ICSE-X Biology Chap 7-9

INDEX
Ch-wise Q's & Answers
Ch. 7 Human Circulatory System
Ch. 8 The Excretory System
Ch. 9 The Nervous System
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7 Human
Circulatory
System
Blood plays the major role in circulation. Every day, blood donors assist patients of all ages,
including accident and burn victims, heart surgery , organ transplant patients, and cancer
patients. However, many patients continue to die or su! er unnecessarily as a result of a lack
ofaccess to safe blood transfusion.
Chapter Notes
Circulatory System and Its Types Blood Vessels
Blood Human Heart
ABO Blood Group and Rh Factor Hepatic Portal System
Tissue Fluid
TOPIC 1
CIRCULATORY SYSTEM AND ITS TYPES

All living organisms including humans have specialised systems to transport
nutrients and other necessary materials to the cell and wastes away from the
cell. The transportation of nutrients, gases, wastes and other substances from
one part of our body to the other part, is carried out by blood, and is termed as
circulation. The organs, which are responsible for the flow of blood and lymph
through various parts of the body, constitute the circulatory system.
The circulatory system is one of the most important systems of the body. It
ensures the exchange of substances between cells of the body and external
environment and transports them from one part to another.
For circulation:
(1) Simple organisms like sponges, coelenterates etc., use water from their
surroundings.
(2) Complex organisms, like humans use body fluids (blood and lymph).
Example 1. What is the medium for transport in the human body?
Ans. Body fluids are the medium of transport in the human body. These fluids
can pick up substances and distribute them to various parts of the body.
Types of circulatory system
The circulatory system can either be open or closed, depending on whether
the blood flows freely in a cavity or is contained in vessels.
(1) A closed circulatory system is found in all vertebrates and some invertebrates.
It circulates blood unidirectionally from the heart, around the body, and
back to the heart.
(2) An open circulatory system is found in arthropods, pumps blood into a
cavity called a hemocoel where it surrounds the organs and then returns to
the heart(s) through ostia (openings).
Humans have a closed circulatory system. Blood pumped by the heart always
flows through a closed network of blood vessels. It consists of blood vascular
system and lymphatic system.
Blood vascular system
(1) Blood- The Circulating Fluid
(a) Red blood cells (RBCs)
(b) White blood cells (WBCs)
(c) Platelets
(2) Blood Vessels- The connecting tubes
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(a) Arteries
(b) Veins
(c) Capillaries
(3) Central Pumping Organ: The Heart
Important
 William Harvey was the first to propose the complete theory of the circulation
of blood in 1628. According to him, blood was pumped out of the heart and into
the tissues through one type of vessel and back to the heart through another
type of vessel. The blood, in other words, moved in a closed cycle through the
body.
William Harvey
Example 2. State any three points of differences between open and closed
system of circulation.
Ans. Differences between open and closed system of circulation are:
Open system Closed system
In this system, blood is pumped by In this system, blood is pumped
the heart, through large vessels, into by the heart, through a closed
open spaces or body cavities called network of vessels.
sinuses.
The body tissues are in direct contact The body tissues are not in direct
with blood. contact with blood.
Blood flows at low pressure. Hence, it Blood flows at high pressure.
is a slower and less efficient system Hence, it is a faster and more
of circulation. efficient system of circulation.
The flow of blood is not regulated by The flow of blood can be
valves. regulated by valves.
This system is present in arthropods This system is present in annelids,
and molluscs. echinoderms, and vertebrates.
Human Circulatory System 3

..
.

OBJECTIVE Type Questions
Multiple Choice Questions
[ 1 mark ]
1. The mineral ion needed for the formation of blood clot is:
(a) Potassium (b) Sodium
(c) Calcium (d) Iron [ICSE 2016]
Ans. (c) Calcium
[Marking Scheme]
Explanation: Calcium ions are necessary for the coagulation of blood.
Thrombin enzyme combines with calcium ion to form fibrin clot, which
coagulate the blood.
What Examiners Say
 Most candidates answered correctly.
2. In which of the following vertebrate group's heart does not pump
oxygenated blood to different parts of the body?
(a)Pisces and Amphibians
(b)Amphibians and Reptiles
(c) Amphibians only
(d)Pisces only [Diksha]
Ans. (d) Pisces only
Explanation: Fishes have a two-chambered heart which transports

deoxygenated blood to gills but doesn’t transport oxygenated blood to
different parts of the body.
SUBJECTIVE Type Questions

