NCERT Solutions for Class 10 Science
Chapter 7 “Control and Coordination”
Answer The Following Question.
Answer
:
Difference between reflex
action and walking:
|
Reflex action |
Walking |
(a) Take place without
thought (b)Controlled by spinal
cord. (C) It is involuntary
action |
(a) Takes place afterthought. (b) Controlled by the cerebellum. (c) It is a voluntary action. |
2. What happens at the synapse between two neurons?
Answer
:
A tiny gap between the last portion of the axon of one neuron and the dendron of the
other neuron is known as a synapse. It acts as a one-way valve to transmit
impulses in one direction only. This uni-direction transfer of impulses occurs
as the chemicals are produced on only one side of the neuron i.e., the axon's
side. From the axon, the impulses travel across the synapse to the dendron of the
other neuron.
3. Which part of the
brain maintains posture and equilibrium of the body?
Answer
:
The Cerebellum, a part of the hindbrain is responsible for maintaining posture and equilibrium of the body.
4. How do we detect the
smell of an agarbatti (incense stick)?
Answer
:
The thinking part of our
brain is the forebrain. It has separate areas specialized for hearing,
smelling, sight, taste, touch, etc. The forebrain also has regions that collect
information or impulses from the various receptors. When the smell of an
incense stick reaches us, our forebrain detects it. Then, the forebrain
interprets it by putting it together with the information received from other
receptors and also with the information already stored in the brain.
5. What is the role of the brain in reflex action?
Answer
:
Reflex actions are sudden
responses, which do not involve any thinking. For example, when we touch a hot
object, we withdraw our hand immediately without thinking as thinking may take
time which would be enough to get us burnt. The sensory nerves that detect heat are connected to the nerves that move the muscles of the hand. Such a
connection of detecting the signal from the nerves (input) and responding to it
quickly (output) is called a reflex arc.
The reflex arcs —connections present between the input and output nerves — meet
in a bundle in the spinal cord.
Reflex arcs are formed in
the spinal cord and the information (input) reaches the brain. The brain is
only aware of the signal and the response that has taken place. However,
the brain has no role to play in the creation of the response.
6. What are plant
hormones?
Answer
:
Plant hormones or
phytohormones are naturally occurring organic substances. These are synthesized
in one part of the plant body (in minute quantities) and are translocated to
other parts when required. The five major types of phytohormones are auxins,
gibberellins, cytokinins, abscisic acid, and ethylene.
7. How is the movement of
leaves of the sensitive plant different from the movement of a shoot towards
light?
Solution: Difference
between the movement of leaves of sensitive plants and the movement of a shoot towards the light :
8. Give an example of a
plant hormone that promotes growth.
Answer:
Auxin promotes the growth of
cells.
9. How do auxins promote
the growth of a tendril around a support?
Answer:
When tendrils come in
contact with any support, the part of the tendril in contact does not grow as
rapidly as the part away from the object due to auxin secreted moving away from
the object in contact. This rapid growth on one side causes tendril to circle
around the object.
10. Design an experiment
to demonstrate hydrotropism.
Answer
:
Take a tin box with a hole
at the bottom. Fill it with moist sawdust. Sow some gram seeds in it. Keep the tin
box in a tilted position. When seeds start germinating, water the sawdust only
in the lower side of the tin box. You will observe that the radicle moves towards
the wet sawdust. This shows that the root is positively hydrotropic.
11. How does chemical coordination take place in animals?
Answer:
The chemical coordination
is maintained by hormones. These are secreted by endocrine glands. These
hormones are poured into blood through which they reach the target tissue or
organ to act.
12. Why is the use of
iodized salt advisable?
Answer
:
Iodine is necessary for
the thyroid gland to make thyroxin hormone. In case, iodine is absent in our
diet, there is a possibility of Goitre. Iodized common salt contains the proper
content of iodine. To avoid a deficiency of iodine, iodized salt is recommended.
13. How does our body
respond when adrenaline is secreted into the blood?
Answer:
When adrenaline reaches
the various target organs through blood. All these organs respond together to
enable our body to deal with situations like running away from a scary situation.
When adrenaline reaches the heart, it beats faster to supply more oxygen to our
muscles. The small arteries around the digestive system and skin contract to
divert the blood towards the muscles. All these responses enable our body to deal
with situations.
14. Why are some patients
with diabetes treated by giving injections of insulin?
Answer
:
Diabetes is caused due to
non or less secretion of the hormone insulin by the pancreas. In such a person, the blood
sugar level is high. Insulin converts extra sugar present in the blood into
glycogen. Patients suffering from diabetes are given insulin injections to
control their blood sugar levels.
