Dear Students/Parents We at 'Apex Institute' are committed to provide our students best quality education with ethics. Moving in this direction, we have decided that unlike other expensive and 5star facility type institutes who are huge investors and advertisers, we shall not invest huge amount of money in advertisements. It shall rather be invested on the betterment, enhancement of quality and resources at our center. We are just looking forward to have 'word-of-mouth' publicity instead. Because, there is only a satisfied student and his/her parents can judge an institute's quality and it's faculty members coaching. Those coaching institutes, who are investing highly on advertisements, are actually, wasting their money on it, in a sense. Rather, the money should be invested on highly experienced faculty members and on teaching gears. We all at 'Apex' are taking this initiative to improve the quality of education along-with each student's development and growth. Committed to excellence... With best wishes. S . Iqbal ( Motivator & Mentor)

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2. The heart is one of the most important organs of human body. It is a muscular organ responsible for pumping blood through the
blood vessels by repeated, rhythmic contractions.The term cardiac (as in cardiology) means “related to the heart” and comes from
the Greek word kardia, for “heart.”
The heart pumps the blood, which carries all the vital materials that help in various body functions. For example, the brain requires
oxygen and glucose, which, if not received continuously, will cause it to loose consciousness. Muscles need oxygen, glucose and
amino acids, as well as the proper ratio of sodium, calcium and potassium salts in order to contract normally. The glands need
sufficient supply of raw materials from which they manufacture the specific secretions. If the heart ever ceases to pump blood, the
body begins to shut down and after a very short period of time death occurs.
All vertebrates including humans have a single heart.
Location of Heart
In the human body, the heart is usually situated in the middle of the thorax with the largest part of the heart slightly offset to the
left (although sometimes it is on the right, underneath the breastbone). The heart is usually felt to be on the left side because the
ventricle of left heart is stronger (it pumps to all body parts). The left lung is smaller than the right lung because the heart occupies
more of the left hemithorax.
The heart is located in the mediastinum, the central subdivision of the thoracic cavity. The heart apex is the blunt point situated in
an inferior (pointing down and left) direction. A stethoscope can be placed directly over the apex so that the beats can be counted.
It is located posterior to the 5th intercostal space just median of the left mid-clavicular line.
HUMAN HEART
The content for PMT Biology is
very vast and does not allow
students to engage in inquiry
and develop meaningful
knowledge. An essential topic
for PMT is presented here to
enable students grasp the
topic, analyse the type of
questions appearing in PMTs,
and score HIGH.

3. Mediastinum
It is the space between the two lungs, i.e., the central subdivision of thoracic cavity. It extends from the sternum in front to
the vertebral column behind and contains all the thoracic viscera except lungs. It is flanked on either side by the right and left
pulmonary cavities, which house the lungs.
Structure of Heart
The human heart is a muscular organ of a somewhat conical or pyramidal form with upper broad part, the base and lower narrow,
the apex.The apex is slightly directed to the left.
The heart has actually two separate pumps: a right one that pumps blood through the lungs, and a left one that pumps blood
through the peripheral organs. In turn, each of these is a pulsatile two-chambered part composed of an atrium and a ventricle.
Each atrium is a weak primer pump for the ventricle, helping to move blood into the ventricle. The ventricles then supply the main
pumping force that propels the blood to whole body.
An average adult heart is about 12 cm. Its weight varies in males from 280-340 g (average 300 g) and in females from 230-280 g
(average 250 g).Weight of the heart is said to be about 0.45% of body weight in males and 0.40% in females.
The heart is enclosed in a fibrous sac known as the pericardium and is surrounded by the lungs. The pericardium is made up of 2
layers, parietal and visceral pericardium. In between the two layers, a space called pericardial cavity is present which is filled
with a pericardial fluid. The pericardium protects the heart from shocks and mechanical injuries and also allows free movements
of heart.
embryonic origin of heart
The mammalian heart is derived from embryonic mesoderm that differentiates after gastrulation into mesothelium, endothelium,
and myocardium. Mesothelial pericardium forms the inner lining of the heart. The outer lining of the heart, lymphatic and blood
vessels develop from endothelium. Myocardium develops into heart muscle.
external structure
Human heart is 4 chambered,consisting of two atria and two ventricles. The left and right atria are separated externally by a shallow
vertical interatrial groove. The atria are demarcated externally from the ventricles by an oblique groove called atrioventricular
sulcus. There are also present coronary sulcus, anterior interventricular sulcus and posterior interventricular sulcus.
