1. What is irritability?
It is the ability of a living thing to detect changes in the environment and make appropriate reaction.
2. What is a stimuli?
Change in environment
3. What are the cells that are responsible for detecting stimuli?
receptors
4. What are the structures that are responsible for giving out response?
effectors
5. What are the two main type of effectors in the human body?
(1) muscles
(2) glands
6. What are the organs that contains receptors called?
Sense organs
7. Which 5 major sense organs are there in the human body? What stimuli can different sense organs sense and what are the receptors involved?
(1) eye: light receptors: light
(2) ear: mechanoreceptors; sound
(3) nose: chemoreceptors; chemicals in the air
(4) tongue: chemoreceptors; chemicals in the food
(5) skin: mechanoreceptors: pressure
skin: thermoreceptors: temperature changes
8. What is the function of the eye?
Detect light
Important note: NOT produce vision!
9. What are the external structures of the eye? What are their functions?
(1) Eyebrows: prevent sweat from entering the eye
(2) Eyelashes: prevent dirts from entering the eye
(3) Eyelids: They can open and close to allow blinking which spread tear and hence protect the eye.
10. What are the substances in the tears?
(1) water
(2) sodium chloride
(3) bacteria killing enzyme
11. What is the function of tears?
(1) Maintain moisture and cleanliness of the eyes
(2) kill bacteria
12. What is the internal structures of the eye?
Outer layer: sclera, cornea, conjunctiva
Middle layer: choroid, iris, ciliary muscle, suspensory ligament, lens
Inner layer: retina
Others: pupil, anterior chamber (aqueous humour), posterior chamber (vitreous
humour), blind spot, yellow spot.
13. What is the features of sclera and their corresponding functions?
Features White, opague, made of tough fibres
Function:
(1) protect the inner structures of the eye
(2) maintain the shape of the eye
14. What is the features of the cornea and their corresponding functions?
Features: transparent, the frontal part of protected by a layer of transparent cells called conjunctiva
Function:
(1) allow light to pass into the eye
(2) refract light that enters the eye
15. What are the functions of the choroid and their corresponding functions?
Structures:
(1) light absorbing melanin: can reduce internal reflection of light, assist in producing a clear image.
(2) blood capillaries: provide nutrients and oxygens to the cells of the eyes as well as bringing away the wastes.
16. What are the features of the iris and the corresponding functions?
(1) contain pigments
(2) muscular, can contract
Function: control the size of the pupil so as to adjust the amount of light entering the eye.
17. There are two types of cells in the retina. What are they? What are each of them responsible for?
(1) rod cells: responsible for detecting dim light
(2) cone cells: responsible for detecting light of different colour
18. What is the yellow spot. What are the features of it?
The yellow spot is situated at the middle part of the retina.
It contains cone cells only.
19. What is blind spot?
It is the location where the optic nerve leaves the retina.
There are no light sensitive receptors at the blind spot.
20. What are the relationships between the ciliary body, ciliary muscles, suspensory ligament and the lens?
The ciliary body is composed of ciliary muscles. The contraction and relaxation of the circular muscles and the radial muscles of the ciliary muscles will affect the tightness of the suspensory ligaments, and hence affect the thickness of the lens connected to the suspensory ligaments.
21. What is the features of the lens and their corresponding functions?
(1) It is made up of transparent and living cells
(2) there is no nucleus
(3) It is biconvex and very elastic (the elasticity of the lens itself can turn the lens into ball shape, but it is flattened due to the pulling force of the suspensory ligaments).
Function: Refract light onto the retina
22. Where does the aqueous humour come from? What is the function of it?
It comes out from the blood capillaries of the ciliary body
Function: to allow nutrients and oxygen to diffuse towards the cornea, conjunctiva and the lens.
23. What is/are the feature(s) of the vitreous humour of the posterior chamber and its/their corresponding functions?
Jelly like liquid.
Functions:
(1) maintain the shape of the eyeball
(2) help refract light onto the retina
24. What are the processes in the formation of vision?
(1) light from outside the eye is refracted onto the retina,
(2) the retina contains light sensitive cells which detect the light and send signal to the cerebrum,
(3) the cerebrum analyse the signals and produce vision.
25. List all the structures that are responsible for refracting light onto the retina.
Conjunctiva, cornea, aqueous humour, lens, vitreous humour.
26. List the structure that accurately refract light onto the retina.
Lens (because the thickness of it can be adjusted)
27. What are the characteristics of the image formed on the retina?
It is a real image that is upside down and laterally inverted.
It is smaller than the real object.
28. Describe the mechanism of the formation of vision after light reaches the retina.
(1) light reaches the retina which contains light sensitive cells,
(2) the light sensitive cells are stimulated to produce nerve impulses,
(3) the nerve impulses is transmitted through the optic nerve to the
cerebrum’s optic centre,
(4) the optic centre analyses the nerve impulses to produce vision.
29. What are the characteristics of rod cells?
(1) contains a pigment called visual purple
(2) sensitive to dim light (light of low intensity)
(3) cannot differentiate colour
(4) located all over the retina except the yellow spot and blind spot
30. What are the characteristics of cone cells?
(1) sensitive to light of high intensity
(2) three types: either sensitive to red, blue or green light
(3) they are concentrated at the yellow spot
31. What happens when the image falls onto the blind spot.
Since there are no sensitive cells at the blind spot, there will be no nerve impulse produced, therefore no image can be seen.
