CBSE Class 10 Science HOTs Control And Coordination Set 02

Question. Which part of a nerve cell contains a nucleus?
(a) Axon
(b) Dendrite
(c) Cyton
(d) Nerve endings
Answer: (c) Cyton

Question. Reflex arc is formed by
(a) muscle \( \rightarrow \) brain \( \rightarrow \) receptor
(b) muscle \( \rightarrow \) spinal cord \( \rightarrow \) receptor
(c) receptor \( \rightarrow \) brain \( \rightarrow \) muscles
(d) receptor \( \rightarrow \) spinal cord \( \rightarrow \) muscle
Answer: (d) receptor \( \rightarrow \) spinal cord \( \rightarrow \) muscle

Question. Which of the following tissues provide control and coordination in animals?
(a) Nervous and Skeletal
(b) Muscular and Skeletal
(c) Muscular and Transport
(d) Nervous and Muscular
Answer: (d) Nervous and Muscular

Question. A student accidentally places her hand on a flame of candle and quickly pulls her hand away. The flame represents
(a) a response
(b) a stimulus
(c) an impulse
(d) an effector
Answer: (b) a stimulus

Question. How many pairs of cranial nerves are present in man?
(a) 12
(b) 21
(c) 31
(d) 41
Answer: (a) 12

Question. Reflex actions are mediated through
(a) brain
(b) effectors
(c) spinal cord
(d) receptors
Answer: (c) spinal cord

Question. Synapse is defined as a
(a) gap between two muscle cells
(b) gap between two neurons
(c) gap between two bones
(d) gap between muscle and bone
Answer: (b) gap between two neurons

Question. The spinal cord is protected by
(a) aorta
(b) vertebral column
(c) pleura
(d) diaphragm
Answer: (b) vertebral column

Question. Which option correctly shows the order of events when a bright light is focused on our eyes? 
(a) Bright light \( \rightarrow \) receptors in eyes \( \rightarrow \) sensory neuron \( \rightarrow \) spinal cord \( \rightarrow \) motor neurons \( \rightarrow \) eyelid closes
(b) Bright light \( \rightarrow \) receptors in eyes \( \rightarrow \) spinal cord \( \rightarrow \) sensory neuron \( \rightarrow \) motor neurons \( \rightarrow \) eyelid closes
(c) Bright light \( \rightarrow \) receptors in eyes \( \rightarrow \) sensory neuron \( \rightarrow \) motor neurons \( \rightarrow \) spinal cord \( \rightarrow \) eyelid closes
(d) Bright light \( \rightarrow \) receptors in eyes \( \rightarrow \) spinal cord \( \rightarrow \) motor neurons \( \rightarrow \) sensory neuron \( \rightarrow \) eyelid closes
Answer: (a) Bright light \( \rightarrow \) receptors in eyes \( \rightarrow \) sensory neuron \( \rightarrow \) spinal cord \( \rightarrow \) motor neurons \( \rightarrow \) eyelid closes

Question. Which of the following statements are true about the brain?
(i) The main thinking part of the brain is hind brain.
(ii) Centres of hearing, smell, memory, sight, etc. are located in fore-brain.
(iii) Involuntary actions like salivation, vomiting, blood pressure are controlled by the medulla in the hind-brain.
(iv) Cerebellum does not control posture and balance of the body.
(a) (i) and (ii)
(b) (i), (ii) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer: (c) (ii) and (iii)

Very Short Answer Type Questions

Question. Name the two main organs of our central nervous system. Which one of them plays a major role in sending command to muscles to act without involving thinking process? Name the phenomenon involved.
Answer: The two main organs of CNS are brain and spinal cord.
Spinal cord plays a major role in sending command to muscles to act without involving thinking process. This phenomenon is called reflex action.

Question. Name the two types of neurons? How is the functioning of one different from the other?
Answer: Two types of neurons are:
(i) Sensory neurons – They pass information from the receptors to the brain.
(ii) Motor neurons – They transmit information from the brain to the effector organs.

Question. Which is the control centre of a reflex action? What is the route taken by the reflex action called?
Answer: Spinal cord is the control centre of a reflex action. The route taken by the reflex action is called reflex arc.

Question. Distinguish between spinal nerve and cranial nerve.
Answer:
Spinal nerve:
(i) They arise from spinal cord.
(ii) There are 31 pairs of spinal nerves.
Cranial nerve:
(i) They arise from brain.
(ii) There are 12 pairs of cranial nerves.

Question. How does the nervous system serve for coordination of all other systems in the body?
Answer: (i) Nervous system receives information of changes in the external environment, analyses and interprets the information to produce sensations like vision or pain.
(ii) It also receives information of changes in the interior of the body and coordinates the activities of the visceral organs in the light of those changes and maintains a constant internal environment.

