Ch15 Detecting the environment

Question 1

Irritability

Answer 1

Irritability is the ability of detecting stimuli and giving responses in organism. It is important for survival.

Question 2

What does the receptor consist of?

Answer 2

Sensory cells which are concentrated to form part of a sense organ. 

Question 3

Sense organ, type of receptor and stimulus detect

Answer 3

The Eye, photoreceptor, detect light
Ear , mechanoreceptor, detect sound
Nose, chemoreceptor, detect chemicals in the air
Tongue , chemoreceptor, detect chemicals in the food
Skin , mechanoreceptor, detect pressure
Thermoreceptor, detect temperature change

Question 4

Structures around the eyes

Answer 4

The eyebrow prevents sweat from running into the eyes
The eyelash dust and prevents it from entering the eye
The eyelid can be closed to protect the eye from dirt and strong light And spread tears over the eye surface when we blink
The tear gland produces tears, which contains sodium, chloride and lysosome that can kill bacteria, and keep the eye, moist and clean
Tear duct drains tears into the nasal cavity

Question 5

The eyeball

Answer 5

The eyeball is located in a socket in the skull called the orbit. It is attached by three pairs of eye muscles. These muscles enable the eyeball to rotate in different direction. Front surface of the eyeball and the inner surface of the eyelids are covered by a transparent membrane called conjunctiva. Help keeps front part of the eye, moist and lubricated.

Question 6

Sclera

Answer 6

-maintains the shape of the eyeball and protect the inner structure
-provides a surface for the attachment of eye muscles

Question 7

Cornea

Answer 7

-transparent, allows light to enter the eyes
-helps refract and focus light onto the retina
-no capillaries

Question 8

Choroid

Answer 8

-middle layer of eyeball
-contains black pigment which absorbs light to reduce the reflection of light to help form sharp image
-rich in capillaries, supply oxygen and nutrients to the retina and sclera and remove waste from them

Question 9

Iris

Answer 9

-muscle
-control the size of the pupil, to regulate the amount of light entering the eyes
-continuous with choroid

Question 10

Pupil

Answer 10

-allow light to enter the eyes
-size controlled by iris

Question 11

Retina

Answer 11

-contains many photoreceptors and nerve fibres
-innermost layer of the eyeball

Question 12

Optic nerve

Answer 12

-nerve fibre are grouped together to form the optic nerve
-optic nerve transmits nerve impulses

Question 13

Yellow spot

Answer 13

Central region of the retina is the yellow spot. High density of cone cells. No rod cells

Question 14

Blind spot

Answer 14

Region where the optic nerve leaves the eyeball is called blind spot. No photoreceptors.

Question 15

Lens

Answer 15

-transparent, elastic and biconvex in shape
-refract and focus light
-no capillaries
-made up of living cell. No nuclei

Question 16

Suspensory ligament

Answer 16

-holds the lens
-held by ciliary body/circular ciliary muscle

Question 17

Circular ciliary muscle

Answer 17

-controls the tension of the suspensory ligaments, changing the thickness of the lens

Question 18

Aqueous humour and vitreous humour

Answer 18

Both maintains the shape of the eyeball and refract and focus light onto the retina
A: supplies oxygen and nutrients to the cornea and lens

Question 19

Why is no blood capillaries in the lens important for the formation of clear image?

Answer 19

To let light pass through without obstruction to the retina.

Question 20

Two changes in the lens at old age, that may result in poor vision

Answer 20

Lens become cloudy (cataract)
The lens become less elastic (long sight)

Question 21

Why is the pupil always black?

Answer 21

All the light entering the eye is absorbed by the retina and choroid. No light can reflect out from the eyes.

Question 22

Rod cells

Answer 22

Sensitive to dim light
Responsible for black-and-white vision
Located throughout the retina, none at yellow spot and blindspot

Question 23

Cone cells

Answer 23

Sensitive to bright light
Responsible for colour vision
Concentrated at yellow spot, but none at blind spot

Question 24

In bright light

Answer 24

The circular muscle of iris contract,
The radial muscle of iris relax,
The pupil constrict .

Question 25

In dim light

Answer 25

The radial muscle of iris contracts,
The circular muscle of iris relax,
The pupil dilates .

Question 26

The importance of pupil reflex

Answer 26

The pupil reflex prevents too much light from entering the eyes.
This prevents the damage of photoreceptors in the retina .

Question 27

Focusing on near objects

Answer 27

(The circular ciliary muscles contracts
The tension of suspensory ligaments reduced / slackened
The lens become more convex / thicker)
Refraction of light increases

Question 28

Focusing on distant objects

Answer 28

The circular ciliary muscles relax
The suspensory ligaments increases
The lens becomes less convex
Refraction of light decreases

Question 29

Describe how the image under retina generates vision in the brain

Answer 29

The photoreceptors on the retina are stimulated and produced nerve impulse. The nerve impulses were carried along the optic nerve to visual centre of the cerebrum and interpreted as vision.

Question 30

Pinna/ ear flap

Answer 30

Collect soundwaves

Question 31

Auditory canal (outer ear)

Answer 31

Traps, dirt and bacteria to prevent them from entering the middle ear

Question 32

Ear drum (outer ear)

Answer 32

Convert sound waves into vibrations

Question 33

Ear bones (middle ear)

Answer 33

Amplify and transmit vibrations to the oval window

Question 34

Oval window (middle ear)

Answer 34

Transmit vibrations from the ear bones to the inner ear

Question 35

Round window (middle ear)

Answer 35

Releases the fluid pressure in the cochlea into the air in the middle ear 

Question 36

Cochlea (inner ear)

Answer 36

Detect vibration
Perilymph of the cochlea and endolymph of the cochlea
Sensory hair cells in the central canal of the cochlea

Question 37

Sensory hair cell

Answer 37

They can detect the vibration of endolymph and produce nerve impulse.

Question 38

Round window

Answer 38

Releases the fluid pressure in the cochlea into the middle ear .

Question 39

Eustachina tube

Answer 39

Equalizes pressure between the middle ear and the atmosphere

Question 40

Semicircular canal

Answer 40

Detect the direction of head movement , send nerve impulses to the brain and the brain coordinates muscles to maintain body balance