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Biology Ch.7-8.2 > 7.4 Sensory Organs > Flashcards

7.4 Sensory Organs Flashcards

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1
Q

Where are sensory receptors in animals and humans found?

A

Sensory organs.

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2
Q

Define sensory organs.

A

Groups of sensory and other specialized cells that respond to a specific stimuli or facilitate the detection of sensory information.

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3
Q

What do sense organs include?

A

Eye (responsible for vision); ears (responsible for hearing); the nose (responsible for detecting odors); tongue (responsible for detecting flavor).

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4
Q

Is the skin a sense organ? If so, why?

A

yes, skin is a sense organ, because it contains sensory receptors for pain, touch, pressure, temperature.

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5
Q

Define orbit.

A

The bony socket in the skull in which the eye is located is called the orbit; the eye, with the exception of the front, is surrounded by bone.

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6
Q

How many types of light-sensitive receptors does the eye contain? What are they called?

A

The eye contains 2 types of light-sensitive receptors: rods and cones.

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7
Q

Which between the rods and cones is more sensitive?

A

Rod have a higher sensitivity to light than cones do.

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8
Q

What does the rod do?

A

detect motion in dim light and makes them useful for night vision.

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9
Q

What’s one disadvantage of rod?

A

They only detect black and white, and they provide images of low sharpness.

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10
Q

What are cones?

A

Cones are sensitive only to bright light, but they allow the perception of color and sharp, detailed images.

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11
Q

Give an illustration to what humans do in dim light.

A

In dim light we have a difficulty distinguishing the true color of objects, and the images we perceive in low light conditions are less detailed and less harp than in bright light.

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12
Q

How many types of cones do humans have?

A

3 types of cones that detect light of different wavelength.

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13
Q

What are cones primarily sensitive to?

A

Blue, green, or red light.

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14
Q

Where are cones and rods located?

A

In a thin layer that lines the back of the eye called the retina.

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15
Q

What is the retina considered as?

A

The light-sensitive part of the eye.

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16
Q

What happens when light stimulates the eye?

A

When light stimulates the rods and cones in the retina, a cranial nerve called the optic nerve carries the nerve impulses to the brain.

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17
Q

What does the brain do once it receives the nerve impulses from the optic nerve?

A

The brain produces a visual image by analysing all the signals from each receptor cell; the closer the light sensitive cones are to each other, the sharper the image formed by the brain.

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18
Q

Define fovea.

A

Cone cells are most densely packed in the region of the retina called the fovea.

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19
Q

What type of image does the fovea produce?

A

the sharpest and most detailed color perception is produced form images that fall on the fovea.

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20
Q

Can rods be found in the fovea?

A

No. Rods are present at high density throughout most of the retina.

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21
Q

Define blind spot.

A

The region of the retina where the optic nerve leaves the eye is called the blind spot because no light-sensitive receptors are found in this region; thus, light falling on this region of the retina cannot be detected.

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22
Q

Define choroid. Where is it found?

A

Behind the retina is the choroid, a black layer that absorbs excess light scattered from the retina, thus preventing blurring of vision

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23
Q

What does the choroid contain?

A

Many blood vessels for nourishing the cells the eye.

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24
Q

define sclera.

A

the white, tough, opaque outer layer of the eye is called sclera.

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25
Q

What is the sclera covered by?

A

at the front of the eye, the sclera is covered by a thin delicate membrane, called the conjunctiva.

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26
Q

Describe the conjunctiva.

A

Transparent, and it is kept moist by tears, a bodily fluid that contains an enzyme (lysozyme) that can kill bacteria.

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27
Q

What happens when the eyelid blinks? What else protects the eye from bacteria?

A

When the eyelid blink, tears wash across the surface of the eye, keeping it moist and clearing away dust. The eyelids and eyelashes also help protect the eye by keeping larger particles away from it.

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28
Q

What is iris?

A

The iris is the opaque, pigmented, circular structure of the eye that encircles a small black hole.

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29
Q

What other colors can the iris be?

