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Taste and smell are involved with
specific receptor cells called
chemoreceptors
respond to chemicals in an aqueous
solution like mucus
food dissolved in saliva
airborne chemicals dissolved in
mucous membrane
The Tongue
Taste Buds
Filiform
papilla
Fungiform
papilla
Circumvallate Papilla
Connective tissue
Tongue epithelium
Why are they important?
Umami- savory/meaty
Bitter- alkaloid
Sour- H+
Salty- metallic ions
Sweet- sugar
Facial nerve
(afferent) 2/3 anterior
portion of tongue
Glossophyngeal
posterior 1/3 of tongue
Vagus nerve- few
taste buds on epiglottis
an pharynx
These afferent fibers
synapse in
medullathalamus
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 reflex
bad tasting food causes gagging or
reflexive vomiting
taste can change over time
taste is 80% smell
Mouth also contains:
Thermoreceptors
Mechanoreceptors
Nociceptors- sensitive nerve fibers that
are aware of painful stimuli
Olfactory
epithelium
Olfactory tract
Olfactory bulb
Nasal
conchae
(a)
Route of
inhaled air
Figure 15.21a
Olfactory
tract
Mitral cell (output cell)
Glomeruli
Olfactory bulb
Cribriform plate of ethmoid bone
Filaments of olfactory nerve
Olfactory
gland
Lamina propria connective tissue
Axon
Basal cell
Olfactory receptor cell
Olfactory
epithelium
Supporting cell
Mucus
(b)
Dendrite
Olfactory cilia
Route of inhaled air
containing odor molecules
Figure 15.21a
palpabre
cornea
Lacrimal
caruncle
sclera
Medial
commisure
lateral
commisure
tear
drainage
canal
iris
palpabre
pupil
bright light
normal light
dim light
FLOW OF TEARS
Lacrimal gland
Lacrimal ducts
Sup. or inf. lacrimal canal
Lacrimal sac
Nasolacrimal duct
Nasal cavity
Superior oblique
Superior rectus
optic nerve
Medial
rectus
Inferior oblique
Lateral rectus
Inferior rectus
Fibrous tunic- sclera and cornea (outer
most layer)
Composed of dense avascular
connective tissue
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) and
•
Cones (color vision, not evenly distributed,
concentrated in fovea)
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 Focusing
• Cornea Shape
Accommodation- adjust configuration of
• Lens Shape
• Pupil Size
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 ft
You see
Normal vision
What condition
does this
person have?
20/10
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
Geometrical illusions
Successive contrast : afterimages ...
fixate the black dot in the center for 60 seconds ...
… and then look at a the black dot in the right panel !
what do you see?
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
malleus
incus
stapes
oval
window
round
window
external auditory
canal
tympanic
membrane
Auditory
tube
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
Biology 100
Human Biology
semicircular
canals
vestibulochoclear
nerve
cochlea
Auditory ossicles
Malleus Incus
Stapes
Cochlear nerve
Scala vestibuli
Oval
window
2
Helicotrema
Scala tympani
Cochlear duct
3
1
Tympanic
Round
membrane
window
(a) Route of sound waves through the ear
Basilar
membrane
Basilar membrane
High-frequency sounds displace
the basilar membrane near the base.
Fibers of basilar membrane
Medium-frequency sounds displace
the basilar membrane near the middle.
Low-frequency sounds displace the
basilar membrane near the apex.
(b) Different sound frequencies cross the
basilar membrane at different locations.
Base
(short,
stiff
fibers)
Apex
(long,
floppy
fibers)
Frequency (Hz)
Static Balance – utricle and sacule
Dynamic Balance- semicircular
canals
(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
IDENTIFY