C H A P T E R 1 7

SENSORY SYSTEM

OLFACTION• Sense of smell• Olfactory organs in nasal cavity• Olfactory epithelium lines the

interior portion of the nasal cavity• Covered with olfactory

receptors(hairs/cilia)• Underneath, the lamina propria

(areolar tissue), contains olfactory glands or Bowman’s glands (olfactory glands)• Secretions that form a thick

mucus• Also contain blood vessels and

nerves

OLFACTORY RECEPTORS• Highly modified neurons• Contain odorant binding proteins • Odorants are chemicals that stimulate olfactory receptors• They bind to the proteins which causes the initiation of an

action potential to the CNS• Millions of olfactory receptors • Dog has 72x what humans have

OLFACTORY PATHWAYS• Very sensitive• 4 molecules of odorants can activate an olfactory receptor• Message must be sent to the olfactory cortex within the

temporal lobe before you’re aware of it

• Odorants stimulate Olfactory Receptors action potential initiated pass through the Ethmoid bone to the olfactory bulbs within the cerebrum message passed to the olfactory nerves hypothalamus (remember emotions) which trigger emotional/behavior responses

• perfumes

GUSTATION • Taste-provides information about foods/liquids

consumed• Gustatory Receptors = taste receptors, on superior

surface of tongue• Gustatory Receptors + specialized epithelial cells =

taste buds• Approx. 3000 per adult• Contain about approx. 40 gustatory receptors each• Projections or taste hairs that collect chemicals

LINGUAL PAPILLAE

• Lingual papillae (3 types)• Filiform papillae =

friction (don’t contain taste buds)

• Fungiform papillae = contain 5 or so taste buds

• Circumvallate papillae = 100 taste buds—form “V” shape in back of tongue

GUSTATORY PATHWAY

• Taste buds are controlled by the facial, glossopharyngeal, and vagus nerves. • Conscious perception of taste is processed with

other sensory data• Texture of food• Taste

• Afferent Neural connection between Olfaction and Gustation• More sensitive to taste when your sense of olfaction is

working properly• When your ill, airborne molecules cannot reach the olfactory

receptors = meals taste dull

GUSTATORY PATHWAY• Dissolved chemicals contact taste hairs depending

upon the chemical, various protein channels will open initiates an immediate release of neurotransmitter to the postsynaptic cell postsynaptic cell generates action potential CNS• Primary taste sensations• Sweet• Salt• Sour• Bitter• Umami = amino acids, peptides found in beef/chicken products• Water = in pharynx, hold water in mouth triggers hormone

secretion leading to water loss in kidneys

TASTE LAB

• Get with a partner (need a notebook and pencil)• On the paper, draw a simple illustration of the tongue

• Grab 2 q-tips per partner

• Dip the q-tip into the unknown solution and roll it on various regions of your tongue• See if you can identify regions of hypersensitivity and the

type of taste being stimulated• Once identified, pencil them in on your tongue diagram

C H A P T E R 1 7

VISION/EQUILIBRIUM & HEARING

ACCESSORY STRUCTURES OF THE EYE

Eyelids• Palpebrae• Keep surface lubricated• Free from dust/debris• Protect surface

• Palpebrae fissure• Gap between each palpebrae or eyelids• Lateral/medial canthus (connection of palpebrae)

• Eyelashes• Long hairs• Prevent foreign matter and insects from reaching the

surface

ACCESSORY STRUCTURES OF THE EYE

Eyelashes are associated with abnormally large sebaceous glands• Tarsal glands• Along the inner margin• Secrete a lipid-rich product, prevents palpebrae from sticking

together• Lacrimal Caruncle• At the medial canthus• Thick secretions• Can be invaded by bacteria/infection

