Chapter 12: Nervous System III Senses

Free nerve endings

the simplest receptors, are common in epithelial tissues, where the ends of dendrites branch and extend between epithelial cells; are responsible for the sensation of itching and other sensations

taste pore

an opening in the taste bud

After sound enters the meatus where does it go next?

the sound waves pass to the end of the tube and alter the pressure on the tympanic membrane.

scala vestibuli

the upper compartment; which leads from the oval window to the apex of the spiral.

what happens when rhodopsin molecules absorb light?

they change shape and release opsin, in trillionths of a second

ciliary body

thickest part of the middle tunic; extends anteriorly and inward from the choroid coat and forms a ring inside the front of the eye

pain receptors

also called nociceptors respond to tissue damage. Triggering stimuli include exposure to excess mechanical, electrical, thermal, and chemical energy.

How does the tympanic membrane respond to sound?

it vibrates back and fourth, reproducing the vibrations of the sound-wave source.

The ciliary body is attached to the _____ via suspensory ligaments.

lens

photo-

light

rhodopsin

light-sensitive pigment in the rods the retina; visual purple; embedded in membranous discs stacked in these receptor cells;

scala tympani

lower compartment; extends from the apex of the spiral to the membrane-covered opening in the wall of the middle ear, facing the tympanic cavity (round window)

What is the enzyme in tears that has antibacterial properties, reducing the risk of eye infections

lysozyme

sensation

occurs when sensory neurons reach threshold and the resulting action potentials cause the brain to become aware of that sensory event.

perception

occurs when the brain interprets those sensory impulses.

inferior rectus

oculomotor nerve III rotates the eye downward and toward the midline

medial rectus

oculomotor nerve III rotates the eye toward the midline

superior rectus

oculomotor nerve III rotates the eye upward and toward the midline

cone photoreceptors

photoreceptor in the retina of the eye that can detect color; provide sharp images; are less sensitive and do not respond in dim light

Information (sensory impulses) arriving at the cerebral cortex results in _____. Awareness of the location of the source of the stimulation is called _____.

sensation; projection

Thermoreceptors

sense temperature change

special senses

sense that stems from receptors associated with specialized sensory organs, such as the eyes and ears;

The body's ability to interpret different sensory events depends partly on....

the receptors that respond to specific stimuli

what contributes to the sense of equilibrium?

the semicircular canals and associated structures

cochlea-

snail

Both types of receptors rapidly adapt, so within about a minute of continuous stimulation....

the sensation of warm or cold begins to fade.

lateral rectus

Trochlear nerve IV rotates the eye away from the from the midline

At what temperature does the cold receptors stimulate pain receptors, producing a freezing sensation?

(10C) 50F

fast pain fibers

(A-delta fibers) are myelinated. they conduct impulses rapidly, at velocities up to 30 meters per second. impulses are associated with the immediate sensation of sharp pain, which typically seems to originate in a local area of the skin.

slow pain fibers

(C fibers) are unmyelinated. they conduct more slowly than fast pain fibers, at velocities up to 2 meters per second. these impulses cause a delayed, dull, aching pain sensation that may be widespread and difficult to pinpoint.

auricle

(pinna) the outer external ear; also an outpouching of an atrium of the heart.

ciliary processes

- radiating folds on ciliary body

How does smell sensory flow through the nervous system?

-Sensory receptors: Olfactory receptor cells -Impulse in sensory fiber: Olfactory nerve fibers -Impulse reaches CNS: Cerebral cortex -Sensation: A pleasant smell -Perception: The small of a scent

How does taste sensory flow through the nervous system?

-Sensory receptors: Taste bud receptor cells -Impulse in sensory fibers: sensory fibers in various cranial nerves. -Impulse reaches CNS: cerebral cortex -Sensation: A sweet taste -Perception: The taste of something

How does hearing flow through the nervous system?

-Sensory receptors: hair cells in cochlea -Impulse in sensory fibers: auditory nerve fibers -Impulse reaches CNS: midbrain and cerebral cortex -Sensation: a crunching sound -Perception: the sound of an object

How does sight flow through the nervous system?

-Sensory receptors: rods and cones in retina -Impulse in sensory fibers: optic nerve fibers -Impulse reaches CNS: midbrain and cerebral cortex -Sensation: a small, round, red object -Perception: the sight of an object

auditory ossicles

3 small bones in the middle of the ear; the malleus, the incus, and the stapes attached to the wall of the tympanic cavity by tiny ligaments and are covered by mucous membrane.