Fill in The Blanks
[ 1 mark]
3. The blood vessel that begins and ends in capillaries is the ............... .
[ICSE 2011]
Ans. Hepatic portal vein
Explanation: The hepatic portal vein is a blood vessel that moves blood


from the spleen, gall bladder, pancreas, and gastrointestinal tract to the
liver.
Related Theory
 Hepatic portal vein carries the nutrient-rich blood to the liver which is
further processed there and returned back to the heart via inferior vena
cava.
Find Relationship
[ 1 mark ]
4. Foetus: Amnion:: Heart: ............... . [ICSE 2017]
Ans. Pericardium
[Marking Scheme]
Explanation: Pericardium is a double-walled sac that encloses the heart

and the big vessels. It prevents the heart from external jerks and over-
expanding when blood volume increases.
What Examiners Say
 Most candidates wrote the correct relationship between the terms.
Related Theory
 The pericardium acts as mechanical protection for the heart and big
vessels, and a lubrication to reduce friction between the heart and the
surrounding structures.
State True/False
[ 1 mark ]
5. Leucocytes show amoeboid movement.
Ans. True
Explanation: Macrophages and leucocytes present in blood exhibits

amoeboid movement. They have the ability to reach the interstitial fluid
by squeezing through the thin walls of blood vessels.
Related Theory
 White blood cells (also called leukocytes) are the colourless and complete
cell. These are found in blood and are bigger than RBCs but their numbers
are less. They are formed in red bone marrow, spleen, thymus and lymph

nodes from myelocytes. They show amoeboid movement and these are
destroyed outside blood vessels and the process by which they come out
is known as diapedesis.
Match the Columns
[ 1 mark for each matching]
6. Column (I) Column (II)
(A) SA Node (i)0.8 seconds
(B) Muscle fibres located in heart (ii) Pacemaker
(C) Cardiac cycle (iii)Cardiac muscle
(D)Heart muscle (iv)Purkinje fibres
Ans. (A)-(ii), (B)-(iv), (C)-(i), (D)-(iii)
Name the Following
[ 1 mark ]
7. The smallest common blood vessel formed by the union of capillaries.
Ans. Venule
Related Theory
 Veins begin as tiny vessels called venules and get gradually larger as they
reach near your heart. Venules receive blood from capillaries.
8. The compound formed when hemoglobin combines with carbon
dioxide in blood.
[ICSE 2019]
Ans. Carbamino-haemoglobin/HbCO2
[Marking Scheme]
What Examiners Say

 Incorrect answer was written by most candidates. They wrote
carboxyhaemoglobin instead of carbaminohaemoglobin.
Caution
 Understand the difference between carboxyhaemo-globin and
carbaminohaemoglobin clearly. Keep in mind, carbaminohemoglobin is
hemoglobin + carbon dioxide and carboxyhemoglobin is hemoglobin +
carbon monoxide.

Give Technical Terms
[ 1 mark]
9. The vein that carries oxygenated blood.
[ICSE 2015]
Ans. Pulmonary vein
[Marking Scheme]
What Examiners Say
 This question was answered correctly by most candidates.
Caution
 Keep in mind, the major blood vessels connected to your heart are the
aorta, the superior vena cava, the inferior vena cava, the pulmonary artery
(which takes oxygen-poor blood from the heart to the lungs where it is
oxygenated), the pulmonary veins (which bring oxygen-rich blood from
the lungs to the heart), and the coronary arteries (which supply blood to
the heart muscle).
State the Location

[ 1 mark ]
10. Tricuspid valve [ICSE 2014]
Ans.
etween (operative) right auricle and right ventricle./at right atrio
B
ventricular aperture.
[Marking Scheme]
What Examiners Say
 Confusion regarding the right and left side of the heart was evident in the
answers. Most candidates did not specify the location as ‘between right
auricle and right ventricle’ instead wrote ‘on the right side of heart’.
State the Function

[ 1 mark ]
11. Coronary artery. [ICSE 2011]
Ans. Coronary artery function as carrier of oxygenated blood to the heart
muscle.
Related Theory
 The coronary arteries wrap around the outside of the heart. Small branches

dive into the heart muscle to bring it blood.
Differentiate
[ 1 mark ]
Differentiate between the following pairs on the basis of what is given in
brackets:
12. LUBB and DUP (names of the valves whose closure produce the sound).
[ICSE 2016]
Ans. LUBB—Bicuspid and tricuspid valve.
DUP—Semilunar valves.[Marking Scheme]
What Examiners Say

 A lot of confusion prevailed among the candidates regarding the valves in
the heart and the sound produced during their closure. Most mentioned
only one valve for each sound and lost marks. However, a few candidates
answered correctly.
Caution
 Structure and working of human heart should be understood with
reference to opening and closure of valves and the sounds of LUBB and
DUP.
Give Reason
[ 1 or 2 marks ]
13. Carbon monoxide is dangerous when inhaled.
[ICSE 2019, 14]
Ans. Hemoglobin has a strong affinity for carbon monoxide, forming a stable
compound carboxy haemoglobin. This cuts down the capacity of blood
to transport oxygen which may even lead to death. Therefore, carbon
monoxide may be dangerous when inhaled.
asily combines with haemoglobin to form carboxyhaemoglobin
E
which cuts off supply of oxygen to tissues.
[Marking Scheme]
What Examiners Say
 Most of the candidates were vague in their answers. Supply of oxygen to

tissues being cut off, was not mentioned by many candidates.
Assertion Reason Based Questions [A-R]

