Equilibrium

Objective:

To explain in short essays or diagrams how the vestibular system responds to circular motion and works with the brainstem to maintain sensory orientation and balance, at the level of 85% proficiency for each student.

In order to achieve this objective, you will need to be able to:

Diagram the three planes of the ear canals in the vestibular system and label the motion associated with each plane.
Describe the processes at work in the vestibular system when the human body responds to circular motion.
Describe the role of the vestibular system in maintaining sensory orientation and balance.
Describe the pathways from the semicircular canals to the eyes and the brain.

Materials:

Group Supplies:

masking tape

Swivel chair

turntable

500 mL plastic dish

250 mL water

1 piece of fake fur fabric

clear tape

1 Velcro strip

scissors

Descriptions of vestibular pathways are available as a supplement: Vestibular Pathways.

Methods:

WALKING THE LINE

Place a 2-meter strip of wide masking tape on the center of a hallway floor.
Ask a student to volunteer to be spun and be the "spinnee"; another student will be the "spinner" and will spin the student.
Line up the rest of the class about one meter away from either side of the tape.
Have the spinnee face the line and shut his/her eyes.
Instruct the spinnee to keep his/her arms by his/her side during spinning. The spinner will spin the spinnee 5 times from behind and stop the spinnee so that he/she faces the line and is perpendicular to it.
Then ask the spinnee to open his/her eyes and immediately "walk the line."
All students should write down their observations.

SPINNING WATER

Glue or tape a 4 x 2 cm strip of fake fur fabric on the bottom of a circular plastic dish toward the dish's side.
Fill the dish with about 5 cm of water and use Velcro strips to attach the dish to the outer 4 cm of the turntable. Test to make sure that the Velcro strips are sufficient to hold the dish on the turntable. Begin spinning the turntable slowly.
The observer should describe the motion, or the lack of motion, of the dish, the water, and the hairs of the fur.
The recorder should enter these observations into the table.
The observer and recorder should repeat Steps 4 and 5 as the spinner changes the speed of the turntable. Three different phases of motion should occur: speeding up (acceleration), constant speed, and slowing to a stop (deceleration).

EYE TRACKING

Ask a student to volunteer to be spun (spinnee), and another volunteer to do the spinning (spinner).
Have the other students in the group stand in front of the spinnee so they can see his/her eyes.
The spinner should stand behind the spinnee. The spinnee should have his/her eyes closed during the spinning procedure.
The spinner should turn the spinnee five times. The spinnee should keep his/her arms at his/her side during the spinning. The spinner should make sure that the spinnee stops facing the rest of the students in the group.
Have the spinnee open his/her eyes immediately after the spin.
The rest of the group should observe the eye movement.
If time permits, repeat the procedure with another volunteer spinner and spinnee team.
The students should again record what eye movement is observed in each spinnee.

Results:

Walking the Line

Subject	Observations

Spinning Water

	motion of the dish.	motion of the water	motion of the hairs of the fur
speeding up (acceleration)
constant speed
slowing to a stop (deceleration).

Eye Tracking

Subject	Observations of Eye Movements

Discussion:

Would the results of the walking the line experiment change if the subject:

had his/her eyes closed?
were spun with the head in a different position?

Would the results of the fake fur experiment change if a fluid was used with a viscosity different than water?
Would the results of the eye tracking experiment change if the subject:

had his/her eyes open?
were spun with the head in a different position?