1. Detection of Environment
Eye
Ear
Skin

2. stimuli: changes in internal and external environments to living organisms
sensory system: system perceives stimuli so organisms can respond to changes correctly
irritability: ability to respond to stimuli

3. receptors: organs used to detect stimuli, specific, consists one or many sensory cells which they will send impulses to brain through nerve fibres
effectors: part of body that reacts to a stimulus or produces responses

4. central nervous system
stimulus
receptor
central nervous system
effector
ATP
response

5. muscle attachment to skull
Location of the Eye
tear gland
orbit
oblique muscle
eyelash
optic nerve
pupil
muscle attachment to skull
iris
rectus muscles
eyelid
oblique muscle
eyeball

6. Location of the Eye responsible for detecting light
eyeball is a spherical structure which is protected in a bony socket in the skull called orbit
eyeball attached to orbit by six muscles
rotation of eye is brought about by contraction of the muscles

7. Structure around the Eye
blinking helps to keep the surface of eyeball moist and clean by distributing tears produced by tear glands over the eyeball
tears contain sodium chloride, hydrogencarbonate and lysozyme which is used to kill bacteria

8. rate of tear flow and blinking will increase when foreign substance reaches eye surface
excess tear can drain away into nasal cavity through duct in the corner of the eye
eyelashes also help to stop dirt and sweat from running into eyes

9. Structures and Functions of Eye
suspensory ligaments
ciliary muscle
eye muscle
sclera
conjunctiva
choroid
aqueous humour
retina
yellow spot
pupil
lens
cornea
iris
blind spot
vitreous humour
optic nerve

10. wall of eyeball is made up of three layers: sclera, choroid and retina
The outer layer of wall
white, tough and opaque coat to protect eyeball
keeps shape of eye and provides anchorage for eye muscles

11. Cornea a transparent layer continue from sclera
allows light to pass through
light is refracted into interior of eye as it is curved
protected by a transparent layer called conjunctiva

12. Choroid middle layer of eyeball
deeply pigmented to absorb light and prevent internal reflection of light
contains lots of blood vessels to supply eye with food and oxygen and removes waste

13. Lens within ring form by ciliary body transparent biconvex in shape
compose of living cells
Lens

14. Suspensory ligaments and ciliary body
ciliary muscle
suspensory ligaments are used to hold lens in position. They are run from free edge of ciliary body
ciliary body contains ciliary muscles which can change thickness of lens by alternate contraction and relaxation during focusing
suspensory ligaments

15. Iris Pupil continuous with choroid lies just over ciliary body
coloured part of eye as it is pigmented
Pupil
hole in the centre of iris
size of it is controlled by radial muscles and circular muscles of iris

16. Aqueous and Vitreous Humour
watery fluid filled the anterior chamber in front of the lens inside the eyeball is aqueous humour
jelly-like substance filled the posterior chamber behind the lens is vitreous humour
aqueous humour
vitreous humour

17. they help in refracting light and maintaining shape of eyeball
aqueous humour also helps cornea and lens to obtain food and oxygen from blood vessels in choroid layer by diffusion

18. Retina the innermost layer in eye
contains many light-sensitive cells, rods and cones, and nerve fibres
cones are sensitive to light of high intensity and responsible for colour vision. There are three types of cones which sensitive to blue, red and green

19. yellow spot is the part in the centre of retina which possesses cones only and it lies on the optical axis of eye
rods are sensitive to light of low intensity and abundant in the periphery of retina

20. Yellow Spot densely packed with cones no rod is present
gives the most distinct image and the greatest colour discrimination

21. Optic Nerve
optic nerve is a nerve which contains nerve fibres from rods and cones
it leaves the eyeball at the blind spot
no sensitive cells at blind spot but only nerve fibres
no nerve impulse can be generated when light falls on the blind spot although image is formed on it, so it is incapable of detecting images

22. Blind spot the point where the nerve fibres leave the eye-ball
no photo-receptors
cannot detect any image
optic nerve
blind spot

23. What can you tell about the image ?
hand lens
window frame
cardboard
image
What can you tell about the image ?
Ans: The image is smaller than the object but the shape remains the same and it is laterally inverted.

24. Does the light beam bend after passing through the attached lens ?
water with sodium fluorescein
convex lens
plasticine
front view of the lens of the projector
projector
Does the light beam bend after passing through the attached lens ?
Ans: Yes.

