Chapter 17 The Special Senses Lecture Outline Five special senses Olfaction = smell Gustation = taste Vision = sight Hearing Equilibrium Special sensory receptors: 1. Distinct cells 2. Complex organ / unique epithelium Olfaction Organ: Olfactory epithelium Location: Nasal cavity Superior nasal conchae Cribriform plate Components: 1. Olfactory receptor cells Bipolar neurons Odorants 2. Supporting cells Simple columnar epithelium 3. Basal cells Stem cells 4. Lamina propria Areolar connective tissue Olfactory glands Mucus Receptor cells Dendrite Knob Olfactory cilia Mucus Odorant binding proteins Odorants Axon = olfactory nerve Olfactory foramina Cribriform plate Olfactory bulb 1. odorant + odorant binding protein, cilia 2. G protein adenylate cyclase 3. ATP camp 4. Na + channels open depolarization 5. action potential olfactory bulbs 6. olfactory tracts a. olfactory cortex b. hypothalamus & limbic system Convergence Central adaptation Disorders Uncinate fits Anosmias Gustation Organ: Taste buds Location: Lingual papillae Oral surfaces Components: 1. Gustatory cells Epithelium Gustatory hairs Tastants Sensory dendrites 2. Basal cells Stem cell Taste pore Primary taste sensations: Cravings: 1. Sweet Carbohydrates 2. Sour Vitamin C 3. Salty Minerals 4. Bitter Defense 5. Umami (Glutamate) Protein 1. tastant in saliva taste pore 2. bind gustatory hair 3. neurotransmitter release sensory dendrites 4. action potentials solitary nucleus Facial nerve (VII) Glossopharyngeal (IX) Vagus (X) 5. thalamus a. gustatory cortex b. hypothalamus & limbic system Salt & sour receptors: chemically gated ion channel Sweet, bitter, umami receptors: G protein second messenger Central adaptation Vision Organ: Eyes: photoreceptors Accessory structures: 1. Eyebrows 2. Eyelids A. Lacrimal caruncle Sebaceous & sweat glands B. Eye lashes C. Tarsal glands Sebaceous glands Sty 3. Conjunctiva Mucous membrane Conjunctivitis 4. Lacrimal apparatus A. Lacrimal gland Lacrimal fluid Mucus Antibodies Lysozyme Amy Warenda Czura, Ph.D. 1 SCCC BIO130 Chapter 17 Handout
B. Lacrimal canaliculi Nasolacrimal duct 5. Extrinsic eye muscles Diplopia Strabismus Eye 1. Fibrous tunic Dense connective tissue A. Sclera B. Cornea Corneal transplant 2. Vascular tunic / Uvea Blood & lymphatic vessels A. Choroid Melanocytes B. Ciliary body Circular smooth muscle Lens Suspensory ligaments Fluid anterior chamber C. Iris Smooth muscle & elastic fibers Pupil Parasympathetic = decrease Sympathetic = increase Melanin 3. Neural tunic / Retina A. Pigmented layer Simple cuboidal epithelium Melanin Vitamin A Phagocytic B. Neural layer 1. Photoreceptors a. Rods b. Cones 2. Horizontal cells 3. Bipolar cells 4. Amacrine cells 5. Ganglion cells Optic disc Macula lutea Fovea centralis Macular degeneration Detached retina 4. Cavities / Segments A. Posterior cavity Vitreous humor Floaters B. Anterior cavity Iris Aqueous humor Ciliary body Scleral venous sinus Glaucoma 5. Lens Crystalin proteins Suspensory ligaments Cataract Vision Physiology Visible light: 380-750 nm Photons Refraction Focal Point Focal distance 1. distance to lens 2. shape of lens Focusing Accommodation: 6m - 10cm Presbyopia Myopia Hyperopia Astigmatism Radial keratotomy Visual acuity 20/20 = normal 20/15 = better 20/200 = legally blind Photoreception 1. Photoreceptors A. Inner segment B. Outer segment Visual pigments 2. Visual pigment = rhodopsin A. Retinal Vitamin A B. Opsin Protein Cis Trans Photobleaching / bleaching Rods: all photons = gray Cones 1. Blue: 420nm 2. Green: 530nm 3. Red: 560nm Color blindness 1. dark cgmp Na + channels open depolarization neurotransmitter release 2. photon a. cis trans retinal b. active PDE c. cgmp off Na + channels close d. hyperpolarization no neurotransmitter e. EPSP f. horizontal cells inhibit or facilitate g. bipolar cells ganglion cells h. amacrine cells Amy Warenda Czura, Ph.D. 2 SCCC BIO130 Chapter 17 Handout
