Unit 2 -special senses

Where are smell receptors located?

Superior nasal cavity, cribriform plate, and nasal septum

What do olfactory receptor axons form?

Olfactory nerves (CN1)

What are 2 things that are part of the olfactory nerve?

Olfactory bulb and olfactory tract

How does the sense of smell travel?

Olfactory bulb → olfactory tract → eventually to cerebral cortex

What two regions does a smell impulse travel to?

Temporal and frontal lobe

What and where are taste buds located?

Groups of cells in papillae on tongue

Gustatory Sensation

Sense of taste

Gustatory pathway

Taste buds → CN VII, IX, X → limbic system and/or thalamus → parietal lobe

Palpebrae

eyelids

Conjunctiva

Membrane lines inside of palpebrae and covers front of eye, except cornea

Lacrimal apparatus

tears

Lacrimal glands - function

produces tears

Lacrimal glands- location

superior to lateral eye

Lacrimal duct

tube from gland to conjunctiva of upper lid

Lacrimal canal

medial corner of eye

Nasolacrimal duct

Drains → under inferior conchae in nasal cavity

Extrinsic eye muscles

6 per eye, move eye

Fibrous tunic

outer layer of eye divided into 2 regions (sclera, cornea)

Sclera

white tough tissue

Cornea

Avascular, covers front of eye, transparent

Vascular tunic

middle layer

Choroid

lines inside the sclera; dark layer that absorbs light

Ciliary muscle

attach to lens via suspensory ligaments; contracts to change shape of lens

Ciliary processes

folds secrete aqueous humor

Iris

colored portion; circular and radial muscle fiber layers; dilates and constricts to change size of pupil to allow more or less light into eye

Pupil

opening in iris; black circle

Lens

avascular, focuses light

Nervous tunic

rentina (inner layer)

Photoreceptor layer

Rods- for dim light, black and white Cones- bright light, color

Macula luta

specific area of retina straight back from pupil

Central fovea

central portion of macula lutea; highest concentration of cones→ most visual acuity/resolution; No rods here

Optic disk

blind spot, no photoreceptors

Anterior cavity

lens forward to cornea; contains aqueous humor

Posterior cavity

Lens back to retina; contains vitreous humor to prevent eyeball collapse and keep retina tight against choroid

Fibers continue to visual cortex

occipital lobe

External ear

Auricle, external auditory canal, tympanic membrane, ceruminous glands

Auricle

(pinna), collects sounds waves

External auditory canal

passes into temporal bone

Tympanic membrane

eardrum, vibrates when sounds waves hits it

Ceruminous glands

produce cerumen (wax)

Middle ear

air filled cavity, between tympanic membrane and oval window, eustachian tube (auditory): enters from nasopharynx

3 auditory ossicles

connected by synovial joints, (malleus, incus, and stapes)

Oval window

Stapes rests on oval window, entrance to inner ear (Scala vestibuli specifically)

Round window

below oval window, covered with small membrane, dampens vibration

Inner ear

Bony labyrinth, Membranous labyrinth, cochlea

Bony labyrinth

tubelike cavities in temporal bone, 3 semicircular canals, vestibule, cochlea, all filled with perilymph, surrounds and protects membranous labyrinth

Membranous labyrinth

membranous tubes containing sensory receptors for hearing and equilibrium, filled with endolymph - utricle,m saccule, ampullae, 3 semicircular ducts, cochlear duct

Cochlea

membranous cochlear duct passes through the middle → 3 '“snail” shaped, fluid filled chambers

Scala vestibuli

(upper chamber) contains perilymph

Scala tympani

(lower chamber) contains perilymph

Cochlear duct

contains endolymph, vestibular membrane- forms top of cochlear duct. basilar membrane - bottom membrane of cochlear duct

Organ of corti

rests on basilar membrane, hair cells with long microvilli, tectorial membrane

what do the vestibular and basilar membranes form?

the central fluid-filled chamber: cochlear duct

What fluid vibrations affect the endolymph and hair cells?

vibrations in the scala vestiboli and scala tympanihaw

What do fluid vibrations in the Scala vestibule and tympani affect?

Endolymph and hair cells in the cochlear duct

Microvilli

contact with tectorial membrane

Auditory Pathway

Auricle, External Auditory canal, Tympanic membrane, Malleus, Incus, Stapes, Oval window, Perilymph, Endolymph, Hair cells, Vestibulocochlear Nerve (CN VIII)

Fibers ascend to…

inferior colliculus, thalamus, primary auditory cortex in the temporal lobe

Vestibule

contains utricle and saccule- made of hair cells, Gel-like membrane on hair cells, otoliths in membrane, static equilibrium

Semicircular canals

for dynamic equilibrium

Semicircular ducts

membranous portion, contains endolymph

Ampulla

expanded portion at the end of semicircular ducts, inside is hair cells covered by gel-like membrane