The Special Senses A. Visual sensations 1. Accessory structures of the eye 1. Accessory structures of the eye 2. Anatomy of the eyeball 2. Anatomy of the eyeball a. Fibrous tunic a. Fibrous tunic b. Vascular tunic b. Vascular tunic c. Retina (nervous tunic) c. Retina (nervous tunic) d. Lens d. Lens e. Interior of the eyeball e. Interior of the eyeball 3. Image formation 3. Image formation a. Refraction of light rays a. Refraction of light rays b. Accommodation and near point of vision b. Accommodation and near point of vision c. Constriction of the pupil c. Constriction of the pupil 4. Convergence 4. Convergence 5. Physiology of vision a. Photoreceptors and a. Photoreceptors and photopigments photopigments b. Receptor potential and b. Receptor potential and neurotransmitter release neurotransmitter release 6. Visual pathway 6. Visual pathway B. Auditory sensations 1. External (outer) ear 1. External (outer) ear 2. Middle ear 2. Middle ear 3. Internal (inner) ear 3. Internal (inner) ear 4. Physiology of hearing 4. Physiology of hearing 5. Physiology of equilibrium 5. Physiology of equilibrium

Surface Anatomy and Accessory Structures of the Eye 1. eyelids 2. eyelashes 3. eyebrows 4. extrinsic eye muscles 5. lacrimal apparatus

Lacrimal Apparatus 1. lacrimal gland 2. lacrimal ducts 3. lacrimal puncta 4. lacrimal canals 5. nasolacrimal duct

Anatomy of the Eyeball 1. fibrous tunic a. cornea a. cornea b. sclera b. sclera_______________ canals of Schlemm Sclera pupil iris

Anatomy of the Eyeball Con’t 2. vascular tunic a. choroid a. choroid b. ciliary body b. ciliary body (1) ciliary muscle (1) ciliary muscle (2) ciliary processes (2) ciliary processes c. iris c. iris (1) sphinctor pupillae (1) sphinctor pupillae (2) dilator pupillae (2) dilator pupillae Dilator pupillae Sphinctor pupillae Constriction Dilation

Anatomy of the Eyeball Con’t 3. nervous tunic (retina) a. pigmented layer a. pigmented layer b. nervous layer b. nervous layer Terms: fovea centralis optic disc optic disc (blind spot) (blind spot)

Anatomy of the Eyeball, Con’t 3. b. nervous layer (1) photoreceptor layer (1) photoreceptor layer (a) rods (a) rods (b) cones (b) cones (2) bipolar layer (2) bipolar layer (a) bipolar cells (a) bipolar cells (b) amacrine cells (b) amacrine cells (c) horizontal cells (c) horizontal cells (3) ganglion cell layer (3) ganglion cell layer

Lens 1. biconvex 2. crystallins 3. suspensory ligaments 4. focuses light Ciliary body Ciliary Processes lens Suspensory ligaments Canals of Schlemm iris

Cavities of the Eye 1. anterior cavity a. posterior chamber a. posterior chamber b. anterior chamber b. anterior chamber c. aqueous humor c. aqueous humor d. fluid flow d. fluid flow e. canals of Schlemm e. canals of Schlemm f. intraocular pressure f. intraocular pressure Anterior Chamber Posterior Chamber 2. posterior cavity a. vitreous humor b. tugor c. not replaced

The formation of images on the retina involves three processes: 1. refraction of light rays 2. accommodation of the lens 3. constriction of the pupil

Refraction of Light 1. light passes through different media different media 2. light bends at interfaces interfaces 3. 60% at cornea 4. 40% by lens

Accomodation 1. biconvex lens 2. point of intersection 3. near object = more convex 4. far object = less convex 5. role of ciliary muscle

Constriction of the Pupil 1. part of accommodation reflex 2. limits peripheral light

Convergence of the Eyes 1. single binocular vision 2. corresponding points 3. complementary photoreceptors 4. near vision = medial rotation of eyes

The Visual Process

Photoreceptors 1. central fovea 2. visual axis 3. rods and cones 4. outer segments 5. visual pigments 6. glutamate 7. dark vs light conditions conditions

Visual Acuity Rod cells not present in central fovea increase in concentration to ora serrata dim light and peripheral vision 100% cone cells in central fovea diminish in number toward ora serrata three different types: blue, red, green cone cells bright light required to break pigments 1:1 relationship with bipolar cells visual acuity and color vision 6 – 600 rod cells converge on 1 bipolar cell, as well as amacrine and horizontal cells. Cone cells

Photoreceptors

DARK rod cell Na+ channels open membrane depolarizes Na+ inflow stimulates glutamate release glutamate inhibits bipolar cells LIGHT rod cell Na+ channels close membrane hyperpolarizes no Na+ inflow prevents glutamate release bipolar cells initiate action potential visual pathway started X DARK VERSUS LIGHT CONDITIONS

Dark versus light conditions

The Visual Pathway The visual pathway begins with stimulation of the bipolar neurons by photoreceptor cells rod cells converge on 1 bipolar cell, as well as amacrine and horizontal cells 2. Cone cells have a 1:1 relationship with bipolar cells

Visual Pathway 1. bipolar cells 2. ganglion cells 3. optic nerve (II) 4. optic chiasma a. medial retina vs a. medial retina vs b. lateral retina b. lateral retina 5. optic tracts 6. thalamus 7. optic radiations 8. primary visual areas

Hearing and Equilibrium

External Ear Auricle (pinna) External auditory meatus Tympanic membrane Ceruminous glands

Middle Ear 1. petrous portion of temporal bone temporal bone 2. mastoid air cells 3. auditory tube 4. ossicles ________________ 5. oval window 6. round window

Auditory Ossicles 1. malleus 2. incus 3. stapes ____________stapedius tensor tympani

Internal Ear 1. bony labyrinth a. 3 semicircular canals a. 3 semicircular canals (1) frontal (1) frontal (2) horizontal (2) horizontal (3) sagittal (3) sagittal b. vestibule b. vestibule c. cochlea c. cochlea________________perilymph

Internal Ear 1. bony labyrinth a. 3 semicircular canals a. 3 semicircular canals (1) frontal (1) frontal (2) horizontal (2) horizontal (3) sagittal (3) sagittal b. vestibule b. vestibule c. cochlea c. cochlea________________perilymph

Internal Ear 2. membranous labyrinth a. 3 semicircular ducts a. 3 semicircular ducts b. utricle and saccule b. utricle and saccule c. cochlear duct c. cochlear duct_________________endolymph

Cochlea 1. scala vestibuli 2. scala tympani 3. scala media (cochlear duct) (cochlear duct)

Cochlea 1. scala vestibuli 2. scala tympani 3. scala media (cochlear duct) (cochlear duct) 4. vestibular membrane 5. basilar membrane 6. spiral organ of Corti 7. 16,000 hair cells 8. tectorial membrane

Physiology of Hearing

How do you detect differences in pitch?

Physiology of Equilibrium 1. static equilibrium (saccule and utricle) perception of head orientation when the perception of head orientation when the body is stationary body is stationary 2. dynamic equilibrium (mainly semicircular ducts) perception of motion or acceleration (linear vs angular) *linear acceleration- utricle and saccule (linear vs angular) *linear acceleration- utricle and saccule

Static Equilibrium 1. utricle and saccule 2. hair cells 3. otoliths of macula 4. inertia

Dynamic Equilibrium 1. semicircular ducts 2. hair cells 3. ampullae 4. cupula 5. inertia