15: Detecting the Environment Flashcards
(96 cards)
1
Q
What is the definition of irritability?
A
Irritability is the ability of detecting stimuli and giving appropriate responses.
2
Q
State the type of receptor and the stimulus detected in the eye.
A
Photoreceptors which detect light.
3
Q
State the type of receptor and the stimulus detected in the ear.
A
Mechanoreceptors which detect sound.
4
Q
State the type of receptor and the stimulus detected in the nose.
A
Chemoreceptors which detect chemicals in the air.
5
Q
State the type of receptor and the stimulus detected in the tongue.
A
Chemoreceptors which detect chemicals in food.
6
Q
State the types of receptors and the stimuli detected in the skin.
A
Thermoreceptors which detect temperature, and mechanoreceptors which detect pressure.
7
Q
State the function of the eyebrow.
A
It prevents sweat from running into the eye.
8
Q
State the function of the eyelash.
A
It traps dust and prevents it from entering the eye.
9
Q
State the functions of the eyelid.
A
It can be closed to protect the eye from dirt and strong light.
It also spreads tears over the eye surface when we blink.
10
Q
State the functions of the tear gland.
A
It produces tears which contain sodium, chloride and lysozyme that can kill bacteria. Tears also keep the eye moist and clean.
11
Q
State the function of the tear duct.
A
It drains tears into the nasal cavity.
12
Q
State the structure in which the eyeball is located in the skull.
A
The orbit
13
Q
How many pairs of eye muscles are attached on the eyeball to the skull?
A
3
14
Q
State the functions of the conjunctiva.
A
It covers part of the front surface of the eyeball and the inner surface of eyelids, but not the cornea. It helps keep the front part of the eye moist and lubricated.
15
Q
State the properties and functions of the sclera.
A
It is the outermost layer of the eyeball, which is a tough white coat.
It protects the inner structures and maintains the shape of the eyeball.
It also provides a surface for the attachment of eye muscles.
16
Q
State the properties and functions of the cornea.
A
It is a transparent layer of tissue at the front part of the eye. It allows light to enter the eye.
Its curved surface helps refract and focus light onto the retina.
It has no capillaries and it obtains nutrients and oxygen from the aqueous humour.
17
Q
State the properties and functions of the choroid.
A
It is the middle layer of the eyeball. It contains a black pigment which absorbs light, which reduces reflection of light within the eye and helps form a sharp image.
It is rich in capillaries which supply nutrients and oxygen to the retina and sclera and remove wastes from them.
18
Q
State the properties and functions of the iris.
A
It is continuous with the choroid.
It is made up of muscles, it controls the size of pupil so as to regulate the amount of light entering the eye.
It contains a pigment which determines its colour.
19
Q
State the properties and functions of the pupil.
A
It is the opening at the centre of the iris. It allows light to enter the eye.
Its size is controlled by the iris.
20
Q
State the properties and functions of the retina.
A
It is the innermost layer of the eyeball.
It contains many photoreceptors / light-sensitive cells, including rod cells and cone cells, and nerve fibres.
21
Q
State the properties and functions of the optic nerve.
A
It is grouped from the nerve fibres in the retina.
It transmits nerve impulses generated from the photoreceptors in the retina to the sensory area of the cerebrum of the brain.
22
Q
State the properties of the yellow spot.
A
It is the central region of the retina.
It has a high density of cone cells but it has no rod cells.
23
Q
State the properties of the blind spot.
A
It is the region of the retina where the optic nerve leaves the eyeball.
It has no rod cells or cone cells.
24
Q
Use three words to describe the appearance of the lens.
A
Transparent, elastic, biconvex
25
State the properties and functions of the lens.
It is transparent, elastic, and biconvex in shape.
It **refracts and focuses light** onto the retina. Its thickness can be adjusted by the ciliary body so that light from objects at different distances is focused onto the retina.
It is made up of living cells which have **no nuclei**.
It has **no capillaries** and it obtains nutrients and oxygen from the aqueous humour.
26
State the properties and functions of the suspensory ligament and ciliary body.
The lens is held in position by **suspensory ligaments** which are connected to the **ciliary body**.
The ciliary body consists of a ring of muscles called **ciliary muscles**. It controls the tension of the suspensory ligaments, thereby changing the thickness of the lens.
27
State the properties and functions of the aqueous humour.
It fills the anterior chamber between the cornea and the lens.
It is a watery fluid produced by **the ciliary body**. It supplies nutrients and oxygen to the **cornea and lens** by diffusion from the capillaries in the choroid.
