Special Senses
name the three cranial nerves that carry impulses for taste
1. VII (facial): anterior ²/₃ tongue 2. IX (glossopharyngeal): posterior ¹/₃ tongue 3. X (vagus): epiglottis taste buds
external ear consists of
1. auricle (pinna) 2. external auditory canal 3. tympanic membrane
layers of the eyelid (superficial to deep)
1. epidermis 2. dermis 3. hypodermis 4. skeletal muscle (orbicularis oculi) 5. tarsal plate and tarsal glands
inner ear consists of
1. equilibrium apparatus (semicircular canals & vestibule) 2. hearing apparatus (cochlea)
middle ear consists of ossicles in the antrum of the temporal bone
1. malleus-attached to tympanic membrane 2. incus-attached to malleus and stapes 3. stapes-attached to incus and oval window->cochlea
layers of cells in the retina
1. pigmented epithelium (Deep) 2. photoreceptors 3. bipolar neurons 4. ganglion cells (Superficial)
what are the two types of photoreceptors and what do they detect?
1. rods: allow for dim light vision 2. cones: allow for color and sharpness of vision
four tastes
1. sour 2. sweet 3. salty 4. bitter
how many extrinsic eye muscles; name them
1. superior rectus muscle 2. inferior rectus muscle 3. medial rectus muscle 4. inferior oblique muscle 5. superior oblique muscle 6. lateral rectus muscle
what is the importance of smell in tasting?
80% of taste is due to smell, you can't taste well without smell
where is the canal of Schlemm (sclera venous sinus) located? what flows into this canal?
a. around the eye b. aqueous humor
what is the significance of the fibrous sclera?
a. blood vessels b. nerves
vascular tunic (uvea)
a. choroid b. ciliary body c. iris
what are the two parts of the ciliary body?
a. ciliary process: makes aqueous humor (CSF-like fluid) b. ciliary muscle: controls shape of the lens by suspensory ligament
which two muscles are located in the iris? smooth or skeletal? which muscle controls how much light passes?
a. dilator pupillae b. constrictor pupillae c. both they are all smooth muscle
cochlea; consists of 3 membranous tubes encased by a bony labyrinth
a. hearing; 2 ³/₄ turns b. oval window, cochlear duct with organ of corti, round window
what are the functions of the choroid?
a. melanin: to absorb light b. blood vessels: to help nourish the retina
fibrous tunic
a. sclera: "white" of eye, dense irregular connective tissue b. cornea: clear
aqueous humor is made by the _______ _______ of the _______ _______
a/b. choroid plexus c/d. ciliary process
where is the lacrimal gland located?
above the eye; frontal bone, superior and lateral to the eye
how do both (far and close distance) get refracted onto the retina?
accommodation (the lens)
what is the significant of the auditory tube?
allows for equalization of pressure when pressure builds in the antrum (middle ear)
function of middle ear
amplify the waves to fluid of inner ear
anterior cavity
anterior and posterior chamber (in front and behind iris)
how does the cornea get its nourishment?
aqueous humor
what is the central fovea (fovea centralism)?
area of sharpest vision, only cones are here
is the lacrimal gland innervated by the autonomic or somatic nervous system?
autonomic nervous system
what makes the optic nerve?
axons of ganglion cell
ampulla with receptor cells
bending of hairs cause by endolymph(fluid) movement
refraction
bending of light from one medium to the next
what types of cones are there?
blue, green, red cones
which glands prevent foreign objects from entering the external auditory canal?
ceruminous (wax) glands
what do you call an infection of the tarsal glands?
chalazion (cyst in eyelid)
accommodation
changing the shape of the lens by ciliary muscle to keep the focal distant constant; automatic adjustment of the eye to give us clear vision
what types of receptors are found in the nasal epithelium?
chemoreceptors
what types of receptors are taste buds?
chemoreceptors-gustatory cells
how does the lens change its shape? explain the function of the ciliary muscle
ciliary muscle (smooth) surround the lens and are attached to it via the suspensory ligaments; controls shape of the lens
what is a cataract?
clouding of the lens, light can't come in->no vision
function of external ear
collect sound waves and transmit them to middle ear
auditory tube (Eustachian tube) connects what?
connects middle ear cavity to nasopharynx
which muscle(s) in the iris are innervated by the parasympathetic nervous system?
constrictor pupillae
beginning with the cornea name the structures that light must pass through in order to get to the retina
cornea->anterior chamber with aqueous chamber->iris/pupil->posterior chamber with aqueous humor->lens->posterior cavity with vitreous humor->rods and cones of the retina
how do the olfactory nerves enter the brain?
cribriform plate of the ethmoid bone->olfactory bulb->olfactory tract
what is conduction deafness? name some causes
damage that occurs to the structure of the external, middle, or inner ear (anything before the organ of corti) causes: something blocking passage ways or repeated ear infections, cause the structures not to move as well
what is sensoneural deafness? name some causes
damage to the sensory pathway, inner ear, nervous tissue damage (anything after the organ of corti) causes: exposure to loud noise, head trauma, and virus/disease
what gives the iris its color?
