THE SPECIAL SENSES 5 SPECIAL SENSES 1 2

THE SPECIAL SENSES

5 SPECIAL SENSES 1. 2. 3. 4. 5. Olfaction Gustation Hearing Equilibrium Vision

OLFACTORY ORGANS Located in nasal cavity on either side of nasal septum Figure 17– 1 a

WHAT ARE THE SENSORY ORGANS OF SMELL?

OLFACTORY ORGANS Made up of 2 layers: olfactory epithelium lamina propria

OLFACTORY EPITHELIUM Figure 17– 1 b

OLFACTORY EPITHELIUM Contains: olfactory receptors supporting cells basal (stem) cells

LAMINA PROPRIA Contains: areolar tissue blood vessels nerves olfactory glands

OLFACTORY GLANDS Secretions coat surfaces of olfactory organs

OLFACTORY RECEPTORS Highly modified neurons Figure 17– 1 b

OLFACTORY RECEPTION Involves detecting dissolved chemicals as they interact with odorant-binding proteins

WHAT ARE THE SENSORY ORGANS OF TASTE?

TASTE (GUSTATORY) RECEPTORS Clustered in taste buds

TASTE BUDS Associated with epithelial projections (lingual papillae) on dorsal surface of tongue

TASTE BUDS Figure 17– 2

EACH TASTE BUD Contains: basal (stem) cells gustatory cells: Extend taste hairs through taste pore Survive only 10 days before replacement

PRIMARY TASTE SENSATIONS Sweet Salty Sour Bitter

WHAT ARE THE SENSORY ORGANS OF HEARING AND EQUILIBRIUM?

THE EAR Figure 17– 20

THE EAR 1. 2. 3. External ear Middle ear Inner ear

WHAT ARE THE STRUCTURES OF THE EXTERNAL EAR, AND HOW DO THEY FUNCTION?

EXTERNAL EAR Auricle Surrounds entrance to external acoustic canal Protects opening of canal Provides directional sensitivity External acoustic canal Canal that runs from auricle to tympanic membrane Tympanic membrane (Eardrum) Is a thin, semitransparent sheet Separates external ear from middle ear

EXTERNAL EAR Figure 17– 20

CERUMINOUS GLANDS Integumentary glands along external acoustic canal Secrete waxy material (cerumen): keeps foreign objects out of tympanic membrane slows growth of microorganisms in external acoustic canal

WHAT ARE THE STRUCTURES OF THE MIDDLE EAR, AND HOW DO THEY FUNCTION?

3 AUDITORY OSSICLES 1. 2. 3. Malleus (hammer) Incus (anvil) Stapes (stirrup)

AUDITORY TUBE (EUSTACHIAN TUBE) Permits equalization of pressures on either side of tympanic membrane

VIBRATION OF TYMPANIC MEMBRANE Converts arriving sound waves into mechanical movements Auditory ossicles conduct vibrations to inner ear

WHAT ARE THE PARTS OF THE INNER EAR, AND WHAT ARE THEIR ROLES IN EQUILIBRIUM AND HEARING?

INNER EAR Figure 17– 20

INNER EAR Contains fluid Subdivided into: vestibule semicircular cochlea canals

INNER EAR

PARTS TO INNER EAR Vestibular Complex Combination of vestibule and semicircular canals Vestibule Receptors provide sensations of gravity and linear acceleration Semicircular Canals Contain semicircular ducts Receptors stimulated by rotation of head Cochlea Contains cochlear duct Receptors provide sense of hearing

PARTS TO INNER EAR

EQUILIBRIUM Sensations provided by receptors of vestibular complex

SOUND Consists of waves of pressure through air or water

WAVELENGTH Distance between 2 adjacent wave troughs Frequency Number of waves that pass fixed reference point at given time Physicists use term cycles instead of waves Hertz (Hz) Number of cycles per second (cps)

PITCH Our sensory response to frequency Increased frequency results in a higher pitch Decreased frequency results in a lower pitch

AMPLITUDE Intensity of sound wave Sound energy is reported in decibels

THE POWER OF SOUNDS Table 17– 1

HOW DO WE HEAR? 1. 2. 3. 4. 5. Sound waves enter external acoustic canal Soundwaves vibrate the tympanic membrane Vibrations are transferred to and through the auditory ossicles Vibrations are transferred to fluid in cochlea Nerve endings pick up vibrations and send signal to brain

HOW DO WE HEAR?

AGING EFFECTS Tympanic membrane gets less flexible Articulations between ossicles stiffen

WHAT ARE THE ACCESSORY STRUCTURES OF THE EYE, AND WHAT ARE THEIR FUNCTIONS?

ACCESSORY STRUCTURES OF THE EYE 1. 2. 3. Eyelids Superficial epithelium of eye Structures associated with production, secretion, and removal of tears

EYELIDS (PALPEBRAE) Continuation of skin Blinking keeps surface of eye lubricated, free of dust, and debris

EYELASHES Robust hairs that prevent foreign matter from reaching surface of eye

TARSAL GLANDS Associated with eyelashes Secrete lipid–rich product that helps keep eyelids from sticking together Contribute to gritty deposits that appear after good night’s sleep

CONJUNCTIVA Epithelium covering inner surfaces of eyelids and outer surface of eye Conjunctivitis Results from damage to conjunctival surface Figure 17– 3 b

CORNEA Transparent part of outer fibrous layer of eye

LACRIMAL GLAND (TEAR GLAND) Secretions contain lysozyme, an antibacterial enzyme Lubricates, cleanses, disinfects eye

WHAT ARE THE INTERNAL STRUCTURES OF THE EYE, AND WHAT ARE THEIR FUNCTIONS?

ORBITAL FAT Cushions and insulates eye Figure 17– 4 c

EYEBALL Is hollow Is divided into 2 cavities: large posterior cavity smaller anterior cavity

OUTER SURFACE OF EYE 1. 2. Sclera (white of eye) Cornea

MIDDLE LAYER OF EYE Includes: iris ciliary body Iris Contains muscle fibers Changes diameter of pupil Ciliary body Assist in changing shape of lens for focusing images

MIDDLE LAYER OF EYE

LENS Lies posterior to cornea Forms anterior boundary of posterior cavity

INNER LAYER OF EYE (RETINA) 1. 2. Outer pigmented part Inner neural part: contains visual receptors and associated neurons

RETINA Rods and cones are types of photoreceptors Figure 17– 6

RODS Do not discriminate light colors Highly sensitive to light intensity

CONES Provide color vision Densely clustered in fovea

VISUAL AXIS Imaginary line from center of object, through center of lens, to fovea Figure 17– 4 c

COLOR BLINDNESS Inability to detect certain colors Figure 17– 17

OPTIC DISC Circular region just medial to fovea Origin of optic nerve NO RODS OR CONES IN THIS REGION Creates a blind spot Figure 17– 6 b, c

BLIND SPOT Figure 17– 7

CATARACT Condition in which lens has lost its transparency

ASTIGMATISM Condition where light passing through cornea and lens is not refracted properly Visual image is distorted

VISUAL PATHWAY Figure 17– 19

DEPTH PERCEPTION By comparing relative positions of objects between left–eye and right–eye images Figure 17– 19