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- 1. © 2012 Pearson Education, Inc. 18 The Nervous System: General and Special Senses PowerPoint® Lecture Presentations prepared by Steven Bassett Southeast Community College Lincoln, Nebraska
- 2. Introduction • Stimulation of the receptor directly or indirectly alters the production of action potentials in a sensory neuron. • The sensory information arriving at the CNS is called a sensation. • A perception is a conscious awareness of a sensation. • Sensory receptors are the interface between the nervous system and the internal and external environment © 2012 Pearson Education, Inc.
- 3. Receptors • General senses • Refers to temperature, pain, touch, pressure, vibration, and proprioception • Receptors throughout the body • These sensations arrive at the primary sensory cortex, or somatosensory cortex • Special senses • Sensations of smell (olfaction), taste (gustation), balance (equilibrium), hearing, and vision • Specialized receptor cells that are structurally more complex than those of the general senses © 2012 Pearson Education, Inc.
- 4. Figure 18.1 Receptors and Receptive Fields © 2012 Pearson Education, Inc. Receptive fields Receptive field 1 Receptive field 2
- 5. Receptors • Receptor specificity — each receptor responds to one type of stimulus • Receptive field — the area that a receptor monitors • Tonic receptors — always send signals, thus information is based on the frequency of the action potentials • Phasic receptors — send action potentials only if stimulated • Peripheral adaptation — receptors may stop sending AP even if the stimulus is still present • Central adaptation — CNS ignoring a AP from a receptor © 2012 Pearson Education, Inc.
- 6. The General Senses • Classification of the General Senses • One classification scheme: • Exteroceptors: provide information about the external environment • Proprioceptors: provide information about the position of the body • Interoceptors: provide information about the inside of the body © 2012 Pearson Education, Inc.
- 7. The General Senses • Sensory Limitations • Humans do not have receptors for every possible stimulus. • Our receptors have characteristic ranges of sensitivity. • A stimulus must be interpreted by the CNS. Our perception of a particular stimulus is an interpretation and not always a reality. © 2012 Pearson Education, Inc.
- 8. The General Senses • Receptors for general senses classified by location: • Exteroceptors provide information about the external environment. • Proprioceptors monitor body position. • Interoceptors monitor conditions inside the body. • Receptors for general senses classified by type of stimulus: • Nociceptors = tissue damage • Thermoreceptors = change in temperature • Mechanoreceptors = physical distortion, contact, or pressure • Chemoreceptors = chemical composition of body fluids © 2012 Pearson Education, Inc.
- 9. The General Senses • Mechanoreceptors • Encapsulated tactile receptors • Tactile corpuscle: common on eyelids, lips, fingertips, nipples, and genitalia • Ruffini corpuscle: in the dermis, sensitive to pressure and distortion • Lamellated corpuscle: consists of concentric cellular layers / sensitive to vibrations © 2012 Pearson Education, Inc.
- 10. Figure 18.3e Tactile Receptors in the Skin Sensory nerve fiber Collagen fibers © 2012 Pearson Education, Inc. Ruffini corpuscle Lamellated corpuscle Capsule Dendrites Ruffini corpuscle Hair Root hair plexus Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 11. Figure 18.3f Tactile Receptors in the Skin Ruffini corpuscle Lamellated corpuscle Lamellated corpuscle LM ´ 125 Lamellated corpuscle © 2012 Pearson Education, Inc. Dermis Dendritic process Accessory cells (specialized fibrocytes) Concentric layers (lamellae) of collagen fibers separated by fluid Concentric layers (lamellae) of collagen fibers separated by fluid Dendritic process Hair Root hair plexus Merkel cells and tactile discs Tactile corpuscle Free nerve ending Sensory nerves
- 12. Figure 18.4 Baroreceptors and the Regulation of Autonomic Functions Baroreceptors of Digestive Tract Provide information on volume of tract segments, trigger reflex movement of materials along tract Baroreceptors of Bladder Wall Provide information on volume of urinary bladder, trigger urinary reflex © 2012 Pearson Education, Inc. Baroreceptors of Carotid Sinus and Aortic Sinus Provide information on blood pressure to cardiovascular and respiratory control centers Baroreceptors of Lung Provide information on lung stretching to respiratory rhythmicity centers for control of respiratory rate Baroreceptors of Colon Provide information on volume of fecal material in colon, trigger defecation reflex
- 13. Figure 18.5 Chemoreceptors Blood vessel Chemoreceptive neurons Carotid body LM ´ 1500 © 2012 Pearson Education, Inc. Trigger reflexive adjustments in depth and rate of respiration Trigger reflexive adjustments in respiratory and cardiovascular activity Via cranial nerve IX Via cranial nerve X Chemoreceptors in and near Respiratory Centers of Medulla Oblongata Sensitive to changes in pH and PCO2 in cerebrospinal fluid Chemoreceptors of Carotid Bodies Sensitive to changes in pH, PCO2, and PO2 in blood Chemoreceptors of Aortic Bodies Sensitive to changes in pH, PCO2, and PO2 in blood
- 14. The Special Senses • The special senses include: • Olfaction (smell) • Gustation (taste) • Equilibrium • Hearing • Vision © 2012 Pearson Education, Inc.