Each of our 10,000 taste buds houses ____ to _____ taste cells.

50 to 150

Olfaction undergoes sensory adaptation rather rapidly, so the intensity of an odor drops about ______ % within a second following the stimulation.

50%

How much of flavor derives from the sense of smell?

75% to 80%

What are the two groups of hair cells?

A single row of about 3,500 inner hair cells and three rows of 15,000-20,000 outer hair cells.

What is the term for the ability of the brain to prioritize the sensory input it receives and to ignore unimportant stimuli?

Adaptation

How is the brain able to interpret whether an incoming sensation is touch vs. sound vs. vision?

Based on the region of the brain that receives the impulses

The olfactory receptor neurons are the only nerve cells to what?

Be in direct contact with the outside environment, and as such are prone to damage.

The more intense stimulation of the hair cells...

Causes more action potentials per second to reach the brain, and we perceive a louder sound.

The basilar membrane is stiffer and narrower at the base of the cochlea compared to the apex, where it is more flexible and wider, as a result....

Different frequencies of vibration move different regions along the length of the basilar membrane.

What happens once a pain receptor is actived?

Even by a single stimulus, it may continue to send impulses into the CNS for some time.

What are the three groups of general senses?

Exteroreceptive, Interoceptive, and Proprioceptive senses

What are the three layers of wall of the eye, in order, from superficial to deep?

Fibrous tunic, vascular tunic, and nervous tunic

taste cells

Group of modified epithelial cells on each taste bud Function as receptors

How does the ear differentiate between sounds of different frequencies (pitches)?

Hair cells at different locations in cochlea respond to different pitches.

List in order the structures making up the signal pathway of the maculae.

Hair cells, vestibular branch, vestibulochochlear nerve, brain

How does the iris appear blue or green?

If melanin is present only in the epithelial cells on the iris's posterior surface, the iris reflects more colors of light

retina

Inner layer of the eye wall that contains the photoreceptors; nearly transparent sheet of tissue that is continuous with the optic nerve in the back of the eye and extends forward as the inner lining of the eyeball

What three are classified as accessory organs of the eye?

Lacrimal apparatus, extrinsic muscles, eyelids

Tear formation goes as....

Lacrimal gland, superior and inferior canaliculi, lacrimal sac, nasolacrimal duct

iodopsins

Light-sensitive pigments in cones of the eyes; similar to rhodopsin in that that they are composed of retinal combined with a protein, the protein, however differs from the protein in the rods.

How are sounds of different amplitudes (volumes) differentiated?

Louder sounds cause more bending of the hair cells triggering more action potentials which are perceived as louder sounds.

superior oblique

Oculomotor nerve III rotate the eye downward and away from the midline

what structure exits the back of the eye?

Optic nerve

What is the sheet of gelatinous material and the crystals of calcium carbonate embedded on its surface?

Otolithic membrane; otoliths

After the vibrations enter the perilymph at the oval window then travel along the scala vestibuli, where does it go next?

Pass through the vestibular membrane to enter the endolymph of the cochlear duct, where they move the basilar membrane.

The outer ear consist of ....

auricle, external acoustic meatus, and tympanic membrane

optic disc

Region in the retina of the eye where sensory fibers exit, becoming part of the optic nerve; a central artery and vein also pass through at the optic disc; lack photoreceptors, so it is commonly referred to as the blind spot of the eye

External acoustic meatus

S-shaped tube, that leads inward for about 2.5cm

What are the fibers in the cornea and their function?

Sensory fibers that enter its margin and radiate toward its center; are associated with many pain receptors that have very low thresholds

As sound vibrations cause movements of the basilar membrane, what is happening?

Some of the inner hair cells are pushed up against the tectorial membrane, bending their hairs.

What collect sound waves and where does it go?

The auricle of the ear helps collect sound waves traveling through air and directs them into the external acoustic meatus.

After passing through the vestibular membrane, where does the sound wave go next?

The vibrations enter the perilymph of the scala tympani, and the movement of the membrane covering the round window dissipates their force into the air in the tympanic cavity.

taste hairs

Tiny projections (microvilli) that protrude from the outer ends of the taste cells and extend from the taste pore; sensitive part of the receptor cells.

rods

Type of light receptor that provides colorless (black and white) vision; have long, thin projections at their terminal ends; produce more general outlines of objects; are hundreds of times more sensitive to light as a result these provide vision in dim light

Impulses from receptors at the base of the tongue and the pharynx travel of the ___________.

