NCERT Solutions

Class 10 Science

control and coordination

Q1) Which of the following is a plant hormone?

  1. Insulin
  2. Thyroxin
  3. Oestrogen
  4. Cytokinin

Answer: (d)Cytokinin

Q2)The gap between two neurons is called a

  1. dendrite
  2. Synapse
  3. Axon
  4. Impulse

Answer: (b)synapse

Q3)The brain is responsible for

  1. Thinking
  2. regulating the heart beat.
  3. balancing the body.
  4. all of the above.

Answer: (d)All of the above.

Q4)What is the function of receptors in our body? Think of situations where receptors do not work properly. What problems are likely to arise?

Answer:
All information from our environment is detected by the specialised tips of some nerve cells. These receptors are usually located in our sense organs, such as the inner ear, the nose, the tongue, and so on. So gustatory receptors will detect taste while olfactory receptors will detect smell. We detect that we are touching a hot object by the action of receptors present on various organs or tissues. If olfactory receptor not works properly then we are not able to smell things like aggarbatti, perfumes, flavour of food.

Q5)Draw the structure of a neuron and explain its function.

Answer:

A neurons consists of three parts:
(i) Cell body: It is a typical animal cell which contains cytoplasm and a nucleus.
(ii) Dendrites: A number of long and thin fibres comes out from the cell body of the neurons, they are nerve fibre. The shorter fibres on the cell body of neurons are called dendrites.
(iii) Axon: The longest fibre on the cell body of neurons is called axon. It has an insulating and protective sheath (or cover)of myelin around it.

Function of Neuron:-
? The impulses of information travel from dentrites to the cell body, and then along the axon to its end.
? These impulses cross the synapse. At the end , the impulses travel form one neuron to the other up to the spinal cord or to the concerned part of the body.

Q6) How does phototropism occur in plants?

Answer:
Photo means light. The response of plant towards the environmental triggers, light which change the directions that plant parts grow in is called phototropism. The directional, or tropic, movements can be either towards the light, or away from it. So, in two different kinds of phototropic movement, shoots respond by bending towards light while roots respond by bending away from it. For example: Sunlight bends towards the sun from where the light is coming. This is the response of sunflower towards the plants.

Q7) Which signals will get disrupted in case of a spinal cord injury?

Answer:
Reflex actions are involuntary actions and controlled by the spinal cord thus, gets disrupted in case of spinal cord injury.

Q8) How does chemical coordination occur in plants?

Answer:
Plants do not have nervous system but still sense the things because of stimulus such as gravity, light, chemicals(hormones), water, touch (touch -me -not plant).Hormones are responsible for the chemical coordination of plants by integrating their behaviour by affecting growth of a plant resulting in movement of that plant part in response to a stimulus. When sunlight falls on the shoot from one side, the auxins hormone causes the shady side of the shoot to grow faster, making the shoot bend towards sunlight.

Q9) What is the need for a system of control and coordination in an organism?

Answer:
Controlled movement must be connected to the recognition of various events in the environment, followed by only the correct movement in response. In other words, living organisms must use systems providing control and coordination. In keeping with the general principles of body organisation in Multicellular organisms, specialised tissues are used to provide these control and coordination activities.
(i) Coordination is needed for all human activities like, thinking and behaviour. Our breathing process, hearts beats, we dance, read, write by the action of our nervous system. Our nervous system gets information from surroundings and processes it and then respond according to it. The endocrine system (hormonal system) helps in integrating various metabolic activities like reproduction, development, all reflex actions (cope up with various give up situations).
(ii)The hormonal system in plants helps in process of photosynthesis; they need carbon dioxide, water and sunlight. The stomatal opening in leaves opens up to allow in carbon dioxide gas, the roots bend towards water and the stem grows towards sunlight, the tendrils in climbing pants are supported by the hormonal system of the plant body.
Thus, we have need of control and coordination system in an organisms.

Q10) How are involuntary actions and reflex actions different from each other?

Answer:
Involuntary action is the set of muscle movement which do not require thinking. But it is controlled by brain for example beating of heart beat. While on the other hand, the reflex action is rapid and spontaneous action in response to any stimulus. For example closing of eyes immediately when bright light is focused.

Q11) Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

Answer:

Nervous system Hormonal system
Made up of neurons made up of secrotory cells
messages transmitted in the form of electrical impulses messages transmitted in the form of chemicals called harmones.
messages are transmitted along nerve fibre. messages are transmitted along blood stream.
Effect of message usually lasts for a very short while. Effect of message usually lasts longer.
Messages travel very quickly. Messages travel more slowly.

Q12) What is the difference between the manner in which movement takes place in a sensitive plant and the movement in our legs?

Answer:

Movement in sensitive plants Movement in our legs
The movement in a sensitive plant is a response to stimulus which is a voluntary action. Movement in our legs is a voluntary action.
No special tissue is there for the transfer of information. A complete system CNS and PNS is there for the information exchange.
Plant cells do not have specialised protein for movaments. Animal cells have specialised protein which help muscles to contract.