[ 2 marks ]
In each of the following questions, a statement of Assertion (A) is given
followed by a corresponding statement of Reason (R). Select the correct
answers to codes (a), (b), (c) or (d) as given below:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.
14. Assertion (A):An artificial pacemaker can replace the SA node of heart.
Reason (R):An artificial pacemaker is capable of stimulating the
heart electrically to maintain its beat.
Ans. (a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Explanation: The artificial pacemaker stimulates the heart electrically at
regular intervals to maintain its beats. Thus, it replaces the SA node as the
originator of the cardiac impulse.
Case Based MCQs

(Other Questions Type, for Extra Practice) [ 5 marks ]

Read the following passage and answer the questions that follows:
15. The heart is a muscular pump that serves two functions: (1) to collect
blood from the tissues of the body and pump it to the lungs and (2) to
collect blood from the lungs and pump it to all tissues of the body. The
human heart lies in the protective thorax, posterior to the sternum and
costal cartilages, and rests on the superior surface of the diaphragm. The
heart assumes an oblique position in the thorax, with two-thirds to the
left of midline. It occupies a space between the pleural cavities called the
middle mediastinum, defined as the space inside the pericardium, the
covering around the heart.

1
5
2
4 3
(A) Using the diagram, write the correct sequence of the letters which
represent the process of blood flow.
(B) Make a graphic representation of double circulation in the human
heart.
(C) What would happen if conducting tubes of circulatory system develops
a leak? How this could be avoided?
Ans. (A)In the given diagram of human heart, the parts marked as 1, 2, 3, 4 and
5 are aorta, left atrium, left ventricle, right ventricle and right atrium
respectively. Thus, the correct sequence of the letters which represent
the process of blood flow described in the question is 2, 3, 1, 5, 4.
(B)
Pulmonary artery Lungs Pulmonary vein
Dexoygenated blood Oxygenated blood
Right Pulmonary Circulation Left

ventricle atrium
Right Left
Systemic Circulation
atrium ventricle
Superior & Veins Tissues Arteries Aorta

Inferior
vena cavae
(C) Leakage will result in loss of blood from circulatory system, and loss
of efficiency of pumping system. It may sometimes result in death. To
avoid it, blood platelets releases thromboplastin. This helps in sealing
the place of injury through blood clotting.
Short Answer Type-I Questions [SA-I]

[ 2 marks ]
16. Explain Diapedesis. [ICSE 2014]

Ans. P
rocess of squeezing out of WBC/leucocytes through minute
walls of blood capillaries (operative)
[Marking Scheme]
What Examiners Say
 Most candidates lost marks for writing ‘oozing out’ instead of ‘squeezing
out of WBCs from capillaries’
Long Answer Type Questions [LA]

[ 10 marks ]
17. The diagram given below represents a section of the human heart.
Answer the questions that follow:
(A) Which parts of heart are in the diastolic phase? Give a reason to
support your answer.
(B) Label the parts numbered 1 and 2 in the diagram. What type of
blood flows through them?
(C) What causes the heart sounds ‘LUBB’ and ‘DUP’?
(D) Name the blood vessels that supply oxygenated blood to the heart
muscles.
(E) Draw neat labelled diagrams of a cross section of an artery and a
vein. [ICSE 2017]
Ans. (A) Ventricles are in diastolic phase as tricuspid and bicuspid valves are
open and semilunar valves are closed.
(B) (1)Pulmonary artery — Deoxygenated blood flows through them.
(2)Pulmonary veins — Oxygenated blood flows through them.
(C) The ‘LUBB’ sound is caused by closure of tricuspid and bicuspid valves
and ‘DUP’ sound is caused by closure of semilunar valve.
(D) Coronary arteries supply oxygenated blood to the heart muscles.

(E)
(A)Ventricles
Tricuspid and Bicuspid valves are open /
semilunar valves are closed.
(B)1. Pulmonary artery, Deoxygenated blood.
2. Pulmonary veins, Oxygenated blood.
(C)LUBB – Closure of Tricuspid and bicuspid
valves.
DUP – Closure of semilunar valves
(D)Coronary arteries
(E)Artery Vein
Difference in the size of lumen and thickness

of muscle layer
[Mod. Marking Scheme]
What Examiners Say
 (A)Most candidates identified the parts of the heart in diastolic phase but
many of them could not give a reason to support the answer.
 (B)Many candidates were confused in labeling the parts numbered 1 and
2 and the type of blood flowing in them.
 (C)The causes of, the heart sounds ‘LUBB’ and‘DUB’ was answered
correctly by most candidates.
 (D)Majority of the candidates named the blood vessels that supply
oxygenated blood to heart muscles correctly.
 (E)Several errors were noticed in drawing the cross section of an artery
and a vein, their labelling and the size of lumen.

