Nystagmus

Nystagmus may be defined as involuntary eye movements characterized by slow and quick phases in opposite directions. The eye movements following rotation of the head are known as nystagmus. They show how complex, yet orderly, some of our reflex processes are. If the head is rotated slowly to the left, the eyes move slowly to the right. As soon as the eyes have moved as far to the right as possible, they then move quickly to the left.

Nystagmus may be demonstrated by the use of a swivel type chair. This demonstration will require the assistance of at least four persons in addition to the subject. The subject will be seated in the swivel chair and the four assistants will position themselves equally around the chair to insure the safety of the subject.

Basilar Membrane Cross SectionBasilar Membrane Cross Section

Figure 25.2 Cross Section of the Cochlea

Basilar membrane Cochlea Cochlear duct Cochlear nerve fibers Hair cells Organ of Corti Scala tympani Scala vestibuli Tectorial membrane Vestibular membrane

Exercise 25.2.

Have the subject sit in the swivel chair with their legs crossed, feet in the chair; and gripping the arms of the chair.

The four assistants should hold the chair in place using their feet.

One of the assistants should slowly rotate the subject clockwise. All should observe the subject's eye movement as the subject stares straight ahead during the spinning. Make one revolution about every three seconds for ten seconds.

Give the subject time to recover from the spinning before allowing him/her to get out of the chair.

Repeat the above demonstration with another subject; however\ rotate him/her in a counterclockwise direction. Observe his/her eye movements.

Repeat the above demonstration with still yet another subject; however; have the subject close his/her eyes during rotation and then have them open his/her eyes upon stopping.

Exercise 25.3

Study the wall chart of the ear. Identify the following structures on the wall chart: ampulla of the lateral semicircular canal, ampulla of the posterior semicircular canal\ ampulla of the superior semicircular canal, auricle, cochlea, cochlear branch of the vestibulocochlear nerve VIII, external auditory canal, eustachian tube, facial nerve VII, incus, lateral semicircular canal, malleus, oval window, posterior semicircular canal, round window, stapes, superior semicircular canal, tympanic membrane, vestibule, and vestibular branch of the vestibulocochlear nerve VIII.

Exercise 25.4

Examine a microscope slide of a cross section of the cochlea on low power. Identify the following structures: basilar membrane, cochlear duct, hair cells, scala tympani, scala vestibuli, tectorial membrane, and vestibular membrane.

Examine a microscope slide of a section through the crista ampullaris on low power. Identify the crista ampullaris.

Exercise 25.5

Study the model of the ear. Identify the following structures on the model: auricle (orpinna), cochlea, eustachian tube, external auditory canal, incus, lateral semicircular canal, malleus, oval window, posterior semicircular canal, round window, stapes, superior semicircular canal, tympanic mem-brane, vestibule, and vestibulocochlear nerve VIII

Exercise 25.6

An otoscope is used to view the external auditory canal and tympanic membrane of the ear.

Take an alcohol cotton ball and wipe the ear piece of the otoscope. To turn on the otoscope, depress the red button and turn the black ring. Gently pull outward and upward on the auricle (pinna) of the ear. Carefully place the otoscope into the external auditory canal. Examine the external auditory canal and observe the tympanic membrane which will cover the end of the external auditory canal.

After you have finished examining your lab partner's external auditory canal, wipe the earpiece of the otoscope with an alcohol cotton ball.

Crista Ampullaris
Crista ampullaris Cochlea

The tube like passageway that leads from the outside to the tympanic membrane is called the (1) .

The fluid that is located between the membranous labyrinth and the bony labyrinth is known as (2).

The branch of the vestibulocochlear nerve VIII that carries sensory information away from the ampulla of each semicircular canal and the vestibule is known as the (3) .

Name the three bones of the middle ear.

The tube that serves to connect the middle ear to the pharynx and which equalizes pressure on the two sides of the tympanic membrane is known as the (7)

The triangular shaped appendage on the lateral side of the head that contains elastic cartilage is called the

The coiled snail like structure of the inner ear is known as the (9) .

The specific semicircular canal that projects toward the back of the head is called the (10) semicircular canal.

The upper chamber of the cochlea that contains perilymph is called the (11) .

The sensory receptors that sit on top of the basilar membrane are known as (12) .

Name the three parts of the bony labyrinth.

The small round opening at the stapedial end of the scala tympani is referred to as the (16) .

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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