Vagus nerve (X)

What are the two free nerve ending thermoreceptors in the skin?

Warm and cold receptors.

What happens when the hair cells stimulate impulses on fibers of the cochlear nerve?

We hear, once this information reaches the auditory centers in the temporal lobes

How does the iris appear brown?

When melanin is within the body of the iris as well as in the posterior epithelial covering

How does the iris appear gray?

When the same distribution of melanin is denser in the body of the iris

olfactory bulb

a brain structure located above the nasal cavity beneath the frontal lobes; within the cranial cavity on either side of the crista galli of the ethmoid bone

general sense

a sense detected through receptors widely distributed throughout the body; including the skin, various organs, and joints.

Olfactory organ

appears as yellowish brown masses of epithelium that cover the upper parts of the nasal cavity, the superior nasal conchae, and a portion of the nasal septum.

Baroreceptors

are also called pressoreceptors, in certain blood vessels detect changes in blood pressure.

Muscle spindles

are located throughout skeletal muscles; each consists of several small, modified intrafusal fibers enclosed in a connnective tissue sheath.

Lamellated (Pacinian) corpuscles

are nerve endings encased in relatively large, ellipsoidal structures composed of connective tissue fibers and cells. they are common in the deeper dermal tissues of the hands, feet, penis, clitoris, urethra, and breasts and also in the connective tissue capsules of synovial joints. heavier pressure and stretch stimulate lamellated corpuscles; also detect vibrations in tissues.

Mechanoreceptors

are several types and respond to mechanical forces by detecting changes that deform the receptors. They include a number of receptors in the skin that respond to physical contact, and several receptors in the ear that provide information about balance and vibrations from sound.

Tactile (Meissner's) corpuscles

are small, oval masses of flattened connective tissue cells in connective tissue sheaths; two or more sensory fibers branch into each corpuscle and end within it as tiny knobs.

sweet receptors

are usually stimulated by carbohydrates, but a few inorganic substances, including some salts of lead and beryllium.

Exteroreceptive senses

associated with changes at the body surface; include senses of touch, pressure, temperature, and pain

Interoceptive senses

associated with changes in the viscera

Fortunately, _____ _______ along the basement membrane of the olfactory epithelium regularly divide and yield cells that differentiate to replace lost olfactory receptor neurons.

basal cells

Refraction

bending of light as it passes between media of different densities.

anterior chamber of eye

between the cornea and the iris

posterior chamber of ye

between the iris and vitreous humor, occupied by the lens

if all three type of cones are not stimulated, what color do we see?

black

vestibule

bony chamber in the inner ear; between the cochlea and the semicircular canals, houses membranous structures that serve both hearing and equilibrium

utricle

chamber in the inner ear associated with static equilibrium

What is the immediate result of stimulating a receptor?

change in membrane potential

Olfactory receptors are a type of receptor called______ that sense_____.

chemoreceptors; chemicals dissolved in liquid

The middle, or vascular, tunic of the eyeball (uveal layer) includes?

choroid coat, the ciliary body, and the iris.

What are the two groups of contractile cells of the iris?

circular and radial set

What structure contains the hearing receptors?

cochlea

scala media

cochlear duct; runs inside the tube opposite the spiral lamina

vitreous body

collagen fibers and fluid in the posterior cavity of the eye; supports the internal structures of the eye and helps maintain the eye's shape.

The photoreceptors called cones are responsible for _______ vision?

color

Each type of ______ responds to different wavelength of light. This is because each type contains a different type of _______

cone; iodopsin

lacrimal apparatus

consist of the lacrimal gland, which secretes tears, and a series of ducts, which carry the tears into the nasal cavity; a gland that is in the orbit, superior and lateral of the eye.

radial set (pupillary dilator)

control the size of the pupil, through which light passes; is composed of specialized contractile epithelial cells (myoepithelial cells), when it contracts, the diameter of the pupil increases the amount of light entering the eye increases

circular set (pupillary constrictor)

control the size of the pupil, through which light passes; is smooth muscle and act as a sphincter, when it contracts, the pupil gets smaller and the amount of light entering the amount of light entering the eye decrease.

When light passes through a convex surface, the light rays bend, resulting in _______ of light

convergence.

