IPHY 3430 SPECIAL SENSES

Special Senses receptor types:

1) chemoreceptors

2) mechanoreceptors

3) photoreceptors

Which of the following is NOT a Special Sense?

touch

What are the five special senses?

1) smell -chemoreceptors

2) taste- chemoreceptors

3 & 4) hearing and equilibrium (balance)- mechanoreceptors

5) sight -photoreceotors

Olfaction (smell)

Olfactory chemoreceptors located within pseudostratified ciliated columnar epith.

Chemoreceptors synapse with interneurons of brain within the olfactory bulbs

Olfactory Bulb

CNS

Olfactory receptor cell

PNS

Olfactory Receptors

1) mucous traps the molecules from inhaled air

2) the olfactory response gets activated

3) all the receptors activated by the same molecule type synapse in the GLOMERULUS: amplify the signal

4) activated interneurons send signals to the brain thru the OLFACTORY tract to olfactory cortex

The tongue has four types of papilla, but two are

Vallate (circumvallate) papilla

Fungiform papilla

Taste buds

1) each papilla contains many taste buds

2) each taste bud has 50-100 cells and a taste pore

3) Has basal cells

4) Has supporting cells

Tongue basal cell

Immature cells that replace old/damaged cells every 7-10 days

Tongue Supporting cells

insulatory

Taste pore

opening in taste bud where molecules get dissolved in saliva

Gustatory receptor cells

Are activated when the microvillus (hair) comes in contact with molecules

Types of taste sensations

sweet, sour, salty, bitter, umami

Axons (taste fibers)

transport signal to CNS

Flavor

Is a combination of taste, smell, and texture

Iris

The colored portion of the eye made up of smooth muscle, Contracts/enlarges to change size of pupil and regulates light entering eye

Pupil

This is the hole within the iris that can change it's diameter

Scelera

The white of the eye, an extension of the dura matter (covered with conjunctiva)

Eyelid (palpebra): Palpebral Fissure

This is the opening created when the eyelid is up

Lacrimal gland

Made of serous cells that produce tears, the role of the tears is that is washes away irritants away from the surface of the eye

How does the lacrimal gland drain

Goes from the lacrimal canaliculi, to the lacrimal sac, nasolacrimal duct, to the nasal cavity

Movement of the eye

Movement is controlled by 6 extrinsic muscles, is made up of skeletal muscle that is connected to the scelera

Strabismus

Misaligned eyes (cross eyed), results in double vision, lack os stereoscopic vision, amblyopia

What causes strabismus

A problem with one of more of the extrinsic eye muscles, the eyes do not align properly

Amblyopia

This is reduced vision in the weaker eye

What are the layers of the eye?

fibrous tunic, vascular tunic, sensory tunic

Fibrous tunic

the outer layer of the eye (extension of the dura matter), provides protection and mechanical support, AVASCULAR,

1) Sclera = DENSE IRREG CT

2) Cornea = DENSE IRREG CT

The sclera is covered by what?

Conjunctiva

Conjunctiva

Mucous membrane --> strat columnar epith with Goblet cells

Vascular tunic

lines the inner surface of the sclera, has three major parts: choroid, iris, ciliary body

Choroid

vascular, dark surface absorbs excess light

Ciliary Body

smooth muscle,

-Controls shape of lens, which focuses light on the back surface of the eye

-Capillaries within produce aqueous humor

Ciliary processes of ciliary body

produces aqueous humor

Scleral venous sinus

drains/removes the aqueous humor from the eye

Aqueous humor

fluid in the eye, found between the cornea and the lens that circulates thru the anterior segment of the eye.

•Supplies nutrients/oxygen to lens & cornea

•Blood filtrate from ciliary bodies

•Removed at scleral venous sinus

Sensory tunic

Retina, 2 layered structure: pigmented layer and neural layer

Retina (pigmented layer)

Lies against the choroid, is a single epithelial layer that contains melanin granules, absorbs light, and nourishes the neural layer

Retina (neural layer)

Touching the lumen of the eye, has 3 types of neural cells: photoreceptor cells, bipolar cells, ganglion cells

Photoreceptor cell

specialized nerve cell stimulated by light; for example, rods and cones of the retina

Rod cells

most abundant, very sensitive to light (good for night vision), absorbs photons of green light, primarily on the side of the retina

Cone cells (color vision)

3 subtypes that respond to blue, red, and green light, works best in bright light (does not function well in low light conditions), concentrated within the retina at the back of the eye

How does light travel to the brain

cones/rods activated by light, bipolar cells activated by the cones/rods, ganglion cells are activated by the bipolar cells, and then the axons of ganglion cells contained within the optic nerve take the signal to the brain

Optic disc

location at back of eye where axons of ganglion cells leave eye = BLIND SPOT

Macula lutea

a yellowish central area of the retina that is rich in cones and that mediates clear detailed vision

Fovea centralis

very center of macula lutea; ALL cones, maximum visual acuity, an image focuses here when you are looking directly at it

Lens

simple cuboidal epithelium, concentric layers of fibers (produced by epithelial cells), changes shape to focus light, separates the anterior segment from the posterior segment of the eye.

