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biology > ch 6 coordination (eye) (p. 1-6) > Flashcards

ch 6 coordination (eye) (p. 1-6) Flashcards

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1
Q

define irritability.

A

irritability is the ability of living organisms to detect changes in their environment and produce responses.

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2
Q

what is irritability brought about by?

A
  • receptors
  • coordination systems
  • effectors
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3
Q

the environmental changes act as ____. they are detected by different ____ in the body.

A

stimulus ; receptors

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4
Q

an organ that contains receptors is called a ____.

A

sense organ

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5
Q

the receptors detect stimuli and send out ____ along nerve fibres. when ____ reach the brain, ____ are produced.

A

nerve impulses ; nerve impulses ; sensations

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6
Q

5 main sense organs of our body:

A
  • eyes
  • ears
  • tongue
  • nose
  • skin
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7
Q

what is stimuli detected by? identify and give examples.

A

receptors.
e.g. eyes, ears

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8
Q

give examples of coordination systems.

A
  • nervous system
  • endocrine system
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9
Q

stimuli is detected by ____ –> ____ –> ____ bring out response.

A

receptors ; coordination systems ; effectors

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10
Q

define stimulus.

A

the change in the external or internal environment of an organism that results in a response.

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11
Q

define receptor.

A

a cell or an organ that can detect stimulus.

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12
Q

define coordination.

A

a group of tissue and organs that work together to allow communication and coordination of receptors and effectors.

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13
Q

define effector.

A

a cell or an organ that brings about a response.

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14
Q

define response.

A

the way an organism reacts which is caused by a stimulus.

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15
Q

what are the stimuli detected by
1. the eye
2. the ear
3. the nose, tongue
4. skin

A
  1. light
  2. sound vibrations and body movement
  3. chemicals
  4. touch, pressure, pain, heat and cold
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16
Q

what are the senses produced by
1. the eye
2. the ear
3. the nose, tongue
4. skin

A
  1. sight
  2. hearing and balance
  3. smell, taste
  4. touch
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17
Q

each eye is held in a socket of the skull called the ____.

A

orbit

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18
Q

the front surface of the eyeball is protected by a movable ____ and an immovable ____ which allow blinking.

A

upper eyelid ; lower eyelid

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19
Q

____ secrete tears.

A

tear glands

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20
Q

what do tears secreted by the tear glands contain?

A

sodium hydrogencarbonate, sodium chloride, and an enzyme.

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21
Q

what are the functions of the tear and the enzyme?

A

the tear keeps the front surface of the eyeball moist and clean. the enzyme kills bacteria.

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22
Q

excess tear is drained into the ____ through a ____.

A

nasal cavity ; tear duct

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23
Q

what are the features of the sclera?

A
  • the outermost white, tough, opaque layer
  • protects the inner structures and maintains the shape of the eyeball
  • provides a surface for the attachment of eye muscles
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24
Q

what are the features of the choroid?

A
  • the middle layer of the eyeball
  • contains a black pigment which absorbs light to reduce reflection of light within the eye
  • contains blood vessels which supply nutrients and oxygens to the cells and remove waste from them
25
Q

what are the features of the retina?

A
  • the inner layer of the eyeball
  • contains photoreceptors, also called light-sensitive cells: rod cells and cone cells. these cells are connected to nerve fibres, which all leave the eyeball at one region to form the optic nerve
  • at the region where the nerve fibres leave the eyeball to form the optic nerve, there is no light-sensitive cells. this region is known as the blind spot
  • at the centre of the retina is the fovea (yellow spot), which has a high density of light-sensitive cells.
26
Q

what is the blind spot?

A

the region where the nerve fibres leave the eyeball to form the optic nerve, there is no light sensitive cells.

27
Q

what is the fovea?

A

it is at the centre of the retina. it has a high density of light-sensitive cells.

28
Q

what are the features of the conjunctiva?

A
  • a thin transparent layer at the front of the eye
  • allows light to enter the eye
29
Q

what are the features of the cornea?

A
  • a transparent area of sclera at the front of the eyeball
  • refract light into the eye
30
Q

what are the features of the iris?

