anatomy 403: neuro 4: special senses

special senses

• what cranial nerve is associated with olfaction?

CN I - olfactory n.

special senses

• what cranial nerve is associated with gustation?

CN VII - facial n., CN IX - glossopharyngeal n., CN X - vagus n.

special senses

• what cranial nerve is associated with vision?

CN II - optic n.

special senses

• what cranial nerve is associated with hearing and balance?

CN VIII - vestibulocochlear n.,

olfaction

• olfaction is a chemical sense

• olfactory receptors are within the ________

  • superior part of the nasal cavity

  • inferior surface of the cribiform plate

olfactory epithelium

olfaction

• the olfactory epithelium consists of three kinds of cells

  • ________: bipolar neurons, transduce odorant molecules into neural signal

  • supporting cells: equivalent to glia, nourish, protect, insulate

  • ________: divide and give rise to new olfactory receptors

    • this is the exception to the normal rule of the nervous system

olfactory receptors, basal cells

olfactory pathway

• olfactory nerves terminate in the olfactory bulbs

• olfactory bulb neurons project to the cortex via the _______

  • it’s the only sense to bypass the thalamus and goes to the limbic system

olfactory tract

olfactory pathway

• olfactory tract axons project to the primary olfactory area (______, _____) located at the inferior and medial surface of the temporal lobe

• olfactory tract projects to the limbic system (amygdala) and hypothalamus

  • this is why smell has an immediate, emotional impact

piriform cortex, entorhinal area

what structure is this?

olfactory bulb

what structure is this?

olfactory tract

gustation

• taste or gustation, is a chemical sense

  • what are the five primary tastes?

sour, sweet, bitter, salty, umami

taste buds

• what are the three kinds of epithelial cells for taste buds?

sensory cells, support cells, and basal cells

taste buds

• _______: constantly renewed (~100 days), long microvilli at the apical surface that extend into the taste pore. these cells are not neurons but are in contact with axons of sensory neurons

sensory cells

taste buds

• ______: equivalent to glia, nourish, etc.

support cells 

taste buds

• ______: divide, mature, and replace old sensory cells

basal cells

taste buds

• taste buds are found on _______

papillae

papillae

• ______: form an inverted V-shaped row at the back of the tongue 

vallate papillae

papillae

• ______: are mushroom-shaped elevations scattered over the entire surface

fungiform papillae

papillae

• ______: are located in the small trenches on the lateral margins of the tongue

foliate papillae

papillae

• ______: contain tactile receptors but no taste buds. they increase friction between the tongue and food, making it easier for the tongue to move food in the oral cavity

filiform papillae

what structure is this?

foliate papillae

what structure is this?

vallate papillae

what structure is this?

fungiform papillae

what structure is this?

filiform papillae

cranial nerves and taste

• ______ serve the anterior two-thirds of the tongue

facial (CN VII)

cranial nerves and taste

• _______ serves the posterior one-third of the tongue

glossopharyngeal (CN IX

cranial nerves and taste

• ______ serves the throat and epiglottis

vagus (CN X)

cranial nerves and taste

• general sensation?

trigeminal (CN V)

anatomy of the eyeball

• what is the top arrow pointing to?

outer fibrous layer

anatomy of the eyeball

• what is the middle arrow pointing to?

an intermediate vascular layer

anatomy of the eyeball

• what is the lower arrow pointing to?

an inner neural layer

fibrous (outer) layer

• ______: the outer layer of the eye, is a strong dense collagenous connective tissue layer, 2 divisions of the sclera and cornea

fibrous tunic

fibrous (outer) layer

• _______: tough opaque outer covering, forms the white part of the eye, provides protection, maintains the shape of the eyeball, serves as the site of muscle attachment for the extrinsic eye muscles

sclera

fibrous (outer) layer

• ______: transparent anterior surface of the outer tunic, main refractive index of the eye

  • avascular with regularly spaced collagen fibers that are smaller than the wavelength of light

cornea

fibrous layer

• what structure is this?

sclera (diagram)

fibrous layer

• what structure is this?