These have coronary arteries, through which the heart receives blood.
The left atrium is smaller than the right atrium. Each atrium has an appendage called an auricle which increases its surface area.The
superior vena cava, inferior vena cava and coronary sinus open into right atrium.The left atrium receives four openings of pulmonary
veins.
Ventricles are thick walled.The left ventricle is longer and narrower than the right ventricle. Its walls are about three times thicker
than the right ventricle. The pulmonary trunk arises from the right ventricle. It divides into left and right pulmonary arteries that
carry deoxygenated blood to the lungs.The aorta arises from the left ventricle.
internal structure
atrium
The two thin walled atria are separated by interatrial septum. The right atrium receives blood from superior vena cava, inferior
vena cava and coronary sinus.The superior vena cava, carries blood from upper body and the inferior vena cava carries blood
from the lower body region. Coronary sinus carries blood from the heart itself.
The right atrium receives deoxygenated blood. The left atrium receives oxygenated blood from the lungs through two pairs
of pulmonary veins. An oval depression known as fossa ovalis is present in the right atrium near interatrial septum. It marks the
position of an opening between two atria in the foetus i.e. foramen ovale but in the adult it persists only as a depression.
Ventricle
The two ventricles are separated from each other by a thick, curved partition, the interventricular septum.The inner surface of the
ventricles is raised into a network of low, muscular ridge called the columnae carneae, or trabeculae carneae, and a few large,
conical, muscular elevations termed the musculi papillares, or papillary muscles. A prominent muscular trabeculum, called the
moderator band, extends from the interventricular septum to the anterior papillary muscle in the right ventricle.

4. The left and right pulmonary arteries carry deoxygenated blood to the lungs.The aorta arising from the left ventricle, is divisible into
the ascending aorta, arch of aorta and descending aorta. The right and left coronary arteries arise from the ascending
aorta.The arch of the aorta (also called aortic arch) gives rise to the brachiocephalic artery (innominate artery), left common
carotid artery and left subclavian artery. The descending aorta runs through the thorax and abdomen and hence it is divisible
into thoracic and abdominal parts.
The pulmonary trunk is connected with the aorta by the ligamentum arteriosum that represents the remnant of an embryonic
connection between the pulmonary trunk and aorta. In embryo the ligamentum arteriosum is called ductus arteriosus.
Coronary arteries arise from the ascending aorta and supply blood to the heart. The coronary arteries exit from behind the aortic
valve cusps in the very fist part of the aorta and lead to a branching network of small arteries, arterioles, capillaries, venules, and
veins similar to those in other organs. Most of the cardiac veins drain into a single large vein, the coronary sinus, which empties
into the right atrium.
Left common carotid artery
Brachiocephalic artery
Superior vena cava
Aortic arch
Right pulmonary artery
Ascending aorta
Pulmonary aorta
Right pulmonary veins
Opening of superior vena cava
Right atrium
Pulmonary semilunar valve
Opening of inferior vena cava
Tricuspid valve
Right ventricle
Inferior vena cava
Fissures
Columnae carneae
Interventricular septum
Left ventricle
Papillary muscle
Chordae tendineae
Bicuspid valve
Aortic semilunar valve
Left atrium
Left pulmonary veins
pulmonary veins
Opening of left
Left pulmonary artery
Descending aorta
Ligamentum arteriosum
Left subclavian artery
Fig.: Internal structure of human heart.
Heart valves
atrioventricular valves
Located between the atrium and ventricle in each half of the heart are the atrioventricular (AV) valves, which permit blood to flow
from atrium to ventricle but not backward from ventricle to atrium. The right AV valve is called the tricuspid valve because it has
three fibrous flaps, or cusps.The left AV valve has two flaps and is therefore called the bicuspid valve. Its resemblance to a bishop’s
headgear (a “mitre”) and hence has earned another commonly used name, mitral valve.
Semilunar valves
The openings of the right ventricle into the pulmonary trunk and of the left
ventricle into the aorta also contain valves, the pulmonary and aortic
valves, respectively. These valves are also referred to as the semilunar
valves, due to the half-moon shape of the cusps. These valves permit
blood to flow into the arteries during ventricular contraction but prevent
blood from moving in the opposite direction during ventricular relaxation.
