Vision

Question 1

What is the path through which tears travel from the lacrimal gland to the nostril (lacrimal apparatus)?

Answer 1

1. lacrimal gland
2. ducts
3. lacrimal punctum
4. lacrimal canaliculus
5. lacrimal sac
6. nasolacrimal duct
7. inferior meatus of nasal cavity
8. nostril

Question 2

What are the three functions of tears?

Answer 2

1. Cleanse and lubricate the eye surface
2. Deliver oxygen and nutrients to the conjunctiva.
3. Protect from infection (contain lysozyme and antibodies).

Question 3

What are the three layers or tunics of the eyeball, starting from the outermost to the inner layer?

Answer 3

Fibrous, vascular, and neural tunics

Question 4

Name the two structures of the fibrous tunic.

Answer 4

The sclera (white of the eye) and cornea.

Question 5

What are the three structures composing the vascular tunic?

Answer 5

Iris, ciliary body, and choroid.

Question 6

What structure of the vascular tunic is a muscular ring that secretes aqueous humor?

Answer 6

Ciliary body.

Question 7

What is the function of the choroid?

Answer 7

It contains high density of blood vessels, provides nutrients and waste removal to eye structures.

Question 8

Where is the retina found?

Answer 8

In the neural tunic, lining the back of the eye.

Question 9

(a) What is the cornea? (b) what function does it serve? (c) Is it capable of regeneration after sustaining damage?

Answer 9

(a) A transparent membrane that protects the eye (b) It allows light to enter the eye (c) Yes, it contains stem cells.

Question 10

Which eye structures are responsible for light refraction?

Answer 10

The cornea and lends bend (refract) light and focus it on the retina.

Question 11

Are images projected onto the retina in an inverted or non-inverted manner?

Answer 11

Images are projected as 2-D, in an inverted and reversed manner.

Question 12

Describe the iris.

Answer 12

The iris is an adjustable diaphragm, found between the cornea and lens, that controls pupil diameter, thus the amount of light entering.

Question 13

(a) What is the pupil (b) Which two muscles of the iris control pupil diameter? (c) Which one is closest to the pupil?

Answer 13

(a) ) Aperture through which light enters the eye. (b) Sphincter pupillae and dilator pupillae. (c) The dilator pupillae.

Question 14

Which muscle of the iris receives sympathetic input, and which one receives parasympathetic innervation?

Answer 14

The dilator pupillae receives sympathetic input while the sphincter pupillae recieves parasympathetic innervation.

Question 15

What response does the pupil have for close-up vision, and why?

Answer 15

Pupil constriction (through stimulation of the sphincter pupillae by the parasympathetic nervous system ) to increase the depth of focus and decrease spherical aberration.

Question 16

What is spherical aberration?

Answer 16

It is an optical phenomenon that occurs when light rays passing through the periphery of a lens or optical system focus at a different point than those passing through the center. This can result in a blurring or distortion of the image.

Question 17

What does the term “focal point” refer to?

Answer 17

The focal point refers to the specific point on the retina where light rays converge after being refracted by the cornea and lens.

Question 18

Describe the lens.

Answer 18

A clear, biconvex, and flexible structure structure suspended in the eye by suspensory ligaments. Function include light refraction and adjustment of focal length.

Question 19

What muscle controls the lens shape?

Answer 19

The ciliary muscles.

Question 20

(a) Where is the aqueous humor produced and drained? (b) What function does it serve?

Answer 20

It is produced by the ciliary body and flows out through the trabecular meshwork in the drainage angle. (b) Supplies nutrients to the avascular structures of the eye, cornea, and lens, and maintains intraocular pressure (IOP).

Question 21

How does the lens accommodate to close-up vision?

Answer 21

Parasympatheic stimulation causes contraction of ciliary muscles and relaxation of the zonular fibers resulting in the bulging of the lens.

Question 22

What is emmetropia?

Answer 22

Emmetropia means normal eye. An emmetropic eye sees distant objects clearly, without using accommodation.

Question 23

How is eye convergence produced?

Answer 23

By contraction of both medial rectus muscles which orients the visual axis of each eye toward the object for close-range vision

Question 24

What are the 3 processes involved in the adjustment to close-range vision?

Answer 24

Pupillary constriction, lens thickening (accommodation), and inward rotation of the eyes (eye convergence)

Question 25

What liquid fills the globe of the eyeball, and what is its function?

Answer 25

Vitreous humor. It maintains the round shape of the eye and help with vision clarity (it is clear so light can pass through)

Question 26

What is the overall function of the retina?

Answer 26

It receives the image that the cornea focuses through the lens and transforms this image into electrical impulses that are carried by the optic nerve to the brain

Question 27

What is macula (yellow spot) and the fovea?

Answer 27

In the macula there is a concentration of cone cells. These cells are responsible for color vision, sharp visual acuity and central vision. The highest concentration of cones is in the fovea, a tiny area in the center of the macula.

Question 28

What are the six types of cells found in the neural layer of the retina involved in vision?

Answer 28

Photoreceptors (rods and cones), bipolar cells, ganglion cells, amacrine cells, and horizontal cells.

Question 29

Which cells do photoreceptors contact and transmit the electrical signals?

Answer 29

Bipolar cells.

Question 30

Sequence the light path from photoreceptor cells to the optic nerve (CN II).

Answer 30

1. Photoreceptors
2. Bipolar cells
3. Ganglion cells

Question 31

What is the definition of phototransduction?

Answer 31

The conversion of light energy to electrical signals by photoreceptors.

Question 32

Define rhodopsin and identify ist primary components, along with its location.

Answer 32

Rhodopsin is a light-sensitive protein found in the disc membranes of the rod cells. Its main components include a protein called opsin and a light-absorbing molecule called retinal.

Question 33

Are Na+ channels opened or closed at night, and why? Which molecule stimulates their opening, and is it available at night?

Answer 33

They are opened since there is cGMP available, the molecule that activate the sodium channels.

Question 34

What are the three types of cones?

Answer 34

Short wavelength cones (blue), medium wavelength cones (green), long wavelength cones (red).

Question 35

Which neurotransmitter is released by the inner segment of the rods, and to which neuron?

Answer 35

Glutamate, to bipolar cells,

Question 36

What is the definition of “bleaching” in the context of vision?

Answer 36

It refers to the temporary loss of sensitivity to light in rods, where trans retinal needs to be regenerated to 11-cis retinal

Question 37

Describe the visual projection pathway.

Answer 37

1. optic nerve
2. optic chiasm
3. optict tract
4. thalamus (lateral geniculate nucleus)
5. occipital lobe

Question 38

What is the optic chiasm?

Answer 38

It is the point where the optic nerves from both eyes partially cross in the brain, allowing each hemisphere to receive visual information from both the left and right visual fields.