Caution
 Learn the technical terms for contraction and relaxation of heart and
carefully understand their importance.
 Regular practise of diagrams showing cross-sections of artery, vein and
capillary to be done
 Structural differences between them to be stressed upon.
 Draw a simple sketch of the heart, to learn the right and left side of the
heart, position of valves and the blood vessels entering and leaving the
heart.

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8 The Excretory
System
Nothing is more aggravating and upsetting than discovering that your freshly washed or
painted car is covered in bird droppings. Bird droppings contain uric acid, which can easily
stain fabrics and eat through paints if left untreated (most commonly seen on vehicles).This is
howexcretion applies in ourday to day life.
Chapter Notes
Excretion and Excretory Organs Osmoregulation
Human Excretory System
Nephron
Urine Formation
Disorders of Excretory System
TOPIC 1
EXCRETION AND EXCRETORY ORGANS
The process of removing waste products produced in the cells of living organism
is called excretion. It is an essential process in all forms of the life. It involves
elimination of metabolic wastes like ammonia, urea, uric acid etc., from the
tissues. Thus, excretion is one of the major ways the body maintains homeostasis.
Example 1. What is homeostasis?
Ans. Homeostasis refers to the ability of the body to maintain a stable internal
environment despite changes in external conditions.
Excretory Organs
Every living organism generates waste in its body and has a mechanism to
expel it. In humans, the excretory system takes care of waste generation and
elimination. The excretory system is made up of numerous organs that work in
union to ensure that waste is effectively removed from our body.
Excretion in humans is brought about by the following organs:
Kidney
These are the primary excretory organs of the excretion of liquid waste products
in the form of urine.
Kidney
A pair of kidney
Skin
The skin performs its excretory function via the sweat glands and sebaceous
glands. Sweat gland produces sweat that contains salt, excess oils, water, and
other unnecessary substances which are then excreted out of the body through
small pores. Similarly, sebaceous gland helps in excretion of sebum which
consists of lipids, fatty acid etc.

Sebaceous gland
Pore
Hair
follicle Eccrine
sweat
Apocrine glands
sweat
glands
Sweat and sebaceous glands

Important
 Sweat glands are primarily concerned with cooling of body.
Lungs
The lungs are very important excretory organs as they expel carbon dioxide
from the body via exhalation. The lungs use cells known as alveoli to remove
the carbon dioxide from our blood.
Lungs
A pair of Lungs
Liver
Liver helps in excretion of various waste substances in the body. It converts toxic
ammonia into urea, a harmless fluid. It does not directly eliminate excretory
substances.
Liver
Liver
The Excretory System 3

Example 2. Name two substances found both in urine and sweat.
Ans. Urea, uric acid and water. (Any two)
Example 3. What is the difference between excretion and secretion? Are
they same?
Ans. No, they are not same. Excretion is the passing out of substances that have
..
no further use in the body. E.g., urine.
Secretion is giving out of some substances that have some utility for the
body. E.g., tears, sweat, saliva, milk, insulin etc.

[ 1 mark ]
1. The main nitrogenous waste formed in the human body:
(a) uric acid (b) urea
(c) ammonia (d) creatinine [ICSE 2022]
Ans. (b)urea
Explanation: The major nitrogenous waste produced in humans is urea. It
is removed from the body by the kidneys.
2. The nephrons discharge their urine at the:
(a) urinary bladder
(b) urethra
(c) renal pelvis
(d) renal pyramid [ICSE 2016]
Ans. (c) renal pelvis [Marking Scheme]
Explanation: The urine is formed in the tubules of the kidney. This urine is
filtered in the cavities of the kidney, called the calyces. The urine from the
calyces enters the renal pelvis, which is the region where urine is discharged.
The urine from the renal pelvis is then transferred to the ureters.
What Examiners Say
 Most candidates made the right choice.
Fill in The Blanks

[ 1 mark ]
3. Ureter is the connecting link between .............. and .............. .
Ans. kidney, urinary bladder
Explanation: The ureter is a tube that carries urine from the kidney to the
urinary bladder. There are two ureters one attached to each kidney.
Related Theory
 The muscular layers are responsible for the peristaltic activity that the
ureter uses to move the urine from the kidneys to the bladder.

