Lecture 20Outline of Last Lecture I. Cranial NervesII. Names of the Cranial NervesIII. Functional Grouping of Cranial NervesIV. Visceral Sensory ComponentsV. Visceral Motor FibersVI. Comparing Cranial Nerves and Spinal NervesVII. The Autonomic Nervous SystemOutline of Current LectureI. The eyeII. Accessory structures of the eyeIII. Visual pathwayIV. The earV. Introduction to the circulatory systemCurrent LectureI. The Eye (continued)a. Lensi. Consists of numerous layers of fibersii. Enclosed in a connective tissue capsule iii. Held in place by suspensory ligament iv. Normally transparent v. Divides the eyeball into anterior and posterior segmentsvi. The lens changes shape so that we can focus on nearby objects in the visual field vii. The lens is key to focusing because it is adjustableviii. The elderly get cloudiness in the lens = cataracts b. Vitreous body i. Transparent, jelly-like substance= vitreous humor ii. Fills the posterior segment of the eyeiii. Maintain pressure within the eye 1. hold retina flush against the choroid layerc. the retina forms as an outgrowth of the brainII. accessory structures of the eye (covered in lab)a. eyebrows b. eyelidsc. conjunctivad. lacrimal apparatus III. Visual Pathwaya. Photoreceptors (rod cells, cone cells)b. Bipolar neuronsc. Ganglion neurons; their axons form:i. Optic nerves BIOL_315 1nd Editionii. Optic chiasma: an anterior part of diencephalon; some axons cross over here; relates to depth perception in visioniii. Optic tract: runs along the side of the diencephalond. Lateral geniculate nucleus of the thalamusi. Optic radiation: formed by axons of lateral-geniculate neuronsIV. The eara. Sensory organ of hearing and equilibriumb. Outer eari. Pinna (also called auricle)1. Elastic cartilage covered by skin2. Collects sound waves and directs  eardruma. The soundwaves set the eardrum vibratingii. External auditory canal (meatus)1. Leads from the pinna to the tympanic membrane 2. Lateral 1/3= cartilage3. Medial 2/3 = bonec. middle ear i. middle ear cavity (tympanic cavity)1. hollowed out of petrous portion of the temporal bone2. lined by moist membrane 3. filled with airii. boundaries1. superior: tegem tympani 2. inferior: boney floor3. lateral: tympanic membrane4. medial: oval and round windows5. posterior: mastoid antrum, mastoid air cells, mastoid processa. middle ear infections can spread to the mastoid process6. anterior: opens into the pharyngotympanic tubeiii. Pharyngotympanic tube1. Auditory tube2. Connects the middle ear cavity with the throat3. Lateral 1/3 of its wall is bone4. Medial 2/3 of wall is cartilage 5. Tube is usually closed 6. When open, it functions to equalize air pressure between the atmosphereand the middle ear7. Act as a passageway for infections to spread from the pharynx to the middle ear 8. Shorter and straighter in children , so children tend to have more middle-ear infectionsiv. Ossicles1. 3 tiny bones that extend across the middle ear cavitya. Malleus: attaches to tympanic membrane at one end and the incus at the otherb. Incus: the intermediate bone of the series i. Articulates with the malleus and stapes c. Stapes: the footplate fits into the oval window2. Function to amplify sound wavesa. By about 20 timesb. By transferring force on the larger tympanic membrane  oval window d. Inner Eari. Bony labyrinth: series of interconnected cavities within petrous portion of the temporal bone 1. Secretes a perilymph2. Semicircular canals: 3 rings, 90* to each other, bulbous ends of these canals are the ampullae3. Vestibule: egg shaped cavity, central part of bony labyrinth , communicates with the ampullae and with the cochlea 4. Cochlea: cavity with the shape of a snailii. Membranous labyrinth: continuous series of membrane-walled tubes and sacs lying inside of the bony labyrinth 1. Surrounded by perilymph2. Inside is lined by epithelieum, containing patches of hair cells : receptor cells for hearing and balancea. Hair cells signal the vestibulocochlear nerve 3. Semicircular ducts:a. Inside the semicircular canalsb. 3 of them: posterior, anterior, and lateralc. Have ampullae of their own d. Hair cells are on a ridge: crista within each ampulla i. groups of hear cells are covered with a cap or capula of jelly-like materialii. monitor angular acceleration of the head (head rotation)iii. innervated by vesitbulocochlear nerve4. utricle and sacculea. in the vestibule of the body labyrinth b. utricle communicates with the ampullae of the semicircular ductsc. saccule communicates with the cochlear duct d. each contain a macula: small spot of epithelium containing hair cells i. on each there is a jelly-like mass called an otolithic membrane 1. containing particles of calcium salts called statoconia or otoliths (ear stones)5. cochlear ducta. lies within the cochleab. subdivides into 2 channels: i. scala vestibule: above it ii. scala tympani : below it c. floor: basilar membraned. roof: vestibular membranee. contains the spiral organ of Cortii. stretch of epithelium that houses the hair cells for hearing ii. long apical microvilli are imbedded in an overlying tectorialmembranef. spiral ganglion: neuron cell bodies are within the modiolus iii. auditory pathway in the ear1. sound waves vibrate tympanic membrane2. moves malleolus , incus, and stapes3. vibrating footplat of the stapes pushes on the oval window4. vibrations in perilymph of scala vestibule 5. vibrations pass through vestibular membrane  endolymph 6. cochlear duct  basilar membrane  spiral organ of corti 7. hair cells bend back and forth make impulses in CN VIIIiv. auditory pathway to the brain1. hair cells in the spiral organ2. cochlear neurons of VIII3. synapse on next neuron in cochlear nuclei in the rostral part of the medulla oblongata 4. fibers (some of which crossover) ascend through the brain stem (in a tractcalled the lateral lemniscus)5. some of these fibers synapse in the superior olivary nucleus in the pons or in the inferior colliculus of the midbrain6. most fibers extend up to synapse on the next neurons in the medial geniculate nucleus of the thalamus 7. fibers run from the thalamus to the primary auditory area of the cerebral cortex, in the temporal lobe, Brodmann’s areas 41 and 42Introduction to the Circulatory SystemV. Why do we have a circulatory system? a. To keep the tissue fluid cleanb. The cells expel their wastes into the tissue fluidc. From this fluid they obtain necessary nutrients and oxygend. Circulatory system