Question. What are cranial nerves? How many cranial nerves does a human being have?
Answer: Cranial nerves are those nerves which arise from different parts of the brain. A human being has 12 pairs of cranial nerves.

Question. Name the part of brain which is responsible for the following actions:
(i) Maintaining posture and balance
(ii) Beating of heart
(iii) Thinking
(iv) Blood pressure
Answer: (i) Cerebellum (ii) Medulla (iii) Cerebrum (iv) Medulla

Short Answer Type Questions

Question. (a) What are receptors? (b) Define stimulus?
Answer: (a) It is a cell or group of cells specialised to detect a particular stimulus and to initiate the transmission of impulses \( via \) the sensory nerves.
(b) It is the change in the external or internal environment of an organism that provokes a physiological and behavioural response in the organism.

Question. (a) (i) Name one gustatory receptor and one olfactory receptor present in human beings. (ii) Write a and b in the given flow chart of neuron through which information travels as an electrical impulse. 
Dendrite \( \rightarrow \) a \( \rightarrow \) b \( \rightarrow \) End point of Neuron
(b) What do you understand by the term ‘target organ’? Give any one example.
Answer: (a) (i) Gustatory receptor—Tongue; Olfactory receptor—Nose.
(ii) a–Cell body/Cyton; b–Axon.
So, electric impulse flow chart will be as follows:
Dendrite \( \rightarrow \) Cell body/Cyton \( \rightarrow \) Axon \( \rightarrow \) End point of neuron.
(b) Specific tissue or organ on which hormones act are called target organs, e.g. digestive system.

Question. (a) Where are pons present in the brain? Which activity do they control? (b) Different parts of brain are associated with specific functions. Name the part of human brain which perform the following functions: (i) Picking up a pencil (ii) Riding a bicycle
Answer: (a) Pons are situated below the cerebellum and above the medulla oblongata in the hind-brain. They are responsible for regulating the respiratory activity.
(b) (i) Hind-brain (cerebellum)
(ii) Hind-brain (cerebellum)

Question. (a) What are cranial nerves? How many cranial nerves does a human being have? (b) Write the difference between cerebellum and cerebrum.
Answer: (a) Cranial nerves arise from the brain and spread throughout the head. There are twelve pairs of cranial nerves.
(b)
Cerebrum:
(i) It is the largest highly developed and prominent part of the brain.
(ii) It is the controlling centre for senses. It is responsible for memory, intelligence, hearing, etc.
Cerebellum:
(i) It is the second largest part of the brain and lies at the posterior part of the brain.
(ii) It controls the skeletal muscle activities and maintains the equilibrium of the body.

Question. (a) Which is the largest part of the brain? What are its functions? (b) Distinguish between spinal nerve and cranial nerve.
Answer: (a) Cerebrum is the largest part of the brain. Its various regions carry out different activities, i.e. occipital lobe for vision, temporal for auditory reception, parietal for touch, smell, temperature and consciousness and frontal lobe for muscular activities.
(b)
Spinal nerve:
(i) They arise from spinal cord.
(ii) There are 31 pairs of spinal nerves.
Cranial nerve:
(i) They arise from brain.
(ii) There are 12 pairs of cranial nerves.

Question. (a) What are sensory and motor neurons? Write their function.  (b) Different parts of brain are associated with specific functions. Name the part of human brain which perform the following functions: 
(i) Sensation of feeling full (ii) Vomitting
Answer: (a) Two types of neurons are:
(i) Sensory neurons – They transmit information from the receptors to the central nervous system.
(ii) Motor neurons – They transmit information from the brain to the effector organs.
(b) (i) Fore-brain (a centre for hunger)
(ii) Hind-brain (medulla)

Question. State the functions of any three of the structural and functional unit of nervous system.
Answer: The structural and functional unit of nervous system is neuron and their functions are as follows:
(i) Cell body: Stimulus received from dendrite is changed into impulse in the cyton.
(ii) Dendrites: They receive sensation or stimulus, which may be physical, chemical, mechanical or electrical. They pass the stimulus to cyton.
(iii) Axon: It conducts impulse away from the cell body.

Question. What is a reflex action? Describe the steps involved in a reflex action. 
Answer: Reflex Action: It is defined as an unconscious, automatic and involuntary response of effectors, i.e. muscles and glands, to a stimulus, which is monitored through the spinal cord.
Mechanism of Reflex Action: It involves the following steps :
(i) Receptor organ like skin perceives the stimulus and activates a sensory nerve impulse.
(ii) Sensory organ carries message in the form of sensory impulse to the spinal cord.
(iii) The spinal cord acts as modulator. The neurons of spinal cord transmit the sensory nerve impulse to motor neuron.
(iv) Motor nerve conducts these impulses to the effectors like leg muscles which responds by pulling back the organ away from the harmful stimulus.