Emmertropic eye

Normal, light focuses on retina

Myopic Eye

Nearsighted eye, harder to see far away, where the eye is too long to focus images in front of retina, to correct it has to do with the concave lens

Hyperopic eye

Farsighted, harder to see up close, where the is is too short, the image focuses behind retina, to correct it has to do with the concave lens

Presbyopia

The lens becomes less elastic as we age

Lasik surgery

• Surface of cornea is reshaped using a laser

• This functions to re-directlight properly onto retina surface

Astigmatism

•Abnormal shape of cornea surface (such as a bulge) causes light rays to diffract/scatter differently

•Result in two or more focal points

Anterior segment of the eye

between the cornea and the lens, contains the aqueous humor

Glaucoma

Condition where aqueous humor is drained slower than it is produced

•Increase in intraocular pressure damages retina

posterior segment of eye

behind the lens, contains vitreous humor

Vitreous humor

jelly-like substance found behind the lens in the posterior cavity of the eye that maintains its shape, 98% water, collagen, supports lens and retina

Detached retina

A hole or small tear in the retina allows vitreous humor to leak between the pigmented and neural layers of retina, Photoreceptor cells will eventually die if the neural layer is not reattached to the nourishing underlying layer

What are the three structures of the ear

External ear, middle ear, inner ear: function is hearing and equilibrium

External ear

Collects and directs sound waves

Middle ear

Amplifies and transmits sound waves

Inner ear

Sensory organs for hearing and equilibrium

Structures of the external ear

Auricle (pinna), external acoustic meatus, tympanic membrane (eardrum)

Auricle (pinna)

outer fleshy portion of ear; provides protection

External acoustic meatus

An air filled canal, made of STRAT SQUAM EPITH. , has hairs that keeps insects and foreign material out, ceruminous glands, perforated eardrum

Ceruminous glands

secrete cerumen (wax) which inhibits microorganism growth

Tympanic membrane (eardrum)

This is what separates the external and middle ear, FIBROUS DENSE CT, and lined by mucous membrane on middle ear side, gets vibrated when sound wave hit it

Perforated Eardrum

membrane will heal but scar tissue can affect hearing

Middle Ear Structure

air filled cavity, contains auditory ossicles, connects to nasopharynx via pharyngotympanic (auditory) tube

Auditory Ossicles

small bones that transmit vibration from tympanic membrane towards inner ear

What are the small bones of the Auditory Ossicles

1) Malleus

2) Incus

3) Stapes

Pathway of vibration:

tympanic membrane (eardrum) --> malleus --> incus --> stapes --> oval window (connects to inner ear)

Skeletal Muscles associated with auditory ossicles

-Small muscles tense up to control strong vibrations which could damage receptors in the inner ear: tensor tympani and stapedius

Tensor Tympani

the muscle attached to the malleus; tensing the tensor tympani decreases vibration

Stapedius

the muscle attached to the stapes; tensing the stapedius decreases vibration

Pharyngotympanic (auditory) tube

allows you to equalize pressure with outside air

Oval Window (entrance for sound vibration)

vibrations from stapes pass to fluid of inner ear through oval window

Round window (exit for sound vibration)

where vibrations leave inner ear after they have activated receptors

Inner Ear structure (labryinth)

contains sensory receptors for hearing and equilibrium, fluid filled, consists of a membranous duct contained within bone

Bony Labyrinth of inner ear

Contains perilymph, thought to be the same as CSF

Has three regions:

1) cochlea

2) vestibule

3) semicircular canals

membranous labyrinth of inner ear

contains endolymph, ionically distinct from perilymph, do not mix

Regions float in bony labyrinth:

1) cochlear duct (in cochlea); sound

2) Utricle (in vestibule)

3) Saccule (in vestibule)

4) Semicircular ducts ( in the semicircular canals

What three things in the membranous labyrinth are responsible for equilibrium

Utricle, Saccule, Semicircular ducts

The Pathway of Vibration

Enters at oval window --> travels through SCALA VESTIBULI (perilymph) --> passes into SCALA MEDIA (endolymph) --> crosses BASILAR MEMBRANE (sound receptors) into SCALA TYMPANI (perilymph) --> exits at round window

Spiral Organ of Corti

A region of the cochlear DUCT, simple columnar epithelium that contains receptor cells, the cells that make this up sit on the Basilar Membrane

Structures of Spiral organ of Corti

Hair cells, Hairs (stereocilia), tectorial membrane, fibers of cochlear nerve, supporting cells

Hair cells

mechanoreceptor cells that respond to movement, found in the inner ear that transduce stimuli for the senses of hearing and balance

Hairs (stereocilia)

Extensions of hair cells that are embedded in otolithic membrane, are organelles of hair cells that initiate an electrical impulse when bent

Tectorial membrane

rigid sheet of collagen fibers that stereocilia are embedded within

Fibers of the cochlear nerve

Sensory neurons

Supporting cells

cells that insulate, support and protect

The function of spiral organ of corti

Basilar membrane vibrates when sound wave passes from scala media to scala tympani, this vibration causes Stereocilia of hair cells to bend, which generates impulse

Utricle

responds to acceleration in horizontal direction (contain macula)

Saccule

responds to vertical movements (contain macula)

What type of fluid fills the utricle and saccule?

endolymph

Otolithic Membrane

jelly like disc that sits atop sensory epithelium & shifts in response to movement (bend stereocilia)

Otoliths

calcium carbonate crystals that add weight to membrane and cause more dramatic shift

3 membranous structures found in semicircular canals

Contains a Crista ampullaris

crista ampullaris

region of sensory epithelium that respond to rotational forces

Structures of a Crista Ampullaris - supporting cells

simple columnar epithelium; support & protect hair cells

Structures of a Crista Ampullaris - hair cells

mechanoreceptors; respond to rotational forces

Structures of crista ampullaris - stereocilia

extensions of hair cells that are embedded in cupula; initiate an impulse when bent