• Sty• Infection of a sebaceous gland or tarsal gland causing swelling

ACCESSORY STRUCTURES OF THE EYE

• Conjunctiva• Epithelium covering the inner surface of eyelids• Conjunctivitis: “pink eye”, damage, irritation to the

conjunctiva• Redding due to blood vessel dilation• Caused by infection

ACCESSORY STRUCTURES OF THE EYE

• The Lacrimal Apparatus• Produces, distributes, and removes tears• Reduce friction, remove debris, prevent bacterial infections,

provide nutrients to that tissue• Parts• Lacrimal gland: secretes the tear substance with a lysozyme,

to attack bacteria• Lacrimal puncta: 2 small pores that drain tears to canaliculi• Lacrimal Canaliculi: small canals that lead to the sac for

disposal of tears• Lacrimal Sac: collects a portion of the tears before depositing

them into the duct• Nasolacrimal duct/canal: found in the lacrimal bone, delivers

the tears to nasal cavity

THE EYE

• Wall of the eye-3 layers• Fibrous Tunic• Outermost layer• Contains: sclera and cornea• Provides support and protection, attachment for muscles,

focusing• Vascular Tunic• Middle layer• Contains: iris, ciliary body, and choroid• Provides route for vessels, regulates amount of light, secreting

and reabsorbing the aqueous humor, controls shape• Neural Tunic• Innermost layer• Retina• Contains light receptors

CORNEA

• Transparent• No blood vessels• Doesn’t interfere with the

passageway of light• Has numerous free nerve

endings = sensitive

SCLERA

• White portion of the eye• Contains small

blood vessels and nerves

IRIS

• Contains vessels, pigmented cells, and layers of muscle fibers• Change the shape

changes the size of the pupil• Pupillary dilator muscles• Pupillary constrictor

muscles• Central opening = pupil• Melanocytes• Density = color

CILIARY BODY

• Contains ciliary muscle• Change lens shape

CHOROID

• Delivers oxygen and nutrients to the retina

RETINA• Contains photoreceptors• Rods: variations of light,

allow to see in low lighting• Cones: color vision, require

more light, provide sharper vision

• Not evenly distributed• 125 Million Rods along the

periphery of retina• 6 Million Cones on retina’s

posterior surface• Fovea Centralis, area of

sharpest vision, reason why you look directly at something, highest concentration of rods/cones

OPTIC DISC• Region where the Optic

nerve enters the eye• No photoreceptors

because it is an opening• “blind spot”

CHAMBERS OF THE EYE• Anterior Cavity• Anterior chamber (cornea

to iris)• Posterior chamber (iris to

lens)• Filed with aqueous humor :

circulating fluid for nutrient/waste transport, and cushion

• Posterior Cavity• Everything behind the

anterior cavity• Filled with Vitreous Humor:

gelatinous mass that stabilizes the shape

THE LENS• Posterior to cornea• Held in place by

suspensory ligaments that originate from the choroid• Change shape to focus

image on photoreceptors due to refraction called accommodation• Lens becomes rounder to

focus on a nearby object or flatter for a distant object

• Astigmatism: light failing to refract properly due to an misshapen cornea/lens

VISUAL ACUITY• Clarity of vision is rated against a

normal standard• 20/20 a person can see details at 20

feet as clearly as a normal person should at 20 feet

• 20/15 a person can see at 20 feet what a normal person can see at 15

• 20/30 a person can see at 20 feet what a normal person can see at 30

• 20/200 is legally blind• Caused by cataracts, glaucoma, corneal

scarring, detachment of retina, accidental injuries or heredity factors.

SIGHT LAB

Groups of 3• 2 groups Visual Acuity • 2 groups Peripheral vision disc• 1 group Astigmatism/blind spot• 1 group Page 455 in packet part B• 1 group study with models

EMOTIONAL TEARS

• proteins carrying hormones found in tears• Prolactin• Hormone in greater levels in women than men

• When you have an emotional response, it is due to the onset production of hormones• These hormones are produced in the lacrimal gland

which then are released through tears• Prolactin levels increase tremendously during

breastfeeding, stimulates lactation• Women have a strong emotional responses while breast

feeing

LASIK SURGERY

• Operation• Patient is awake, given anesthetic eye drops• Step 1: Remove the conjunctiva tissue like a flap• Step 2: Remodel the cornea because the uneven amounts

push on the lens causing a change in its shape or excess causes blurred vision

• http://www.youtube.com/watch?v=O4kDC4sZ5Jg

VISUAL DISORDERS

• Cataracts• Clouding or discoloration of the lens• Due to a precise balance of structural and biochemical

characteristics• Symptoms: blurry vision, faded colors, glare, poor night

vision, double vision• Lens transplants to fix• Develops as you age

• Glaucoma• Intraocular pressure rises because the aqueous humor

can’t be filter properly• Pressure distorts the soft tissues of the eye • Treated with drugs, surgery to enable drainage

