Download Overview/Motivation

Overview/Motivation
 Biology/Anatomy: To learn what role the ear plays besides hearing
Materials
 Stop watch
 Blackboard
 Diagram of the Ear
Goals
 Learn how the ear helps body movements and balance
 Know the different parts/systems of the ear
Vocabulary
 Inner Ear
o Cochlea
o Vestible
o Semicircular Canals
o Fluids: Endolymph and Perilymph
o Utricle
 Vestibular system
 Static Balance
 Dynamic Balance
 Acceleration
Introduction
 How many of you guys play sports?
 Anybody here skateboard/do gymnastics/soccer?
 Who here thinks that its important to have a good sense of balance in order to
play sports?
 Well, what do you guys think is the most important part of the body for
having a good sense of balance?
Demonstrations/Activities
 Have each kid see how long that can stand with one leg behind the other knee.
 Same thing, but now with eyes closed.
 Same thing, but now with waving arms (dynamic balance)
 Same thing, but now with waving arms and eyes closed.
 Guess what the world record for balancing on one foot is?
o 55 hours, 35 minutes, Guinness 1996!
Discussion of Results
 How many of you have ever spun around really quickly, only to feel really
dizzy after you’ve stopped moving. Did you notice a strange feeling in your
ear?
 It turns out that the ear is one of the body’s primary organs for having
balance! Of course, balance depends on visual information: that’s why it was
harder when your eyes were closed. But you could still balance! It also
depends on feedback from your muscles. But the most important organ is
certainly your ear.
 So how does the ear help? Vestibular system! 60% of balance
o The vestibular system consists of three semicircular canals , the
utricle , and the saccule . Each of the semicircular canals lies
anatomically in a different plane, each plane at a right angle to each
other. Thus, each deals with different movement: up and down, side to
side, and tilting from one side to the other. All contain sensory hair
cells that are activated by movement of inner ear fluid (endolymph).
As the head moves, hair cells in the semicircular canals send nerve
impulses to the brain by way of the vestibular portion of the acoustic
nerve (VIII cranial nerve). These nerve impulses are processed in the
stem of the brain and in the brain's cerebellum. (DYNAMIC
BALANCE AND STATIC BALANCE: dealing with rotational
movement)
 Can anyone give examples of static (center of gravity constant)
or dynamic balance (center of gravity not constant)?
 Static: standing on one leg
 Dynamic: standing on one leg while moving arms.
 Which is more important? For sports?
o The ends of the semicircular canals connect with the utricle, and the
utricle connects with the saccule. While the semicircular canals
provide information about movement of the head, the sensory hair
cells of the utricle and saccule provide information to the brain (again
through the vestibular portion of the acoustic nerve) about head
position when it is not moving. How? A dense structure called the
macula is located in the wall of the saccule and utricle. The macula is
made up of nerve endings that are capped by tiny stone-like structures.
These stones (called otoconia or cupulolithiasis) are actually crystals
or granules of calcium carbonate. They are imbedded in the cupula,
which is a gelatinous layer that lines the macula. During head
movement, the combined forces of linear acceleration and gravity
displace the tiny stones, and thereby generate messages. (Dealing with
sense of acceleration/gravity)
 Can anyone give examples when this would be important?
o The vestibular system is the first system to fully develop 6 months
after birth.
 So why do you feel dizzy after spinning?
o When you spin, fluid in the semicircular canals of your ear moves
around. This stimulates the hair cells. When you stop spinning, the
fluid still moves a bit. Because the fluid is still activating hair cells,
your brain stills gets a message that you are moving and you feel
dizzy.
 Without this, we would have trouble with many simple activities. Balance
and equilibrium help us stay erect when standing, know where we are in
relation to gravity, and help us walk, run, and move without falling. The
functioning of the vestibular system depends on information from many
systems, hearing as well as vision and muscle feedback.
Possible Q+A Material


How does hearing work?
o Sound waves cause the tympanic membrane (eardrum) to vibrate.
Humans can hear sounds waves with frequencies between 20 and
20,000 Hz. The three bones in the ear (malleus, incus, stapes) pass
these vibrations on to the cochlea. The cochlea is a snail-shaped, fluidfilled structure in the inner ear. Inside the cochlea is another structure
called the organ of Corti. Hair cells are located on the basilar
membrane of the cochlea. The cilia (the hair) of the hair cells make
contact with another membrane called the tectorial membrane. When
the hair cells are excited by vibration, a nerve impulse is generated in
the auditory nerve. These impulses are then sent to the brain.
How can you improve balance?
o Improve the other things: Vision + Muscle tone.
o Do exercises with eyes open and eyes closed: this will make you more
sensitive to your vestibular system.
What floats?
http://www.ontariosciencecentre.ca/scizone/games/patrick/balance.asp
http://www.ontariosciencecentre.ca/scizone/games/stork/default.asp
http://www.ontariosciencecentre.ca/scizone/games/default.asp