Like the AV valves, they act in a purely passive manner. Whether they are
open or closed depends upon the pressure differences across them.
Two other valves Eustachian valve and Thebasian valve are also
present. The openings of inferior vena cava and coronary sinus into
the right atrium are guarded by Eustachian valve and Thebesian valve,
respectively.
Left AV
(bicuspid) valve
Aortic semilunar
valve
Openings to
coronary arteries
Pulmonary
semilunar valve
Right AV
(Tricuspid) valve Fig.: Valves of the heart

5. Location and functions of heart valves have been summarised in the given table.
Table: Valves of heart
Name Location Function
1. Bicuspid valve (Mitral valve) Between left atrium and ventricle (has
two flaps)
Allows the blood to move from left atrium to
left ventricle.
2. Tricuspid valve Between right atrium and ventricle
(has three flaps)
Allows the blood to move from right atrium
to right ventricle.
3. Aortic semilunar valve Between aorta and left ventricle Allows unidirectional flow of oxygenated
blood from left ventricle to aorta. Prevents
back flow.
4. Pulmonary semilunar valve Between pulmonary artery and right
ventricle
Allows unidirectional flow of deoxygenated
blood from right ventricle to pulmonary artery.
Prevents back flow.
5. Eustachian valve Right atrium Guards the opening of inferior vena cava.
6. Thebasian valve (Coronary valve) Right atrium Guards the opening of coronary sinus.
There are no valves at the entrances of the superior and inferior venae cavae (plural of vena cava) into the right atrium, and of the
pulmonary veins into the left atrium. However, atrial contraction pumps very little blood back into the veins because atrial contraction
constricts their sites of entry into the atria, greatly increasing the resistance to backflow.Actually, a little blood is ejected back into the
veins, and this accounts for the venous pulse that can often be seen in the neck veins when the atria are contracting.
functioning of valves
The opening and closing of the AV valves are passive processes resulting from pressure differences across the valves. When the
blood pressure in an atrium is greater than in the corresponding ventricle, the valves is pushed open and blood flows from atrium
to ventricle. In contrast, when a contracting ventricle achieves an internal pressure greater than that in its connected atrium, the AV
valve between them is forced closed. Therefore, blood does not normally move back into the atria and is forced into the pulmonary
trunk from the right ventricle and into the aorta from the left ventricle.
To prevent the AV valves from being pushed up into the atria when the ventricles are contracting (a condition called prolapse), the
valves are fastened to muscular projections (papillary muscles) of the ventricular walls by fibrous strands chordae tendineae. The
papillary muscles do not open or close the valves. They act only to limit the valves’ movement and prevent the backward flow of
blood.
Another important point concerning the heart valves is that, when open, they offer very little resistance to flow. Consequently, very
small pressure differences across them suffice to produce large flows. In disease states, however, a valve may become narrowed
or not open fully so that it offers a high resistance to flow even when open. In such a state, the contracting cardiac chamber must
produce an unusually high pressure to cause flow across the valve.
The aortic and pulmonary artery semilunar valves function quite differently from the AV valves. The high pressure in the arteries at
the end of systole causes the semilunar valves to snap to the closed position, in contrast to the much softer closure of the AV valves.
Because of smaller openings, the velocity of blood ejection through the aortic and pulmonary valves is far greater than that through
the much larger AV valves.
HiStoLogy of Heart
The heart consists of an outermost smooth coelomic epithelium – visceral pericardium, the middle thick muscular layer – the
myocardium, which is composed of cardiac muscle cells and the innermost layer – the endothelium consisting of the simple
squamous epithelial cells.
cardiac muscle cells
contractile muscles
The cardiac muscle cells of the myocardium are arranged in layers that are tightly bound together and completely encircle the blood-
filled chambers.There are dark areas crossing the cardiac muscle fibres called intercalated discs; they are actually cell membranes

6. that separate individual cardiac muscle cells from one another. When the walls of a chamber contract, they come together like a
squeezing fist and exert pressure on the blood they enclose.This causes pumping of blood.
Similar to smooth and skeletal muscle, it is an electrically excitable tissue that converts chemical energy stored in the bonds of ATP
into force generation.Action potential propagates along cell membranes, Ca2+ enters the cytosol, and the cycling of force-generation
cross-bridges is activated.
