What number cranial nerve is the optic nerve?
II
What number cranial nerve is the oculomotor nerve?
III
What number cranial nerve is the trochlear nerve?
IV
What number cranial nerve is the abducens nerve?
VI
Which opening of the skull does the optic nerve pass through?
optic canal
Which opening of the skull does the oculomotor nerve pass through?
superior orbital fissure
Which opening of the skull does the trochlear nerve pass through?
superior orbital fissure
Which opening of the skull does the abducens nerve pass through?
superior orbital fissure
Is the optic nerve sensory, motor, or mixed?
What is its role?
sensory
associated with vision
Is the oculomotor nerve sensory, motor, or mixed?
What is its role?
primarily motor
controls voluntary muscles that raise eyelids and the inferior oblique, inferior rectus, medial rectus, and superior rectus
controls involuntary muscles that adjust amount of light and help focus lens
Is the trochlear nerve sensory, motor, or mixed?
What is its role?
primarily motor
motor impulses to superior obliques
Is the abducens nerve sensory, motor, or mixed?
What is its role?
primarily motor
motor impulses to lateral rectus
Pupil size changes in response to what...
pupillary reflexes triggered by factors like light intensity, gaze, accommodation, or emotional state
Explain how pupil size is controlled by the autonomic nervous system when subject to bright light.
impulses along parasympathetic nerve fibers to pupillary constrictors of iris
Explain how pupil size is controlled by the autonomic nervous system when subject to dim light.
impulses along sympathetic nerve fibers to pupillary dilators of iris
When the iris is constricted, which muscles of the iris are contracted?
circular muscles
When the iris is dilated, which muscles of the iris are contracted?
radial muscles
Explain how we did the activity with the Snellen Chart.
-stand 20 ft away from the chart
-cover one eye
-determine smallest line of print you can read
-go up to chart and read what your visual acuity is
-do for both eyes
Explain what it means to have 20/15 vision.
You can see something at 20 ft that a normal person can see at 15 ft.
Explain what it means to have 20/100 vision.
you can see something at 20 ft that a normal person can see at 100 ft
An individual is diagnosed with myopia. What is the most likely cause of the vision problem? What type of lens will correct his vision?
cause= eyeball too long so image focuses in front of retina
Concave lens will diverge light waves before they hit the cornea, moving the focal point back so that it is on the retina
Explain how we determined astigmatism.
-stand 10 ft back from chart
-cover one eye
-decide whether any lines appear blacker or clearer
-if any do, you have astigmatism
What causes astigmatism?
irregular curvature of cornea or lens makes it impossible to get entire image in focus at the same time
How did we determine colorblindness?
used Ishihara's Tests for Colour Blindness
What causes colorblindness?
lack of a gene for one of the iodopsins (chlorolabe, cyanolabe, or erythrolabe)
Why is color blindness more common in males than in females?
genes for colorblindness are on the X chromosome
males only have on X chromosome, so if that X chromosome is lacking one of the iodopsin genes, that individual will suffer from some degree of color blindness
How was visual accommodation measured?
-obtain a flashcard with "Anatomy & Physiology" on it
-hold it out at arms length and slowly bring it closer to the eye until the print is no longer in focus
-measure in cm how long it is
Explain the accommodation reflex. Include the name of the cranial nerve responsible for controlling the ciliary muscles in your explanation.
In order to view close objects, the refractory power of the lens must increase by becoming thicker. To accomplish this, the ciliary muscles must contract and slacken the pull on the lens.
In order to view distant objects, the refractory power of the lens
Why does accommodation distance generally increase as you grow older?
What is the name of this condition?
The lens becomes less flexible as you age, so it does not thicken to see close objects as well.
The far-sightedness associated with aging is presbyopia.
How did we measure the blindspot?
-make dot on margin of paper
-cover pencil, except tip, with paper
-position eyes 30 cm above paper
-slowly move pencil to right until you lose view of it, mark it
-mark again when it reappears
-measure distance between marks
What equation is used to find the size of the blindspot?
