special senses
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Special Senses. Ch 15. The Special Senses. Taste Smell Vision Hearing Balance. Taste. Taste and smell are involved with specific receptor cells called chemoreceptors . respond to chemicals in an aqueous solution. food dissolved in saliva. - PowerPoint PPT PresentationTRANSCRIPT
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?