But unlike skeletal muscle cells, which can be rested for prolonged periods and only a fraction of which are activated in a given muscle
during most contractions, every heart cell contracts with every beat of the heart. Beating about once every second, in an
average life span, cardiac muscle cells may contract almost 3 billion times without resting. Remarkably, despite this enormous
workload, the heart has only a limited ability to replace its muscle cells. Recent experiments suggest that only about 1 per cent of
heart muscle cells are replaced per year.
Autorhythmic muscles
Approximately 1 percent of cardiac cells do not function in contraction
but have specialised features that are essential for normal heart
excitation. These cells constitute a network known as the conducting
system of the heart and are in electrical contact with the cardiac
muscle cells via gap junctions. The conducting system initiates the
heartbeat and helps spread the impulse rapidly throughout the heart.
They constitute the nodal tissue.
A patch of this tissue is present in the right atrium near the opening of
superior vena cava called the sino-atrial node (SAN). Another mass
of this tissue is seen in the right atrium called the atrio-ventricular
node (AVN). A bundle of nodal fibres, atrioventricular bundle
(AV bundle) continues from the AVN which passes through the
atrioventricular septa to emerge on the top and immediately divides
into a right and left bundle. These branches give rise to minute fibres
throughout the ventricular musculature of the respective sides and are
called Purkinje fibres. These fibres alongwith right and left bundles
are known as bundle of His.
The nodal musculature has the ability to generate action potentials
without any external stimuli, i.e., it is autoexcitable. The SAN can generate the maximum number of action potentials, i.e., 70-
75 min–1, and is responsible for initiating and maintaining the rhythmic contractile activity of the heart. Therefore, it is called the
pacemaker. Our heart normally beats 70-75 times in a minute (average 72 beats min–1).The cardiac muscles contract in much the
same way as skeletal muscle, except that the duration of contraction is much longer. Conversely, the specilised autorhythemic muscles
contract only feebly because they contain few contractile fibrils.
Why does Sa node work as pacemaker?
The AV nodal fibres when not externally stimulated discharge at 40-60 times/min and Purkinje fibres discharge at approx. 15 to
40 times/min in contrast to the normal rate of SA node i.e., 70-80 times/ min.The discharge rate of SA node is considerably faster
than the natural self excitatory discharge rate of either of them.
Each time the sinus node discharges, its impulse is conducted into both A-V node or the Purkinje fibres, also discharging their
excitable membranes. But the sinus node discharges again before either the A-V node or the Purkinje fibres can reach their own
thresholds for self-excitation.Therefore, the new impulse from the sinus node discharges both theA-V node and the Purkinje fibres
before self-excitation can occur in either of these.
Thus, the SA node controls the beat of the heart because its rate of rhythmical discharge is faster than that of any other part of
the heart and is virtually always the pacemaker of the normal heart.
Heart beat
To pump the blood into blood vessels, heart regularly contracts and relaxes in a rhythmic manner. It is known as ‘heart beat’.
Each heart beat includes one systole (contraction phase) and one diastole (relaxation phase) of the heart to distribute and receive
Interventricular septum
Purkinje fibres
AV node
AV bundle
SA node
Internal septum
Left bundle
branch
Fig.: Conducting system of the heart

7. blood to and from the body.The heart of a healthy person beats 72 times per minute. Beating is an inherent capacity of the heart.The
heart of a resting human being pumps about 5 litres of blood per minute.
types of heart beat
The heart beat is of two types : neurogenic and myogenic. The neurogenic heart beat is initiated by a nerve impulse
coming from a nerve ganglion (mass of nerve cells) situated near the heart. It is present in the heart of some annelids and most
arthropods.The myogenic heart beat is initiated by a patch of modified heart muscle itself. It is found in hearts of molluscs and
vertebrates.
origin of heart beat
The mammalian heart is myogenic. It means the heart beat originates from a muscle, however, it is regulated by the nerves.The heart
beat originates from the sinoatrial node (SAN) or pacemaker.
conduction of heart beat
Another mass of neuromuscular tissue, the atrioventricular node (AV node or pacesetter) picks up the wave of contraction
propagated by SA node. The bundle of His and the Purkinje fibres convey impulse of contraction from the AV node to the
myocardium of the ventricles.When this system functions normally, the atria contract about one sixth of a second ahead of ventricular
contraction, which allows filling of the ventricles before they pump the blood through the lungs and peripheral circulation.
