From Lecture 2/11/09 12 cranial nerves

During Lecture, we learned more on the 12 cranial nerves and their function. Cranial nerve I. is the olfactory never. It is a sensory nerve and it functions to conduct nerve impulses for the sense of smell sending afferents to the olfactory bulb. Cranial nerve II is the optic nerve. It is a sensory nerve and its specific function is sending visual afferents from the eye to the brain.  Crania nerve III is the Oculomotor. It is a mixed nerve. This means is has both sensory and motor neurons. A function for this nerve is eye movement up, down and medial. It also helps with lens accommodation and pupil constriction.  Cranial nerve IV is called Trochlear. It is also a mixed nerve. It helps with eye movements down and lateral and has afferents from muscle receptors. Cranial nerve V is called Trigeminal. It is a mixed nerve. One function is to help with chewing.  Cranial nerve VI is called Abducens with is a motor nerve and it helps with lateral eye movements.  Cranial nerve VII is called Facial. It is a mixed nerve. One function is to stimulate salivary and tear glands. Cranial nerve VIII is called Vestibulocochlear. Is is a sensory nerve and its specific function is hearing and balance. Cranial nerve IX is called Glossopharyngeal. It is a mixed nerve. It also helps stimulate salivary glands. Help functions is swallowing muscles in the pharynx. Also taste from posterior 1/3 of tongue and blood pressure receptors.  Cranial nerve X is called vagus and is also a mixed nerve. Function/controls soft palate, pharynx, heart and digestive organs. Sensation from ear canal, diaphragm, abdominal and chest vesceral organs. Cranial nerve XI is called Accessor and is a motor nerve and helps control muscles of palate, pharynx, larynx, and some neck and shoulder muscles. The last of the 12 cranial nerves is Cranial XII, also known as Hypoglossal. It is a motor nerve and helps with tongue movement.

After learning about the nerves that help with eye movements, I began wondering why some people have one eye that is weaker/slower than the other.  I have worn glasses for quite a few years. One of the things my eye Doctor told me was that my left eye is weaker than the other and if I stare at something and look from left to right, the left eye takes a second to catch up.

I did some research on weak eye muscles in one eye. While looking at different website, I came across a term I haven't heard before. It is called: Amblyopia.  It is another name for Lazy eye. It occurs when one eye develops differently than the other eye. As a result one eye is weaker than the other. Sometimes a difference in focusing ability causes one eye to be used more often. Other times, misalignment of the eyes causes one of the eyes to shut off to avoid double vision. Regardless of the cause, the result is a weakened, or amblyopic, eye.