cornea (diagram)

anatomy of the eyeball

• _______: middle layer of the eyeball, three parts: choroid, ciliary body, and iris

vascular tunic

anatomy of the eyeball

• ______: highly vascularized, provides nutrients to the posterior (deep) surface of the retina, lines most of the sclera

choroid

anatomy of the eyeball

• ______: anterior portion of the vascular tunic, consists of ciliary processes and ciliary muscle. the ciliary processes contain capillaries and secrete aqueous humor (fluid that fills the anterior and posterior cavitites)

  • extending from the ciliary process are zonular fibers (suspensory ligaments) that attach to the lens 

ciliary body

anatomy of the eyeball

• _______: are arranged longitudinal, oblique, and circularly. contraction or relaxation of the ciliary muscle changes the tension on the zonular fibers, which alters the shape of the lens, adapting it for near or far vision

ciliary muscle

anatomy of the eyeball

• ______: colored part of the eye, sphincter and dilator muscles control the diameter of the pupil

iris

vascular layer of the eyeball

• the ciliary processes contain capillaries and secrete _______, fluid that fills the anterior and posterior cavities, eye equivalent to choroid plexus)

aqueous humor

what structure it this?

iris (diagram)

what structure is this?

ciliary body

vascular layer of the eyeball

• contraction/relaxation of the ciliary muscle changes the _____ of the lens

• within the cells of the lens, proteins called _______ are arranged like the layers of an inion and make up the refractive media of the lens

• the lens is asvacular

shape, crystallin

vascular layer of the eyeball

• constrictor pupillae (circular) are innervated by _______ fibers

parasympathetic

vascular layer of the eyeball

• dilator pupillae (radial) are innervated by ______ fibers

sympathetic

neural layer

• _______: non-visual portion, absorbs stray light and helps keep image clear

retinal pigmented epithelium (RPE)

neural layer

• what are the three layers of neurons in the eye?

photoreceptor, bipolar, ganglion

neural layer

• what does the photoreceptor layer do?

detects light

neural layer

• what does the bipolar neuron layer do?

relay to ganglion neurons

neural layer

• what does the ganglion neuron layer do?

output to thalamus

neural layer

• what other neuronal types modify the signal?

horizontal and amacrine cells

neural layer

• the _____ is the site where the optic nerve (CN II) exits the eyeball

optic disc

neural layer

• the optic nerve (CN II) is formed by the collected axons of the ganglion layer neurons 

• the ________, a branch of the opthalmic artery and the central retinal vein also travel within the optic nerve

central retinal artery

neural layer

• the retina covers the posterior ¾ of the eyeball

• central artery of the retina: branches to supply ______ to the retina

nourishment

neural layer

• _______ (yellow spot, fewer blood vessels) is in the exact center of the posterior portion of the retina, at the visual axis of the eye

macula lutea

neural layer

• _____: a small depression in the center of the macula lutea, contains only cones and is the area of highest visual acuity or resolution

fovea centralis

neural layer

• what is this structure?

optic nerve

interior of the eye

• what two fluid-filled cavities does the interior of the eye contain?

anterior and posterior

interior of the eye

• what does the anterior cavity contain?

aqueous humor

interior of the eye

• where is the anterior cavity located?

between the cornea and lens

interior of the eye

• what does the posterior cavity contain?

vitreous humor

interior of the eye

• ______: between the cornea and lens, contains aqueous humor

• ______: vitreous cavity/chamber, more gel-ike, made by the cilkiary process, helps hold the retina in place

anterior, posterior

what is the light pathway?

cornea → aqueous humor → pupil → lens → vitreous humor → ganglion cell layer → rods and cones

what is the path for the visual information pathway?

rods and cones → ganglion cell layer → optic nerve → optic chiasm → optic tract → laterla geniculate body → visual cortex, area 17

visual pathways

• half of the ganglion cell axons cross the midline at the ______ and the other half do not cross it 

optic chiasm

what structure is this?

optic nerve

what structure is this?

optic chiasm (diagram)

what structure is this?

