#Textbook/Exercises Question and Answers –
Q1- Which of the following is a plant hormone ?
Ans. (d) Cytokinin
Q2-The gap between two neurons is called a :
Ans. (b) Synapse
Q3-The brain is responsible for :
Ans. (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 ?
Ans.(i)Receptors or sense organs are groups of highly specialized cells which receive the stimuli. Each receptors is specialized to receive a specific stimulus and change it into appropriate nerve impulse.
(ii) When receptors fail to work properly, the body functions will be disturbed and may be health- hazard or fatal.
Q5- Draw the structure of a neuron and explain its function.
Ans. (i) Figure 7.1 Structure of neuron (page no.115)
(ii) (a)Dendrites receive the stimuli and conduct the nerve impulses towards the cyton.
(b) Axon conducts the nerve impulse away from the cyton towards dendrite of another neuron or target muscle or glandular cell.
Q6-Which signals will get disrupted in case of spinal cord injury?
Ans. Spinal cord control reflex actions of the body because the reflex arcs are formed in it.So in case of injury to spinal cord, the signals of reflex actions will be disrupted and the body will not be able to give quick and automatic mechanical responses to harmful stimuli. this increases the chances of damage to the body by such stimuli.
Q7- How does the phototropism occur in plants?
Ans. In phototropic movements, shoots respond by bending towards light, while roots respond by blending away from it. when growing plants receive light, plant hormone,auxin formed at shoot tip, helps the cells to elongate.in case light comes from one direction, auxins move towards shade side of shoot. They thus stimulate the cells to grow longer on the side of shade. Thus plant bends towards light.
Q8- How does chemical coordination occur in plant?
Ans. Due to stimulation, cells release chemicals which are able to diffuse all over the original cell. Cells lying nearby can detect this chemical using special molecules on their surface. They can identify information and are able to transmit it. It is potentially able to reach all the cells of the body, without having nervous connections. It can be carried out continuously and persistently , Different plant hormones help in coordination to growth, development and responses to the environment. Their point of formation and action differs but are able to become the region of action.
Q9- What is the need for a system of control and coordination in an organism?
Ans. (i) So that various organs of body operate harmoniously to ensure their smooth functioning.
(ii) To maintain a constant internal environment, called homeostasis, inside the body.
(iii) To adjust themselves according to the change in environment.
Q10- How are involuntary actions and reflex actions different from each other?
Ans. Involuntary actions are those muscular movements which are not under will or any thinking control, e.g., heart movements, blood pressure , salivation, vomiting, etc., and are controlled by specific centres located in the mid brain and hind brain.
Reflex actions are spontaneous automatic mechanical responses in which will is not involved like the involuntary actions but are controlled by the spinal cord e.g., withdrawal of hand when pricked with a needle, secretion of saliva on sight of delicious food, etc.
Q11- Compare and contrast nervous and chemical mechanisms for control and coordination in animals.
|1. Speed of action||Always quick acting.||May be quick or slow acting.|
| 2. Mode of transmission of|
|As electrical nerve impulse.||As chemical messengers(hormones).|
|3. Path of transmission||Through nerve fibers.||Through blood.|
|4. Durability||Short-term effect.||long lasting.|
Q12- What is difference between the manner in which movement in a sensitive plant and movement is our legs takes place?
Ans. Quick folding of leaflets of mimosa pudica ( sensitive plant touch-me-not) and drooping of whole leaf occur due to changes in the amount of water in its motat cells. No nervous and muscular tissue are involved. But the movements in our legs are due to contraction and relaxation of muscle proteins regulated by nervous tissue. Muscle cells bring about movements by changing their shape.
NCERT Solutions for Class 10 Science Chapter 7