A
  • a pigmented muscular structure at the front part of the choroid
  • controls the amount of light entering the eye by adjusting the size of the pupil
31
Q

what are the features of the pupil?

A
  • a hole at the centre of the iris
  • allows light to enter the eye
32
Q

what are the features of the lens?

A
  • a transparent, elastic, biconvex shaped structure
  • refracts and focuses light onto the retina
33
Q

what are the features of the suspensory ligament?

A

connects the lens to the ciliary body.

34
Q

what are the features of the ciliary body?

A
  • a ring of ciliary muscle behind the iris
  • controls the refraction of light into the retina by changing the thickness of the lens
35
Q

what are the features of the aqueous humour?

A
  • a watery fluid filling the anterior chamber of the eye
  • allows nutrients and oxygen from the capillaries of the choroid to diffuse to the conjunctiva, cornea and lens
  • maintains the shape of the eyeball and refracts light into the retina
36
Q

what are the features of the vitreous humour?

A
  • a jelly-like fluid filling the posterior chamber of the eye
  • maintains the shape of the eyeball and refracts light into the retina
37
Q

how does the human eye react to a bright light condition?

A

in a bright light condition, the circular muscles of the iris contracts while the radial muscles of the iris relaxes, the size of the pupil is smaller. thus, the amount of light entering the eye decreases.

38
Q

what is the importance of decreasing the size of the pupil in a bright light condition?

A

to prevent too much light from entering the eyeball that may damage the light-sensitive cells on the retina.

39
Q

how does the human eye react to a dim light condition?

A

in a dim light condition, the circular muscles of the iris relaxes while the radial muscles of the iris contracts, the size of the pupil is larger. thus, the amount of light entering the eye increases.

40
Q

what is the importance of increasing the size of the pupil in a dim light condition?

A

it allows more light to enter the eyeball so as to form a clear image on the retina.

41
Q

what are the two kinds of light-sensitive cells?

A

rod cells and cone cells.

42
Q

what many types of rod cells are there?

A

one.

43
Q

how many types of cone cells are there?

A

three.

44
Q

what is the shape of rod cells?

A

rod shape.

45
Q

what is the shape of cone cells?

A

cone shape.

46
Q

what light are rod cells sensitive to?

A

dim light

47
Q

what light are cone cells sensitive to?

A

bright light

48
Q

what vision are rod cells responsible for?

A

black and white vision

49
Q

what vision are cone cells responsible for?

A

colour vision

50
Q

explain rod cells’ distribution on the retina.

A

rod cells are more abundant at the periphery of the retina. throughout the retina, but none at the fovea and blind spot.

51
Q

explain cone cells’ distribution on the retina.

A

cone cells are more abundant at the centre of the retina. they are concentrated at the fovea, none at blind spot.

52
Q

what are the three types of cone cells each sensitive to?

A

red, green and blue light.

53
Q

what light stimulates all types of cones equally?

A

white light

54
Q

how does the brain perceive the colour of an object?

A

it depends on the relative numbers of the three types of cone cells being stimulated.

55
Q

how does a person perceive a green object

A
  • when green light falls on the retina
  • green cones are stimulated
  • nerve impulses are transmitted to the brain
  • we perceive the object as green in colour
56
Q

how is an image formed on the retina?
- light reflected from the object is refracted by the ____.
- the ____ makes fine adjustments for focusing, so that light is focused on the retina.
- the imaged formed is ____, ____ and ____ than the object.
- the image is detected by ____ and ____ on the retina and generate nerve impulses, which travel through the optic nerve to the ____ of the brain, producing a ____ image of the object.

A

cornea
lens
real ; inverted ; smaller
rods ; cones ; optic centre ; upright

57
Q

define accommodation.

A
  • the ability of the eye to focus an object at different distances from the eye
  • achieved by changed the curvature of the lens
58
Q

when focusing on a near object:

A

ciliary muscles contract, tension of the suspensory ligaments are reduced, the lens is more convex.

59
Q

when focusing on a distant object:

A

ciliary muscles relax, tension of the suspensory ligaments are increased, the lens is less convex.

biology (4 decks)

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