Sense Organs

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Sense Organs

• The Eye

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• Iris the muscle that
• adjusts the pupil to
• regulate the amount of
• light that enters the eye.
• Pupil the aperture in the middle of the iris of
  the eye. The size of the aperture can be
  adjusted to control the amount of light
• Lens a transparent, bi-convex body situated
  behind the iris of the eye to focus an image on
  the retina
•  
• Retina the innermost layer of the eye contains
  rods and cones, bipolar cells and ganglion cells

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• Sclera the thick,
• white outer layer that
• gives the eye its
• shape
• Cornea the clear part of the sclera at the front
  of the eye
• Choroid layer the middle layer of the eye, which
  absorbs light and prevents internal reflection.
  This layer forms the iris at the front of the eye

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• Rods photoreceptors in the eye more sensitive
  to light than cones, but unable to distinguish
  colour
• Cones colour receptors in the eye (red, green,
  blue)
•  
• Fovea centralis concentration of
• cones on the retina located directly
• behind the centre of the lens.
• Vision is the most acute here.
•  
• optic nerve conducts information received from
  rods and cones to the brain for interpretation.
• Blind spot an area on the retina where
• there are no rods or cones present locate
• where blood vessels enter the eye

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How the eye works

• As light enters the eye, the pupil will dilate if
  there isnt enough light or it will constrict if
  theres too much.
• As well, the shape of the lens changes depending
  on how far away the object is.

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• Accommodation in the eye, adjustment that the
  ciliary body makes to the shape of the lens to
  focus on objects at varying distances
• When the object is far away, the lens is
  flattened
• When the object is close, the lens is rounded
•  

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• Light enters the eye through the pupil. As it
  does, light rays become bent at the cornea and
  the lens in such a way that an inverted and
  reversed image of the object focuses on the
  retina.
• Information from this image is captured by rods
  and cones, which transmit their info to bipolar
  cells and then ganglion cells (optic nerve).
• Cones transmit information to a single bipolar
  cell, but require more light to become
  stimulated. As a result, cones see more detail
  and are best suited for lighted situations
  (daytime).
• Rods, however, are very sensitive to light and
  cannot distinguish color. As well, many rods
  connect to a single bipolar cell (up to 100 rods
  per bipolar cell). This causes images to be
  blurry. As a result, rods are best suited to
  situations where there isnt much light and
  details are not important.

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Disorders of the Visual System

• Cataracts- cloudy or
• opaque areas on the lens
• of the eye that increases
• in size over time and can
• lead to blindness if not
• medically treatment.
• Glaucoma build-up of
• the aqueous humor in the
• eye that irreversibly
• damages the nerve fibres
• responsible for peripheral
• Vision.

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Disorders of the Visual System

• Myopia near-sightedness, or difficulty in
  seeing things that are far away. The condition
  is caused by too strong ciliary muscles or a
  too-long eyeball

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Disorders of the Visual System

• Hyperopia far-sightedness, or difficulty in
  seeing near objects. This condition is caused by
  weak ciliary muscles or a too short eyeball
• focus

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Disorders of the Visual System

• Astigmatism abnormality in the shape of the
  cornea or lens that results in uneven

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Treatments of Eye Disorders

• Corrective lenses glasses, contact lenses
• ? with near-sightedness, the image focuses in
  front of the retina. This can be fixed using a
  concave lens
• ? with far-sightedness, the image focuses behind
  the retina. This can be fixed using convex
  lenses
• ? astigmatisms are unique and may require
  combinations of convex and/or concave lenses to
  bring images into focus on the retina

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Treatments of Eye Disorders

• Laser surgery two types
• ? Photorefractive keratectomy (PRK)
  non-invasive, simple procedure
• ? LASIK surgery more complex, some surgery
  required (corneal)
• ? Both surgeries may diminish eyesight

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Treatments of Eye Disorders

• Corneal transplant
• ? Corneas come from organ donors no need to
  match blood types
• ? Recovery long most patients do well though
• ? Recurrence of disease unusual

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Vitreous humor-the transparent gelatinous
substance filling the eyeball behind the
lens Aqueous humor- watery fluid that fills the
space between the cornea and the lens in the eye.
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The Ear
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The human ear has three sections

• 1. Outer ear
• consists of the pinna (earlobe and ear) and the
  auditory canal
• auditory canal contain hairs and sweat glands,
  some of which are modified to secrete wax to trap
  foreign particles

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The human ear has three sections

• Middle ear
• tympanic membrane the eardrum a membrane of
  thin skin and fibrous tissue that vibrates in
  response to sound waves.
• ossicles the group of three small bones between
  the eardrum and the oval window of the middle
  ear transmit sound waves from the eardrum to the
  inner ear
• malleus - hammer
• incus anvil
• stapes stirrup

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• Eustachian tube bony passage extending from the
  middle ear to the nasopharynx that plays a role
  in equalizing air pressure on both sides of the
  eardrum.
• Yawning can cause
• the air to move through
• the tubes and the
• ear will pop