inhibit or facilitate i. action potential 3. optic nerve A. Superior colliculi B. Suprachiasmatic nucleus C. Thalamus 1. visual cortex 2. visual association areas Rods: convergence (grainy) Cones: little convergence (sharp) Hearing and Equilibrium Organ: Ears: hair cells Ear 1. External ear A. Auricle / Pinna B. External auditory canal Ceruminous glands Cerumen C. Tympanic membrane 2. Middle ear A. Auditory ossicles 1. Malleus 2. Incus 3. Stapes B. Auditory tube C. Muscles 1. Tensor tympani 2. Stapedius 3. Inner ear A. Semicircular canals Vestibule Vestibular complex / apparatus Equilibrium receptor cells Endolymph B. Cochlea Oval window Round window Organ of corti Perilymph Hearing Sound 1. Frequency Hertz (Hz) Pitch 2. Intensity Decibels (db) Volume Organ: Organ of corti Hair cells Tectorial membrane Basilar membrane Supporting cells Perilymph Stereocilia Mechanoreceptor Sound transmission & signaling 1. Sound external auditory canal tympanic membrane 2. malleus incus stapes 3. oval window perilymph in cochlea 4. distortion of basilar membrane sterocilia brush tectorial membrane 5. ion channels open depolarization 6. EPSP spiral ganglion 7. vestibulochochlear nerve A. inferior colliculi B. thalamus auditory cortex pitch: depth into cochlea volume: number of cells Deafness Conduction deafness Otosclerosis Sensorineural defaness Tinnitus Equilibrium and Orientation Vestibular apparatus / complex Maculae + Crista ampullaris 1. Static equilibrium Organ: Maculae 1. Supporting cells 2. Hair cells Stereocilia Kinocilium 3. Otolithic membrane Otoliths 1. hair cells neurotransmitter (signal) 2. acceleration otolithic membrane distortion 3. bend stereocilia & kinocilium 4. increase signalling 5. EPSP vestibular ganglion 2. Dynamic equilibrium Organ: Crista ampullaris 1. Supporting cells 2. Hair cells 3. Cupula Endolymph 1. hair cells neurotransmitter (signal) 2. rotation endolymph waves 3. cupula bend stereocilia & kinocilium 4. increase signaling 5. EPSP vestibular ganglion Maculae & Crista ampullaris info Vestibulocochlear nerve A. Cerebellum B. Vestibular nuclei in brainstem Nystagmus Vertigo Amy Warenda Czura, Ph.D. 3 SCCC BIO130 Chapter 17 Handout
Motion sickness Amy Warenda Czura, Ph.D. 4 SCCC BIO130 Chapter 17 Handout
Olfactory 1. Odorant binds odorant binding protein on olfactory receptor cell cilia in mucus 2. G-protein is activated which activates adenylate cyclase 3. ATP is converted into camp 4. camp causes sodium channels to open resulting in depolarization 5. If threshold is reached an action potential is transmitted to the olfactory bulbs 6. The nervous impulse from the olfactory bulbs travels down the olfactory tracts to be routed to: a. olfactory cortex of the temporal lobe of the cerebrum for interpretation (* smell is the only type of sensory info that reaches the cerebral cortex without first synapsing in the thalamus: no sensory dampening!) b. hypothalamus and limbic systems to elicit emotional response to odors -the signaling can also stimulate reflexes for salivation, digestive secretion, sneezing and coughing -olfactory pathways converge and are subject to rapid central adaptation Amy Warenda Czura, Ph.D. 5 SCCC BIO130 Chapter 17 Handout
