8 24 slides 1 hour & 30 min Special Senses

The Special Senses Introduction *Special senses are? Define each.

II. The EYE

A. Accessory Structures of the Eye 1. Eyelids 2. Eyelashes 3. Conjunctiviva = Membrane Anterior outer eye surface and inside . of eyelids Secretes mucus: Conjunctiva Posterior Surface Eyelid

Conjunctivitis = Inflamation of Conjunctiva; Pink Eye caused by bacteria or virus and is very contagious

Accessory Structures of the Eye … 4. Lacrimal gland Functions:

B. Layers of the Eye 1. The Fibrous Layer a. Sclera: Location = White of Eye; 5/6 eyeball Function: Protects, Shapes, and Anchors muscles b. Cornea: Transparent Convex Bulge, anterior 1/6 eye Function: lets light in and bends it a bit to help in focusing

2. Vascular Layer Choroid: Brown Membrane; back and sides of layer Function: Blood vessels & absorbs stray light b. Ciliary body: Thickened Ring of Tissue encircling the Lens made up of mostly smooth muscle Lens c. Iris: In front of Ciliary Body and behind Cornea; colored Pupil: hole formed by iris that lets light into back of eye

b. Sensory cells & Neurons 3. Sensory Layer = RETINA - Innermost layer a. Pigmented layer b. Sensory cells & Neurons i) Sensory Receptor cells (1) Rods Location: Function

(2) Cones BLUE GREEN RED Function: Densest in the center Sensory Layer … BLUE GREEN RED (2) Cones Function: Densest in the center Three types of cones Different cones are sensitive to different wavelengths Color blindness is the result of the lack of one cone type 560 nm (red cones) 530 nm (green cones) 420 nm (blue cones) Light absorption by cone populations 380 450 500 550 600 650 700 750 Wavelengths (nanometers)

Color Blindness = Lack of one or more cone types

ii) Bipolar Layer: in front cones and rods which Retina … Central artery and vein of retina ii) Bipolar Layer: in front cones and rods which relay vision info to them - neurons iii) Ganglion Layer: in front of Bipolar Layer which relay vision into to them - Neurons Axons form: - Optic Disc: round area where the optic nerve leaves the eyeball = BLIND SPOT Cannot see images focused on the optic disc Optic disc Sclera Optic nerve Choroid

Ciliary body Vitreous humor in posterior segment Iris Retina Margin of pupil Choroid Sclera Aqueous humor (in anterior segment) Fovea centralis Optic disc Optic nerve Lens Cornea Ciliary zonule (b) Figure 8.4b

Fovea centralis Macula Blood vessels Optic disc Retina Lateral Medial Figure 8.8

C. Lens Biconvex crystal-like structure Held in place by a suspensory ligament attached to the ciliary body

Lens … Cataracts: Clouding of the lens Some congenital, most are related to age-related thick and hard lens + Smoking & Sun

D. Two Segments and Fluids of the Eye Anterior Segment Aqueous humor Watery fluid Helps maintain intraocular pressure Provides nutrients for the lens and cornea

Posterior Segment Vitreous humor Gel-like substance posterior to the lens Prevents the eye from collapsing Helps maintain intraocular pressure

E. Focusing Light must be focused to a point on the retina for optimal vision The eye is set for distance vision (over 20 feet away) Accommodation—the lens must change shape to focus on closer objects (less than 20 feet away)

F. Eye Reflexes Bright light causes pupils to constrict through action of radial, circular, and ciliary muscles Viewing close objects causes accommodation Viewing close objects causes convergence (eyes moving medially)

G. Disorders of the Eye Emmetropia—eye focuses images correctly on the retina Myopia Hyperopia Astigmatism

III. The Ear A. Introduction Houses two senses Hearing Equilibrium (balance) B. The ear is divided into three areas External Ear Middle Ear Inner ear

External (outer) ear Middle ear Internal (inner) ear Vestibulocochlear nerve Auricle (pinna) Semicircular canals Oval window Cochlea Vestibule Round window Pharyngotympanic (auditory) tube Tympanic membrane (eardrum) Hammer (malleus) Anvil (incus) Stirrup (stapes) External acoustic meatus (auditory canal) Auditory ossicles Figure 8.12

1. The External Ear hearing only Structures: Auricle (pinna) External acoustic meatus (auditory canal) Narrow chamber in temporal bone Ends = tympanic membrane Air-filled

2. Middle Ear Auditory tube connecting middle ear with the throat Allows for equalizing pressure when ___ Three bones (ossicles) in cavity Malleus (hammer) Incus (anvil) Stapes (stirrup) Function Transmit Vibrations of sound to inner ear

3. Inner Ear or Bony Labyrinth Sense organs for hearing and balance Bony chambers within the temporal bone Bony & Membraneous Labyrinth Internal (inner) ear Vestibulocochlear nerve Semicircular canals Oval window Cochlea Vestibule Round window

Semicircular canals Ampulla Vestibular nerve Vestibule (a) BONY lABYRINTH Ampulla Vestibular nerve Vestibule (a) Figure 8.14a

(3) Inner Ear or Bony Labyrinth … C. Physiology 1. Static Equilibrium These receptors respond to angular or rotary movements and movements of head Vestibular Apparatus: Equilibrium receptors Semicircular Canals 2. Dynamic Equilibrium

Cupula of crista ampullaris Endolymph Flow of endolymph Cupula of crista ampullaris Cupula Nerve fibers Direction of body movement (b) (c) Figure 8.14b-c

3. Hearing Cochlea– Organ of Corti Cochlear nerve attached to hair cells transmits nerve impulses to auditory cortex on temporal lobe Vibrations from sound waves move a membrane

Perilymph in scala vestibuli Spiral organ of Corti Vestibular membrane Temporal bone Perilymph in scala vestibuli Spiral organ of Corti Vestibular membrane Afferent fibers of the cochlear nerve Temporal bone Cochlear duct (contains endolymph) Perilymph in scala tympani (a) Figure 8.15a

Hair (receptor) cells of spiral organ of Corti Tectorial membrane Vestibular membrane Hair (receptor) cells of spiral organ of Corti Tectorial membrane Fibers of the cochlear nerve Supporting cells Basilar membrane (b) Figure 8.15b

Homeostatic Imbalances of the Ears-- DEAFNESS

END

Lacrimal sac Lacrimal gland Excretory ducts of lacrimal gland Lacrimal canaliculus Nasolacrimal duct Inferior meatus of nasal cavity Nostril (b) Figure 8.2b

Excretory duct of lacrimal gland Lacrimal gland Conjunctiva Anterior aspect Eyelid Eyelashes Tarsal glands (a) Eyelid Figure 8.2a

II. The EYE Eyebrow Site where conjunctiva merges with cornea Eyelid Eyelashes Pupil Palpebral fissure Lacrimal caruncle Lateral commissure (canthus) Medial commissure (canthus) Sclera (covered by conjunctiva) Iris Eyelid Figure 8.1

Pigmented layer of retina Neural layer of retina Central artery and vein of retina Optic disc Sclera Optic nerve Choroid (b)

humor (in anterior segment) Sclera Ciliary body Choroid Ciliary zonule Retina Cornea Fovea centralis Iris Pupil Optic nerve Aqueous humor (in anterior segment) Lens Scleral venous sinus (canal of Schlemm) Central artery and vein of the retina Vitreous humor (in posterior segment) Optic disc (blind spot) (a) Figure 8.4a