chapter 15

what are some special senses

-smell

-taste

-sight

-hearing

-equilibrium

gustation:

taste

olfaction:

smell

taste buds are found in:

papillae of the tongue mucosa

papillae come in three types:

filiform

fungiform

circumvallate

what are the three major epithelial cell types in taste buds

supporting cells- insulate the receptors

basal cells- dynamic stem cells

gustatory cells- taste cells

what are the five basic taste sensations

sweet

salt

sour

bitter

umami

in order to be tasted, a chemical must:

must be dissolved in saliva

must contact gustatory hairs

which cranial nerves carry impulses from taste buds to the solitary nucleus of the medulla

cranial nerves:

VII (facial) IX (glossopharyngeal)

taste is 80%:

smell

thermoreceptors, mechanoreceptors, nociceptors also influence:

taste

the organ of smell is the:

olfactory epithelium, which covers the superior nasal concha

olfactory receptor cells are bipolar neurons with:

radiating olfactory cilia

olfactory receptors are surrounded and cushioned by:

supporting cells

olfactory receptor cells synapse with:

with mitral cells in the olfactory bulb

what do glomerular mitral cells do

they process odor signals

mitral cells can send impulses to:

• the olfactory cortex

• the hypothalamus, amygdala, limbic system

70% of all sensory receptors are in the:

in the eye (dominant sense)

lacriamal caruncle contains-

glands that secrete a whitish, oily secretion

tarsal plates of connective tissue support-

the eyelids internally

lavator palpebrae superiroris-

gives the upper eyelid mobility

describe the lacrimal gland

• consists of the lacrimal gland and associated ducts

• lacrimal glands secrete tears

how many extrinsic eye muscles

six straplike extrinsic eye muscles

• enable the eye to follow moving objects

• maintain the shape of the eyeball

describe fibrous tunic

forms the outermost coat of the eye and is composed of

• opaque sclera (posteriorly)

• clear cornea (anteriorly)

describe the choroid region

a dark brown membrane that forms the posterior portion of the uvea

• supplies blood to all eye tunics

• absorbs stray light

describe ciliary body

• a thickened ring of tissue surrounding the lens

• composed of smooth muscle bundles (cilliary muscles)

describe the iris

• the colored part of the eye

• pupil- central opening of the iris

iris functions

regulates the amount of light entering the eye

describe the retina

a delicate two layer membrane

what are the two layers of the retina

• pigmented layer- the outer layer that absorb light and prevents its scattering

• neural layer, which contains: photoreceptors that transduce light energy

describe ganglion cell axons

• run along the inner surface of the retina

• leave the eye as the optic nerve

describe the optic disc

• the site where the optic nerve leaves the eye

• lacks photoreceptors (the blind spot)

the neural retina receives its blood supply from what two sources

• the outer third receives its blood from the choroid

• the inner two-thirds is served by the central artery and vein

the lens separates the internal eye into what two segments

anterior and posterior segments

the posterior segment is filled with clear gel called:

vitreous humor

what does vitreous humor do:

• transmits light

• supports the posterior surface of the lens

• holds the neural retina firmly against the pigmented layer

the anterior segment is composed of what two chambers

• anterior- between the cornea and the iris

• posterior- between the iris and the lens

describe aqueous humor

• a plasmic like fluid that fills the anterior segment

• drains via the canal of schlemm

• supports, nourishes, and removes wastes

describe a lens

a biconvex, transparent, flexible, avascular structure

• allows precise focusing of light onto the retina

• is composed of epithelium and lens fibers

axons of the retinal ganglion cells form the:

optic nerve

medial fibers of the optic nerve decussate at the:

optic chiasm

most fibers of the optic tracts continue to the:

thalamus

optic radiations travel from the thalamus to the:

visual cortex

some nerve fibers send tracts to the midbrain ending in the:

superior colliculi

• controls extrinsic eye muscles

the three parts of the ear are-

inner, outer, and middle ear

the outer and middle ear are involved with-

hearing

the inner ear functions in both-

hearing and equilibrium

the auricle (pinna) is composed of:

• the helix (rim)

• the lobule (earlobe)

describe the external auditory canal

short, curved tube filled with ceruminous glands

describe the tympanic membrane (eardrum)

• thin connective tissue membrane that vibrates in response to sound

• transfers sound energy to the middle ear ossicles

• boundary between outer and middle ears

describe the tympanic cavity

a small, air filled, mucosa lined cavity in the petrous part of the temporal bone

what is the epitympanic recess

superior portion of the middle ear and contains the mastoid antrum

the tympanic cavity contains what three small bones:

• malleus

• incus

• stapes

describe the cochlea

a spiral, conical, bony chamber

• extends from the anterior vestibule

• coils around a bony pillar called the modiolus

• contains the cochlear duct, which ends at the cochlear apex

the cochlea is divided into what three chambers

• scala vestibuli

• scala media (cochlear duct)

• scala tympani

the scala tympani terminates at the:

round window

the scala media is filled with-

endolymph

the “floor” of the cochlear duct is composed of:

• the bony spiral lamina

• the basilar membrane , which supports the organ of corti

the route of sound to the inner ear follows this pathway:

1. outer ear- pinna, auditory canal, eardrum

2. middle ear- malleus, incus, and stapes to the oval window

3. inner ear- scalas vestibuli and tympani to the cochlear duct

4. impulses from the cochlea pass via the spiral ganglion to the cochlear nuclei

5. from there, impulses are sent to the thalamus

6. from there impulses pass to the auditory cortex

7. auditory pathways decussate so that both cortices receive input from both ears