optic tract

external ear

• the external ear consists of the ______

auricle (pinna)

external ear

• the structure of the auricle is made of _______

• contains the opening of the external auditory meatus

• _____ = ear wax

elastic cartilage, cerumen

middle ear

• the middle ear is a small, air-filled cavity in the temporal bone that is lined by ______

• the auditory ossicles are connected to one another by synovial joints and attached by ligaments

• three ossicles: malleus, incus, and stapes

epithelium

middle ear

• the malleus is in contact with the _______

tympanic membrane

middle ear

• the head of the malleus articulates with the _____

incus

middle ear

• the incus articulates with the _____

stapes

middle ear

• the footplate of the stapes fits into the oval window of the _____

cochlea

middle ear

• ______ limits movement and increases tension on the eardrum (CN V)

tensor tympani muscle

middle ear

• ______ dampens large vibrations of the stapes due to loud noises, to protect the oval window (CN VII)

stapedius muscle

middle ear

• _______ connects the middle ear with the nasopharynx, equilibrates pressure

auditory tube 

inner ear

• what are the two main divisions of the inner ear?

the outer bony labyrinth and inner membranous labyrinth

inner ear

• functionally, the three main areas are what?

semicircular canals, vestibule, and the cochlea

inner ear

• the semicircular canals and vestibules help with what?

balance

inner ear

• the cochlea helps with what?

audition

internal ear

• the bony labyrinth is lined with ______ and contains ______

periosteum, perilymph

internal ear

• membranous labyrinth. =set of membranous tubes containing _______ for hearing and balance and filled with _______

  • utricle, saccule, 3 semicircular canals, cochlea

sensory receptors, endolymph

internal ear

• the cochlea, a bony spiral canal divided into three parallel channels:

  • ______ filled with endolymph

  • ______ begins at the oval window, filled with perilymph

  • ______ ends at the round window, filled with perilymph

cochlear duct, scala vestibuli, scala tympani

organ of corti

• cochlear duct

  • the ______ supports inner and outer hair cells

  • hair cells are connected to the peripheral process of a pseudo-unipolar neuron of the spiral ganglia

    • the spiral ganglia neurons project into the brain stem via the ______, a division of the vestibulocochlear nerve (CN VIII)

basilar membrane, cochlear nerve

what structure is this cn?

cochlear nerve

what structure is sg?

spiral ganglia

what structure is bm?

basilar membrane

mechanism of hearing

• vibrations in the air cause tympanic membrane to vibrate, transferred to malleus a the ____ (pointy part of the tympanic membrane)

• vibration is transferred through the incus and stapes to the membrane covering the oval window

• vibration goes from oval window to perilymph of the scala vestibule → endolymph of cochlear duct → basilar membrane → round window

• as the basilar membrane vibrates, the ______ (apical part of the cell) of the hair cells contact the tectorial membrane, hair cells bend

umbo, microvilli

mechanism of hearing

• basal surface of hair cells are in contact with the 1st order sensory neurons whose cell body is in ______

spiral ganglion

mechanism of hearing

• inner and outer hair cells have different functions

  • inner hair cells ____ sound

  • outer hair cells ____ sound 

• pitch is determined by vibration of different parts of the basilar membrane

  • narrow, stiff at base → high frequency, high pitch wider

  • more flexible at apex → low frequency, low pitch

signal, amplify 

mechanism of hearing

• pathway

  • inner hair cells → spiral ganglion cells → cochlear nuclei, brain stem → coordinating centers in brain stem → medial geniculate nucleus of the thalamus → primary auditory cortex (_____, ______)

Brodmann’s areas 41,42 and superior temporal gyrus 

mechanism of equilibrium

• the receptor organs for equilibrium of the vestibular apparatus includes the ____, _____, and _____

utricle, saccule, and semicircular canals 

mechanism of equilibrium

• what are the two types of equilibrium?

static and dynamic

mechanism of equiibrium

• ______: maintenance of the position of the body relative to the force of gravity

static equilibrium

mechanism of equilbrium

• ______: is the maintenance of body position in response to sudden movements and acceleration 

dynamic equilibrium