Anatomy and Physiology Special Senses

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Anatomy and PhysiologySpecial Senses

• Community Education
• Mr. Kestner
• Chapter 11

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Information

• Special senses allow the human body to react to
  environment by providing for sight, hearing,
  taste, smell, and balance maintenance
• These senses are possible because body has
  structures that receive sensations, nerves that
  carry sensory messages to brain, and brain that
  interprets and responds to messages

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The EYE

• The eye is the organ that controls the special
  sense of light
• It receives light rays and transmits impulses
  from the rays to the optic nerve, which carries
  to brain where interpreted as vision
• It is well protected
• Partially enclosed in a bony socket of the skull

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The EYE

• Eyelids and eyelashes help keep out dirt and
  pathogens
• Lacrimal glands in the eye produce tears, which
  constantly moisten and cleanse eye
• Tears flow across eye and drain through
  nasolacrimal duct into nasal cavity
• Mucous membrane, called conjunctiva, lines
  eyelids and covers front of eye to provide
  additional protection and lubrication

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The EYE

• Three main layers to the eye
• Sclera
• Outermost layer, tough connective tissue
• Frequently referred to as white of the eye
• Sclera maintains shape of eye
• Extrinsic muscles attached to outside of sclera
  responsible for moving eye within socket

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The EYE

• The cornea is a circular, transparent part of
  front of sclera
• It allows light rays to enter eye
• Choroid coat
• Middle layer of eye
• Interlaced with many blood vessels, which nourish
  eye

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The EYE

• Retina
• Innermost layer of the eye
• Made of many layers of nerve cells, which
  transmit light impulses to optic nerve
• Two special cells are cones and rods
• Cones are sensitive to color and are used mainly
  for vision when it is light
• Rods are used for vision when it is dark or dim

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The EYE

• The iris is the colored portion of the eye
• It is located behind the cornea on the front of
  the choroid coat
• The opening in the center of the iris is called
  the pupil
• The iris contains two muscles, which control the
  size of the pupil and regulate the amount of
  light entering the eye

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The EYE

• The lens is a circular structure located behind
  the pupil and suspended in position by ligaments
• It refracts (bends) light rays so the rays focus
  on the retina

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The EYE

• The aqueous humor is a clear, watery fluid that
  fills the space between the cornea and iris
• It helps maintain the forward curvature of the
  eyeball and refracts light rays
• The vitreous humor is the jellylike substance
  that fills the area behind the lens
• It helps maintain the shape of the eyeball and
  also refracts light rays

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The EYE

• When light rays enter the eye, they pass through
  a series of parts that refract the rays so that
  the rays focus on the retina
• These parts are the cornea, aqueous humor, pupil,
  lens, and vitreous humor
• In the retina, light rays (image) are picked up
  by rods and cones, changed into nerve impulses,
  and transmitted by optic nerve to occipital lobe
  of cerebrum, where it is interpreted
• If rays are not refracted correctly, vision is
  blurred

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Diseases/Abnormalities

• Cataracts
• Occur when normally clear lenses become cloudy,
  or opaque
• Occurs gradually, usually as a result of aging,
  but may be the result of trauma
• Symptoms include blurred vision, halos around
  lights, gradual vision loss, and in later stages,
  a milky-white pupil
• Sight is restored by the surgical removal of the
  lens
• Corrective lenses, or a surgically implanted lens
  corrects vision and compensates for removed lens

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Diseases/Abnormalities

• Conjunctivitis (pink eye)
• Contagious inflammation of the conjunctiva and is
  usually caused by a bacterium or virus
• Symptoms include redness, swelling, pain, and, at
  times, pus formation in the eye
• Antibiotics, frequently in the form of an eye
  ointment, are used to treat conjunctivitis

