1. Which of the following is a plant hormone?
Ans:- d) cytokinin.
2. The gap between two neurons is called a
Ans:- (b) Synapse
3. The brain is responsible for
(b) Regulating the heartbeat.
(c) Balancing the body.
(d) all of the above.
Ans:- (d) all the above
4. 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:- The receptors in our body collect information about changes in the environment
around us in the form of stimuli. They are located in our sense organs such as the
inner ear, nose, tongue, eye, etc. These then pass the information in the form of
nerve impulses to the central nervous system (spinal cord and brain) where the message is interpreted and instructions are sent to effectors that reveal responses.
When receptors do not work properly, the environmental stimuli are not able to
create nerve impulses and the body does not respond.
5. Draw the structure of a neuron and explain its function.
Functions:- The information acquired at the end of the dendritic tip of a neuron sets
off a chemical reaction which creates an electrical impulse. This impulse travels from
the dendrite to the cell body, and then along the axon to its end. At the end of the axon, the electrical impulse sets off the release of some chemicals, which cross the synapse and start a similar impulse in a dendrite of the next neuron.
In this way, nervous impulses travel in the body. Thus, nervous tissue is made up of an organized network of neurons that are specialized for conducting information via electrical impulses from one part of the body to another.
6. How does phototropism occur in plants?
Ans. Movement of shoot towards light is called phototropism. This movement is caused due to 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.
7. Which signals will get disrupted in case of a spinal cord injury?
Ans:- In case of a spinal cord injury, reflex actions and involuntary actions will get disrupted.
8. How does chemical coordination occur in plants?
Ans:- In plants, chemical coordination occurs with the help of plant (phytohormones). Different plant hormones help to coordinate growth, development, and responses to the environment. They are synthesized at places away from where they act and diffuse to the area for action, for example, auxin promotes cell growth, gibberellins promote stem growth, cytokinins promote cell division and abscisic acid inhibits growth and its effects include wilting of leaves.
9. What is the need for a system of control and coordination in an organism?
Ans:- The body of a multicellular organism consists of a number of components and sub-
components and each is specialized to perform a particular function. Therefore, it is
necessary that various organs of the body of an organism work together in a proper
manner for proper functioning to a stimulus. In human beings nervous system and
endocrine system work together to control and coordination.
10. How are involuntary actions and reflex actions different from each other?
Ans:-(a) Involuntary action involves the autonomic nervous system.
(i) They occur in response to internal stimuli.
(ii) They are connected with the functioning of internal body parts.
(iii) It occurs without the will of the organism. E.g., heartbeat, breathing, etc.
(iv) These are regulated by medulla oblongata (hindbrain).
(b) Reflex action involves all parts of the voluntary nervous system though they are not
(i) They operate against harmful stimuli which are generally external.
(ii) They are connected with emergency i.e, response to stimuli.
(ii) Some reflexes involve the brain, rather than the spinal cord.
(iv) Reflex action is generally controlled by the spinal cord.
11. Compare and contrast nervous and hormonal mechanisms for control and
coordination in animals.
Ans. In human beings, the nervous system controls the various functions by small units
called neurons. Neurons receive the information through sensory nerves and transfer
them through motor nerves.
Whereas, hormones coordinate the activities and growth of the body. Important
functions like sugar level metabolism, growth, and development, etc. are controlled
by hormones secreted by endocrine glands. Hence, in human beings, hormones show
long-lasting responses. The action of hormones is highly specific.
12. What is the difference between the manner in which movement takes place in a
sensitive plant and the movement in our legs?
Ans:- Movement in a sensitive plant
(i) It occurs in response to an external stimulus like touch and shock.
(ii) Plant cells change shape by changing the amount of water.
(iii) No nerves are involved.
(iv) There is no specialized tissue in plants for the conduction of information.
(v) Plant cells do not have specialized proteins.
Movement in our legs
(i) It occurs in response to our requirements and is a voluntary action.
(ii) Movement in our legs is voluntary action which is controlled by the cerebellum part
(iii) Nerves carry the message for movement of legs.
(iv) There is specialized nervous tissue in animals for conduction of information and
muscle cells to help in movement.
(v) Animal cells have specialized protein which helps muscles to contract or relax.
How does nervous tissue maintain muscle movement?
Ans:-Nervous Tissue processes information, makes decisions based on the information, and conveys the decision to muscles for action. When the nerve cell reaches the muscle, the muscle fiber must move. The simplest motion of movement at the cellular level is the muscle cell movement which moves by changing their shape to be shortened. Muscle cells have special proteins that change both their shape and their arrangement in the cell in response to nervous electrical impulses. When this happens, the new arrangement of these proteins gives a shorter form to the muscle cells. Thus, in this way, nervous tissue maintains muscle movement.