Chapter 2
Senses and Sense Organs
Short
Questions:
Q1. Define stimuli?
Ans: The things which cause any reaction whether it
is a hot object, the moving ball etc. are called stimuli.
Q2: What are sensory cells?
Ans: Our body senses or detects the stimuli with the
help of group of special cells. These are called sensory cells.
Q3. What is epidermis?
The top and the outer layer is called epidermis. It
is made up of dead and flattened cells.
Q4. Define Dermis?
The lower layer of skin is called dermis. The dermis
contains wet, oil glands, blood vessels and fats.
Q5: How many taste buds are present on
our tongue?
Ans: Four type of taste buds are present on our
tongue.
1. Bitter 2. Sour 3. Sweet 4. Salt
Q6. What is cornea?
Ans: In the front of eye there is a clear round
window called cornea.
Q7. Define lens?
A piece of transparent material with one or more
curved surface used for reflecting light.
Q8: What is accommodation?
The elasticity and thickness of lens is controlled
by ciliary muscles. This process is called accommodation.
Q9. What is iris?
Sheet of muscles behind
the lens is called iris.
Q10: Define cochlea?
Inner ear has a coiled
structure called cochlea which is actual hearing organ. It sends signals to
brain.
Q11: What is retina?
Ans: Layer of sensitive
cell at the back of the eye in which light make chemical change.
Q12. Define pupil?
Ans: In the center of lens, there is a round hole
called pupil.
Q13. Define reflex action?
Ans: Some muscles of our body work automatically as
a reaction against any reaction. This action is known as reflex action.
Q14: What is function of tear glands?
Ans: These produces tear and when we blink this
liquid spreads over the surface of eye.
Long
Question
Q1. Describe the
structure of human eye?
Main parts of our eye
are
i.
Cornea
ii.
Iris
iii.
Pupil
iv.
Lens
v.
Retina
vi.
Optical nerve
i. Cornea:
At the front of eye
there is a clear round window called cornea.
ii. Iris :
It is the colourful
part of eye. It controls the amount of light entering in the eye.
iii. Pupil:
In the center of the
coloured part there is a round hole called pupil.
iv. Lens:
A piece of transparent
material with one or more than one curved surface that is curved for refracting
and bending of light.
v. Retina :
It focuses light onto a
layer of sensory cells at the back of eye.
vi. Optical
nerve:
When the light hits the
retina the cell make nerve signal. The signal pass along the optical nerve to
the brain.
Long Q2:
What is the difference between long sighted and short sighted?
Long Sighted:
Some people can see distant object clearly but cannot focus
on very near objects. They are said to be long sighted.
Curing long sighted:
Long sighted is caused by the eye ball being too short so the
images are focused behind the retina. Long sighted people can be helped when a
convex lens is placed in front of each eye. The lens help to focus light on
retina.
Short sightedness:
Some people can see near objects clearly but cannot focus on
the distant object. They are called short sighted.
Curing short sighted:
It occurs when the eye ball is too long and image are focused
in the front of retina. Short sighted people can be helped it they wear contact
lenses that are concave.
Q3: Describe the structure of human ear?
Ans: It consists of three parts
i.
Outer ear
ii.
Middle ear
iii.
Inner ear
1. Outer ear:
The outer ear consists of pinna and a long tube called ear
canal. The pinna collects sounds waves from surrounding and the sound waves
then travel along the ear canal.
2. Middle ear:
The outer ear is thin membrane called
ear drum on the other side of ear drum is middle ear which is filled with air.
3. Inner ear:
Inner ear is filled with liquid. This
part of ear has a coiled structure called cochlea. The cochlea is actual
hearing organ and sends signals to brain.