State True/False
[ 1 mark ]
4. Urethra carries urine from kidney to the urinary bladder. [ICSE 2011]
Ans. False
Explanation: Ureter carries urine from kidney to the urinary bladder.
Name the Following

[ 1 mark]
5. The structural and functional unit of kidney. [HOT ] [ ICSE 2011]
Ans. Nephron
6. The duct which transports urine from the kidney to the urinary bladder.
[ICSE 2020]
Ans. Ureter
Related Theory
 Contractions of the smooth muscle push urine down through the ureters
and into the bladder.
Give Technical Term

[ 1 mark]
7. Pigment providing colour to urine. [ICSE 2016 ]
Ans.Urochrome
Related Theory
 Urochrome is derived from breakdown of heme, which is deposited in blood
and then is excreted by kidney with urine. It gives yellow colour to urine.
State the Function

[ 1 mark ]
8.Afferent nerve. [ICSE 2011]
Ans. Transmits impulses from receptor organ to spinal cord
Differentiate
[ 1 mark ]
brackets:
9. Ureter and Urethra (Function) [ICSE 2018]
Ans.

Ureter: Conducts urine from the kidney to the urinary bladder/
transports urine from Renal pelvis to bladder.
Urethra: Expulsion of urine from the urinary bladder/eliminates
urine from the body/expels urine and semen.
[Marking Scheme]
What Examiners Say
 Most of the candidates answered correctly.
Caution
 Students are advised to write the words 'from' and 'to' when structures are
involved in transport of certain substances.
Give Reasons
[ 1 or 2 marks ]
10. Urine is slightly thicker in summer than in winter. [HOT ] [ICSE 2011]
Ans. In summer, body loses large amount of water through sweating. Blood
in order to maintain its osmotic concentration reabsorbs large amount of
water from the tubules and put back in blood, thus, less water is left to be
released as urine. This makes urine thicker in summer whereas in winter,
due to less reabsorption, urine is thinner.

[ 2 marks ]
11.Assertion (A):Excretion is a passive process.

Reason (R): It is the process of movement of waste materials out of the
body.
Explanation: Excretion is the process of removing unnecessary and waste
materials out of the body. As it is excreting materials out of the body, it is

a passive process.
Related Theory
 Secretion is an active process by which molecules are transported from
one place to other.
Short Answer Type-II Questions [SA-II]

[ 3 marks ]
12. Mention the three major steps involved in the production of urine.
[ICSE 2022]
Ans. The three major steps involved in the formation of urine are:
(1) Glomerular filtration: Blood is filtered in the glomerulus and filtrate is
formed.
(2) Tubular reabsorption: When the glomerular filtrate comes to the tubule
part of the nephron, the essential components like glucose, ions, water,
etc., are reabsorbed.
(3) Tubular secretion: Various secretions like creatinine, uric acid, etc., are
secreted in it to form urine.

[ 10 marks ]
13. The figure given below shows a part of a nephron. Answer the questions
that follows:
1 2
(A) In which region of the kidney is the above structure present?

(B) Label the parts numbered 1 to 4.
(C) What is the technical term for the process that occurs in part 3?

Define the process.
(D) Why is fluid X not called urine? Justify your answer.
(E) Draw a neat, labelled diagram of the urinary system of man.
[Mod. ICSE 2020]
Ans. (A) Nephrons are located in the cortex of the kidney.
(B) Part 1 – Afferent arteriole
Part 2 – Efferent arteriole
Part 3 – Glomerulus
Part 4 – Bowman‘s Capsule
(C) The technical term for the process that occurs in part 3 i.e., glomerulus
is ultrafiltration.
The removal of fluid from a patient is known as ultrafiltration, and it is
one of the kidney functions that dialysis treatment replaces. Due to a
driving pressure, fluid passes through a semipermeable membrane (a
membrane that allows some substances to pass through but not others).
(D) Fluid X is called filtrate and not urine. The liquid X entering the renal tubule is
extremely dilute and consists of useful materials namely glucose and some
salts like sodium. When the glomerular filtrate passes down the tubule,
selective reabsorption of water along with useful substances take place.
The liquid that passes into the collecting tubules is termed as final urine.
(E)
I
Urethra
Urinary System of Man

Caution
 Students should carefully learn the structure and significance of nephron.
Lay stress on reason for ultrafiltration in urine formation.