It is due to the fact the heart actually is composed of two muscle syncytiums:the atrial syncytium,and the ventricular syncytium.
The atria are separated from the ventricles by fibrous tissue that surrounds the atrioventricular (A-V) valvular openings between the
atria and ventricles. Normally, potentials are not conducted from the atrial syncytium into the ventricular syncytium directly through
this fibrous tissue. Instead, they are conducted only by way of the A-V bundle.
How nerve impulses travel so rapidly throughout the heart?
Cardiac muscle fibres are made up of many individual cells connected in series and in parallel with one another.At each intercalated
disc the cell membranes fuse with one another in such a way that they form permeable “communicating” junctions (gap
junctions) that allow almost totally free diffusion of ions. Therefore, from a functional point of view, ions move with ease
in the intracellular fluid along the longitudinal axes of the cardiac muscle fibres, so that action potentials travel easily from
one cardiac muscle cell to the next, past the intercalated discs. Thus, cardiac muscle is syncytium of many heart muscle cells
in which the cardiac cells are so interconnected that when one of these cells becomes excited, the action potential spreads
to all of them, spreading from cell to cell throughout the latticework interconnections.
The conduction of cardiac impulse can be summarised as :
SA node → Atrial syncytium → Junctional fibres →AV node →AV bundle → Bundle branches → Purkinje fibres →Ventrical syncytium.
Fig.: Organisation of theA-V node
A-V node
Transitional fibres
Internodal pathways
Atrioventricular fibrous tissue
Penetrating portion of A-V bundle
Distal portion of A-V bundle
Left bundle branch
Located in ventricular septum
Right bundle
branch
SA Node

8. ectopic pacemakers
Occasionally, some other part of the heart develops a rhythmical discharge rate that is more rapid than that of the sinus node. For
instance, this sometimes occurs in the A-V node or in the Purkinje fibres when one of these becomes abnormal. In either case, the
pacemaker of the heart shifts form the sinus node to the A-V node or to the excited Purkinje fibres. Under rarer conditions, a place
in the atrial or ventricular muscle develops excessive excitability and becomes the pacemaker.
A pacemaker elsewhere than the sinus node is called an“ectopic”pacemaker.An ectopic pacemaker causes an abnormal sequence
of contraction of the heart and can cause significant debility of heart pumping.
artificial pacemaker
SA node may become defective due to various reasons. It then fails to generate cardiac impulse at the normal rate.The heart beat
becomes slow and irregular and tissues receive less blood.This disorder may be corrected by implanting an artificial pacemaker in
the patient’s chest.This instrument stimulates the heart electrically at regular intervals to beat at normal rate.
regulation of heart beat
When a person is at rest, the heart pumps only 4 to 6 litres of blood each minute. During severe exercise, the heart may be required to
pump four to seven times this amount.The basic means by which the volume pumped by the heart is regulated are of three types:
(i) Intrinsic regulation : Under most conditions, amount of blood pumped per minute by heart is determined almost entirely by
the rate of blood flow into heart from the veins i.e., venous return. This intrinsic ability of heart to adapt to increasing volumes of
blood is called Frank-Starling mechanism. It says that the greater the heart muscle is stretched during filling, the greater is the
force of contraction and the greater is the quantity of blood pumped into the aorta i.e., within physiologic limits, the heart pumps all
the blood that returns to it through veins.
It can be explained as that when an extra amount of blood flows into the ventricles, the cardiac muscle is stretched to greater length,
causing the muscle to contract with increased force because the actin and myosin filaments are brought to a more nearly optimal
degree of overlap for force generation. Therefore, the ventricle, because of its increased pumping, automatically pumps the extra
blood into the arteries.
This ability of stretched muscle, up to an optimal length, to contract with increased work output is characteristic of all striated
muscles. Another factor also increases heart pumping when its volume is increased. Stretch of the right atrial wall directly increases
the heart rate by 10 to 20 per cent; this, too, helps increase the amount of blood pumped each minute, although its contribution is
much less than that of the Frank-Starling mechanism.
(ii) Neural Regulation : The cardiac centre lies in the medulla oblongata of the brain.The cardiac centre is formed of cardio-
inhibitor and cardio-accelerator parts.The former decreases the rate of heart beat and the latter accelerates it.The cardio-inhib-
itor is connected with the heart through vagus nerve (it carries–parasympathetic nerve fibres) and cardio-accelerator through
sympathetic nerve fibres.