25. water with sodium fluorescein
convex lens
plasticine
front view of the lens of the projector
projector
Does the light beam meet at a point ? (This point is the focus of the lens)
Ans: Yes.

26. What is the shape of the image ?
water with sodium fluorescein
convex lens
plasticine
front view of the lens of the projector
projector
What is the shape of the image ?
Ans: The image is inverted and smaller than the object.

27. What do the water and the back of the flask represent ?
water with sodium fluorescein
convex lens
plasticine
front view of the lens of the projector
projector
What do the water and the back of the flask represent ?
Ans: The water represents vitreous humour while the back of flask represents retina.

28. Change of Pupil Size
pupil is the hole in iris which allows light to pass through
pupil limits amount of light entering the eye
two kinds of iris muscle control size of pupil: - circular iris muscle: makes pupil constrict as they contract
- radial iris muscle: pupil dilates as they contract

29. change of size of pupil is a reflex action and automatic
reduce amount of light pass through
Under Bright Light
circular muscles contract
radial muscles relax
pupil size decrease

30. Under Dim Light radial muscles contract circular muscles relax
increase amount of light pass through
circular muscles relax
pupil size increases

31. Accommodation thick lens shorter focal length thin lens
longer focal length
accommodation is the ability of the eye to adjust thickness of lens for viewing near and distant objects
helped by the action of ciliary muscles

32. Focusing Near Objects ciliary muscles contract
more light rays bend and image of near objects formed on retina
ring of ciliary body moves inwards and becomes smaller in diameter
lens becomes thicker and more curved
tension of suspensory ligaments reduces

33. circular ciliary muscle contracts decrease in circumference
tension of suspensory ligament decreases
lens becomes more convex

34. Focusing near object
Light from near object

35. Focusing Distant Objects
ciliary muscles relax
image of distant objects formed on retina
ring of ciliary body moves outwards and becomes wider in diameter
lens becomes thinner and more flattened
tension of suspensory ligaments increases

36. circular ciliary muscle relaxes increase in circumference
tension of suspensory ligament increases
lens becomes less convex

37. Focusing far away object
Light from far away object

38. water with sodium fluorescein
thinner convex lens
front view of the lens of the projector
convex lens
projector
How is the distance between the lens and the projector related to the thickness of the lens?
Ans: The thicker the lens, the shorter is the distance between the lens and the projector.

39. Common Eye Defects -- Short Sight
it occurs when light of distant object focused in front of retina
may be due to eyeball too long or lens becomes too curved
only near object can be seen clearly
corrected by wearing concave lenses which diverge light from distant object before reaching the eye to ensure its image fall on retina sharply

40. Short sight
Light from distant object

41. Correction of short sight
Light from distant object
Diverging lens
( Concave lens )

42. Common Eye Defects -- Long Sight
it occurs when light from near objects focused behind the retina
may due to eyeball too short or lens becomes too thin
only distant object can be seen clearly
corrected by wearing convex lenses which converge light from near object before reaching the eye

43. Long sight
Light from near object

44. Correction of long sight
Light from near object
Converging lens
( Convex lens )

45. Common Eye Defects -- Colour Blindness
cone cells are responsible for colour vision
there are three kinds of cone cells responsible for detecting red, green and blue lights
relative number of cones presents and being stimulated determined the colour perceived
colour blindness is a hereditary defect and cannot be corrected by wearing glasses

46. Can You See?
Ans: 5
Ans: 8
Ans: Nothing
Ans: A line

47. Function of Mammalian Ear
enable mammal to hear so that they can escape from danger
detect changes in position during movement

48. Structure and Functions of Different Parts of Ear
middle ear
ear is divided into three parts: outer ear, middle ear and inner ear
inner ear
Outer Ear
outer ear
outer ear includes pinna and an auditory canal

49. pinna pinna a flap of cartilage covered with skin
serve to collect sound waves and detect direction of the sound
in some mammals, pinnae are movable so they can detect sound source efficiently as they can move their pinnae to the direction of sound source
pinna

50. auditory canal auditory canal eardrum
lined with hairs and wax-secreting cells to prevent entry of dust or small insects
a membrane present at the end of auditory canal and it is called eardrum (typanum)
eardrum serve as a device to convert sound waves into vibrations as when sound waves strike it, they are translated into mechanical waves
auditory canal
eardrum