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The human ear has three sections

• 3. Inner Ear
• Vestibule involved in balance and equilibrium
• Semicircular canals three tubes involved in
  balance and equilibrium

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• Cochlea involved in hearing. A spiral-shaped
  cavity of the inner ear that resembles a snail
  shell and contains nerve endings essential for
  hearing.
• Vibrations from the stapes bone hits the oval
  window, which causes it to vibrate.
• The oval window then pushes on the fluid within
  the vestibular canal of the cochlea.
• The movement of the fluid within the cochlea
  places pressure on the basilar membrane causing
  it to move. When it moves it causes the hair
  cells attached to it to move.
• The hair cells stimulate the
• tectorial membrane causing it to
• generate an impulse.
• The impulse travels to the
• auditory nerve where it is sent
• to the brain.

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How the ear works

• PINNA-Funnel-shaped flap that directs sound waves
  into the auditory canal
• AUDITORY CANAL-Canal that carries sound waves to
  the eardrum
• TYPANIC MEMBRANE- A thin membrane that is
  vibrated by sound waves
• OSSICLES Three bones () They are the smallest
  bones in the human body. The eardrum vibrates,
  and this vibrates the
• hammer, than the anvil and the stirrup one after
  another
• The stirrup then vibrates the Oval Window
• COCHLEA- This is a spirally coiled tube
  containing fluid and the actual organ of hearing
  (the Organ of Corti). Each Organ of Corti
  contains thousands of sensitive hairs that are
  vibrated by sound waves. The hairs initiate
  nervous impulses in the
• Auditory Nerve which carries messages to the
  brain

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Disorders of the Auditory System

• Nerve Deafness
• caused by damage to hair cells in the spiral
  organ
• typically found with aging and cannot be reversed
• hearing loss uneven, some frequencies more
  affected than others

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Disorders of the Auditory System

• Conduction Deafness
• usually caused by damage to the outer or middle
  ear that affects transmission to the inner ear
• not usually a total loss of hearing can be
  helped with hearing aids

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Disorders of the Auditory System

• Ear Infections
• caused by fluid build-up behind the eardrums,
  common in children
• fluid builds up because of the shallow angle of
  the auditory tube

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Treating Auditory Disorders

• Hearing Aids
• Eustachian tube implants
• also called tympanostomy tube surgery used to
  treat infections
• tiny plastic tubes are placed in a slit in the
  eardrum, relieving the pressure from the built-up
  fluid and allowing in to drain

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Filler

• Cholinesterase- an enzyme,
• found in the heart, brain, and
• blood, that breaks down
• acetylcholine to acetic acid
• and choline. If the
• acetylcholine did not break
• down then it would remain
• in the synapse.

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• Cochlea involved in hearing. A spiral-shaped
  cavity of the inner ear that resembles a snail
  shell and contains nerve endings essential for
  hearing.
• Vibrations from the stapes bone hits the oval
  window, which causes it to vibrate.
• The oval window then pushes on the fluid within
  the vestibular canal of the cochlea.
• The movement of the fluid within the cochlea
  places pressure on the basilar membrane causing
  it to move. When it moves it causes the hair
  cells attached to it to move.
• The hair cells stimulate the
• tectorial membrane causing it to
• generate an impulse.
• The impulse travels to the
• auditory nerve where it is sent
• to the brain.

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How the ear works

• PINNA-Funnel-shaped flap that directs sound waves
  into the auditory canal
• AUDITORY CANAL-Canal that carries sound waves to
  the eardrum
• TYPANIC MEMBRANE- A thin membrane that is
  vibrated by sound waves
• OSSICLES Three bones () They are the smallest
  bones in the human body. The eardrum vibrates,
  and this vibrates the
• hammer, than the anvil and the stirrup one after
  another
• The stirrup then vibrates the Oval Window
• COCHLEA- This is a spirally coiled tube
  containing fluid and the actual organ of hearing
  (the Organ of Corti). Each Organ of Corti
  contains thousands of sensitive hairs that are
  vibrated by sound waves. The hairs initiate
  nervous impulses in the
• Auditory Nerve which carries messages to the
  brain

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• ATP- adenosine triphosphate serves as a source
  of energy used to power the Na/K pump.
• Glucose and oxygen and required for cellular
  respiration to obtain energy.
• CNS cannot regenerate.
• Stroke- lack of oxygen to the brain.
• May use blood clotting drugs, which need to be
  taken within at least 3 hrs.
• Asprin reduces the thickness of platelets, so it
  decreases clots form forming. However if the
  blood is thinned and an aneurysm (broken blood
  vessel) occurs then the bleeding can be worst.
• Spinal cord injury- Damage is usually permanent
  and can lead to paralysis(a loss or impairment of
  voluntary movement in a body part).
• Found a gene that inhibits spinal regeneration. A
  protein that prevents tissue growth is now being
  researched.

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• PET scan
• Positron emission tomography
• uses short-lived radioactive substances to
  produce three-dimensional colored images of those
  substances functioning within the body.