The amount of blood pumped each minute (cardiac output) often can be increased more than 100 per cent by sympathetic
stimulation.
Strong sympathetic stimulation can increase the heart rate in young
adult humans from the normal rate of 70 beats per minute up to
180 to 200 and, rarely, even 250 beats per minutes. Sympathetic
stimulation increases the force of heart contraction to as much as
double normal, thereby increasing the volume of blood pumped and
increasing the ejection pressure.
Strong stimulation of the parasympathetic nerve fibres in the vagus
nerves to the heart can stop the heartbeat for a few seconds, but then
the heart usually “escapes” and beats at a rate of 20 to 40 beats
per minute as long as the parasympathetic stimulation continues. In
addition, strong vagal stimulation can decrease the strength of heart
muscle contraction by 20 to 30 per cent.
The vagal fibres are distributed mainly to the atria and not much to
the ventricles, where the power contraction of the heart occurs. This
explains the effect of vagal stimulation mainly to decrease heart rate
rather than to decrease greatly the strength of heart contraction.
Sympathetic chains
Vagi
A-V
node
S-A
node
Sympathetic
nerves
Sympathetic
nerves
Fig.: Cardiac sympathetic and parasympathetic nerves

9. Nevertheless, the great decrease in heart rate combined with a slight decrease in heart contraction strength can decrease ventricular
pumping 50 per cent or more.
Ventricular escape
Strong parasympathetic stimulation can completely stop either the excitation by SA node or transmission of cardiac impulse from atria
to ventricles. The ventricles stop beating for 5 to 20 seconds, but then some point in the Purkinje fibres, usually in the ventricular septal
portion of the A-V bundle, develops a rhythm of its own and causes ventricular contraction at a rate of 15 to 40 beats per minute. This
phenomenon is called ventricular escape.
(iii)Hormonal regulation : Adrenaline (epinephrine) and noradrenaline (norepinephrine) hormones are secreted by the
medulla of the adrenal glands. Noradrenaline accelerates the heart beat under normal conditions while adrenaline does the function
at the time of emergency.These hormones directly influence the SA node.
Thyroxine hormone secreted by thyroid gland increases oxidative metabolism of the body cells.This requires more oxygen and thus
indirectly increases heart beat.
effect of temperature on heart function
Increased body temperature, as occurs when one has fever, causes a greatly increased heart rate, sometimes to as fast as double
normal. Decreased temperature causes a greatly decreased heart rate, falling to as low as a few beats per minute when a person
is near death from hypothermia in the body temperature range of 60° to 70°F. These effects presumably result from the fact that
heat increases the permeability of the cardiac muscle membrane to ions that control heart rate, resulting in acceleration of the self-
excitation process.Contractile strength of the heart often is enhanced temporarily by a moderate increase in temperature, as occurs
during body exercise, but prolonged elevation of temperature exhausts the metabolic systems of the heart and eventually causes
weakness.Therefore, optimal function of the heart depends greatly on proper control of body temperature.
PuLSe
Pulse is the alternate expansion and elastic recoil of an artery with each systole. Pulse is the strongest in the arteries closest
to the heart. Normal pulse rate ranges from 70–90 per minute.
Tachycardia is the term applied to a rapid heart or pulse rate (over 100/ minute). Bradycardia is the term indicating a slow heart
or pulse rate (under 50/ minute).
Heart rate
Pulse per minute is called as heart rate. Human heart beats 72 times per minute, this is designated as heart rate. It increases during
exercise, fever, anger and fear.
Table: Differences between heart beat and pulse
Heart beat Pulse
1. It is the rhythmic contraction and relaxation of heart. It is the rhythmic contraction and relaxation in aorta and its main
arteries.
2. It is regulated by the nervous and endocrine systems. It is due to the flow of blood from the heart and is dependent on the
rate of heart beat.
3. One complete heart beat consists of one systole and one
diastole and lasts for about 0.8 seconds.
Pulse is a regular jerk of an artery. It depends on the rate of heart
beat.
cardiac outPut
The amount of blood pumped by heart per minute is called cardiac output. Cardiac output of humans is approximately 5 litres
per minute. Cardiac output is also the volume of blood flowing through either the systemic or the pulmonary circuit per minute. It
is determined by multiplying the heart rate with the volume of blood ejected by each ventricle during each beat, which is called the
stroke volume.
