Module 3.1 Vision Flashcards
What are the five special senses?
Vision, smell, taste, hearing and equilibrium (balance)
What are the two parts of the outer layer of the eye?
Sclera and cornea
What is included in the middle layer of the eye?
Choroid, the ciliary muscle, and the iris.
The pupil is a hole in the ____.
Iris
The inner sensory layer is the _____.
Retina
What are the two types of photoreceptors and their functions?
The more numerous cells are rods which are stimulated in dim light. Rods are more sensitive to light but do not generate sharp or color images. The cones operate in bright light helping to generate sharp color images.
The interior of the eye (posterior to the lens) is filled with_____
Vitreous fluid
True or False: The vision pathway begins as the optic tracts, crosses at the optic chiasm and then moves through the optic nerve.
False
Where is the LGN located?
Thalamus
True or False: The nasal visual field is the visual field on the lateral sides of each eye.
False
Why is touch not considered a special sense?
Does not have specialized receptor cells or specialized somatic and visceral afferents.
How does the sense of touch function?
Uses general receptors composed of modified dendrites of sensory neurons. General somatic and visceral afferents received combined info on pressure, vibration, pain, and heat.
Where is the aqueous humor located?
Space between the cornea and the lens.
How many layers does the eye have? What are they?
3 layers: the outer fibrous layer, middle layer, and the inner sensory layer.
What are the functions of the choroid?
Its dark color prevents light from dispersing throughout the eye and it is highly vascularized to supply blood to the other layers of the eye.
What is the function of the ciliary body?
To change lens shape allowing it to focus.
What is the function of the iris?
Uses its muscle fibers to contract or dilate based on the amount of light in the environment, lets more or less light in through the pupil.
What is the vitreous body?
The interior of the eye posterior to the lens
What is the main function of the vitreous fluid?
To hold the retina in place to the choroid.
Where is the lens located?
Posterior to the iris and pupil.
What is the pathway of light to the retina?
Through the cornea, aqueous humor, lens, and vitreous humor.
What is the pathway of visual info from the retina onwards?
The photoreceptors to the optic nerve, optic chiasm, optic tracts, lateral geniculate nucleus of the thalamus, primary visual area of the occipital lobe.
Where is the optic chiasm located?
At the base of the hypothalamus.
The medial fibers of the optic nerve ….
Cross over to the other side when they reach the optic chiasm.
Where do the optic tracts form and where do they terminate?
They form at the optic chiasm and terminate at the lateral geniculate nucleus (LGN) of the thalamus.
What do the optic radiations connect?
The thalamus and the primary visual area of the occipital lobe.
What allows for 3-D vision?
Overlapping information in the nasal visual fields allows for 3-D vision, called the binocular visual field.
True or false: Only the medial fibers cross at the optic chiasm.
True
The left side of the brain receives information from the _________ of the left eye and the ________ of the right eye.
The left side of the brain receives information from the medial side of the left eye and the lateral side of the right eye (bilateral right visual fields).
The medial rectus turns the eye _____. The medial rectus is controlled by CN _____.
Medially, CN III, oculomotor.
What is a cataract?
Cataracts are lenses that slowly become hardened and cloudy over time.
What is another name for double vision?
Diplopia
How many muscles control the eye and what are they called?
6 Extrinsic eye muscles.
What are the 2 extrinsic eye muscles that are not innervated by the oculomotor nerve?
The lateral rectus and superior oblique.
What innervates the lateral rectus muscle?
The abducens nerve CN VI.
What innervates the superior oblique muscle?
The trochlear nerve CN IV.
How does the superior oblique move the eye?
Depresses, laterally, and internal rotation.
How does the inferior oblique move the eye?
Elevates, laterally, and external rotation.
How does the inferior rectus move the eye?
Medially and depresses.
How does the superior rectus move the eye?
Medially and elevates.
What is a common cause of diplopia? How can this be observed and tested clinically?
Damage to the abducens nerve. Patient’s eye rests medially from lack of muscle tone; the nasal visual pathway cannot be maintained. If patient is told to look straight ahead and follow finger and one eye cannot move laterally.