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Diseases/Abnormalities

• Glaucoma
• A condition of increased intraocular pressure
  caused by an excess of aqueous humor
• Common after age 40 and is leading cause of
  blindness
• Symptoms include loss of peripheral vision, halos
  around lights, limited night vision, and mild
  aching
• Glaucoma is usually controlled with medications
  that decrease amount of fluid produced in severe
  cases, surgery is performed to create an opening
  for the flow

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Diseases/Abnormalities

• Strabismus
• When the eyes do not move or focus together
• Eyes may move inward (cross-eyed), or outward, or
  up and down
• Caused by muscle weakness in one or both eyes
• Treatment methods include eye exercises, covering
  the good eye, corrective lenses, and/or surgery
  on the muscles that move the eye

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EARS
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The EAR

• The ear is the organ that controls the special
  senses of hearing and balance
• It transmits impulses from sound waves to the
  auditory nerve, which carries the impulses to the
  brain for interpretation and hearing
• The ear is divided into three main sections
• The outer ear
• The middle ear
• The inner ear

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The EAR

• The outer ear contains the visible part of the
  ear, called the pinna, or auricle
• The pinna is elastic cartilage covered by skin
• It leads to a canal, or tube, called the external
  auditory meatus, or auditory canal

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The EAR

• Special glands in this canal produce cerumen, a
  wax that protects the ear
• Sound waves travel through the auditory canal
  until they reach the eardrum, or tympanic
  membrane
• The tympanic membrane separates the outer ear
  from the middle ear it vibrates when sound waves
  hit it and transmits the sound waves to the
  middle ear

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The EAR

• The middle ear is a small space, or cavity, in
  the temporal bone
• It contains three small bones (ossicles)
• Malleus (hammer)
• Incus (anvil)
• Stapes (stirrup)
• Bones are connected and transmit sound waves from
  TM to inner ear

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The EAR

• The middle ear is connected to the pharynx by a
  tube called the eustachian tube
• This tube allows air to enter the middle ear and
  helps equalize air pressure on both sides of the
  tympanic membrane
• The inner ear is the most complex portion of the
  ear it is separated from the middle ear by a
  membrane called the oval window

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The EAR

• The first section is the vestibule, which acts as
  the entrance to the two other parts of the inner
  ear
• The cochlea, shaped like a snails shell,
  contains delicate, hair-like cells, which compose
  the organ of Corti, a receptor of sound waves
• The organ of Corti transmits the impulses from
  sound waves to the auditory nerve

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The EAR

• This nerve (vestibulocochlear) carries the
  impulses to the temporal lobe of the cerebrum,
  where they are interpreted as hearing

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The EAR

• Semicircular canals are also located in the inner
  ear
• These canals contain a liquid and delicate
  hair-like cells that bend when the liquid moves
  with head and body movements
• Impulses sent from the semicircular canals to the
  cerebellum of the brain help to maintain our
  sense of balance and equilibrium

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The cochlear implant artificially stimulates the
inner ear area with electrical signals, sends
those signals to the hearing nerve, and allows
the user to hear. Although sound quality is
sometimes described as "mechanical" and not
completely like that experienced by a person with
normal hearing, the cochlear implant provides
users with the ability to sense sound that they
couldn't hear otherwise.
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The Tongue
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Tongue and Sense of Taste

• The tongue is a mass of muscle tissue with
  projections called papillae
• Papillae contain taste buds that are stimulated
  by flavors of foods moistened with saliva
• There are four main tastes
• Sweet (center tip)
• Salty (tip sides)
• Sour (sides)
• Bitter (back)
• Taste is influenced by sense of smell

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The Nose
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Nose and Sense of Smell

• The nose is organ for smelling, made possible by
  olfactory receptors, located in upper part of
  nasal cavity
• Impulses from receptors are carried to brain by
  olfactory nerve
• Sense of smell is more sensitive than taste
• Human nose can detect over 6,000 different smells
• Sense of smell is closely related to sense of
  taste clearly illustrated by fact that when you
  have a cold and sense of smell is impaired, food
  does not taste as good
• Olfactory receptors rapidly adapt to odor