It helps to maintain the shape of the eyeball and refract light onto the retina.
28
State the properties and functions of the vitreous humour.
It fills the posterior chamber between the retina and the lens.
It is a jelly-like fluid and it helps to maintain the shape pf the eyeball and refract light onto the retina.
29
Which tissues in the eye does the choroid provide nutrients for?
Retina and sclera
30
Which tissues in the eye does the aqueous humour provide nutrients for?
Cornea and lens
31
Describe the process of how we see.
1. Light rays from an object enter the eye. They are **refracted** and **focused** onto the retina by the **cornea, aqueous humour, lens, and vitreous humour**.
2. A **real and inverted** image is formed on the retina.
3. The photoreceptors on the retina are stimulated by the light. They generate **nerve impulses** which travel along the **optic nerve** to the **visual centre in the sensory area of the cerebrum** of the brain.
4. The visual centre interprets the nerve impulses as an **upright** image of the object.
32
State which tissues in the eye is / are responsible for most of the refraction of light from an object entering the eyes.
Cornea
33
State which tissues in the eye is / are responsible for fine focusing of the light rays from an object entering the eyes.
Lens
34
State the colours which cone cells are the most sensitive to.
Red, green, and blue
35
State 4 differences between rod cells and cone cells.
1. Rod cells have a **rod shape** while cone cells have a **cone shape**.
2. Rod cells are **more numerous** than cone cells in the retina.
3. Rod cells have a pigment sensitive to **light of low intensity** and are important for vision in **dim light**. Cone cells have a pigment sensitive to **light of high intensity** and are important for vision in **bright light**.
4. Rod cells cannot detect colour and are responsible for **black and white vision**, while cone cells can detect colour and are responsible for **colour vision**.
36
Compare and explain the difference in visual acuity of cone cells and rod cells.
Cone cells have **higher visual acuity** when compared to rod cells. This is because each cone cells connects with one nerve cell, but several rod cells connect with a nerve cell. If two adjacent cone cells are stimulated by two light sources, **two separate nerve impulses** will be sent to the brain which allows the brain to distinguish between the two light sources. However, if two or more adjacent rod cells connected to the same nerve cell are stimulated by multiple light sources, **only one nerve impulse** will be sent to the brain and the brain will interpret it as **one light source only**.
37
Describe the distribution of rod cells on the retina.
Rod cells are mainly located on the **periphery** of the retina. **None** of them are found at the **yellow spot and blind spot**.
38
Describe the distribution of cone cells on the retina.
Cone cells are **concentrated at the yellow spot**. Only a few cone cells are present on the periphery of the retina and there are no cone cells at the blind spot.
39
Explain why light falling on the blind spot cannot be detected.
The blind spot contains **no photoreceptors**. Images can be formed on the blind spot, but they **cannot be detected** by photoreceptors, thus **no nerve impulses** will be sent to the visual centre of the cerebrum of the brain. Therefore, the image falling on the blind spot cannot be seen.
40
Name the sets of muscles in the iris.
Circular muscles and radial muscles.
41
Describe the changes in the iris and pupil when a person walks from dim light to bright light.
The circular muscles of the iris **contract more and more**, and the radial muscles of the iris **relax more and more**. As a result, the pupil **constricts** and **less light** is allowed to enter the eye.
42
Describe the changes in the iris and pupil when a person walks from bright light to dim light.
The circular muscles of the iris **relax more and more**, and the radial muscles of the iris **contract more and more**. As a result, the pupil **dilates** and **more light** is allowed to enter the eye.
43
Explain the importance of the constriction of the pupil in bright light.
This response **prevents** the photoreceptors in the retina from being **damaged** by bright light.
44
Explain the importance of the dilation of the pupil in dim light.
This response allows the photoreceptors to be **stimulated** by a higher intensity of light to generate nerve impulses so that a **clear image** can be seen.
45
What is eye accommodation?
It refers to the ability of the eye to focus on object at different distances.
46
State how the curvature of the lens can be changed.
It can be changed by the action of ciliary muscles. As the ciliary muscles contract, the tension in the suspensory ligaments is reduced and the lens becomes thicker. As the ciliary muscles relax, the tension in the suspensory ligaments is increased and the lens becomes thinner.
47
Describe the changes in our eyes when focusing on an object that becomes nearer.