Light coming into the eye______ as it passes through the cornea and lens, focusing the image on the retina.

converges

The light entering the eye must pass throught..... before it reaches the photoreceptors

cornea, aqueous humor, lens, vitreous humor, and several layers of the retina

outer tunic of eye

cornea, sclera, optic nerve

An odorant molecule molecule may bind to several of the almost 400 types of olfactory membrane receptors that are part of the olfactory receptors cell, which does what?

depolarize the cells and thereby generating action potentials if the depolarization reaches threshold

fovea centralis

depression region of the retina, consisting of densely packed cones, that provides the greatest visual acuity.

tympan-

drum

The organ of hearing consist of...

ear, the outer (external), middle, and inner (internal)

The tympanic membrane is also called the _________ (a non-anatomical term).

eardrum

tympanic membrane

eardrum; thin membrane that covers the auditory canal and separates the outer ear from the middle ear; semitransparent membrane covered by a thin layer of skin on its outer surface and by mucous membrane on the inside.

ampulla

expansion at the end of each semicircular canal that houses a crista ampullaris; communicates with the utricle of the vestibule.

ocul-

eye

palpebra-

eyelid

Sensory impulses from taste receptors cells in the anterior two-thirds of the tongue travel on fibers of ______________;

facial nerve (VII)

Focusing bends the light so the image .......

falls on the fovea centralis.

perilymph

fluid between the bony and membranous labyrinths secreted by cells in the wall.

vitreous humor

fluid between the lens and the retina of the eye

vitre-

glass

Impulses from receptors in the posterior one-third of the tongue and the back of the mouth pass along the _____________.

glossopharyngeal nerve (IX)

alkaloids

group of bitter compounds including a number of poisons such as strychnine, nicotine, and morphine.

ciliary muscle

group of smooth muscles attached to the ciliary body

maculae

hair cells and supporting cells associated with an organ of static equillbrium

Within the spiral organ, hair cells have what role?

hair cells are receptor cells

malle-

hammer

scler-

hard

therm-

heat

Olfactory receptor cells

help sense odors; the receptor cells are similar to those for taste in that they are chemoreceptors sensitive to chemicals dissolved in liquids.

corn-

horn

accommodation

if the tension of the suspensory ligaments relaxes, the elastic capsule rebounds and the lens surface becomes more convex; occurs in the lens when the eye focuses to view a close object.

Once olfactory receptor cells are stimulated, what happens next?

impulses are conducted along their axons through tiny openings in the cribriform plates of the ethmoid bone.

cyclic guanosine monophosphate (cGMP)

in darkness, these nucleotides keep sodium and calcium channels open, thus depolarizing portions of the receptor cell membrane

An inhibitory neurotransmitter is released by rods that are___________?

in the dark

Photoreceptors

in the eyes respond to light energy of sufficient intensity

Stretch receptors

in the lungs respond to degree of inflation

endolymph

in the membranous labyrinth is a slightly different fluid

choroid coat

in the posterior five-sixths of the globe of the eye, loosely joins the sclera; blood vessels pervade the choroid coat and nourish surrounding tissues; also contains abundant pigment-producing melanocytes that give it a brownish-black appearance (which absorbs excess light and helps keep the inside of the eye dark).

opsin

in the presence of light, rhodopsin molecules break down into molecules into this colorless protein

retinal (retinene)

in the presence of light, rhodopsin molecules break down into yellowish organic molecules

What is the stimulus for Golgi tendon organs?

increased tension in tendon

When Golgi tendon organs are stimulated, contraction of the associated muscle is __________.

inhibited

tensor tympani

is inserted on the medial surface on the malleus and is anchored on the cartilaginous wall of the auditory tube; when contracting it pulls the malleus inward.

The variations in eye color are determined by the amount and distribution of melanin in what structure of the eye?

iris

Osseous (boney) labyrinth

is a cavity within the temporal bone

lens

is a clear, membranelike structure largely composed of intercellular material; quite elastic, a quality that keeps it under constant tension (flattened)

iris

is a thin diaphragm mostly composed of connective tissue, smooth muscle, and specialized contractile epithelial cells (colored portion of the eye); extends forward from the periphery of the ciliary body and lies between the cornea and the lens.

membranous labyrinth

is a tube of similar shape that lines within the bony labyrinth.

tympanic cavity (middle ear)

is an air-filled space in the temporal bone that separates the outer and inner ears; bounded by the tympanic membrane laterally and the inner medially.

stapedius

is attached to the posterior side of the stapes and the inner wall of the tympanic cavity; pulls the stapes inward when it contacts.

eyelid (palpebra)

is composed of four layers- skin, muscle, connective tissue, and conjunctiva.

dynamic equilibrium

maintenance of balance when the and body are suddenly moved or rotated;

static equilibrium

maintenance of balance when the head and body are not in motion; sense the position of the head, maintaining stability, and posture when still.

labyrinth

maze

hair cells

mechanoreceptors in the inner ear that triggers action potentials in fibers of the auditory nerve in response to sound vibrations; many have hairlike processes known as stereovilli (also called stereocilia) that extend into the endolymph of the cochlear duct.