Define each variable.
(x/1.5cm) = (d/30 cm) where x = size of blind spot, d = distance between two marks, 1.5 = distance from lens to retina, and 30 = distance from eye to paper
What causes the blind spot?
There are no photoreceptors on the optic disk, so images that focus there cannot be seen.
Explain how we found the distance between retinal cones.
-back away from white index card with two lines
-stop when the two lines can no longer be distinguished as separate lines
-measure distance
-calculate
What equation is used to find the distance between retinal cones?
Define all variables.
(2mm/d) = (x/15mm) where d = distance from card, 2 mm, = distance between lines on the card, 15mm = distance from lens to retina, x = distance between retinal cones (in mm)
Explain how we determined the dominant eye.
-obtain an index card with a hole in the middle
-place a penny on the floor
-locate penny through hole at arm's length
-close each eye to determine which sees penny through hole independently
Most common cause of myopia:
the eyeball is too long from front to back
-focal point falls IN FRONT OF the retina
Most common cause of hyperopia:
the eyeball is too short from front to back
-focal point falls BEHIND the retina
How can convex lens fix hyperopia?
bend light before it reaches cornea and lens, so focal point goes forward and converge on retina
Difference between hyperopia and presbyopia.
hyperopia caused by eyeball being too short
presbyopia is caused by lens loosing elasticity
How does astigmatism affect vision?
cannot focus entire image at the same time
Visual pathway
retina -> optic nerve -> optic chiasm -> optic tracts -> lateral geniculate nucleus (LGN) of thalamus -> visual radiations -> visual cortex
The ___ of the retina lacks photoreceptors.
optic disk
The retina is part of the ___ tunic of the eye.
inner (nervous)
The oculomotor nerve (cranial nerve III) controls what muscles of the eye?
inferior oblique
inferior rectus
medial rectus
superior rectus
The ___ of the middle tunic is deeply pigmented due to the presence of numerous melanocytes.
choroid coat
The second cranial nerve, the __ nerve, is responsible for the sense of sight.
optic
The pigmented muscle of the middle tunic that is responsible for regulating amount of light entering eye is called the ___. Sympathetic impulses will cause the ___ muscles of this structure to contract and dilate the pupil.
iris
radial
The transparent region of outer tunic is the ___. This was the first organ to be successfully transplanted.
cornea
The __, located directly behind the iris, is composed of highly specialized epithelial cells. It lacks blood vessels.
lens
The thin, membranous covering for the anterior potion of the eye is the ______. A common term for infection of this covering is pink eye.
conjunctiva
The superior oblique muscles are controlled by the _____ nerves and the lateral rectus muscles are controlled by the ___ nerves.
trochlear
abducens
The ____ is the tough outer covering of the eye and is comprised of dense fibrous connective tissue.
sclera
The structure responsible for changing shape of lens in order to view objects at various distances is the __________.
ciliary body
The muscles within the ciliary body are controlled by the parasympathetic fibers of the ____ nerve and act to relax the suspensory ligaments.
oculomotor
A football player's helmet came off during a play and he suffered a significant head injury, including damage to his right visual cortex. Describe how this injury will affect his vision. Include the optic chiasma.
In the optic chiasma, nerve fibers from the medial side of each eye cross over to the opposite hemisphere of the brain. The right visual cortex is responsible for images that originate in the medial potion of the left eye and the lateral portion of the ri
Describe the changes that must happen in the eye in order to go from the bright sunshine to a dark tunnel.
In a darkened tunnel, the pupil will dilate which is caused by the contraction of the radial muscles of the iris which are controlled by the sympathetic nervous system. In the rods, the rhodopsin will be synthesized from opsin and retinal, and now the eye
Describe the changes that must happen in the eye in order to go from a dark tunnel to bright sunlight.
In bright sunshine, the pupil will constrict which is caused by the contraction of the circular muscles of the iris which are controlled by the parasympathetic nervous system. In the rods, the rhodopsin will be degraded into opsin and retinal, and now the