Selina Concise Class 8 Biology Solution Chapter No. 7- ‘Nervous System’ For ICSE Board Students.
Selina Concise Biology Solutions for Class 8th Chapter 7 Nervous System with easy language, expert answers and doubt clearing sections. The book is especially designed keeping in mind the syllabus of ICSE board and the difficulty level faced by the students of ICSE boards class 8.
Selina Class 8 Biology Chapter 7 Solution:
Multiple choice questions
1). Put a tick mark against the correct alternative in the following statements:
(a) Medulla oblongata controls :
(i) Smelling (ii) Beating of heart and respiratory movement (iii) Intelligence and will power (iv) Balancing of the body
Answer: Answer is (ii) Beating of heart and respiratory movement, because all these activites controlled by brain stem.
(b) Balance of the body is controlled by :
(i) Spinal cord (ii) Cerebellum (iii) Cerebrum (iv) Medulla
Answer: Answer is (ii) Cerebellum, All the body posture and balancing controlled by hind brain and cerebellum is part of the hind brain.
(c) The smell of good food causes watering of your mouth. It is :
(i) Natural reflex (ii) Acquired reflex (iii) Inborn reflex (iv) Ordinary reflex
Answer: Answer is (ii) Acquired reflex, These can be experienced from the surrounding.
(d) The structural and functional unit of a nervous system is :
(i) Axon (ii) Nephron (iii) Neuron (iv) Dendron
Answer: Answer is (iii) Neuron because nephron is structural and functional unit of a kidney and other are components of CNS.
Short Answer Question
1) You are driving your bicycle at a fast speed. Suddenly, a small boy comes in front of your cycle and without wasting any time in thinking, you immediately apply breaks and the accident is avoided. What name is given to such an action ?
Answer: It is called as reflex action.
2) Name the following:
(a) The long, extended process of a neuron : Axon
(b) The point of contact between two neurons: Synapse
(c) The kind of nerve which carry both sensory and motor neuron: Spinal nerves
(d) The nerve which connects eyes to the brain: Optic nerve
(e) The nerve which connects nose to the brain: Olfactory nerve
(f) The nerve which connects ears to the brain: Auditory nerve
(g) Two sub-divisions of the peripheral nervous system: Afferent division and efferent division.
(h) Two parts of the autonomic nervous system: Sympathetic and parasympathetic nervous system
3) Define the term:
(a) Co-ordination : Co-ordination can be defined as the process of controlling all the metabolic processes efficiently.
(b) Synapse: It is the junction between two neurons and the space between two neurons called synaptic space.
(c) Impulse: Impulses are the signals transmitting from one neuron to the next neuron and carrying out the action potential.
(d) Reflex action: It is an involuntary action which can be occur in response to the any external action such as bite of mosquito.
(e) Reflex arch: It is also called as reflex action, which reacts in response to any type of stimulus.
Long answer question (Write the answers in your note book)
1) Differentiate between the following pairs on the basis of what is indicated in the brackets.
(a) Stimulus and response (definition)
Answer:
Stimulus | Response |
Any kind of change in external or internal environment called stimulus. | Reaction to that stimulus is called response |
(b) Receptor and effector (examples)
Answer:
Receptor | Effector |
Salivary glands and hormones | Photoreceptor |
(c) Motor nerve and sensory nerve (function)
Answer:
Motor nerve | sensory nerve |
Send the signal from the central nervous system to target organ. | Send the signal from the organ to the central nervous system. |
(d) Cranial nerves and spinal nerves (number in pairs)
Answer:
Cranial nerves | spinal nerves |
There are 12 pairs. | There are 31 pairs. |
(e) Cerebrum and medulla oblongata(function)
Answer:
Cerebrum | medulla oblongata |
Play role in vision, taste, smell and intelligence. | Controls the blood pressure, heart beat and vomiting. |
(f) Cerebrum and spinal cord (Arrangement of white and gray matter)
Answer:
Cerebrum | spinal cord |
White matter is present in inner side and gray matter outside. | Gray matter is present in inner side and white matter outside. |
2) With the help of suitable diagram, describe the structure and function of a neuron.
Answer:
The functional unit of nervous system is neuron. Neurons are also called as nerve cells, because they carrying the information in the form of signal from various parts of the body to the brain and again transmitting information from brain to the target organ. As we can see in the diagram the neuron contains all the cellular organelles such as the cell body, dendrites that means extensions which arise from cell body, presence of axon, myelin sheath and axon terminals.
3) Briefly describe the structure of the cerebellum in human brain and mention its functions.
Answer: Cerebellum is located at the base of brain. It is the part of hind brain, present near the spinal cord.
Functions of cerebellum : It maintains the body posture and balancing of the body. It has sensation in body movements.
4) Mention the three functions of spinal cord.
Answer: The functions of spinal cord are as follows :
(a) Autonomic function: It controls the blood pressure and body temperature.
(b) Motor functions : It controls the voluntary actions.
(c) Sensory functions : It regulates the sensation.
5) With the help of a suitable example describe reflex action.
Answer: In reflex action, peripheral nervous system and spinal cord are involved. There is no role of brain. Reflex action can be defined as a sudden response to any type of external or internal stimulus. The example of reflex action includes the touching the hot surface or biting by the mosquito, the person immediately gives action against that stimulus.
6) Briefly differentiate between the following by giving examples:
(a) Voluntary and involuntary actions.
(b) Inborn and acquired reflexes.
Answer:
Voluntary actions | Involuntary actions |
The actions which are under person’s control. | The actions which are not under the person’s control. |
It is controlled by fore brain. | It is controlled by hind brain. |
For example : Riding a bike | For example : Blinking the eyes. |
Inborn reflexes | acquired reflexes |
They are involuntary actions and cannot be learned. | They are voluntary actions and can be learned from surrounding. |
These are slow process. | These are fast process. |
Present from the birth. | They can be learned from experience. |