Gustatory 1. Tastant must be dissolved in saliva and diffuse into the taste pore 2. Tastant binds chemoreceptors on the gustatory hair of a mature gustatory cell 3. The gustatory cell releases neurotransmitters to signal sensory dendrites around it 4. If threshold is reached, action potentials will be transmitted along the facial nerve (VII), the glossopharyngeal nerve (IX), or the vagus nerve (X) (depending on taste bud location), to the solitary nucleus of the medulla oblongata 5. The information is passed to the thalamus for screening and routing to: a. gustatory cortex in the insula of the cerebrum: gustatory information is correlated with other sensory input from other receptors (olfactory receptors, thermoreceptors, mechanoreceptors, and nociceptors) for interpretation (80% of taste is smell!) b. hypothalamus and limbic system to elicit emotional reaction to taste -signaling can also trigger reflexes to stimulate digestive activity Salt and Sour receptors are chemically gated ion channels: they release neurotransmitters rapidly upon binding tastant Sweet, Bitter, and Umami receptors are G-proteins that work through second messengers: release of neurotransmitter is slower The threshold necessary for stimulation of the neural pathway varies with the receptor and person but everyone is generally more sensitive to bitter and acid Gustation pathways undergo rapid central adaptation Amy Warenda Czura, Ph.D. 6 SCCC BIO130 Chapter 17 Handout
Accessory Structures of the Eye -protect or aid function of eye 1. Eyebrows -shade from sun -prevent perspiration trickling in 2. Eyelids -blink via reflexes: every 3-7sec or in response to threat -keep eye surface lubricated and free of dust by spreading glandular secretions A. Lacrimal caruncle -medial corner -contains sebaceous and sudoriferous glands that produce secretions to lubricate eye surface B. Eyelashes -hairs along free margin of each lid -hair root plexus receptors trigger defensive blinking -prevent entry of foreign material into eye C. Tarsal glands -associated with eyelashes -modified sebaceous glands that produce oily secretion to prevent lids from sticking 3. Conjunctiva -transparent mucous membrane -covers anterior surface of eye and interior surface of lids -produces lubricating mucus to keep eyes moist -contains tiny capillaries Conjunctivitis = inflammation of conjunctiva due to microbial infection (pink eye) 4. Lacrimal apparatus -lacrimal gland located lateral and superior to eye -produces lacrimal fluid to cleanse and protect eye surface -lacrimal fluid (tears) contains: a. mucus - lubrication b. antibodies - immune defense against microbes c. lysozyme - enzyme that lyses bacteria -lacrimal fluid from gland flows down across eye surface, is collected in lacrimal canaliculi in medial corner of eye, and is drained to nasal cavity via nasolacrimal duct 5. Extrinsic eye muscles -six strap-like skeletal muscles that originate on the orbit and insert on the outer surface of the eye -motor units consist of only 2-12 fibers -function to provide precise and rapid movement of the eyes Amy Warenda Czura, Ph.D. 7 SCCC BIO130 Chapter 17 Handout
Visual 1. In the dark: cgmp opens sodium channels causing constant depolarization to -40mV, depolarization causes neurotransmitter release 2. Light photon strikes rhodopsin: A. cis retinal trans retinal + release of opsin B. opsin activates phosphodiesterase (PDE) C. PDE breaks down cgmp, Na + channels close D. photoreceptor cells hyperpolarize to -70mV, neurotransmitter release stops E. lack of neurotransmitter triggers EPSP on post synaptic bipolar cell F. synapse is facilitated or inhibited by the horizontal cells G. facilitated bipolar cells trigger EPSP on the ganglion cells H. the synapse is facilitated or inhibited by the amacrine cells I. facilitated ganglion cells trigger an action potential 3. Impulse travels down the optic nerve to be diverged to three locations: A. superior colliculi of mesencephalon to initiate visual reflexes B. suprachiasmatic nucleus of hypothalamus to set circadian rhythms C. thalamus for screening and routing to the primary visual cortex in the occipital lobes, and visual association areas throughout the cerebral cortex for interpretation Rods undergo extensive convergence in the retina: 130million rods 6million bipolar cells 1million ganglion cells (M cells) = vision grainy and blurred Cones show little convergence to their ganglion cells (P cells) resulting in perceptions of color, fine detail, and crisp distinct edges Amy Warenda Czura, Ph.D. 8 SCCC BIO130 Chapter 17 Handout