Cardiac output = Heart rate × Stroke volume
= 72 beats/min. × 0.07 litre/beat
= 5.0 litres/min.

10. These values are within the normal range for a resting, average-sized adult. Coincidentally, total blood volume is also approximately
5 L, so essentially all the blood is pumped around the circuit once each minute. During periods of strenuous exercise in well-trained
athletes, the cardiac output may reach 35 L/min; the entire blood volume is pumped around the circuit seven times a minute. Even
sedentary, untrained individuals can reach cardiac outputs of 20-25 L/min during exercise.
cardiac cycLe
Cardiac cycle is the term referring to the cardiac events that occur
from the beginning of one heart beat to the beginning of the next
heart beat. The contraction phase is called as systole while the
relaxation phase is called as diastole.
The successive stages of the cardiac cycle are briefly described below.
Atrial systole :– The atria contract due to wave of contraction,
stimulated by the SA node.The blood is forced into the ventricles
as the bicuspid and tricuspid valves are open.
Beginning of ventricular systole :– The ventricles begin to
contract due to a wave of contraction, stimulated by theAV node.
The bicuspid and tricuspid valves close immediately producing
part of the first heart sound.
Complete ventricular systole :– When the ventricles complete
their contraction, the blood flows into the pulmonary trunk and
aorta as the semilunar valves open.
Beginning of ventricular diastole :– The ventricles relax and
the semilunar valves are closed. This causes the second heart
sound.
Complete ventricular diastole :– The tricuspid and bicuspid valves open when the pressure in the ventricles falls and
blood flows from the atria into the ventricles. Contraction of the heart does not cause this blood flow. It is due to the fact
that the pressure within the relaxed ventricles is less than that in the atria and veins.
Heart SoundS
Two sounds are heard normally through a stethoscope during each cardiac cycle.The first sound is a low pitched slightly prolonged
“lubb”, caused by sudden closure of the mitral and the tricuspid valves at the start of ventricular systole. The second sound is a
shorter, high pitched “dup” caused by vibrations associated with closure of the aortic and pulmonary semilunar valves just at the
end of the ventricular systole. The first sound has a duration of 0.15 seconds and a frequency of 25-45 Hz. The second sound lasts
about 0.12 seconds with a frequency of 50 Hz.
Heart murmurs
Murmurs are abnormal sounds heard in various parts of the vascular
system. The major cause of cardiac murmurs is due to abnormalities of the
heart valves. It may arise due to improper closing of any heart valve or
in patients with interventricular septal defects that cause blood flow
to be turbulent.
Normally, blood flow through valves and vessels is laminar flow– i.e., it
flows in smooth concentric layers. Turbulent flow can be caused by :
blood flowing rapidly in the usual direction through an abnormally–
narrowed valve (stenosis);
blood flowing backward through a damaged, leaky valve–
(insufficiency);
blood flowing between the two atria or two ventricles through a small–
hole in the wall separating them (called a septal defect).
Normal open valve Stenotic valve
Laminar flow = Quiet Narrowed valve
Turbulent flow = Murmur
No flow = Quiet Leaky valve
Turbulent backflow = Murmur
Normal closed valve Insufficient valve
Fig.: Heart valve defects causing turbulent blood
flow and murmurs.

11. Significance of heart sounds
Heart sounds give valuable information about working of the heart valves.The exact timing and location of the murmur provide the
physician with a powerful diagnostic clue. For example, a murmur heard throughout systole suggests a stenotic pulmonary or aortic
valve, an insufficientAV valve, or a hole in the interventricular septum. In contrast, a murmur heard during diastole suggests a stenotic
AV valve or an insufficient pulmonary or aortic valve.
diagnoStic teStS
Human cardiac functioning can be measured by a variety of methods. Moreover, two and three-dimensional images of the heart can
be obtained throughout the entire cardiac cycle.
echocardiography
Ultrasonic waves are beamed at the heart and returning echoes are electronically plotted by computer to produce continuous images
of the heart. This technique can detect the abnormal functioning of cardiac valves or contractions of the cardiac walls, and can also
be used to measure ejection fraction.