The iris has color due to the amount of, and distribution of,_________.

melanin

The posterior portion of the vascular tunic is pigmented due to the presence of pigment-producing cells called

melanocytes

The posterior portion of the vascular tunic is pigmented due to the presence of pigment-producing cells called________?

melanocytes

In either case, stimulation locally changes the cell's _____ _____, generating a graded _______ _______ that reflects the intensity of stimulation.

membrane potential (receptor potential); electric current

round window

membrane-covered opening between the inner ear and the middle ear.

MSG

monosodium glutamate, used in many prepared foods, is formed from glutamic acid and also stimulates umami receptors

Louder sounds trigger_______ than do quieter sounds.

more action potentials

conjunctiva

mucous membrane covering the inside of the eyelid and much of the anterior surface of the eye

stretch reflex

muscle contraction in response to stretching the muscle

Proprioceptors include both pressure and stretch receptors. The stretch receptors include ________ and the pressure receptors include ________.

muscle spindles; lamellatted corpuscles

Pain receptors are widely distributed throughout the skin and internal tissues, except in the _______ ________ of the ______, which lacks pain receptors.

nervous tissue of the brain.

Enkephalins

neuropeptide that can suppress both acute and chronic pain impulses, therefore can relieve they can relieve strong pain sensations, much as morphine and other opiate drugs do.

Endorphins

neuropeptide with pain-suppressing, morphinelike actions; found in the pituitary and in regions of the nervous system, such as the hypothalamus, that relay pain information.

taste cells have vesicles that contain...?

neurotransmitter

In the olfactory bulbs, the sensory impulses are processed, and as a result, additional impulses travel along the ___________ __________ to portions of the limbic system, a brain center for memory, emotions, and related behavior.

olfactory tracts

oval window

opening to the inner ear, covered by the stapes

What area of the retina is lacking photoreceptors and is referred as the "blind spot"?

optic disc

After visual signals pass through the thalamus, they form ______, which go to the visual cortex. Other fibers go to the brainstem to stimulate ________.

optic radiations; visual reflexes

What are the muscles that move the eyelids

orbicularis oculi and levator palpebrae superioris.

Taste bud

organ containing receptors associated with the sense of taste; scattered in the roof of the mouth, the lining of the cheeks, and the walls of the pharynx.

spiral organ (organ of corti)

organ in the cochlear duct containing the receptors for hearing. it consists of hair cells and supporting cells; is on the superior surface of the basilar membrane and stretches from the apex of the cochlea to the base of the cochlea.

The sclera and the cornea make up the ______ tunic, or layer, of the eye.

outer

referred pain

pain that feels as if it is originating from a part other than the site being stimulated.

cochlea

part of the inner ear that has hearing receptors; is a tube, widest at its base and progressively narrower toward its tip, or apex; shaped like a snail shell, coiled around a bony core, the modiolus

projection

process by which the brain causes a sensation to seem to come from the region of the body being stimulated; allows someone to pinpoint the region of stimulation.

The _______ is a circular opening in the center of the iris.

pupil

iris

rainbow

umami

recognized in Japan means "delicious" but has only recently come to the attention of Western taste researchers; rises from the binding of certain amnio acids, including glutamic acid and also stimulate these receptors.

chemoreceptors

respond to changes in the concentration of chemicals. Receptors associated with the sense of smell and taste are this type. In internal organs detect changes in the blood concentrations of oxygen, hydrogen ions, glucose, and other chemicals.

Proprioreceptors

respond to changes in the tensions of muscles and tendons.

What type of photoreceptor provides black/white/gray vision?

rods

Taste buds are found?

roof of the mouth, the linings of the cheeks, and the walls of the pharynx.

inferior oblique

rotates the eye upward and away from the midline

saccule

saclike cavity that makes up part of the membranous labyrinth of the inner ear

What are degrees the warm receptors are sensitive and unresponsive?

sensitive > (25C) 77F, unresponsive > (45C) 113F

What are temperature are the cold receptors most sensitive?

sensitive between (10C) 50F- (20C) 68F

If the whole muscle is stretched, the muscle spindle is also stretched triggering what?

sensory impulses on its nerve fiber.

crista ampullaris

sensory organ in a semicircular canal that functions in the sense of dynamic equilibrium.