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9 The Nervous
System
As you drive into a parking lot, a skateboarder suddenly ies in front of your car across your
eld of vision. You see the skateboarder in the nick of time and react immediately.You slam on
the brakes and steer sharply to the right — all in the blink of an eye. You avoid a collision, but
just barely. You're shaken up but thankful that no one was hurt. How did you respond so
quickly? Such rapid responses are controlled by your nervous system. In the example above,
your eyes detected the skateboarder, the information travelled to your brain, and your brain
instructed your body to act so as to avoid a collision. This complex system is the command
center for your body. Originating from your brain, it guides almost everything you do, think,
say or feel.
Chapter Notes
Neuron and Its Structure
Human Nervous System
Nerves
TOPIC 1
NEURON AND ITS STRUCTURE
Parts of Neuron
The organ system in an animal that serves to coordinate and control the
functioning of all other organ systems in the body is known as nervous system.
It provides rapid coordination among the organs of the body. This coordination
is in the form of electric impulse and is quick and short lived. Nervous system of
animals is formed by nervous tissue which is composed of neuron and neuroglia
cells. Neuron is the structural and functional unit of neural system. While neurons
may differ according to role (sensory, relay or motor), most share three basic
components: Cell body, Dendrone and Axon.
Cell Body (cyton)
It contains nucleus, mitochondria, other cell organelles and Nissl’s granules
(granular bodies). It is mainly concerned with the maintenance and growth. It
contains a well defined nucleus, surrounded by granular cytoplasm.
Important
 Cyton has all the cell organelles like other cells, except centrosome.
Dendron
They are short fibres projecting from the cyton. Their sub-branches (dendrites)
transmit impulses towards the cyton. They also contain Nissl’s granules.
Important
 Dendrites are also called Dendron or tree branch of nerve cell.
Axon
Axon is a long fibre which transmits impulses away from the cell body. The
branching of axon is called axonite. Each axonite ends as a bulb-like structure
called synaptic knob containing neurotransmitters. Axon may or may not be
covered by a fatty sheath called myelin sheath. The myelin sheath improves the
conduction speed of electrical impulses along the axon, but require additional
space and energy. This covering of myelin is missing at intervals. These gaps on
the sheath are known as nodes of Ranvier.

Important
 The chemical released as the nerve impulse reaches the terminal end of an
axon is acetylcholine.
Synapse
Synapse is a functional junction between axon of one neuron and dendrite of
next neuron. It is separated by a small gap known as synaptic cleft.
Important
 A synapse in the muscle fiber is also known as neuromuscular junction.
Dendrite Axon terminal
button
Soma (Cell's body)
Nucleus
Axon
Myelin sheath
Structure of neuron
Example 1. State differences between dendrite and axon.
Ans. Differences between Dendrite and Axon are:
Dendrite Axon
It is a small projection arising from Axon is a single, long projection
the neuron that conducts the nerve that conducts the nerve impulse
impulse toward the cell body. away from cell body to the next
neuron.
Nissl’s granules are present. Nissl’s granules are absent.
Dendrites are always non- Axons can be myelinated or non-

myelinated. myelinated.
Example 2. Define the following:
(A) Neurotransmitters
(B) Synaptic knobs
Ans. (A)Neurotransmitters: They are often referred to as the body’s chemical
messengers. Their job is to carry chemical signals (“messages”) from
one neuron (nerve cell) to the next target cell. The next target cell can
be another nerve cell, a muscle cell or a gland.
(B)Synaptic knobs: A synaptic knob is a bulb-like structure present at the
The Nervous System 3

tip of the axon. Synaptic vesicles carrying neurotransmitters are found
in synaptic knobs.
Arrangement of Neurons
Neurons are arranged end to end forming a chain. This helps in continuous
transmission of impulses. Each neuron receives an impulse through its dendrites
and transmits it to the next neuron in a sequence through its axon.
When a neuron is suitably stimulated, an electrical disturbance is generated
which is transmitted from the dendrite to the cell body and then to the axon.
From the axon, the impulse travels to its end where the electrical impulse sets
off the release of some more chemicals. These chemicals cross the synapse and
start a similar electrical impulse in the dendrite of the next neuron. In this way,
impulses are transmitted from one neuron to another to finally reach the brain.
..
Important term
 Impulse is a wave of irritability (electrical disturbance that sweeps over the
nerve cell).

[ 1 mark ]
1. The ventral root ganglion of the spinal cord contains cell bodies of the
.............. .
(a) motor neuron
(b) sensory neuron
(c) intermediate neuron
(d) associated neuron [ICSE 2013]
Ans. (a) motor neuron
Explanation: The ventral root ganglion of the spinal cord contains effective
fibres, arising from the motor neuron and the cell bodies of them occupy
the anterior or the ventral gray horns of spinal cord.
Related Theory
 The motor neurons carry impulses back to the effector region organ or
gland after being processed in the spinal cord or brain.
2. In synapse, chemical signal is transmitted from:

(a) dendritic end of one neuron to axonal end of another neuron.
(b) axon to cell body of the same neuron
(c) cell body to axonal end of the same neuron
(d) axonal end of one neuron to dendritic end of another neuron.
[Diksha]
Ans. (d)axonal end of one neuron to dendritic end of another neuron.
Explanation: Dendritic ends are numerous, and pick up signals from other
neurons or sensory organs, send them towards the cell body, and this in
turn continues down the axonal membrane. The axon, on the other hand,
directs the signal towards a particular neuron or group of neurons.
Related Theory
 Impulse transmission in a neuron is unidirectional. Each part of the neuronal
cell is designed to make sure the message goes in the forward direction
and across the chemical synapse between two nerve cells.