- 15. Olfaction (Smell) • Olfaction • Olfactory organs • Nasal cavity • Olfactory epithelium • Bipolar olfactory receptors (N I) • Supporting cells • Basal cells (stem cells) • Lamina propria • Olfactory glands (Bowman’s glands) • Blood vessels • Nerves (axons of N I) © 2012 Pearson Education, Inc.
- 16. Figure 18.6a The Olfactory Organs Olfactory bulb Olfactory nerve fibers (N I) Olfactory tract Cribriform plate of ethmoid Olfactory epithelium The distribution of the olfactory receptors on the left side of the nasal septum is shown by the shading. © 2012 Pearson Education, Inc.
- 17. Figure 18.6b The Olfactory Organs Olfactory nerve fibers Developing olfactory receptor cell Olfactory receptor cell Supporting cell Mucous layer © 2012 Pearson Education, Inc. Substance being smelled Cribriform plate Lamina propria Olfactory epithelium A detailed view of the olfactory epithelium Knob Olfactory cilia: surfaces contain receptor proteins To olfactory bulb Olfactory (Bowman’s) gland Regenerative basal cell: divides to replace worn-out olfactory receptor cells
- 18. Gustation (Taste) • Gustation • The tongue consists of papillae • Papillae consist of taste buds • Taste buds consist of gustatory cells • Each gustatory cell has a slender microvilli that extends through the taste pore into the surrounding fluid © 2012 Pearson Education, Inc.
- 19. Gustation (Taste) • Gustation Pathways • Dissolved chemicals contact the taste hairs (microvilli) • Impulses go from the gustatory cell through CN VII, IX, and X • The impulses eventually arrive at the cerebral cortex © 2012 Pearson Education, Inc.
- 20. Figure 18.8 Gustatory Pathways © 2012 Pearson Education, Inc. Gustatory cortex Thalamic nucleus Medial lemniscus Nucleus solitarius Vagus nerve (N X) Facial nerve (N VII) Glossopharyngeal nerve (N IX)
- 21. Gustation (Taste) Gustatory receptors are clustered in taste buds, which contain gustatory cells that extend taste hairs through a taste pore. Three types of papillae (epithelial projections) on human tongue: Filiform Fungiform Circumvallate Four primary tastes: Salty Bitter Sweet Sour Also water and umami (characteristic of broth) © 2012 Pearson Education, Inc.
- 22. © 2012 Pearson Education, Inc.
- 23. Equilibrium and Hearing The Ear External ear Middle ear Auditory ossicles Auditory tube Inner ear Vestible and semicircular canals Equilibrium Cochlea Hearing ANIMATION The Ear: Ear Anatomy © 2012 Pearson Education, Inc.
- 24. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle © 2012 Pearson Education, Inc. Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea Vestibulocochlear nerve (N VIII) Bony labyrinth of inner ear To nasopharynx
- 25. Figure 18.9 Anatomy of the Ear EXTERNAL EAR MIDDLE EAR INNER EAR Auricle © 2012 Pearson Education, Inc. Auditory ossicles Semicircular canals Petrous part of temporal bone Facial nerve (N VII) External acoustic meatus Elastic cartilage Tympanic membrane Tympanic cavity Oval window Round window Vestibule Auditory tube Cochlea Vestibulocochlear nerve (N VIII) Bony labyrinth of inner ear To nasopharynx
- 26. Figure 18.12a Semicircular Canals and Ducts © 2012 Pearson Education, Inc. Utricle Saccule Vestibular duct Cochlear duct Semicircular canal Anterior view of the bony labyrinth cut away to show the semicircular canals and the enclosed semicircular ducts of the membranous labyrinth Tympanic duct Membranous labyrinth Cristae within ampullae Maculae Organ of Corti Cochlea Endolymphatic sac Bony labyrinth KEY Vestibule Anterior Lateral Posterior Semicircular ducts
- 27. Figure 18.13 The Function of the Semicircular Ducts, Part I Anterior Ampulla Posterior Lateral Anterior view of the maculae and semicircular ducts of the right side A section through the ampulla of a semicircular duct Ampulla filled with endolymph Hair cells Semicircular duct Utricle Endolymph movement along the length of the duct moves the cupula and stimulates the hair cells. © 2012 Pearson Education, Inc. Displacement in this direction inhibits hair cell Saccule Maculae Displacement in this direction stimulates hair cell Kinocilium Stereocilia Hair cell Sensory nerve ending Supporting cell Structure of a typical hair cell showing details revealed by electron microscopy. Bending the stereocilia toward the kinocilium depolarizes the cell and stimulates the sensory neuron. Displacement in the opposite direction inhibits the sensory neuron. At rest Ampulla Direction of duct rotation Direction of relative endolymph movement Direction of duct rotation Crista Cupula Supporting cells Sensory nerve Semicircular ducts Vestibular branch (N VIII) Cochlea Endolymphatic sac Endolymphatic duct
