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Pharmacophysiology > Vision Sensory System > Flashcards

Vision Sensory System Flashcards

1
Q

What is light with regards to reception by the eye?

A

The visual signal.

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2
Q

What are the three criteria that “perceiving” a visual signal requires?

A

1) The eyes capable of detecting, focusing, and responding to light
2) The appropriate neural pathways
3) Brain regions to interpret the signal

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3
Q

Define visual perception.

A

The ability to detect light and interpret it.

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4
Q

What is the purpose of rod and cone cells?

A

To convert visually transduced light into electrical signals.

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5
Q

Where are rods and cones located within the eye?

A

The retina.

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6
Q

Name the steps of visual perception starting with light passing through the threshold.

A

1) Threshold passage
2) Transduction by receptors
3) Conduction by afferent neurons
4) Processing by brain
5) Perception

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7
Q

Define wavelength (l).

A

The distance between successive peaks of EMR.

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8
Q

Between what wavelengths can the human eye perceive and what is this portion of the EMR called?

A

400-750 nm.

Visible spectrum.

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9
Q

What distinguishes one color from another when an eye receives a light input?

A

Different wavelengths are what dictates the color perceived.

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10
Q

What portion of the EM spectrum can snakes “see”?

A

Infrared light.

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11
Q

When light passes through a concave medium, what happens?

A

The light is refracted to diverge relative to the original vector.

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12
Q

When light passes through a convex medium, what happens? What is effective formed?

A

The light is refracted to converge to form a focal point.

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13
Q

What is a focal point? (EMR)

A

The point at which light vectors converge and intersect.

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14
Q

Define what focal length is and what surfaces it is often associated with.

A

Focal length is the distance from a CONVEX surface to the focal point of light passing through the original medium.

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15
Q

With respect to light, which of its characteristics is responsible for why we can see objects that do not emit light? How can this property be defined?

A

Reflection is responsible for why we can see objects. Reflection is when light waves strike and bounce off surfaces we see.

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16
Q

When light bounces off of a surface, why do we see objects in different colors?

A

Different objects will absorb non-perceived wavelengths of the light striking it.

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17
Q

Define refraction.

A

Refraction is when light passes through transparent mediums of varying density.

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18
Q

Briefly given an overview of the eyes organization.

A

The eye is a 3 layered fluid filled ball that is divided into 2 chambers.

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19
Q

What does Layer-1 of the eye consist of? (3 items)

A

1) Sclera (outer layer)
2) White connective tissue capsule around eye
3) Clear cornea at the front

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20
Q

What does Layer-2 of the eye consist of? (4 items)

A

1) Choroid
2) Iris
3) Ciliary muscle
4) Zonular fibers

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21
Q

What is the suspensory ligament composed of?

A

Ciliary muscle and zonular fibers.

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22
Q

What does Layer-3 of the eye consist of? (2 items)

A

1) Retina

2) Photoreceptors

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23
Q

What are the two chambers of the eye and where are each located in the eye?

A

1) Aqueous humor (anterior)

2) Vitreous humor (posterior)

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24
Q

Define the function of the iris and what components of it accomplish this function.

A

Regulates the size of the pupil via circular and radial muscles. Therefore, determines the amount of light that enters the eye.

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25
Q

What is the optic nerve and what is its function?

A

Axons of ganglion neurons in the retina that carry info to the brain.

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26
Q

How does pupil size change relative to light intensity?

A

Bright light = smaller pupil diameter

Low light = bigger pupil diameter

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27
Q

In weak light, which muscles are responsible for pupil size increasing? What kind of nerves are these muscles stimulated by?

A

Outer radial muscles are responsible for pupil size increase and they are stimulated by parasympathetic nerves.

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28
Q

In strong light, which muscles are responsible for pupil size decreasing? What kind of nerves are these muscles stimulated by?

A

Inner circular muscles are responsible for pupil size decrease and they are stimulated by sympathetic nerves.

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29
Q

The kind of surface is the cornea and lens?

A

Convex.

30
Q

Where does the focused light from the cornea and lens travel to next?

A

The retina.

31
Q

How is visual information that reaches the retina oriented?

A

It is reversed from right to left and is upside down.

32
Q

When viewing a distant object, what kind of lens is required for refraction? Why?

A

A flattened lens is required for weak refraction because light rays are nearly parallel when they arrive.

33
Q

When viewing a near object, what kind of lens is required for refraction? Why?

A

A rounded lens is required for strong refraction because light rays are still strongly diverging when they arrive.

34
Q

Define optical accommodation.

A

The normal ability of the lens to adjust its curvature to view near and far objects.

35
Q

How is focus related to lens shape for distant and near objects?

A

For distant objects, focus is enhanced by a flattened lens.

For nearby objects, focus is enhanced by a rounded lens.

36
Q

What two anatomical structures contribute to form a flattened lens? How are they behaving?

A

Ciliary muscles and zonular fibers. Ciliary muscles are relaxed and zonular fibers are tensioned.

37
Q

What two anatomical structures contribute to form a rounded lens? How are they behaving?

