells, which in turn pass graded potentials to the ganglion cells. The graded potentials may be modified by horizontal cells and amacrine cells that link adjacent photoreceptors or ganglion cells, respectively. Action potentials are ultimately generated by ganglion cells. The axons of all the ganglion cells
gather at the optic disc and exit the nervous tunic through the optic disc as the optic nerve. The optic disc is a blind spot because photoreceptors are absent here. 2012 Pearson Education, Inc. Figure 17-7a The Organization of the Retina Horizontal cell Cone Rod Pigmented part of retina Rods and cones Amacrine cell
Bipolar cells Ganglion cells LIGHT The cellular organization of the retina. The photoreceptors are closest to the choroid, rather than near the posterior cavity (vitreous chamber). 2012 Pearson Education, Inc. 17-5 The Ear The External Ear Auricle Surrounds entrance to external acoustic meatus Protects opening of canal Provides directional sensitivity 2012 Pearson Education, Inc.
Figure 17-21 The Anatomy of the Ear Middle Ear External Ear Elastic cartilages Internal Ear Auditory ossicles Oval window Semicircular canals Petrous part of temporal bone Auricle
Facial nerve (N VII) Vestibulocochlear nerve (N VIII) Bony labyrinth of internal ear Cochlea Tympanic cavity Auditory tube To nasopharynx External acoustic meatus 2012 Pearson Education, Inc. Tympanic
membrane Round Vestibule window 17-5 The Ear The External Ear External acoustic meatus Ends at tympanic membrane (eardrum) Tympanic membrane Is a thin, semitransparent sheet Separates external ear from middle ear 2012 Pearson Education, Inc. 17-5 The Ear The External Ear Ceruminous glands Integumentary glands along external acoustic meatus
Secrete waxy material (cerumen) Keeps foreign objects out of tympanic membrane Slows growth of microorganisms in external acoustic meatus 2012 Pearson Education, Inc. 17-5 The Ear The Middle Ear Also called tympanic cavity Communicates with nasopharynx via auditory tube Permits equalization of pressures on either side of tympanic membrane Encloses and protects three auditory ossicles 1. Malleus (hammer) 2. Incus (anvil)
3. Stapes (stirrup) 2012 Pearson Education, Inc. Figure 17-22a The Middle Ear Auditory Ossicles Malleus Incus Stapes Temporal bone (petrous part) Stabilizing ligaments Oval window
The structures of the middle ear. 2012 Pearson Education, Inc. Muscles of the Middle Ear Figure 17-22b The Middle Ear Malleus attached to tympanic membrane Malleus Tendon of tensor tympani muscle Incus Base of stapes
at oval window Stapes Stapedius muscle Inner surface of tympanic membrane The tympanic membrane and auditory ossicles 2012 Pearson Education, Inc. 17-5 The Ear Vibration of Tympanic Membrane Converts arriving sound waves into mechanical movements Auditory ossicles conduct vibrations to inner ear Tensor tympani muscle Stiffens tympanic membrane Stapedius muscle
Reduces movement of stapes at oval window 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Contains fluid called endolymph Bony labyrinth surrounds and protects membranous labyrinth Subdivided into: Vestibule Semicircular canals Cochlea 2012 Pearson Education, Inc. Figure 17-23b The Internal Ear KEY Membranous labyrinth
Tympanic Spiral duct organ The bony and membranous labyrinths. Areas of the membranous labyrinth containing sensory receptors (cristae, maculae, and spiral organ) are shown in purple. 2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Vestibule Encloses saccule and utricle Receptors provide sensations of gravity and linear acceleration Semicircular canals Contain semicircular ducts Receptors stimulated by rotation of head
2012 Pearson Education, Inc. 17-5 The Ear The Internal Ear Cochlea Contains cochlear duct (elongated portion of membranous labyrinth) Receptors provide sense of hearing 2012 Pearson Education, Inc. 17-5 The Ear Stimuli and Location Sense of gravity and acceleration From hair cells in vestibule Sense of rotation From semicircular canals
Sense of sound From cochlea 2012 Pearson Education, Inc. 17-5 The Ear Equilibrium Sensations provided by receptors of vestibular complex Hair cells Basic receptors of inner ear Provide information about direction and strength of mechanical stimuli 2012 Pearson Education, Inc. Figure 17-24d The Semicircular Ducts Displacement in this direction
stimulates hair cell Kinocilium Displacement in this direction inhibits hair cell Stereocilia Hair cell Sensory nerve ending Supporting cell 2012 Pearson Education, Inc. A representative hair cell (receptor) from the
vestibular complex. Bending the sterocilia toward the kinocilium depolarizes the cell and stimulates the sensory neuron. Displacement in the opposite direction inhibits the sensory neuron. Figure 17-25ab The Saccule and Utricle The location of the maculae Gelatinous material Statoconia Hair cells Nerve fibers
The structure of an individual macula 2012 Pearson Education, Inc. Otolith Figure 17-25c The Saccule and Utricle Head in normal, upright position Gravity Head tilted posteriorly Receptor output increases Gravity
Otolith moves downhill, distorting hair cell processes A diagrammatic view of macular function when the head is held horizontally 1 and then tilted back 2 2012 Pearson Education, Inc. 17-5 The Ear Hearing Cochlear duct receptors Provide sense of hearing 2012 Pearson Education, Inc. 17-5 The Ear
Hearing Auditory ossicles Convert pressure fluctuation in air into much greater pressure fluctuations in perilymph of cochlea Frequency of sound Determined by which part of cochlear duct is stimulated Intensity (volume) Determined by number of hair cells stimulated 2012 Pearson Education, Inc. 17-5 The Ear An Introduction to Sound Pressure Waves Consist of regions where air molecules are crowded together Adjacent zone where molecules are farther apart Sine waves
S-shaped curves 2012 Pearson Education, Inc. Figure 17-29a The Nature of Sound Wavelength Tympanic membrane Tuning fork Air molecules Sound waves (here, generated by a tuning fork) travel through the air as pressure waves.
2012 Pearson Education, Inc. Figure 17-30 Sound and Hearing External acoustic meatus Malleus Incus Stapes Oval window Movement of sound waves Tympanic membrane Sound waves
arrive at tympanic membrane. 2012 Pearson Education, Inc. Movement of the tympanic membrane causes displacement of the auditory ossicles. Round window Movement of the stapes at
the oval window establishes pressure waves in the perilymph of the scala vestibuli. Figure 17-30 Sound and Hearing Cochlear branch of cranial nerve VIII Scala vestibuli (contains perilymph) Vestibular membrane Cochlear duct (contains endolymph) Basilar membrane Scala tympani
(contains perilymph) The pressure waves distort the basilar membrane on their way to the round window of the scala tympani. 2012 Pearson Education, Inc. Vibration of the basilar membrane causes vibration of hair cells against the tectorial
membrane. Information about the region and the intensity of stimulation is relayed to the CNS over the cochlear branch of cranial nerve VIII.
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