Fill in The Blanks
[ 1 mark ]
3. There are 31 pairs of spinal nerves, emerging out of the .............. .
Ans. spinal cord
Explanation: The spinal cord is located in the vertebral foramen and is
made up of 31 segments: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1
coccygeal. A pair of spinal nerves leaves each segment of the spinal cord.
Related Theory
 A spinal nerve is a mixed nerve, which carries motor, sensory and autonomic
signals between the spinal cord and the body.
State True / False

[ 1 mark ]
4. Nerves of peripheral nervous system arise from the spinal cord and
from the brain.
Ans. True
Explanation: The peripheral nervous system (PNS) is the part of the nervous
system, that consists of the nerves and ganglia outside of the brain and
spinal cord.
Related Theory
 The main function of the PNS is to connect the central nervous system (CNS)
to the limbs and organs. It serve as a communication relay going back and
forth between the brain and the extremities.
Match the Columns

[ 1 mark for each matching ]
5. Column (I) Column (II)

(A) Nerve impulse (i)Chemical involved in the
transmission of impulses at
synapses.

(B) Synaptic cleft (ii) Gap between the presynaptic
and post synaptic neurons
(C) Neurotrans- (iii)An electric wave like response

mitters of a neuron to a stimulation
Ans. (A)-(iii), (B)-(i), (C)-(ii)
Name the Following

[ 1 mark ]
6. The part of the brain associated with the memory. [ICSE 2020]
Ans. Cerebrum
7. The part of the brain that carries impulses from one hemisphere of the
cerebellum to the other. [HOT ] [ICSE 2016]
Ans. Pons [Mark Scheme]
What Examiners Say
 Only a few students answered correctly. Majority were confused with
corpus collosum and pons.
Caution
 While learning about the brain, lay stress on the location and function of
Pons and corpus callosum.
Give Technical Terms

[ 1 mark ]
8. The structure which joins the two cerebral hemisphere in man.
Ans. Corpus callosum
Related Theory
 The cerebral hemispheres are separated by a deep groove, the longitudinal
cerebral fissure. At the base of this fissure lies a thick bundle of nerve fibres,
called the corpus callosum, which provides a communication link between
the hemispheres.

State the Function
[ 1 mark]
9. Cerebrospinal fluid. [ICSE 2014]
Ans. Protects the brain from external mechanical injuries/distrib-

utes neuroen docrine hormones/nutrients.
[Marking Scheme]
What Examiners Say
 The concept of protecting brain and spinal cord from mechanical injuries
was missing. Instead most candidates wrote shock absorber as the function.
Identify the Odd One

[ 1 mark]
In each set given below, one term is odd. Identify the odd one and name the
category to which the remaining three belong.
10. Dendrites, Medullary Sheath, Axon, Spinal cord. [ICSE 2018]
Ans. Odd term: Spinal cord
Category: Parts of neuron.
Explanation: The spinal cord is a long thin, tubular structure made up of

nervous tissue.
Spinal cord : parts of neuron/nerve cell
[Marking Scheme]
What Examiners Say
 Most of the candidates chose the ODD one out from the given terms
correctly and named the category to which the others belong appropriately.
Briefly Explain
[ 1 mark ]
11. Synapse [HOT ] [ICSE 2016, 12]
Ans. It is the point of contact between the terminal branches of
axon with the dendrites of the next neuron.
[Marking Scheme]
What Examiners Say
 Majority of candidates were able to write the correct explanation. A few

were not specific and wrote an incomplete explanation e.g., point of contact
between two neurons.
Differentiate
[ 1 mark ]
brackets:
12. Cerebrum and Spinal cord. (Arrangement of nerve cells)[HOT ] [ICSE
2013]
Ans. Cerebrum: Cytons are in the inner grey matter. Axons are in
the inner white matter.
Spinal cord: Cyton are in the inner grey matter; axons are in
the outer white matter.
[Marking Scheme]
What Examiners Say
 Majority of candidates failed to write the arrangement of nerve cells in the
brain and spinal cord.
 They explained it in terms of grey and white matter but did not specify
which matter lies outside and which one inside.
Caution
 While studying structure of brain and spinal cord, the arrangement of cytons
and axons in the brain and spinal cord to be given importance.

[ 2 marks ]
13. Assertion (A):Transmission of the nerve impulse across a synapse

occurs by neurotransmitters.
Reason (R):Transmission across a synapse usually requires
neurotransmitters because there is synaptic cleft that
separates one neuron from another.
Explanation: Transmission of the nerve impulse across a synapse is
accomplished by neurotransmitters as there is synaptic cleft that separates
one neuron from one another.
Short Answer Type-II Questions [SA-II]
[ 3 marks ]
14. Name the three membranous covering of the human brain.