determined by genes that influence the density and distribution of melanocytes in the anterior and interior surface of the iris, as well as by the density of the pigmented epithelium.
refraction at close distance
divergent light rays
which retinal fibers cross to the opposite side? which do not?
do cross: medial retinal fibers do not cross: lateral retinal fibers
myopia
eyeball too long-difficult with distant vision
hyperopia
eyeball too short-difficult with near vision
which cranial nerve innervates the lacrimal gland?
facial VII
pitch
frenquency
how can hyperopia be corrected?
glasses-biconvex-bring image to retina
how can myopia be corrected?
glasses-concave-bring image to retina
where does the pathways for taste (gustatory area) end?
gustatory cortex in the insula of the brain
vestibule: static equilibrium (primarily)
head position
what is the function of the vitreous body/humor?
helps stabilize the shape of the eye, when the extrinsic eye muscles change position
astigmatism
irregular curvature of the cornea
explain the flow of tears
lacrimal gland->eye->lacrimal canals->nasolacrimal duct
which extrinsic eye muscle is innervated by the abducens nerve (VI)
lateral rectus muscle
presbyopia
lens loses its ability to change its shape
conjuctiva, found where in the eye?
loosely bound sac attached to the sclera on inner surface of the eyelid
semicircular canals: dynamic equilibrium
maintaing position while moving (rotation of the head)
what type of vision might be lose with a person with a tumor of the pituitary gland?
medial retinal fibers=peripheral vision
what is unique about the cornea?
no blood vessels, stratified squamous(outside), simple squamous (inside), lots of nerve fibers
what is emmetropia?
normal vision; in the healthy eye, when the ciliary muscle is relaxed and the lens is flattened, a distant image will be focused in the retina's surface.
loudness
number of hairs stimulated
what is the function of the aqueous humor?
nutrient and waste transport, form a fluid cushion
where do the pathways for olfaction end in the brain?
olfactory cortex of the temporal lobe; pathway bypasses Thalamus; part of limbic system:smells involved in memory/emotion
which nerve carries olfactory impulses?
olfactory nerve (I)
what is meant by the optic disc or blind spot? what is unique about it?
optic nerve is at optic disc; there are no photoreceptors there
physiology of hearing
organ of corgi->VIII vestibulocochlear nerve->temporal lobe (inferior colliculi)
high frequency sound are heard near the ______ ________
oval window
refraction at far distance
parallel light rays
visual pathway
photoreceptor->bipolar neuron->axons of the ganglion cells-> optic nerve->chiasma-> optic tract-> thalamus(superior colliculi)-> occipital lobe
why does conjunctivitis lead to red eyes? what is happening?
pink eye: due to the dilation of blood vessels deep to the conjuctival epithelium. condition caused by infection, allergic, physical, or chemical irritation of the conjuctival surface.
where are taste buds located?
primarily on the papillae of the tongue
what is the lens made of?
proteins-gives it elasticity
what does it mean that olfaction has a low threshold?
receptors are very sensitive (send an action potential), it doesn't take much to stimulate olfactory receptors
what is the importance of quick adaptation for smell?
repeated odors cause a decrease in stimulation and action potential generated->can't smell odor anymore
nervous tunic
retina
are rods and cones evenly distributed in the retina? if not, where are they primarily located?
rods: densely around the periphery of eyeball (dim light) cones: around central fovea (sharpest vision)
where is the nasal epithelium for smell located?
roof of the nasal cavity
will the lens get more round or flat when you look at something close up?
round
low frequency sound are heard at the end of the _______ _______
scala vestibuli (middle of the cochlea)
utricle and saccule (with receptor cells)
small "otoliths" slide over these receptors acceding to head position. the bending of the hairs on the receptor cells initiates the action potential
which extrinsic eye muscle is innervated by the trochlear nerve (IV)
superior oblique muscle
what extrinsic eye muscles are innervated by the oculomotor nerve (III)
superior rectus muscle, inferior rectus muscle, medial rectus muscle, inferior oblique muscle
what is the significance of the nasolacrimal duct?
tears flow down to nasal cavity=runny nose; important so there isn't an overflow of tears onto the face
through which bone does the external auditory canal travel?
temporal bone
where is the "hearing center" in the brain located?
temporal lobe
what is unique about the synthesis of vitreous humor?
the vitreous humor is formed during development of the eye and is not replaced
what happens to taste buds as you age?
they decrease in number
what is the significance of the tympanic membrane?
to amplify and transmit the sound waves to the middle ear and inner ear through vibrations of it
what is the function of the lens?
to see far: flat, thin lens to see close: round, bulge lens
glaucoma
too much aqueous humor, too much pressure-"chokes" optic nerve
which nerve will carry impulses to the brain?
vestibulocochlear nerve
posterior cavity
vitreous humor or vitreous body (more like gel)
what does it mean to say that someone has 20/20 vision?
you can see from 20 ft what a normal person sees from 20 ft
what does it mean to say that someone has 20/60 vision?
you can see from 20 ft what a normal person sees from 60 ft