A

Ciliary muscles and zonular fibers. Ciliary muscles are contracted via PS nerve firing and zonular fibers are slackened.

38
Q

What determines where light rays converge? (3 items)

A

1) Cornea
2) Lens shape
3) Eyeball length

39
Q

What is the common name for myopia? What are its characteristics? What is its correction?

A

Near-sightedness.

1) Eyeball too long
2) Focus in front of retina
3) Can see near objects clearly

Concave lenses.

40
Q

What is the common name for hyperopia? What are its characteristics? What is its correction?

A

Far-sightedness.

1) Eyeball too short
2) Focus behind retina
3) Can see distant objects clearly

Convex lenses.

41
Q

What are the 3 layers of the retina and where are they located? (front to back)

A

1) Ganglion cells (inner/front of retina)
2) Bipolar cells (middle)
3) Photoreceptors and pigmented epithelium (outer/back of retina)

42
Q

What is the macula lutea?

A

Yellow spot near center of the retina.

43
Q

What is the fovea centralis?

A

A central pit within the macula that contains the highest density of cones. Cones decrease toward periphery where rods are more abundant.

44
Q

What is the optic disc?

A

A distinct region where neurons carrying information from photoreceptors exit the eye as optic nerve.

45
Q

What is the complex pathway of light starting with the cornea? (8 steps)

A

1) Cornea
2) Aqueous humor
3) Pupil
4) Vitreous humor
5) Front surface of retina
6) Ganglion neurons
7) Bipolar cells
8) Photoreceptors

46
Q

What are the two types of photoreceptors?

A

Rods and cones.

47
Q

What are photopigments and what do they consist of?

A

Light sensitive pigments within photoreceptors that consist of membrane-bound opsins and light sensitive retinol.

48
Q

What is the purpose of the outer segment of rods and cones?

A

They consist of folds with photopigments that absorb light.

49
Q

What is the inner segment of rods and cones used for?

A

Serves as basic cell machinery.

50
Q

What does the synaptic terminal of rods and cones do?

A

Releases glutamate as a neurotransmitter.

51
Q

What are the 5 main characteristics of rod cells?

A

1) Specialized for dim light - night vision
2) More photopigments: can detect single photons
3) Saturate in daylight
4) Low acuity - none in central fovea
5) 1 photopigment, rhodopsin

52
Q

What are the 5 main characteristics of cone cells?

A

1) Specialized for day vision
2) Less photopigments, lower sensitivity
3) Saturate in intense light
4) High density in fovea —> high acuity
5) Provide color vision: 3 types of cones each with different photopsins

53
Q

What type of sensory cell remains depolarized at rest and hyperpolarized when exposed to adequate stimulus?

A

Cone cells.

54
Q

In the absence of light, what does the enzyme guanyl cyclase do to keep the membrane of cone cells depolarized?

A

Guanyl cyclase generates cGMP which opens Na+/Ca2+ channels.

55
Q

In the presence of light, what does retinal do to lead to hyperpolarization?

A

It dissociates from opsin, which activates cGMP phosphodieterase which causes the closure of ion channels.

56
Q

How are light signals converted to APs? (broad terms)

A

Interactions of photoreceptors with bipolar and ganglion cells.

57
Q

Why can’t photoreceptor and bipolar cells generate APs?

A

They lack voltage-gated ion channels.

58
Q

What are the first cells to initiate an AP?

A

Ganglion cells.

59
Q

What are the two ways photoreceptors interact with bipolar and ganglion cells?

A

On and off pathways.

60
Q

In the absence of light, photoreceptors are depolarized. What does this mean regarding bipolar cells?

A

It means there is an increased release of glutamate onto the bipolar cells.

61
Q

In the ON pathway, what does glutamate do to lessen neurotransmitter release onto associated ganglion cells?

A

Glutatmate interacts with metabotropic receptors on bipolar cells to hyperpolarize, dereasing neurotrasnmitter release.

62
Q

In the absence of light on bipolar cells, ganglion cells cannot what in the ON pathway?

A

Fire action potentials.

63
Q

BE ABLE TO DESCRIBE VISUAL PATHWAYS.

A

CHACH.

64
Q

Color vision begins with what?

A

The activation of photopigments in retina.

65
Q

How many types of cones do humans have and what do they respond to? (short to long)

A

1) short (blue light)
2) medium (green light)
3) longer (red light)

66
Q

What is color-blindness?

A

A sex-linked recessive genetic disorder where 1 or more cone mechanism is lost.

67
Q

What is the most common form of color blindness?

A

Red-green color blindness, 1/12 men and 1/200 women.

68
Q

Why is red-green colorblindness more prevalent in men?

A

The genes involved in mutation are loacted on the X chromosome.

69
Q

What is a cataract?

A

Cloudiness due to accumulation of proteins in the lens.

70
Q

What is glaucoma?

A

Intraocular pressure build up and retinal damage leading to irreversible blindness.

71
Q

What is macular degeneration?

A

Impairment of macula lutea leads to visual degradation in the center of visual field.

Pharmacophysiology (6 decks)

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