Transcript Bio 257 Day 22

Bio 257 Day 22
Today’s topics:
Special Senses
Eye Anatomy & Physiology
Ear Anatomy & Physiology
Senses
• 5 Special Senses:
–taste, smell, vision,
hearing, equilibrium
Special Senses
• Smell or Olfaction (Nose):
–Chemoreceptors (olfactory
receptor cells)
• nasal mucosa epithelium
underneath cribriform plate
• for any chemical (gas) to be
detected (smelled) it must be
partially water soluble =
dissolve in nasal mucus
Special Senses
– Chemoreceptors (olfactory receptor cells)
• chemical substance dissolves in nasal
mucus and bind to cilia of olfactory cells
stimulating them
• olfactory nerve is stimulated
• nerve impulse is sent to olfactory cortex
(within temporal and frontal lobes)
Special Senses
– Smell:
• not much is known about how
we detect good odors from bad
• smell is tied in with
tastemuch of what is
considered taste is actually due
to olfaction
Special Senses
– Taste (Gustation):
• chemoreceptors = gustatory (taste) cells
on tongue that contain taste hairs
• Taste hairs containing receptors extend
into a small opening called a taste pore
• taste buds = barrel-shaped containing
taste cells & supportive cells (specialized
epithelium)
Special Senses
– Taste (Gustation):
• 5 primary taste modalities
1. Sweet = tip of tongue
2. Sour = sides of tongue
(margins)
3. Salty = widely distributed on
tongue
4. Bitter = back of tongue
5. Umami
sweet
sour
salty
bitter
Special Senses
–
Taste (Gustation):
•
chemical substances must first be
somewhat water soluble & dissolve in
saliva
• Dissolved chemicals bind to specific taste
buds stimulating them
• Facial nerve = front 2/3 of tongue (sweet,
salty, sour)
Special Senses
– Taste (Gustation):
• Glossopharyngeal nerve = back 1/3
of tongue (bitter)
• parietal lobe = gustatory center
Specific Senses
Vision
• Photoreceptors (rods & cones)
housed in eye
• Eye structure:
–Accessory structures & eye
Specific Senses
Vision
• Accessory structures
– Eyelids (likened to
windshield wipers)
– Eyelashes
– Lacrimal apparatus
(gland and
nasolacrimal duct and
associated structures)
– Conjunctiva = mucous
membrane
– 6 extrinsic eye
muscles
Specific Senses
Vision
• Eye structures
–Cavities
–Wall of eye = arranged eye layers
(tunics)
Specific Senses
Vision
•
Eye Cavities (interior)
– Posterior cavity =
large cavity w/ jellylike vitreous humor
(fluid)
– Anterior Cavity
• Anterior
chamber/Posterior
chamber = smaller
cavities w/ watery
aqueous humor
(fluid)
Specific Senses
Vision
• Wall of eye
–3 eye layers (tunics)
• Fibrous tunic
• Vascular tunic
• Neural tunic
Specific Senses
Vision
• Fibrous tunic = outermost layer of
eyedense connective tissue
–Includes sclera & cornea
Specific Senses
Vision
• Fibrous tunic
– sclera = “white” of eye
• support, protect, provide site of eye
muscle attachment
– cornea = transparent “window” of eye
• powerfully focuses light entering eye
(bends light)
• primary focusing structure
Specific Senses
Vision
• Vascular tunic = middle eye layer
 blood vessels & intrinsic eye
muscles
–Includes: iris, choroid coat, & ciliary
body
Vision
• Vascular tunic structures
– Iris (smooth muscles) = colored portion of
eye (melanin)
• regulates amount of light entering eye by
constricting or dilating pupil
– Pupil = circular hole in middle of iris
(similar to camera shutter)
Vision
• Vascular tunic structures
– ciliary body = ciliary muscle + suspensory
ligaments = controls shape of lens
• Lens = transparent elastic
–changes shape for near & far vision =
accommodation
– 2nd most powerful focusing structure
(bends light)
Specific Senses
Vision
• Vascular tunic structures
–choroid coat = irridescent, dark tissue
layer (melanin)keeps interior of eye
dark by absorbing excess light
–highly vasculardelivers O2 and
nutrients to neural tunic
Specific Senses
Vision
• Nervous Tunic = innermost eye
layer
– nerve tissue = photoreceptors &
neurons
– retina = several layers of neurons &
photoreceptors
Specific Senses
Vision
• NervousTunic
– retina photoreceptors
2 types:
1. Cones = for daylight & color
visiongives sharp, clear vision, but
requires more light
 3 types of cones (red, blue, green)various colors seen due to stimulation
of different combinations of these
cones.
