Special Senses

TasteSmellVision

HearingBalance

  • respond to chemicals in

an aqueous solution• food dissolved in saliva• airborne chemicals

dissolved in mucous membrane

Taste and smell are involved with specific receptor cells called chemoreceptors  

The Tongue

Taste Buds

Circumvallate Papilla

Filiformpapilla

Fungiformpapilla

Connective tissue Tongue epithelium

Salty- metallic ions

Sweet- sugarSweet- sugar

Sour- HSour- H++

Bitter- alkaloidBitter- alkaloid

Why are they important?

Umami- savory/meatyUmami- savory/meaty

Dry tongue with a paper towel and Dry tongue with a paper towel and place a little sugar on surface.place a little sugar on surface.What do you taste?What do you taste?

Facial nerve (afferent) 2/3 anterior portion of tongueGlossophyngeal posterior 1/3 of tongueVagus nerve- few taste buds on epiglottis an pharynxThese afferent fibers synapse in medullathalamus gustatory cortex in parietal lobes and fibers to hypothalamus in limbic system

Taste triggers reflex involved in digestion; causes an increase of saliva in mouth (amylase) and gastric juice in stomach

acids cause strong salivary reflexbad tasting food causes gagging or reflexive vomitingtaste can change over time

taste is 80% smell

Mouth also contains: Thermoreceptors

Mechanoreceptors

Nociceptors- sensitive nerve fibers that are aware of painful stimuli

• Specific chemicals cause specific patterns of neurons to fire

• Smell not as good as animals

• Humans can distinguish 10,000 or so chemicals

• Olfactory fatigue or adaptation

• Old people lose sense of smell• What we really smell is pain: ex. chili,

ammonia, menthol (cold)

Olfactory tractOlfactory bulb

Nasalconchae

Route ofinhaled air

Olfactoryepithelium

Mitral cell (output cell)

Olfactorygland

Olfactorytract

Olfactoryepithelium

Filaments of olfactory nerve

Cribriform plate of ethmoid bone

Lamina propria connective tissue

Basal cell

Supporting cell

DendriteOlfactory cilia

Olfactory bulbGlomeruli

Axon

Olfactory receptor cell

Mucus

Route of inhaled aircontaining odor molecules

Cortical Regions Associated with Olfactory Information

• Lose sense of smell lose taste• Cranial nerve trauma• May be genetic or a cold (mucus), allergy,

zinc deficiency• Uncinate- olfactory hallucinations; may be

psychological ex. rotting meat smell• Olfactory auras- prior to epileptic attack

loss of sense of smell

sclera

irispupil

teardrainage canal

cornea

Medial commisure

lateral commisure

palpabre

palpabre

Lacrimal caruncle

bright light normal light dim light

FLOW OF TEARSLacrimal gland

Lacrimal ducts

Sup. or inf. lacrimal canal

Lacrimal sac

Nasolacrimal duct

Nasal cavity

optic nerve

Superior rectus

Inferior oblique Lateral rectus

Inferior rectus

Medial rectus

Superior oblique

Fibrous tunic- sclera and cornea (outer most layer)

Cornea

• 100s of sheets of collagen fibers between sheets of epithelium and endothelium

• Clear because regular alignment

• Role in light bending

• Avascular but does have pain receptors

• Regenerates

Vascular tunic- uvea: choroid, cilliary body, iris, pupil (middle layer)

Choroid- rich vascular nutritive layer; contains a dark pigment

that prevents light scattering within the eye

Cilliary body- lens is attached; contains muscles that change the

lenses shape

Iris- pigmented ring of muscular tissue composed of circular

and radial muscles

• reflex contraction of circular muscle in bright light (small dia of pupil)

• reflex contraction of radial muscle in dim light (large dia of pupil)

Pupil- central hole in iris 

Sensory tunic- retina (inner most layer)

Photoreceptors:

• rods (dim light, contains pigment rhodopsin) 120 million rods

• Cones (color vision, not evenly distributed, concentrated in fovea) 6 million cones

Optic disc- blind spot because its where optic nerve leaves the eyeball (no rods or cones)

Macula lutea- yellow spot, area of high cone

Fovea centralis- in center of macula lutea, contains only cones, area of greatest visual acuity

Vitreous humor- behind lens, gel-like substance with fine collagenic fibrils imbedded in as viscous ground substance- binds with water

• transmits light• supports the posterior surface of the lens and

holds the neural retina firmly against pigmented layer

• contributes to intraoccular pressure, helping to counter act the pulling force of the extrinsic eye muscles

Aqueous humor- in front of lens, anterior segment, watery fluid

• Supplies cornea and lens with nutrients

• Helps to maintain the shape of the eye

• Produced and renewed every 4 hrs by the cilliary body      

Lens- transparent biconvex structure, flexible

• Attached by suspensory ligaments to ciliary body

• focuses image onto retina• changes lens thickness to allow light

to be properly focused onto retina

Coarse Fixed FocusingCoarse Fixed Focusing• Cornea ShapeCornea Shape

AccommodationAccommodation- adjust configuration of- adjust configuration of • Lens ShapeLens Shape• Pupil SizePupil Size

refraction

Focusing on a Near Object

Focusing on a Far Object

• Emmetropia- normal 20:20• Hyperopia- farsighted• Myopia-near sighted• Presbyopia- mature eyes• Astigmatism

20 ft:20 ftYou see Normal vision

20/10

What condition does this person have?

What condition does this person have?