- 28. Figure 18.15ab The Maculae of the Vestibule © 2012 Pearson Education, Inc. A scanning electron micrograph showing the crystalline structure of otoliths Otolith Detailed structure of a sensory macula Gelatinous material Statoconia Hair cells Nerve fibers Statoconia Otolith
- 29. Figure 18.16 Neural Pathways for Equilibrium Sensations Semicircular canals © 2012 Pearson Education, Inc. Vestibular ganglion Vestibular branch Vestibule Cochlear branch Vestibulocochlear nerve (N VIII) Vestibulospinal tracts Vestibular nucleus To cerebellum To superior colliculus and relay to cerebral cortex Red nucleus N III N IV N VI N XI
- 30. Equilibrium and Hearing • The Cochlea • Consists of “snail-shaped” spirals • Spirals coil around a central area called the modiolus • Within the modiolus are sensory neurons • The sensory neurons are associated with CN VIII • Organ of Corti © 2012 Pearson Education, Inc.
- 31. © 2012 Pearson Education, Inc.
- 32. Figure 18.17ab The Cochlea and Organ of Corti Structure of the cochlea within the temporal bone showing the turns of the vestibular duct, cochlear duct, and tympanic duct © 2012 Pearson Education, Inc. Round window Stapes at oval window Semicircular Cochlear branch Vestibular branch Structure of the cochlea in partial section KEY canals From oval window to tip of spiral From tip of spiral to round window Vestibulocochlear nerve (VIII) Cochlear duct Vestibular duct Tympanic duct Apical turn Spiral ganglion Modiolus Vestibular membrane Tectorial membrane Basilar membrane Middle turn Vestibular duct (scala vestibuli—contains perilymph) Organ of Corti Cochlear duct (scala media—contains endolymph) Tympanic duct (scala tympani—contains perilymph) Basal turn Temporal bone (petrous part) Cochlear nerve From oval To round Vestibulocochlear nerve (VIII) window window
- 33. Figure 18.17d–f The Cochlea and Organ of Corti Bony cochlear wall Vestibular duct Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Tympanic duct Organ of Corti Diagrammatic and histological sections through the receptor hair cell complex of the organ of Corti A color-enhanced SEM showing a portion of the receptor surface of the organ of Corti © 2012 Pearson Education, Inc. Three-dimensional section showing the detail of the cochlear chambers, tectorial membrane, and organ of Corti Spiral ganglion Cochlear branch of N VIII Cochlear duct (scala media) Vestibular membrane Tectorial membrane Tympanic duct (scala tympani) Basilar membrane Hair cells of organ of Corti Spiral ganglion cells of cochlear nerve Organ of Corti LM ´ 125 Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers Stereocilia of inner hair cells Stereocilia of outer hair cells Surface of the organ of Corti SEM ´ 1320
- 34. Figure 18.17de The Cochlea and Organ of Corti Three-dimensional section showing the detail of the cochlear chambers, tectorial membrane, and organ of Corti Diagrammatic and histological sections through the receptor hair cell complex of the organ of Corti © 2012 Pearson Education, Inc. Bony cochlear wall Vestibular duct Vestibular membrane Cochlear duct Tectorial membrane Basilar membrane Tympanic duct Organ of Corti Spiral ganglion Cochlear branch of N VIII Cochlear duct (scala media) Vestibular membrane Tectorial membrane Tympanic duct (scala tympani) Basilar membrane Hair cells of organ of Corti Spiral ganglion cells of cochlear nerve Organ of Corti LM ´ 125 Tectorial membrane Outer hair cell Basilar membrane Inner hair cell Nerve fibers
- 35. Figure 18.18 Pathways for Auditory Sensations Auditory cortex (temporal lobe) High-frequency Motor output to cranial nerve nuclei Low-frequency sounds Medial geniculate nucleus (thalamus) © 2012 Pearson Education, Inc. KEY Low-frequency sounds High-frequency sounds First-order neuron Second-order neuron Third-order neuron Fourth-order neuron Cochlea Cochlear branch To ipsilateral auditory cortex Vestibulocochlear nerve (N VIII) Vestibular branch Cochlear nuclei Superior olivary nucleus Motor output to spinal cord through the tectospinal tracts Inferior colliculus (mesencephalon) sounds Thalamus
- 36. Vision Accessory Structures Eyelids Lacrimal apparatus Eye Fibrous tunic Vascular tunic Neural tunic Chambers of the eye Visual pathways © 2012 Pearson Education, Inc.
