Lab Exercise #3: Cranial Nerve Function

CN IV

Trochlear - Motor Nerve for Eye Movement

The corneal reflex, in which touching the cornea of one eye causes both eyes to blink, is used to assess which cranial nerves? Why are we not performing that in today's lab?

- CN V: Trigeminal Nerve - CN VII: Facial Nerve - Not performing in lab for hygienic reasons

CN VI

Abducens - Motor Nerve for Eye Movement

CN XI

Accessory - Shrug Shoulders & Turn Head

Presbyopia

Age-Related farsightedness; due to inelasticity of lense

Light is shined into the right pupil, and only the right pupil constricts. Then light is shined into the left pupil and only the right pupil constricts. This pattern is consistent with a lesion to which cranial nerve? Name the nerve and the side.

CN III on the left side

When assessing a subject's ability to visually track a moving finger, it is discovered that the subject's right eye is unable to follow the movement of the finger as it moves to the right of the subject's head. Which cranial nerve or nerves might be responsible for this problem and should be investigated further?

CN III, IV, & VI

An individual is asked to smile broadly. It is observed that the left corner of the mouth cannot be elevated in a normal fashion. The individual is then asked to wrinkle the brow. The brow is observed to wrinkle in a normal fashion. Which cranial nerve is involved in this facial control issue, and is the lesion in that nerve, to within the CNS?

CN VII within the CNS

"Ask the subject to smile broadly. Record any asymmetry or drooping in the face." What cranial nerve is this assessing?

CN VII: Facial Nerve

During a neurological exam, a subject attempts to shrug his/her shoulders into the resistance of the physician's hands pressing down. The physician notes that whole the right shoulder overcame the resistance easily, the left shoulder seemed significantly weaker. This sign is consistent with a lesion in which cranial nerve?

CN XI on the left side

Describe a test to assess the function of the olfactory nerve. Why are we not doing that in our lab?

Closing one nostril and presenting a common smell to the nostril - proper identification of the cell confirms that the olfactory nerve is functioning. We are not doing this in lab for sanitary reasons.

During a neurological exam a hearing deficit is detected in an individual's left ear. When asked to hum the individual reported that the humming was especially loud on the left side. What type of hearing deficit is this person experiencing?

Conduction Deficit

CN VII

Facial - Facial Expressions, Taste

Hyperopia

Farsightedness; difficulty seeing close objects

CN IX

Glossopharyngeal - Taste, Pharynx Sensation, Salivation, Motor Control of Pharynx

What is the anatomical explanation for why humans have sharper vision in the central aspects of their visual fields than in the peripheral visual fields?

Humans have a fovea centralis which contains the greatest amount of photoreceptors, specifically cones. Cones deal with clarity, color, and central field of vision.

CN XII

Hypoglossal - Tongue Movement

Myopia

Nearsightedness; difficulty seeing distant objects

CN III

Oculomotor - Eye Movement

CN I

Olfactory - Smell

CN II

Optic - Sight

CN V

Trigeminal - Mastication Muscles

Which 2 cranial nerves does the pupillary light reflex assess?

The optic nerve and the oculomotor nerve.

In protocol two, The Blind Spot Test, what must be done to the paper containing the X and the dot mark when the right eye is covered?

The paper needs to be flipped over when the right eye is covered.

What does it mean if someones vision is describes as being 20/15 according to the Snellen eye chart? Which of the 3 is most appropriately detected by a Snellen eye chart: presbyopia, myopia, hyperopia, cataract damage to the fovea centralis.

They can see at 20 feet what the average person can see at 15 feet. The Snellen eye chart can detect for myopia (near sightedness).

Although the cold caloric test, in which cold water is introduced into the ear, can be used to assess the function of the vestibular portion of the vestibulocochlear nerve, what is that test more commonly used for?

This test is more commonly used to assess levels of consciousness.

CN X

Vagus - Muscles in Pharynx & Larynx, Abdominal & Thoracic Viscera, carries out sensory info from abdomen and thorax to the brain

CN VIII

Vestibulocochlear - Hearing & Balance