Sound Transmission and Auditory 1. Sound waves in the air enter the external auditory canal and vibrate the tympanic membrane 2. The tympanic membrane vibrates the malleus which vibrates the incus which vibrates the stapes 3. The stapes vibrates the oval window (20x greater volume = amplification of sound) which creates waves in the perilymph in the cochlea 4. Pressure waves distort the basilar membrane causing the hair cell cilia to brush against the tectorial membrane 5. Flexion of the stereocilia opens ion channels causing depolarization of the hair cell 6. An EPSP is transmitted to the sensory neurons of the spiral ganglion 7. Axons of the spiral ganglion transmit action potentials along the vestibulocochlear nerve to be diverged to: A. inferior colliculi of the mesencephalon to initiate auditory reflexes B. the thalamus for screen and routing to the auditory cortex in the temporal lobe of the cerebrum for interpretation Pitch is determined by the regions of basilar membrane vibrated: low frequency sounds travel further into the cochlea Volume is determined by the number of hair cells stimulated: high volumes stimulate more hair cells Amy Warenda Czura, Ph.D. 9 SCCC BIO130 Chapter 17 Handout
Static Equilibrium receptors = maculae, housed in the vestibule -respond to linear acceleration forces maculae components: 1. supporting cells: simple columnar epithelium 2. hair cells = equilibrium receptor -apical surface has hairs consisting of many sterocilia and on long kinocilium 3. otolithic membrane -jelly-like membrane containing otoliths (stones of calcium carbonate) -has the cilia of the hair cells embedded in it 1. Hair cells in maculae release low levels of neurotransmitter continuously 2. Upon acceleration, otoliths lag behind distorting the otolithic membrane 3. Membrane distortion bends stereocilia and kinocilia of the hair cells 4. from the hair cells increases 5. EPSPs reach threshold on the neurons of the vestibular ganglion 6. (see dynamic equilibrium signaling for routing to CNS) Amy Warenda Czura, Ph.D. 10 SCCC BIO130 Chapter 17 Handout
Dynamic Equilibrium receptors = crista ampullaris housed in the semicircular canals (one in each canal/plane) -respond to angular/rotational movements crista ampullaris components: 1. supporting cells: simple columnar epithelium 2. hair cells = equilibrium receptor -apical surface has hairs consisting of many sterocilia and on long kinocilium 3. cupula -jelly-like mass that contains the cilia of the hair cells -each crista ampullaris is surrounded by endolymph which fills the semicircular canals 1. Hair cells in crista ampullaris constantly signal at low levels 2. Rotation movements cause waves in the endolymph 3. Waves strike the cupula thus bending the stereocilia and kinocilia of the hair cells 4. Hair cells signal more rapidly 5. EPSPs reach threshold on neurons of the vestibular ganglion 6. Information from both the maculae and crista ampularis is passed to the CNS via the vestibulocochlear nerve to be diverged to: A. cerebellum: coordinates equilibrium with visual and proprioceptor input to direct somatic activity to maintain balance B. vestibular nuclei in mesencephalon: coordinates equilibrium, vision, and proprioception to direct head and eye movements to maintain the line of vision forward Amy Warenda Czura, Ph.D. 11 SCCC BIO130 Chapter 17 Handout