o A cushion of fat surrounds most of the eye

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1 Name Period SPECIAL SENSES The Senses of touch o Temperature o Pressure o Pain o Smell o Taste o Sight o Hearing o Equilibrium The Eye and Vision are in the eyes has over a o Most of the eye is enclosed in a bony orbit o A cushion of fat surrounds most of the eye Accessory Structures of the Eye

2 Meibomian or glands modified sebaceous glands of the eyelid produce an oily secretion to lubricate the eye glands modified sweat glands between the eyelashes o Membrane that the eyelids o to the surface of the eye o mucus to the eye apparatus o Lacrimal produces located above the lateral end of each eye o Lacrimal canals lacrimal fluid from into the lacrimal medial location Lacrimal sac provides of lacrimal fluid towards nasal cavity empties lacrimal fluid into the Function of the Lacrimal Apparatus Properties of o Dilute solution (tears) o Contains and, an enzyme that destroys bacteria,, and the eye Empties into the nasal cavity (!) Six Extrinsic Eye Muscles attach to the outer surface of the eye Produce

3 Structure of the Eye The wall is composed of o tunic or outside layer o tunic or middle layer o tunic or inside layer

4 The Fibrous Tunic o White connective tissue layer o Seen anteriorly as the o, central anterior portion o Allows for o o The only human tissue that can be transplanted without fear of rejection ( ) Vascular Tunic or Choroid Layer nutritive tunic w/ dark pigment prevents light from scattering Modified interiorly into two structures o smooth muscle Attaches to by ciliary zonule, a ligament o smooth muscle Sensory Tunic (Retina) Pigmented layer that gives Pupil rounded in the iris Contains (photoreceptors) o Rods ( ) o Cones ( ) Signals pass from photoreceptors via a two-neuron chain o o Signals toward the brain through the Neurons of the Retina and Vision o Most are found of the o Allow and vision o Perception is all in

5 o Allow for vision o Densest in the of the retina o area of the retina with lateral to each blind spot No cells are at the, or blind spot where the optic nerve leaves the eyeball Cone Sensitivity There are types of cones Different cones are to different o One blue, another green and the 3 rd a range including green and red ( red cones ) Color blindness is the result of type

6 Lens crystal-like structure Held in place by a suspensory attached to the ciliary body Internal Eye Chamber Fluids o fluid found in chamber between the o Similar to blood ; secreted by a special area of o Helps maintain intraocular o Provides for the lens and cornea o Reabsorbed into blood through the scleral venous sinus or canal of Schlemm Vitreous humor o substance behind the lens o Keeps the eye from o Lasts a lifetime and is replaced Lens Accommodation Light must be to a point on the for optimal vision The eye is set for vision (over 20 ft away) The must change shape to focus for closer objects

7 Images Formed on the Retina Visual Pathway of the retina nerve bundle of axons carrying retinal impulses Optic nerve at the optic chiasma Optic contain fibers from the lateral side of the eye on the same side and the medial side of the opposite eye Optic tract fibers synapse w/ neurons in the thalamus (axons form optic radiation) of the occipital lobe Eye Reflexes Internal muscles are controlled by the nervous system o Bright light causes pupils to through action of radial and ciliary muscles o Viewing close objects causes accommodation External control eye movement to follow objects Viewing close objects causes (eyes moving medially)

8 The Ear Houses two senses o o (balance) Receptors are mechanoreceptors Different organs house receptors for each sense Anatomy of the Ear The ear is divided into three areas o (external) ear o ear o ear The External Ear Involved in Structures of the external ear o (auricle) o auditory canal The External Auditory Canal Narrow chamber in the temporal bone

9 Lined with skin (wax) glands are present Ends at the The Middle Ear or Tympanic Cavity cavity within the temporal bone o Flanked laterally by eardrum and medially by a bony wall with 2 openings, the oval window & the inferior, membrane-covered round window Only involved in the sense of Two tubes are associated with the inner ear o The from the auditory canal is by the tympanic membrane o The connecting the middle ear with the throat Allows for pressure during yawning or swallowing This tube is otherwise Bones of the Tympanic Cavity Three bones (ossicles) span the cavity o Malleus ( ) o Incus ( ) o Stapes ( ) from eardrum move the, which moves the anvil, which moves the stirrup and presses on the oval window of the inner ear These bones to the inner ear Inner Ear or Bony Labyrinth Includes sense organs for hearing and Filled with A maze of bony chambers within the o Cochlea o Vestibule o Semicircular canals Chemical Senses Taste and Smell Both senses use o Stimulated by chemicals in solution o has four types of receptors

10 o Smell can differentiate a large range of chemicals Both senses complement each other and respond to many of the same stimuli Olfaction The Sense of Smell Olfactory receptors (neurons with long cilia) are in the o Chemicals must be for detection and impulse transmission by the hairs (cilia) Impulses are transmitted via the olfactory nerve Interpretation of smells is made in the Cortex stores snapshots of smells & is tied to the limbic system (emotions) Olfactory Epithelium The Sense of Taste (10,000+) house the receptor organs Location of taste buds o Most are on the tongue o Soft palate o Cheeks The Tongue and Taste The tongue is covered with projections called papillae o papillae sharp with no taste buds o papillae rounded with taste buds o papillae large papillae with taste buds Taste buds are found on the sides of papillae

11 Structure of Taste Buds are the receptors o Have gustatory (long microvilli) o Hairs are by chemicals dissolved in Depolarizes the nerve and the impulse is carried to the brain Impulses are carried to the gustatory complex by several cranial nerves because are found in different areas o Facial nerve o Glossopharyngeal nerve o Vagus nerve Anatomy of Taste Buds Taste Sensations receptors o Sugars o Saccharine o Some amino acids receptors o Acids receptors o Alkaloids

12 receptors o Metal ions Developmental Aspects of the Special Senses embryonic development Eyes are o Developing by the 4 th week o Eyeballs enlarge until age 8 or 9 (lenses throughout life) o Babies can t see near at birth (hyperopic) All special senses are