COLOR VISION• Anatomy of Rods and cones• Rod/cone refer to the outer segment’s

shape• 3 types of cones• Blue Cones (16%)• Green Cones (10%)• Red Cones (74%)• If all 3 are stimulated, you perceive the color

white• Combination is what allows us to understand

different colors/shades

COLOR BLINDNESS

• Unable to distinguish certain colors• Nonfunctional cones• Absent• Unable to manufacture the necessary pigments

• Red-green color blindness• Most common, b/c inherited, other types due to damage• Located on the x chromosome• Remember XY so men have it more often b/c women have XX

which both would need to be carriers • Red cones are missing• Red/green looks the same

COW EYE DISSECTION

SOUND

• 2 senses• Equilibrium• Inform us of the position of the head in space

• Monitors gravity, acceleration, rotation• Hearing• Detect and interpret sound waves

ANATOMY OF THE EAR

• 3 main Regions• External Ear• Visible portion• Collects/directs sound waves and directs them to the middle

ear• Middle Ear• Chamber within the temporal bone• Collect sound waves and transmit them to the inner ear

• Inner Ear• Contains sensory organs for hearing and equilibrium

EXTERNAL EAR• Auricle or pinna• Fleshy flap of cartilaginous tissue• Surrounds the external auditory canal • Protects the opening• Provides direction of sounds

• External Auditory Canal• Passageway for sound waves to travel• Ends at the tympanic membrane

• Tympanic Membrane• “ear drum”• Thin, semi-transparent, delicate• Separates external and middle ear

• Ceruminous Glands• line the E.A.C., secrete waxy material called cerumen, thatPrevents foreign objects from entering

MIDDLE EAR• Filled with air• Communicates with the nasopharynx through the

auditory tube or Eustachian tube• Permits equalization of pressures on either sides, opens to

pharynx• Can also lead to microorganisms entering the middle ear = ear

infections• Auditory ossicles• 3 bones: connect the tympanic membrane with other inner ear

structures• Malleus (tympanic membrane), incus (both bones)and stapes

(oval window)• Vibrations of tympanic membrane, vibrates the 3 ossicles, oval

window hearing/equilibrium structures

INNER EAR• Membranous Labyrinth: network of canals that holds

receptors• Contains endolymph

• Bony Labyrinth: dense bone that surrounds and protects the membranous labyrinth• Vestibule: contains membranous sacs called saccule and utricle

which hold receptors that respond for balance• 3 Semi-circular Canals: enclose semicircular ducts that can be

stimulated by rotation• Cochlea: spiral-shaped, cochlear duct, receptors that respond to

hearing• Round Window: separates the perilymph from air of middle ear• Oval Window: moves the stapes which flaps on it causing stimulation

• Between them is the perilymph, liquid

PATHWAY OF SOUND

• Sound waves external auditory canal and make the tympanic membrane vibrate.

• Tympanic membrane vibration causes movement of auditory ossicles, sound waves amplified

• Stapes moves against oval window, pressure waves generated

• Travel from oval window and through the scala vestibuli (area of cochlea)

• Hair cells in the cochlea detect movement and convert stimulus into nerve impulse which travels to the cochlear nerve.

• Excess waves exit through the round window

BALANCE

• 2 structural and functional components of balance in the inner ear• Stationary Position and Linear Movements of Head• Evaluates position of head relative to gravity• Detects inner acceleration/deceleration• Utricle/Saccule: have hair cells that detect

• Rotational Movements of Head• Evaluates movement of head• 3 semicircular canals with hair cells

• Static balance: orientation of body relative to the pull of gravity• Kinetic balance: maintenance of body position in response to

movement