Specific Senses
Vision
• NervousTunic
– retina photoreceptors
2 types:
2. Rods = for night vision =
very light sensitive
requires less light (fxn
in dim light)
rhodopsin = light
sensitive pigment
Specific Senses
Vision
• Neural Tunic
– retina = arrangement of
photoreceptors
• Macula lutea (yellow spot) = area on
retina
–highest concentration of cones
• Fovea centralis = center of macula
–site center of color & sharpest vision
Specific Senses
Vision
• Neural Tunic
– retina = arrangement of
photoreceptors
• optic disc = circular area medial to
fovea and anterior to optic nerve
–blind spot (no rods or cones)
Specific Senses
Vision
• Visual Pathway:
– Light rays entering the eye from
an object must be bent and fall
on fovea centralis
Specific Senses
Vision
• Visual Pathway:
– light  cornea (bends light)
 anterior cavity (aqueous humor)
 pupil (iris)  lens (bends light)
posterior cavity (vitreous humor)
retina (fovea centralis)
Visual System
Specific Senses
Vision
• Neural Pathway:
retina (fovea)
AP
optic nerves
AP
optic chiasma
AP
thalamus
AP
occipital lobe
Special Senses
• Ear functions:
– Hearing
– Equilibrium
Specific Senses
Hearing
• Mechanoreceptors housed in ear
(cochlear duct)
• Mechanoreceptors = hair cells in
the organ of Corti
Specific Senses
Hearing
• Anatomy of ear
–3 regions
• External ear
• Middle ear
• Inner ear
Specific Senses
Hearing
• External ear includes:
• auricle or pinna –
fleshy/cartilaginous portion
collects sounds
• external auditory meatus = ear
canal
funnels sound waves to
middle ear
Specific Senses
Hearing
• External ear
includes:
•
tympanic membrane
= eardrum
thin sheet
separates external
ear from middle
ear
vibrates, passing
sound waves
Specific Senses
Hearing
• Middle ear includes
• tympanic cavity = space filled with air
houses middle ear bones (ossicles)
3 ossicles (vibrate in order w/
passing sound waves)
–Malleus (hammer)
–Incus (anvil)
–Stapes (stir-up)
Specific Senses
Hearing
• Middle ear
includes:
• eustachian or
auditory tube =
tube leaving
tympanic cavity &
connecting to
pharynx
equalizes
pressure on either
side of eardrum
Specific Senses
Hearing
• Inner ear(vestibulocochlear
apparatus)
• interconnecting
tunnels and
chambers
• consist of
membranous
labyrinth
surrounded by
bony labyrinth &
filled with fluid
Specific Senses
Hearing
• Inner ear
(vestibulocochlear apparatus)
• bony labyrinth = perilymph (fluid)
• membranous labyrinth =
endolymph (fluid)
Specific Senses
Hearing
• Inner ear
(vestibulocochlear
apparatus)
• oval window = is
displaced
by stapes vibrations &
moves inner ear fluid
• round window = is
displaced as fluids
move, removes excess
sound waves
Specific Senses
Hearing
• Bony Labyrinth consists
of
3 areas
– Vestibule
– 3 Semicircular canals
– Cochlea, coiled (snailshaped)
Specific Senses
Hearing
• Vestibule = has membranous sacs
called saccule & utricle, which
house mechanoreceptors for
equilibrium (balance)
Specific Senses
Hearing
• 3 Semicircular canals = house
mechanoreceptors for equilibrium
(balance)
• Cochlea, coiled (snail-shaped) =
contains membranous labyrinth
called cochlear duct
Specific Senses
Hearing
• Cochlea = houses cochlear duct,
which contains mechanoreceptors
for hearing
Specific Senses
Hearing
• Cochlea (cochlear duct) contains hearing receptors
(Organ of Corti) and are stimulated as fluid
(endolymph) & membranes move
– Movement of stapes at the oval window transmits
vibrations that pass through various fluids and
structures
– Vibrations enter the endolymph of the cochlear duct
and different frequencies of vibrations stimulate
different sets of receptor cells
Specific Senses
Hearing
• Hearing Pathway
auricle  external auditory
meatus  tympanic membrane
 malleusincusstapes
 oval window  cochlear duct
Auditory System
Specific Senses
Hearing
• Neural Pathway
cochlear duct (organ of Corti)
Nerve impulse
thalamus
impulse
vestibulocochlear nerve
(cochlear branch)
Nerve impulse
temporal lobe
Specific Senses
Equilibrium
•
Static equilibrium = head
movements while body is
stationary and under
influence of gravity (ie
evaluate position of head
relative to gravity)
– Utricle & saccule (2
chambers of the
vestibule)
• Contain
maculaespecialized
patches of epithelium
w/ hair cells
Hair cells
Specific Senses
Equilibrium
• Dynamic equilibrium = evaluate
changes in the direction and rate of
head movements (ie head & body
rotational movements)
– 3 Semicircular Canals
• Positioned at nearly rt angles to each
other
• Contains crista ampullaris which has
hair cells embedded in a gelatinous
masscupula
Vestibular System
Semicircular Canals
Semicircular Canals
Hair Cell
• hair cells are involved with processing sound by the auditory
system and processing information on balance and equilibrium
by the vestibular system.
• one tiny cell performs these amazing functions in two widely
different systems.
• the cilia at the top of the hair cells is important.
– hair cells at rest, release a small resting level of neurotransmitter from
their base onto the sensory nerve, which fires action potentials.
– smaller stereocilia when bent toward the larger kinocilium (during an
acceleration, for example) cause the hair cell to releases more
neurotransmitterresulting in more action potentials in the sensory
nerve.
– stereocilia bending away from the kinocilium (during a deceleration, for
example), cause the hair cell to releases less neurotransmitterresulting
in fewer action potentials.