1. The ciliary muscles **contract more and more**.
2. The tension in the suspensory ligaments is reduced. The suspensory ligaments become **more and more slackened**.
3. The lens becomes **thicker and thicker** due to its elasticity. The thicker lens **refracts light to a greater extent** so the light rays from the near object are focused onto the retina.
48
Describe the changes in our eyes when focusing on an object that becomes further away.
1. The ciliary muscles **relax more and more**.
2. The tension in the suspensory ligaments is increased. The suspensory ligaments become **more and more tightened**.
3. The lens becomes **thinner and thinner** due to its elasticity. The thinner lens **refracts light to a lesser extent** so the light rays from the far object are focused onto the retina.
49
Explain why eye strains may occur if we look at a near object for a long time.
The ciliary muscles have contracted for a **long time** without rest.
50
State three common eye defects.
Short sight, long sight, colour blindness
51
Describe the problem of vision of patients with short sight.
People with short sight can see near objects clearly but **not distant objects**.
52
State two possible causes of short sight.
1. The lens is **too thick**.
2. The eyeball is **too long**.
These cause the images of distant objects to be formed **in front of the retina**, so a clear image of a distant object cannot be formed clearly on the retina and patients cannot see it clearly.
53
State the method of correction of short sight.
By wearing **concave lens**, which **diverges** light rays from distant objects before they reach the eye.
54
Describe the problem of vision of patients with long sight.
People with long sight can see distant objects clearly but **not near objects**.
55
State two possible causes of long sight.
1. The lens is **too thin**.
2. The eyeball is **too short**.
These cause the images of distant objects to be formed **behind the retina**, so a clear image of a near object cannot be formed clearly on the retina and patients cannot see it clearly.
56
State the method of correction of long sight.
By wearing **convex lens**, which **converges** light rays from distant objects before they reach the eye.
57
Describe the problem of vision of patients with colour blindness.
They cannot distinguish some or all colours.
58
State the most common type of colour blindness.
red-green colour blindness
59
State the cause of colour blindness.
Colour blindness is caused by the **deficiency** of **defect** of one or more of the three cone cell types. It is **inherited**.
60
State the method of correction of colour blindness.
Colour blindness cannot be cured or corrected by wearing lenses.
61
State the regions our ear can be divided into.
Outer ear, middle ear, inner ear
62
State the structures in the outer ear.
Pinna, auditory canal, eardrum
63
State the properties and the functions of the pinna.
It is a flap of **cartilage** covered by skin. It **collects sound waves** in the surroundings and directs them along the auditory canal to the eardrum.
64
State the properties and the functions of the auditory canal.
It produces **wax** which **lubricates the canal** and **traps dirt and bacteria** to prevent them from entering the middle ear.
65
State the properties and the functions of the eardrum.
It is a thin, elastic membrane located at the end of the auditory canal. It **converts sound waves into vibrations**.
66
State the structures in the middle ear.
Ear bones, oval window, round window, Eustachian tube
67
State the properties and the functions of the ear bones.
There are **three** ear bones in each ear. They are the smallest bones in our body.
They **amplify and transmit vibrations** from the eardrum to a flexible membrane called the **oval window**.
68
State the properties and the functions of the oval window.
It transmits vibrations from the ear bones to the inner ear.
69
State the properties and the functions of the round window.
It is located **below the oval window**. It **releases the fluid pressure in the cochlea** into the air in the middle ear.
70
State the properties and the functions of the Eustachian tube.
It is a tube connecting the middle ear to the pharynx.
It is normally closed, but during swallowing it opens to allow air to enter of leave the middle ear. This **equalises the air pressure** on either side of the eardrum.
71
Describe the consequences if the air pressure on either side of the eardrum is not equal.
The eardrum will **bulge**. The bulging eardrum **cannot vibrate freely** in response to sound waves and we cannot hear clearly.
72
State an example when the air pressure on either side of the eardrum is not equal.
When we are on a plane that is taking off or landing, because the **air pressure outside the ear** is **changing rapidly**.
73
State all the structures in the inner ear.
Cochlea and semicircular canals
74
Describe the appearance of the cochlea.
It is a coiled tube with three parallel canals separated by membranes.
75
Name the fluid inside the cochlea.
The fluid in the upper and lower canal is called **perilymph** while the fluid in the central canal is called **endolymph**.
76
State the location of sensory hair cells responsible for hearing.
They are located in the **central canal** of the cochlea.
77
State the properties and functions of the semicircular canals.
They are **not involved in hearing**. They contain **sensory hair cells** to detect the direction of **head movements**.