A

Varying shades of brown, green, hazel, blue, and gray.

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30
Q

What is the structure that looks like a black circle at the center of the iris? What is its function?

A

Pupil, which allows light into the eye.

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31
Q

What is one function of the iris?

A

It controls the amount of light that is allowed to enter the eye by relaxing or contracting to change the diameter of the pupil.

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32
Q

How is the diameter of the pupil controlled?

A

By pupil reflex.

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33
Q

Describe the cornea.

A

It’s the transparent, dome-shaped structure on the eye in front of the iris and pupil. The cornea is NOT covered by the conjunctiva.

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34
Q

Where is the lens located?

A

Behind the iris.

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35
Q

Describe the lens.

A

It’s a flexible structure that can change shape to focus light on the retina.

36
Q

How is the lens placed?

A

By a ring of fibrous strands called suspensory ligaments.

37
Q

Describe the function of the suspensory ligaments.

A

It attaches the lens to the ciliary muscle.

38
Q

What are the ciliary muscles?

A

It is a circular smooth muscle that encircles the lens

39
Q

Where is the aqueous humor found?

A

It’ a liquid that fills the small cavity of the eye between the lens and the cornea.

40
Q

Where is the vitreous humor?

A

It’s a jellylike substance that fills the larger cavity of the eye behind the lens.

41
Q

What do the vitreous and aqueous humors allow the eye to do?

A

They are both transparent and allow light to pass through to the retina.

42
Q

How can the diameter of the pupil be regulated?

A

By cranial reflex action (a reflex involving the brain) called the pupil reflex.

43
Q

What happens in the pupil reflex?

A

The pupil constricts, or decreases in diameter, in a very bright light and dilates, or increases in diameter, in dim light.

44
Q

What is the stimulus in pupil reflex?

A

Light intensity.

45
Q

What is the purpose of the pupil reflex?

A

Protects the retina from damage due to excess light and allows more light into the retina in dim environments for better vision.

46
Q

What are the muscles of the iris responsible for?

A

The changes in pupil diameter observed in a pupil reflex.

47
Q

Describe the muscles of the iris.

A

The iris contains 2 sets of opposing, or antagonistic, muscles that work to pull the pupil open or pull it shut.

48
Q

What type of muscles are these 2 sets?

A

The circular muscle and the radial muscle.

49
Q

Describe the circular muscle.

A

It encircles the pupil.

50
Q

Describe the radial muscle.

A

It radiates out from the edge of the pupil.

51
Q

What happens in low environments?

A

Radial muscles in the iris contract while the circular muscles relax; pupil becomes larger and more light is allowed into the eye.

52
Q

What happens in bright light?

A

Radial muscles relax while circular muscles contract; pupil becomes smaller and less light is allowed into the eye.

53
Q

Where should light be focused?

A

Must be focused on the retina for the brain to perceive a clear image.

54
Q

What must happen to the light rays before falling on the retinas?

A

Light rays reflected from the objects we look at need to be bent(refracted) so that they fall on the retina.

55
Q

what bends the light rays?

A

The cornea bends the light rays as they enter the eye, and the lens performs fine adjustments to sharpen the focus.

56
Q

How is the image perceived by the retina?

A

The image on the retina is upside-down, but the brain performs the necessary interpretations that allow us to see an upright image.

57
Q

What should happen to light rays that are close to the eye?

A

They must be bent more than light rays from distant objects, since light rays from distant objects are almost parallel whereas light rays from close objects are away from each other (diverging).

58
Q

Why is the thickness of the lens adjusted?

A

To control the degree of bending of light rays. A thicker lens bends in light motor strongly than a thin lens

59
Q

Define accommodation.

A

The adjustment in the thickness of the lens to focus light from objects at varying distances.

60
Q

What happens to the ciliary muscles when focusing on distant objects?

A

They relax. This causes the suspensory ligaments to be pulled tight, which pulls on the lens so that it becomes thinner. The parallel rays of light from the distant object are bent only slightly so they are in focus on the retina.