Clouding of lens (hardening or thickening

causes: diabetes mellitus, smoking, UV damage

The Retina

blind spot macula

photoreceptors Rod cell membrane

Binocular vision

Effect: Subjective or illusory contours

Geometrical illusions

The apparent tilt of the mortar lines is caused by orientation-sensitive simple cells in the striate cortex.

Geometrical illusions

Cushion Illusion: This drawing consists solely of rectangles and squares, set straight and true; the curvature is all in your mind.

Luminance & Contrast

Luminance & ContrastThe scintillating grid illusion

Effect: Illusory visual motion

Effect: Illusory visual motion

No, these are a bunch of independent circles

It’s a spiral right?

Successive contrast : afterimages ...

                                            what do you see?

fixate the black dot in the center for 60 seconds ...

… and then look at a the black dot in the right panel !

Outer ear- pinna (auricle), lobule, external auditory canal; elastic cartilage

•External auditory canal has: ceruminous glands- wax secreting glands- protects delicate lining of meatus and helps prevent microorganisms from entering the ear

•Tympanic membrane- membrane that vibrates in response to sound waves

Middle ear- Includes 3 small bones (ossicles)- hammer (mallus), anvil (incus), stirup (stapes)

•Pharyngeotympanic auditory tube (Eustachian tube)- equalizes pressure; connects middle ear to pharynx. •Oval window- found on cochlea; stirrup presses against cochlea•Round window- pressure window on cochlea•Otis media- inflammation of the middle ear; due to bacteria or allergies, common in children whose auditory tubes are short and horizontal

external auditory canal

tympanic membrane

Auditory tube

malleusincus stapes

round window

oval window

Inner ear- bony labyrinth filled with perilymph fluid (similar to CFS) and membranous labyrinth filled with endolymph fluid (similar to K+ rich intracellular fluid); these fluids conduct sound vibrations

•Bony labyrinth (includes vestibule, semicircular canal, and cochlea)•Vestibule- posterior to cochlea and anterior to the semicircular canals•Perilymph fluid suspends 2 membranous sacs: utricle and sacule-- they house equilibrium receptors called maculae that respond to the pull of gravity

• Semicircular canal- contains endolymph fluid; anterior, posterior, and lateral canal; contains equilibrium receptors (ampulla)

• Cochlea- filled with perilymph fluid

• Organ of Corti- rests a top basilar membrane; has long row of hair cells

The Cochlea Unwound

The Cochlea

Vestibulocochlear nerve

perilymph

The Organ of Corti

hair cells

tectorial membrane

basilar membrane

Sensory & motor neurons in the cochlear branch of the vestibulocochlear (VII) nerve

Supporting cells

Properties of sound:Sound travels at 331 m/secIt's a pressure disturbance originating from the

vibrationFrequency- cycles/sec (hertz); Reflects sound

intensityHuman hearing- 20 to 20,000 htz

• Pitch- different frequency's; high vs low; pure tone is a single frequency

• Quality- sound mixture with several frequencies

• Intensity- corresponds to amplitude of height; loudness measured in decibels

Transmission of sound:Airborne soundexternal auditory canaltympanic membranehammer, anvil, stirrupoval windowvestubularcochlear nervecochlear nuclei in medulla superior oliveup the lateral leminiscusinferior colliculusprimary auditory cortex in the temporal lobe

Scala tympani

Cochlear duct

Basilarmembrane

Malleus Incus

Auditory ossicles

Stapes

Ovalwindow

Scala vestibuli

Helicotrema

Cochlear nerve

32

1

Roundwindow

Tympanicmembrane

(a) Route of sound waves through the ear

Fibers of basilar membrane

(b) Different sound frequencies cross the basilar membrane at different locations.

Medium-frequency sounds displacethe basilar membrane near the middle.

Low-frequency sounds displace thebasilar membrane near the apex.

Base(short,stifffibers)

Frequency (Hz)

Apex(long,floppyfibers)

Basilar membrane

High-frequency sounds displacethe basilar membrane near the base.

Static Balance – utricle and sacule

Dynamic Balance- semicircular canals

(semicircular canal)

cupula

hair cells

Endolymph fluid

Vestibular nerve fibers

(semicircular canal)

The effect of gravitational pull on the macula receptor cell in the utricle

Hearing loss- due to disease (ex. meningitus), damage, or age related

Conduction deafness- prevention or blocking sounds from entering inner ear.

Ex. ear wax, ruptured ear drum, middle ear inflammation (otis media), and otosclerosis (hardening of the ossicles of the ear)

Sensoneural deafness- damage to the neural structures from any point from the cochlear hair cells to and including the auditory cortical cells• Partial or complete deafness, or gradual loss

over time

Tinnitus- ringing or clicking sound in the absence of auditory stimuli; 1st symptom of cochlear nerve degeneration

• may result from inflammation of the inner or middle ear

• side effect from medicine such as aspirin

• Symptoms- vertigo, nausea, hearing loss

Meniere's Syndrome- labyrinth disorder; effects both semicircular canals and cochlea

IDENTIFY

Hearing Animation:https://www.youtube.com/watch?v=qgdqp-oPb1Qhttps://www.youtube.com/watch?v=U_HUgzhmq4U

INQUIRY

1. What type of stimulus triggers a response in nociceptors?

2. Two senses that detect chemical concentrations are____.

3. A person with defective otolith sensory receptors may have difficulty ______.

4. Which eye muscle moves the eye to look medially?5. Name the three bones in the middle ear.6. What is the blind spot in the eye called?7. Where are the highest concentration of cones

located?