Question. What is synapse? In a neuron cell how is an electrical impulse created and what is the role of synapse in this context? 
Answer: Synapse is the junction between two adjacent neurons or nerve cells, i.e. between axon ending of one and the dendrite of the next.
Transmission of Nerve Impulse: 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 cyton 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 electrical impulse in a dendrite of the next neuron. In this way nerve impulses travel in the body. Synapse helps in transmitting impulses from one neuron to another.

Question. (a) How is brain protected from injury and shock? (b) Name two main parts of hind-brain and state the functions of each.
Answer: (a) The brain sits inside a bony box. Inside the box, the brain is contained in a fluid filled balloon which provides further shock absorption.
(b) Two main parts of hind-brain are–Medulla and Cerebellum. Their functions are:
Medulla: It controls involuntary actions such as blood pressure, salivation and vomiting are controlled by medulla.
Cerebellum: It is responsible for precision of voluntary actions and maintaining the posture and balance of the body.

Question. Write any three functions of the nervous system.
Answer: (i) It regulates involuntary actions.
(ii) It controls and coordinates voluntary muscular activities.
(iii) It keeps us informed about the outside world through the sense organs.
(iv) It enables us to think, reason and remember.
(v) It controls all the reflex actions in our body, thus protecting it from harm. (any three)

Long Answer Type Questions

Question. Suggest six reflex actions of the body. Explain how the reflex arc is the same in all of them.
Answer: Six reflex actions of the body are:
(i) When we see a speeding car moving towards us, we move aside.
(ii) We withdraw our hands on being pricked by a pin.
(iii) We withdraw our hands on touching very hot substance.
(iv) We close our eyes on seeing direct sun or extremely bright source of light.
(v) We close our eyes on hearing a loud noise.
(vi) We shiver on feeling cold.
Reflex arc in all the above cases is same because in all the cases, the stimulus is received by sense organs. Then this information is carried to spinal cord through sensory nerves. Thus, information from spinal cord is sent to the effectors such as muscles \( via \) motor neurons.
Receptors \( \xrightarrow{\text{Sensory neurons}} \) Spinal cord \( \xrightarrow{\text{Motor neurons}} \) Effectors

PRACTICE QUESTIONS

Question. Which is not the part of hind-brain?
(a) Medulla oblongata
(b) Cerebrum
(c) Cerebellum
(d) Pons
Answer: (b) Cerebrum

Question. Which area of the brain is responsible for control of the body temperature?
(a) Pituitary
(b) Thalamus
(c) Hypothalamus
(d) Hind-brain
Answer: (c) Hypothalamus

Question. Junction of two neurons is called: 
(a) Synapse
(b) Synapsis
(c) Joint
(d) Junction
Answer: (a) Synapse

Question. What is voluntary action?
Answer: A voluntary action is an action which is initiated by our own conscious will. For example, talking, walking, and writing.

Question. What is involuntary action?
Answer: An involuntary action is an action that occurs without conscious control or thought. For example, heart beating, breathing, and digestion.

Coordination in Plants

Question. Which statement is incorrect about auxins?
(a) They promote the growth of root
(b) They promote the growth of shoot
(c) They influence the formation of flower and ripening of fruit
(d) They inhibit the growth of root
Answer: (d) They inhibit the growth of root

Question. The hormone that is used to keep flowers fresh is
(a) cytokinin
(b) gibberellins
(c) auxin
(d) abscisic acid
Answer: (a) cytokinin

Question. The main effect of cytokinin in plants is to
(a) improve the quality of fruits
(b) prevent the growth of lateral buds
(c) regulate opening and closing of stomata
(d) stimulate cell division
Answer: (d) stimulate cell division

Question. Abscisic acid controls
(a) cell elongation and cell wall formation
(b) shoot elongation
(c) cell division
(d) leaf fall and dormancy
Answer: (d) leaf fall and dormancy

Question. In plants the role of cytokinin is: 
(a) Promote cell division.
(b) Wilting of leaves.
(c) Promote the opening of stomatal pore.
(d) Help in the growth of stem.
Answer: (a) Promote cell division.

Question. Auxin is a plant hormone that promotes cell elongation and is produced by the apical meristem. It inhibits the growth of lateral buds which are present at nodes (where leaves attach to the stem). As long as sufficient auxin is produced by the apical meristem, the lateral buds remain dormant. A gardener wants the plants in the hedge that he is growing to become bushier with more branches. Which of the following should he do? 
(a) Spray water on the tips of the stems to increase growth
(b) Dig around the plant roots and apply more manure
(c) Trim the hedge by cutting off the tips of the stems
(d) Remove all the weeds that grow around the hedge
Answer: (c) Trim the hedge by cutting off the tips of the stems