61
Q

What happens to the ciliary muscles when focusing on a close object?

A

They contract; which causes the sensory ligaments to become longer, releasing tension on the lens, which then becomes thicker. The divergent rays of light from the near object are bent strongly so they will be in focus on the retina.

62
Q

How many layers is the skin divided to? What are their names?

A

2 main layers: epidermis and dermis.

63
Q

Define the epidermis.

A

It’s the most external layer of the skin.

64
Q

What happens at the innermost layer of the epidermis?

A

It’s a region of actively dividing cells.

65
Q

What do the cells in the inner layer of epidermis do?

A

Gradually migrate to the surface of the skin, replacing the cells that are worn away by normal activities.

66
Q

What is the outermost layer of the epidermis called?

A

The cornified layer.

67
Q

What does the cornified layer consist of?

A

Dead cells that protect the underlying living cells from damage.

68
Q

What happens to the cells of the inner epidermis when they move towards the surface of the skin?

A

They die and become filled with keratin, which is a tough protein that provides durability to the skin and make it waterproof.

69
Q

What contains keratin?

A

Major component of hair and nails.

70
Q

Describe one thing about the cornified layer.

A

it’s thicker on areas of the body where the skin is subjected to more use or friction, such as the palms of the hand and the soles of the feet.

71
Q

What other cells does the epidermis contain?

A

The epidermis contains cells that produce melanin.

72
Q

What is melanin?

A

A dark brown or black pigment that protects the skin from damage by absorbing harmful UV radiation present in sunlight.

73
Q

Which humans produce more melanin?

A

Dark-colored skin has more melanin and provides more protection against UV radiation than lighter-colored skin does.

74
Q

What is the dermis?

A

The dermis is the layer of the skin that lies beneath the epidermis.

75
Q

What does the dermis contain?

A

Contains collagen fibers, which allow the skin some strength, and elastic fibers, which allow the skin to stretch and return to its relaxed form.

76
Q

What happens when a person grows older?

A

These fibers are produced at slower rates, causing the skin to become wrinkled and loose.

77
Q

What else does the dermis contain?

A

Sweat glands that produce sweat, which moves through sweat ducts and emerges at the surface of the skin through pores.

78
Q

Where do hair follicles lie?

A

Deep within the dermis. Hair is formed at the deepest region of the follicle. The hair grows out through the shaft of the follicle until it emerges from the epidermis at the surface of the skin.

79
Q

What else lies in the dermis?

A

Blood vessels. The dermis contains many nerve endings or sensory receptors that are sensitive to touch, pressure, temperature, and pain.

80
Q

What can these receptors in the dermis do?

A

Detect information about the surrounding environment, such as changes in temperature. These receptors can also alert an individual that damage has occurred or may occur to the body. Like other receptors throughout the body, each type of sensory receptor in the skin detects only a specific stimulus; for example, pressure receptors can detect changes in pressure applied to the skin but cannot detect changes in temperature.

81
Q

What are cells that store fats called?

A

Adipose tissue, under the dermis.

82
Q

What does the layer of adipose do?

A

Insulates the body, reducing heat loss, and also acts as an energy store.

83
Q

What is the skin’s other roles?

A

Excretion, sensitivity, protection, and temperature regulation.

84
Q

Is the skin a sense organ?

A

Yes, it detects various stimuli with its different types of sensory receptors and sending signals that code for sensory information to the CNS, where the signals can be interpreted to make sense of the organism’s environment.

85
Q

What other function does the skin have?

A

It forms a physical barrier, protecting the body from the entry of pathogens, as well as a chemical barrier mediated by melanin which absorbs harmful UV rays, thereby protecting interior cells from this damaging radiation.

86
Q

What do sweat glands, hair follicles, and blood vessels play a role in?

A

Thermoregulation.

87
Q

Define keratin.

A

It is a tough protein that provides durability to the skin and make it waterproof.

Biology Ch.7-8.2 (7 decks)

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