- 37. Figure 18.19a Accessory Structures of the Eye, Part I Lateral canthus Sclera Corneal limbus Pupil Superficial anatomy of the right eye and its accessory structures © 2012 Pearson Education, Inc. Eyelashes Palpebra Palpebral fissure Medial canthus Lacrimal caruncle
- 38. Figure 18.19c Accessory Structures of the Eye, Part I Tendon of superior oblique muscle Lacrimal punctum Superior lacrimal canaliculus Medial canthus Inferior lacrimal canaliculus Lacrimal sac Nasolacrimal duct Inferior nasal concha Superior rectus muscle Lacrimal gland ducts Lacrimal gland Lateral canthus Lower eyelid Inferior rectus muscle Diagrammatic representation of a deeper dissection of the right eye showing its position within the orbit and its relationship to accessory structures, especially the lacrimal apparatus © 2012 Pearson Education, Inc. Opening of nasolacrimal duct Inferior oblique muscle
- 39. Figure 18.21ab Sectional Anatomy of the Eye Fibrous tunic (sclera) Vascular tunic (choroid) The three layers, or tunics, of the eye Neural tunic (retina) © 2012 Pearson Education, Inc. Major anatomical landmarks and features in a diagrammatic view of the left eye Central retinal artery and vein Optic nerve Optic disc Fovea Posterior cavity (Vitreous chamber filled with the vitreous body) Retina Choroid Sclera Ora serrata Fornix Palpebral conjunctiva Ocular conjunctiva Ciliary body Anterior chamber (filled with aqueous humor) Lens Pupil Cornea Iris Posterior chamber (filled with aqueous humor) Corneal limbus Suspensory ligaments
- 40. Figure 18.23a Retinal Organization © 2012 Pearson Education, Inc. Histological organization of the retina. Note that the photoreceptors are located closest to the choroid rather than near the vitreous chamber. LIGHT Amacrine cell Horizontal cell Cone Rod Choroid Pigmented part of retina Rods and cones Bipolar cells Ganglion cells Nuclei of ganglion cells Nuclei of rods and cones Nuclei of bipolar cells The retina LM ´ 70
- 41. Figure 18.24 Pigmented epithelium Suspensory ligaments Posterior cavity (vitreous chamber) © 2012 Pearson Education, Inc. Lens Ciliary process Choroid Retina Anterior chamber Canal of Schlemm Body of iris Ciliary body Conjunctiva Sclera Posterior chamber Anterior cavity Cornea Pupil
- 42. Figure 18.21d Sectional Anatomy of the Eye Dura mater Retina Choroid Sclera Sagittal section through the eye © 2012 Pearson Education, Inc. Ora serrata Conjunctiva Cornea Lens Anterior chamber Iris Posterior chamber Suspensory ligaments Ciliary body Posterior cavity (vitreous chamber) Optic nerve (N II)
- 43. Figure 18.21e Sectional Anatomy of the Eye Lacrimal punctum Lacrimal caruncle Medial canthus Nose Visual axis Ciliary Lens processes Ciliary body Ora serrata Fovea Ethmoidal labyrinth Medial rectus muscle Optic disc Optic nerve Central artery Orbital fat Sagittal section through the eye and vein © 2012 Pearson Education, Inc. Anterior cavity Posterior chamber Anterior chamber Edge of pupil Cornea Iris Suspensory ligament of lens Corneal limbus Conjunctiva Lower eyelid Lateral canthus Sclera Choroid Retina Posterior cavity Lateral rectus muscle
- 44. Figure 18.26 Anatomy of the Visual Pathways, Part II © 2012 Pearson Education, Inc. LEFT SIDE RIGHT SIDE Left eye only Right eye only Binocular vision Optic nerve (N II) Optic chiasm Optic tract Other hypothalamic nuclei, pineal gland, and reticular formation Suprachiasmatic nucleus Superior colliculus Lateral geniculate nucleus Projection fibers (optic radiation) Lateral geniculate nucleus RIGHT CEREBRAL HEMISPHERE LEFT CEREBRAL HEMISPHERE Visual cortex of cerebral hemispheres