[ICSE 2022]
Ans. Dura mater (outermost), arachnoid (middle layer) and pia mater
(innermost).
[ 10 marks]
15. The diagram given below shows the internal structure of a spinal
cord depicting a phenomenon. Study the diagram and answer the
questions:
3
(A)Name the phenomenon that is depicted in the diagram. Define the

phenomenon.
(B)Give the technical term for the point of contact between the two
nerve cells.
(C)Name the parts numbered 1, 2 and 3.
(D)How does the arrangement of neurons in the spinal cord differ from
that of the brain?
(E)Mention two ways by which the spinal cord is protected in our body.
[ICSE 2018]

Ans. (A)The phenomenon depicted in the diagram is reflex action.
A reflex action is an involuntary and instantaneous movement in
response to a stimulus.
(B) Synapse
(C) Part 1: Sensory neuron
Part 2: Motor neuron
Part 3: Grey matter.
(D)In the spinal cord, cytons are located in the inner grey matter and axons
in the outer white matter whereas in the brain, cytons are located in the
outer grey matter and axons in the inner white matter.
(E) The spinal cord, in our body, is protected by: (1) Meninges
(2) Vertebral column.
(A) Reflex action,/ Simple reflex / Reflex act It is an automatic
[Spontaneous, quick] involuntary response to a stimulus.
(B) Synapse
(C) 1. Sensory neuron /afferent fibre / Axon of sensory neuron.
2. Motor neuron / efferent fibre / Axon of motor neuron.
3. Grey matter / Central canal
(D) Spinal Cord—Cytons in the inner grey matter and axons in the outer
white matter/Cytons are inside & Axons are outside.
Brain—Cytons in the outer grey matter and axons in the inner white
matter./Cytons inside, Axons outside.
(E) Meninges, Cerebrospinal fluid, Vertebral column/backbone.
[Marking Scheme]
What Examiners Say
 (A) Most candidates named the phenomenon depicted and wrote the
definition correctly.
 (B) Majority of the candidates did not know the difference between synapse
and synaptic cleft, nerve and neuron.
 (C) Most of the candidates answered correctly. Some candidates, however,
labelled neuron as nerve.
 (D) Many candidates wrote the location of grey and white matter instead
of Cytons and Axons.
 (E) Most candidates wrote two ways by which the spinal cord is protected

in our body, correctly.
Caution
 Students should practice drawing the nervous pathway of Reflex action
and label all the parts.
 Students should be able to identify the neuron involved in a Reflex action
and the location of Synapse.
 Lay emphasise on the arrangement of Cytons and Axons in the Brain and
in the Spinal cord.

ANONDEE SAHA
(99.60%), ICSE Topper 2023
”

(with explanations)
(with explanations)
Important Poins
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INDEX

Ch-wise Q's & Answers

Ch. 7 Human Circulatory System

Ch. 8 The Excretory System

Ch. 9 The Nervous System

*Click above to jump to the respective Chapters of this pdf

CIRCULATORY SYSTEM AND ITS TYPES

2 ICSE Biology Class X

Click here to Access complete Educart book of Biology (Special Discount)

Human Circulatory System 3

4 ICSE Biology Class X

SUBJECTIVE Type Questions

Human Circulatory System 5

6 ICSE Biology Class X

What Examiners Say

Human Circulatory System 7

State the Location

State the Function

8 ICSE Biology Class X

What Examiners Say

Human Circulatory System 9

Assertion Reason Based Questions [A-R]

Case Based MCQs

10 ICSE Biology Class X

Dexoygenated blood Oxygenated blood

Right Pulmonary Circulation Left

Superior & Veins Tissues Arteries Aorta

Short Answer Type-I Questions [SA-I]

Human Circulatory System 11

Long Answer Type Questions [LA]

12 ICSE Biology Class X

Difference in the size of lumen and thickness

Human Circulatory System 13

14 ICSE Biology Class X

Ch-wise Past 10 Years Q's

These books are the best reference books every

I just love Educart books of ICSE. They know exactly

2 ICSE Biology Class X

Sweat and sebaceous glands

The Excretory System 3

4 ICSE Biology Class X

SUBJECTIVE Type Questions

Fill in The Blanks

The Excretory System 5

Name the Following

Give Technical Term

State the Function

6 ICSE Biology Class X

Assertion Reason Based Questions [A-R]

11.Assertion (A):Excretion is a passive process.

The Excretory System 7

Short Answer Type-II Questions [SA-II]

Long Answer Type Questions [LA]

(A) In which region of the kidney is the above structure present?

8 ICSE Biology Class X

Urinary System of Man

The Excretory System 9

Ch-wise Past 10 Years Q's

These books are the best reference books every

I just love Educart books of ICSE. They know exactly

Difference in the size of lumen and thickness