15. Which of the
following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinins
Answer
: (d)
Cytokinin.
16. The gap between two
neurons is called a
(a) Dendrite
(b) synapse
(c) axon
(d) impulse
Answer
: (b)
Synapse.
17. The brain is
responsible for
(a) thinking
(b) regulating the
heartbeat.
(c) balancing the body
(d) all of the above.
Answer
: (d)
All the above.
18. What is the function
of receptors in our body? Think of a situation where receptors do not work
properly. What problems are likely to arise?
Answer:
Receptors detect all the
information from our environment. These receptors are located in our sense
organs. In case any of the receptors do not work properly we will not be able
to perceive that particular information.
19. Draw the structure of
a neuron and explain its function.
Answer
:
Neuron acquires
particular information through dendrites located on its cell body. This
information is then passed on to the axon. Finally, the axon ending passes the
information into the next neuron at the synapse. As soon as the impulse reaches the
dendrite, an electrical impulse is generated due to certain chemical changes in the neuron. When the impulse reaches the axon some chemicals are released which pass
on the impulse to the next neuron. These chemicals are known as neurotransmitters.
20. How phototropism does
occur in plants?
Answer
:
The movement of a shoot toward
light is called phototropism. This movement is caused by more growth of
cells towards the shaded side of the shoot as compared to the side of the shoot
towards the light. More growth of cells is due to the secretion of auxin towards the
shaded side.
21. Which signals will
get disrupted in case of a spinal cord injury?
Answer
:
(i) Reflex action
(ii) Impulses from
various body parts will not conducted to the brain.
(iii) Message from brain
will not be conducted to various organs.
22. How does chemical
coordination occur in plants?
Answer
:
In animals, control and
coordination occur with the help of the nervous system. However, plants do not have
a nervous system. Plants respond to stimuli by showing movements. The growth,
development, and responses to the environment in plants are controlled and
coordinated by a special class of chemical substances known as hormones. These
hormones are produced in one part of the plant body and are translocated to
other needy parts. For example, a hormone produced in roots is translocated to
other parts when required. The five major types of phytohormone are auxins,
gibberellins, cytokinins, abscisic acid, and ethylene. These phytohormones are
either growth promoters (such as auxins, gibberellins, cytokinins, and
ethylene) or growth inhibitors such as abscisic acid.
23. What is the need for a system of control and coordination in an organism?
Answer
:
The maintenance of the
body functions in response to changes in the body by working together with
various integrated body systems is known as coordination. All the movements
that occur in response to stimuli are carefully coordinated and controlled. In
animals, the control and coordination movements are provided by the nervous and
muscular systems. The nervous system sends messages to and away from the brain.
The spinal cord plays an important role in the relay of messages. In the
absence of this system of control and coordination, our body will not be able
to function properly. For example, when we accidentally touch a hot utensil, we
immediately withdraw our hand. In the absence of nerve transmission, we will
not withdraw our hand and may get burnt.
24. How are involuntary
actions and reflex actions different from each other?
Answer
:
The difference between
involuntary and reflex actions is as follows:
|
Involuntary actions |
Reflex actions |
|
It is a set of muscle movements over which we do not have control, Such actions are controlled by the brain. For example- contraction of the muscle of our digestive tract, beating Of the heart, etc. |
It is a rapid,
spontaneous, and involuntary |
25. Compare and contrast the nervous
system and hormonal control and coordination in animals.
Answer
:
Difference between
nervous control and hormonal control:
|
Nervous control |
Hormonal control |
|
(i)
Consists Of nerve impulses
conducted by neurons from one organ to another organ. (ii)
Nervous impulses produce rapid lasting responses. (iii)
Nervous impulses are not specific
in their action. |
(i) It consists Of an endocrine system which secretes chemical messenger's hormones secreted
directly in the blood. (ii) Hormones produce
longer lasting (iii)Action Of hormones
is highly Specific. |
26. What is the
difference between how movements take place in a sensitive
plant and movement in our legs?
Answer
:
Difference between
movement in a sensitive plant and movement in our legs:
|
Movement in
sensitive plant |
Movement in our legs |
|
(i) There is no
specialized tissue in plants for conduction Of information. (ii) Plant cells change
shape by changing the amount of water in them. (iii) Plant cells do not have
specialized proteins. |
(i) There is
specialized nervous tissue in animals for conduction Of information and
muscle cells to help in movement. (iii) Muscle cells have
specialized proteins that help muscles contract or relax. |
===================
Share,
Likes & Comment
===================
No comments:
Post a Comment