51. Middle Ear air-filled cavity behind eardrum
contains three small bones, ear ossicles: outer hammer(malleus), middle anvil(incus) and inner stirrup(stapes)
eardrum

52. oval window leads to inner ear
three ossicles link eardrum with oval window on the other side of the middle ear
oval window leads to inner ear
vibrations from eardrum are transmitted by ear ossicles to the membrane covering oval window
oval window
round window

53. ear ossicles also amplify vibrations before reaching oval window
round window is another opening in the middle ear which allows the exit of pressure caused by ear ossicles pressing on oval window
middle ear is connected to pharynx by a passage called Eustachian tube to equalize pressure on both sides of eardrum

54. Inner Ear bony cavity in skull and filled with fluid called perilymph
inside this bony cavity is a group of membrane-bound structures which contain endolymph and receptors including cochlea and three semicircular canals

55. structure that senses sound coiled tube like a snail’s shell
cochlea
structure that senses sound
coiled tube like a snail’s shell
divided into three canals which the middle one is bound by two membranes
cochlea

56. many sensory hair cells present on the bottom membranes
endolymph is enclosed in the middle canal while canals on either side of middle canal contain perilymph

57. three semicircular canals are involved in detecting movement of head
both cochlea and semicircular canals have nerve fibres running to brain
these nerve fibres form auditory nerve
semicircular canals

58. Equalizing Pressure on both Sides of the Eardrum
eardrum separate outer ear from the middle ear
important to keep pressure in middle ear as the same as atmospheric pressure in order to have normal hearing
Eustachian tube is used to equalize pressure on both sides of eardrum and it connects middle ear to pharynx

59. eardrum bulges inwards
When you are landing…
atmospheric pressure
pressure inside middle ear 
eardrum bulges inwards
(you feel pain)

60. eardrum returns to normal position
Solution: Yawning or Swallowing
During swallowing, Eustachian tube is opened to let more air from mouth enter middle ear to equalize pressure on both sides of eardrum
eardrum returns to normal position

61. When you are travelling up a hill...
atmospheric pressure
pressure inside middle ear 
eardrum bulges
outwards
(you feel pain)

62. Solution: Yawning or Swallowing
During swallowing, Eustachian tube is opened to let air in middle ear to pass out through the Eustachian tube
eardrum returns to normal position

63. Did you have to move your head in order to locate the sound source ?
bell
Did you have to move your head in order to locate the sound source ?
Ans: The answer is supposed to be yes as sound waves travel in air in all directions.

64. Ans: The answer is supposed to be no.
bell
Can you still locate the bell if one of your ears is stuffed with cotton wool?
Ans: The answer is supposed to be no.

65. Detecting Movement of Head
semicircular canals in inner ear detect movement of the head
three fluid-filled semicircular canals are situated at an angle of 90o to each other
each canal is sensitive to movement in different plane

66. at the base of each canal is a swollen part called ampulla which contains sensory cells with protruding hairs embedded in a gelatinous structure

67. Gelatinous mass (cupula) is found inside each ampulla
Semi-circular canals are filled with endolymph

68. Nerve impulses are generated and transmitted along the auditory nerve
Movement of
endolymph
Sensory
hair cells
nerve
ampulla
Endolymph presses against the gelatinous structure and displaces it
Direction of head movement
Nerve impulses are generated and transmitted along the auditory nerve
The sensory hair cells under the gelatinous mass is stimulated
The endolymph displaces the gelatinous mass inside the ampulla
However, the endolymph in the canals will move in opposite direction due to inertia
When the head move, the semi-circular canals will move in the same direction

69. In addition to information from inner ear, the eye and pressure receptors in feet and stretch receptors in tendons also provide messages to brain, informing it about the position of your body

70. Skin
at least five kinds of nerve endings exist in dermis for detecting touch, pressure, temperature, pain and hair movements
receptors in skin present all over the body but are distributed unevenly
largest organ in human body

71. blood capillaries
epidermis
dermis
touch receptor
pain receptor
hair
sweat gland
pressure receptor
touch or pain receptor

72. hand of the blindfolded student
your hand
dividers
hand of the blindfolded student
In which part of the body tested in this experiment is the recorded distance the shortest?
Ans: Usually, the answer is finger tips.

73. hand of the blindfolded student
your hand
dividers
hand of the blindfolded student
What can you tell about the ability of the skin to discriminate touch points with reference to the recorded distance?
Ans: The shorter the recorded distance, the more sensitive the part is.