Transcript Special Senses

Anatomy and Physiology 2
The Special Senses
 Smell
 Taste
 Sight
 Hearing
 These allow us to
experience and interpret
the world around us
Anatomy of the Eye
 A sphere that is about 1in
in diameter
 Only about 1/6 of the eye
is seen and rest is
protected
 The eye is protected by
bone, eyelids and
eyelashes
Anatomy of the Eye
 There are several glands
and ducts around the eye
 Tarsal glands: lubricate
the eye
 Lacrimal gland: produce
tears
 Nasolacrimal duct:
empties tears into the
nasal cavity
Anatomy of the Eye
 Eye muscles
 Lateral rectus: moves
laterally
 Medial rectus: moves
medially
 Superior rectus: elevates
 Inferior rectus: depresses
 Inferior oblique: elevates
and turns laterally
 Superior oblique :
depresses and turns
laterally
Anatomy of the Eye
 Structures:
 Sclera: the “white of the
eye:
 Cornea: where light enters
 Lens: focuses the light that
enters through the cornea
 Iris: the pigmented part of
the eye
 Pupil: controls the amount
of light that enters the eye
 Retina: responds to the
light
Anatomy of the Eye
 Structure:
 Retina continued:
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

Contains rods and cones
which are called
photoreceptors
Cones allow us to see
colors
Rods allow us to see in dim
light and use our
peripheral vision
 Optic nerve: transfers
information to the optic
cortex of the brain
How we see
 When light passes through
cornea and lens the light is
bent or refracted as they
move through the aqueous
humor
 The image is then
projected on the retina
upside down
 That information is then
carried to the optic nerve
and process by the brain
Eye Problems
 Myopic eye (nearsighted):
distant objects appear
blurry, results of an eyeball
that is too long
 Hyperopic eye (farsighted):
close objects appear blurry,
results from a too short eye
 Astigmatism: the cornea
has an unusual curve to it
 Conjunctivitis: bacteria or
viral infection of the
conjunctive (membrane
that covers the eye)
Anatomy of the Ear
 Outer ear:
 Pinna or auricle what is
typically called the ear
 External acoustic
meatus: a narrow
chamber carved into the
temporal bone

Lined with ceruminous
glands that produce
earwax or cerumen
Anatomy of the Ear
 Middle Ear
 Ear drum: vibrates in
response to sound waves
 Ossicles: the three
smallest bones in the
body


Incus (anvil), malleus
(hammer) and stapes
(stirrup)
Vibrations trigger the
coordinated movements of
these bones
Anatomy of the Ear
 Inner Ear
 Bony labyrinth

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
Cochlea
Vestibule
Semicircular canals
 Vestibular apparatus
(responsible for
equilibrium)
Equilibrium
 Static equilibrium
 Static = at rest
 Provides information on
which way is up or down
 Helps maintain posture
and balance when
standing upright
 Dynamic equilibrium
 Provides information
for angular movements
(e.g. twirling, spinning.
Etc.)
How We Hear
 The auricle works to
capture as much sound
waves as possible
 The waves travel through
the ear until they reach the
cochlear duct
 Hair follicles move in
response to the vibrations
 Once the follicles are
triggered they send the
impulse to the cochlear
nerve
Hearing and Equilibrium
Deficits
 Deafness is defined as
hearing loss of any
degree
 Conduction deafness =
problems in the ear
 Sensorineural deafness =
problems in the cochlear
nerve or brain
 Vertigo is the sense of
falling or spinning
 Usually result in nausea and
difficulty in maintaining
balance
Chemical Senses: Smell
 The nose contains
thousands of olfactory
receptors that can
respond to thousands of
different smells
 The olfactory receptors
lead to the olfactory
nerve, which leads to the
olfactory cortex in the
brain (here the smells
are “identified”)
Chemical Senses: Smell
 The olfactory cortex of
the brain is tied to the
emotional part of the
brain, thus many smells
with trigger memories
and emotions
 The receptors are quickly
triggered, but also
quickly adapt to smells
Chemical Senses: Taste
 Taste buds are the
receptors for taste
 The tongue contains about
10,000 taste buds
 The small peg like
projections on the tongue
are called papillae
 The papillae contain tiny
hairs that are linked to 3
nerves that carry the
information to the brain
Chemical Senses: Taste
 5 basic taste sensations:
 Sweet = responds to
sugars, saccharine and
certain amino acids
 Sour: responds to acids
 Bitter: responds to
alkaloids
 Salty: responds to metal
ions
 Umami: recently
discovered to respond to
food additives
Chemical Senses: Taste
 Historically, each taste
on the tongue had “it’s
own part”, but only slight
differences have been
found between the parts
 Typically, cravings are
linked to deficits in the
body, but like smell the
taste part of the brain is
close to the emotionally
part of the brain
Developmental Aspects
 All special senses are
 The lens will continue to
functional at birth;
however, vision is the
only one not fully
functional
 Newborns see only in
gray tones and cannot
see much further that a
foot in front of them
 It takes until about 5
years of age to have fully
functioning vision
grow throughout life
causing “old vision”
 Hearing is very
important to language
development
 Smell and taste also
developmentally
important