32. How can the amount of light entering the eye be controlled?
(1) When light is too strong
Circular muscles of the iris contract, radial muscle relax,
the pupil constricts
(2) When light is insufficient,
The circular muscles of the iris relax, radial muscles contract,
the pupil dilates.
33. What is the meaning of accommodation?
The ability of the eye to focus objects of various distances onto the retina.
34. How can the eye focus on near objects?
(1) circular ciliary muscles contracts,
(2) the tension on the suspensory ligaments lowers and they loosens up,
(3) lens become thicker due to its own elasticity, increasing its curvature,
(4) the light is refracted more through the lens,
(5) the lens focus the light onto the retina.
35. How can the eye focus on distant objects?
(1) circular ciliary muscle relax and pulls on the suspensory ligaments,
(2) the suspensory ligaments increase in tension, tighten up and pull at the lens,
(3) the lens are pulled and become thinner which cause it to reduce in curvature while refracting light,
(4) the light is refracted less before reaching the retina,
(5) the retina received the focused light.
36. What are the characteristics of short sightedness?
Blurred vision is produced when the eye is look at distant object.
This is because the image is formed in front of the retina.
37. What are the possible causes for short sightedness?
(1) the lens too thick
(2) the eyeball too long
38. How can short sightedness be corrected?
Wear concave lens
39. What are the characteristics of long sightedness?
Blurred vision is produced when the eye is looking at near objects. This is because the image of the near objects are focused behind the retina.
40. What are the causes for long sightedness?
(1) lens too thin
(2) eyeball too short
41. How can long sightedness be corrected?
Wear convex lens
42. What is colour blindness?
Inability to identify some or all colour. This is due to lack of or defect in one or more types of cone cells.
43. What is the function of the human ear?
(1) to detect sound waves in the air
(2) detect the movement of the head
44. List all the names of the structures inside the ear.
Outer ear: pinna, auditory canal, eardrum.
Middle ear: ear bones, Eustachian tube, oval window, round window
Inner ear: semi-circular canal, cochlea, auditory nerve, perilymph, endolymph
45. What are the features of the pinna and their corresponding functions?
It is a piece of highly elastic cartilage covered by skin.
Function: It collect and direct sound waves into the ear canal.
46. What are the features of the auditory canal and their corresponding functions?
The pathway of the canal is slightly curved.
Function: It is slightly curved in order to direct sound wave towards the ear drum.
47. What are the features of the ear drum and their corresponding functions?
It is a piece of thin but highly elastic membrane situated between the outer ear and the middle ear.
Function: When sound waves arrive at the ear drum, the ear drum will vibrate and transmit sound waves to the middle ear.
48. What are the features of the middle and their corresponding functions?
Features:
(1) air-filled, connected to the pharynx by the Eustachian tube.
(2) there are three ear bones inside.
Function:
After the ear bones accept the vibration from the ear drum, they amplify the vibration and transmit them to the oval window. The vibration will then be transmitted to the inner ear.
49. What is the feature of the oval window and its corresponding function?
Feature: Thin membrane
Function: Receives vibrations from the ear bones, vibrates itself and transmits the vibration to the liquid inside the cochlea, producing pressure inside the liquid of the cochlea.
50. What is the feature of the round window and its corresponding function?
Feature(s): located below the oval window.
Function: to release the pressure of the liquid inside the cochlea to the middle ear
51. What is the feature of the Eustachian tube and its significance?
Feature: During swallowing, the air will pass through the Eustachian tube /leave the middle ear.
Importance: the pressure between the middle ear and the atmosphere can be equalized.
52. What is the difference between the cochlea and the semicircular canal? What are their functions separately?
Cochlea: detect sound waves
Semi-circular canal: detect the position and movement of the head, assist in maintaining balance.
53. Describe the mechanism of hearing.
(1) The pinna receives the sound waves and direct them to the ear drum,
(2) the ear drum vibrates and the vibration is transmitted to the ear bones,
(3) the ear bones amplify the vibration which is transmitted to the oval window,
(4) the oval window vibrates, causing vibration in the perilymph of the upper canal,
(5) the perilymph of the upper canal transmit the vibration to the endolymph in the central canal,
(6) the central canal contains sensory hair cells which are stimulated by the vibration and produce nerve impulses,
(7) the nerve impulses are transmitted through the auditory nerve to the auditory centre of the cerebrum,
(8) the auditory centre of the cerebrum interpret the nerve impulses and produce the sense of hearing.
54. What is tropism?
The directional growth movement of a part of a plant in response to a unilateral stimulus.
55. What types of tropism does a plant has?
(1) phototropism
(2) geotropism
(3) hydrotropism
56. What are the phototropic response of shoots and roots?
Roots: negative phototropism
Shoots: positive phototropism
57. Describe the mechanism of positive phototropism of the shoot.
(1) Upon being illuminated by unilateral light,
(2) auxins move from the illuminated side to the shaded side of the shoot.
(3) This results in a higher concentration of auxins on the shaded side of the shoot.
(4) When the auxins diffuse to the region of elongation of the shoot,
(5) and since a higher concentration of auxins promote shoot growth,
(6) the shaded side of the shoot grow faster.
(7) Finally, the shoot bends towards the unilateral light.
58. What are the effects of auxins on the shoot and the root?
A higher concentration of auxin promote shoot growth but inhibit root growth.
A lower concentration of auxin promote root growth but inhibit shoot growth.