When the cells are stimulated, they send nerve impulses to the brain and the brain coordinates muscles to **maintain body balance**.
78
State the direction of orientation of the semicircular canals.
The three semicircular canals are oriented in three planes at **right angles** to each other to detect head movements in **all directions**.
79
Describe the process of how we hear.
1. Sound waves collected by the pinion are directed to the eardrum.
2. Sound waves cause the **eardrum to vibrate**.
3. The **ear bones amplify** and **transmit the vibrations** to the oval window.
4. The oval window vibrates, causing the **perilymph** in the cochlea to vibrate.
5. Vibrations in the perilymph are transmitted to the **endolymph** of the cochlea.
6. The **sensory hair cells** in the central canal of the cochlea are stimulate. They generate nerve impulses, which travel along the **auditory nerve** to the **auditory centre in the sensory area of the cerebrum** in the brain to produce the sensation of hearing.
7. Vibrations in the perilymph are transmitted to the round window. The round window releases the fluid pressure into the air in the middle ear.
80
What is the definition of tropism?
Tropism is the **directional growth movement** of a part of a plant in response to a **unilateral stimulus**.
81
What is the definition of phototropism?
Phototropism is the **directional growth movement** of a part of a plant in response to **unilateral light**.
82
Describe how the shoots of plants exhibit phototropic properties.
Generally, shoots grow **towards** unilateral light so they are **positively phototropic**.
83
Explain the importance of the positive phototropism of plant shoots.
This response enables the leaves to reach a position where they can obtain **the maximum amount of light** for **photosynthesis**.
84
Describe how the roots of plants exhibit phototropic properties.
Generally, shoots grow **away from** unilateral light so they are **negatively phototropic**.
85
Explain the importance of the negative phototropism of plant roots.
This response enables the roots to **anchor to the soil for support**.
86
State three reasons why coleoptiles are commonly used in the investigations of phototropism.
1. Their response to light is **easy to observe**.
2. They **grow rapidly**.
3. They are **small and easy to handle**, making them easy to be grown in large numbers.
87
What are the conclusions of Charles Darwin's experiments on phototropism?
1. The time is necessary for growth of the plant.
2. The tip is responsible of detecting unilateral light.
88
What are the conclusions of Boysen-Jensen's experiments on phototropism?
1. A substance is produced in the tips of the coleoptile. It is **chemical in nature** because it can diffuse through the agar block but more the mica plate.
2. The chemical is transmitted to the lower part os the coleoptile where is causes **bending** to occur.
3. The chemical produced in the tip can **pass down the shaded side** of the coleoptile, causing bending towards the illuminated side.
89
What are the conclusions of Paal's experiments on phototropism?
The side with the displaced tip receives a **higher concentration** of the chemical produced in the tip of the coleoptile. This side grows **more rapidly**, causing bending.
90
What are the conclusions of Went's experiments on phototropism?
1. While the chemical produced in the tip diffuses into the agar block, light causes an **uneven distribution** of the chemical.
2. The **shaded side** has a **higher concentration** of the chemical. It **grows more rapidly**, causing the shoot to bend towards light.
91
Name the most common natural occurring auxin.
Indoleacetic acid
92
State the regions in which auxins are produced and transported to.
It is produced in small amounts mainly in rheumatoid arthritis **apical meristems** found at **shoot tips** and **root tips**. It is transported to the **region of elongation**, where it **promotes cell elongation**.
93
State two conclusions on the effect of light on the distribution of auxins.
1. Light **does not destroy** auxins.
2. Light causes auxins to move **from the illuminated side to the shaded side**.
94
State the effect of auxin concentration on the growth of shoots and roots.
High auxin concentrations **promote shoot growth** but **inhibit root growth**.
Low auxin concentrations **promote root growth** but have little effect on shoot growth.
95
Describe the growth response of a shoot exposed to light from all directions.
1. Auxins are produced t the soot tip and root tip.
2. When light comes from all directions, the auxin in the region of elongation of the shoot and that of the root are **distributed evenly**.
3. The shoot grows straight upwards while the root grows straight downwards.
96
Describe the growth response of a shoot exposed to unilateral light.
1. Auxins are produced t the soot tip and root tip.
2. Under unilateral light, auxins **move from the illuminated side to the shaded side** of the shoot and that of the root.
3. In the shoot, the high auxin concentration on the shaded side **promotes growth** there. Thus, the shoot bends towards the light.
In the root, the high auxin concentration on the shaded side **inhibits growth there**. Thus the root bends away from the light.