Golgi tendon organ

sensory receptors that sense tension and are involved in reflexes that help maintain posture; are in tendons close to their attachments to muscles

ceruminous glands

skin inside the ear that has modified sweat glands which secrete wax; helps keep large foreign objects, such as insects out of the ear

choroid

skinlike

Name the structure that contains the hearing receptors in the cochlea.

spiral organ

macula

spot

sour receptors

stimulated by acids; intensity is roughly proportional to the concentration of the hydrogen ions in the substance being tasted.

salt receptors

stimulated by ionized inorganic salts mainly; quality of the sensation the each receptor produces depends upon the type of positively charged ion that it releases into solution such as Na+.

bitter receptors

stimulated by variety of chemicals including many organic compounds. inorganic salts of magnesium and calcium produce sensations too.

In their roles as proprioceptors, the Golgi tendon organs and muscle spindles are _____ receptors, and the lamellated corpuscles in joints are _______ receptors.

stretch; pressure

The intrafusal fibers within a muscle spindle will be _____ when the muscle is stretched.

stretched

suspensory ligaments (zonular fibers)

strong but delicate fibers that extend inward from the ciliary processes and hold the lens in position; on the distal ends are attached along the margin of a thin capsule that surrounds the lens.

What are the five primary taste sensations?

sweet, sour, salty, bitter, and umami

What are the sensory organs of the mouth?

taste buds

lacri-

tears

What happens when a person descends from a high altitude to low altitude?

the air pressure on the outside of the tympanic membrane steadily increases; this may push the tympanic membrane inward, out of its normal position, impairing hearing.

cornea

the anterior sixth of the outer tunic bulges forward as a transparent window of the eye; helps focus entering light rays; largely composed of connective tissue with a thin surface layer of epithelium; contains no blood vessels and the collagen fibers form unusually regular patterns

What are the two such regions of the labyrinth?

the bony labyrinth and the membranous labyrinth

The resultant release of neurotransmitter by the rods inhibits....

the generation of action potentials along the optic nerve.

The transparent structure of the eye that changes shapes to focus light onto the retina is the ______.

the lens

optic nerve

the nerve that carries neural impulses from the eye to the brain in the back of the eye

Papilla

tiny; nipplelike projections

What are some stimulants that can trigger pain receptors?

tissue damage, mechanical damage, temperature extremes, ischemia, and hypoxia in a tissue.

aud-

to hear

olfact-

to smell

Most fibers from the optic______ enter the thalamus and reach the occipital lobe. Other fibers pass into the ______ and function in various visual reflexes.

tracts; brainstem

What is the cornea?

transparent anterior portion of the outer layer of the eye wall

True or false: The extrinsic eye muscles are considered accessory organs of the eye

true

auditory tube (eustachian tube)

tube that connects the middle ear cavity to the pharynx; eustachian tube; allows air to pass between the tympanic cavity; helps maintain equal air pressure on both sides of the tympanic membrane, this is necessary for normal hearing.

semicircular canals

tubular structure in the ear

cyanolabe

type of cone pigment sensitive to blue light

chlorolabe

type of cone pigment sensitive to green light

erythrolabe

type of cone pigment sensitive to red light

What are the accessory organs that assist with visual receptors in the eyes?

upper and lower eyelids and lacrimal apparatus that help protect the eyes and a set of extrinsic muscles that move them.

When the head is upright, the hairs of the macula in the utricle project _____, and those of the saccule project _____.

vertically; horizontally

saliva

watery fluid surrounding the taste bud; released when the mouth waters that plays an important role in both mechanical and chemical digestion;

aqueous humor

watery fluid that fills the anterior cavity of the eye; the epithelium on the inner surface of the ciliary body continuously secretes a watery fluid; the fluid circulates from this chamber through the pupil.

if all three types of cones are stimulated, what color do we see?

white

sclera

white fibrous outer layer of the eyeball; makes up the posterior five-sixths of the outer tunic and is opaque due to many large, seemingly disorganized collagen and elastic fibers.; protects the eye and is an attachment for the extrinsic muscles

lut-

yellow

macula lutea

yellowish depression in the retina of the eye associated with acute vision