Echocardiography is a noninvasive technique because everything used remains external to the body.Other visualisation techniques
are invasive.
cardiac angiography
It requires the temporary threading of a thin, flexible tube called a catheter through an artery or vein into the heart. A liquid
containing radio-opaque contrast material is then injected through the catheter during high-speed X-ray videography.This technique
is useful not only for evaluating cardiac function but also for identifying narrowed coronary arteries.
electrocardiogram
The electrocardiogram (ECG) or EKG – (the k is from the German elektrokardiogramm) is primarily used for evaluating the electrical
events within the heart.The action potentials of cardiac muscle cells can be viewed as batteries that cause charge to move throughout
the body fluids.These moving charges, or currents, are caused by all the action potentials occurring simultaneously in many individual
myocardial cells.
When the cardiac impulse passes through the heart,electrical current also spreads from the heart into the adjacent tissues surrounding
the heart.A small portion of the current spreads all the way to the surface of the body. If electrodes are placed on the skin on opposite
sides of the heart, electrical potentials generated by the current can be recorded; the recording is known as an electrocardiogram
(ECG).
The instrument used to record the changes is an electrocardiograph.
Waller (1887) first recorded the electrocardiogram but Einthoven
(1903) studied ECG in details, therefore, he got Nobel Prize in
1924 for the discovery of ECG. He is also considered “Father of the
Electrocardiography”.
A normal electrocardiogram (ECG) is composed of a P wave, a QRS
wave (complex) and a T wave.The letters are arbitrarily selected and
do not stand for any particular words.
The P wave is a small upward wave that indicates the depolarisation
of the atria (atrial contraction). It is caused by the activation of SA
node.
The QRS wave (complex) begins after a fraction of second of the P
wave. It begins as a small downward deflection (Q) and continues as large upright (R) and triangular wave, ending as downward
wave (S) at its base. It represents ventricular depolarisation (ventricular contraction).
The T wave is dome-shaped which indicates ventricular repolarisation (ventricular relaxation).

12. Table : ECG intervals
Intervals Normal duration (s) Events in the heart during interval
Average Range
PR interval1 0.182 0.12–0.20 Atrial depolarisation and conduction through AV node
QRS duration 0.08 to 0.10 Ventricular depolarisation and atrial repolarisation
QT interval 0.40 to 0.43 Ventricular depolarisation plus ventricular repolarisation
ST interval (QT minus QRS) 0.32 Ventricular repolarisation
1 Measured from the beginning of the P wave to the beginning of the QRS complex.
2 Shortens as heart rate increases from average of 0.18 at a rate of 70 beats/min to 0.14 at a rate of 130 beats/min.
clinical significance
Any deviation from the normal ECG shape indicates a possible abnormality or disease. Enlargement of the P wave indicates
enlargement of the atria. During atherosclerotic heart disease and rheumatic fever, the P–R interval is lengthened.This is due
to the inflammation of atria and AV node.
The enlarged Q and R waves indicate a myocardial infarction (heart attack). The S–T segment is elevated in acute myocardial
infarction and depressed when the heart muscle receives insufficient oxygen.
T wave is flat when the heart muscles receive insufficient oxygen as in atherosclerotic heart disease. It may be elevated when
the body’s potassium level is increased.
rate of heartbeat as determined from the electrocardiogram
The rate of heartbeat can be determined easily from an electrocardiogram because the heart rate is the reciprocal of the time
interval between two successive heartbeats. If the interval between two beats as determined from the time calibration lines is 1
second, the heart rate is 60 beats per minute. The normal interval between two successive QRS complexes in the adult person is
about 0.83 second.This is a heart rate of 60/0.83 times per minute, or 72 beats per minute.
recording ecg
When ECG of a person is to be recorded, four leads (metal electrodes) are attached in the arms and legs. It is done after cleaning and
putting a special jelly, which improves electrical conduction. With the help of a rubber suction cup, an additional electrode is placed
on the chest. Now the electrocardiograph is switched on, which detects and amplifies the electrical current of the heart and transmits
to the recording pen.The latter draws a wavy line that is called the deflection waves or the electrocardiogram.
bLood PreSSure
Blood pressure is defined as the force or pressure which the blood exerts on the walls of the artery in which it is contained. The
arterial blood pressure is the result of the discharge of the blood from the left ventricle into the already full aorta.
When the left ventricle contracts pushing the blood into the aorta, the pressure produced is known as systolic blood pressure
(120 mm Hg). When the complete diastole occurs and the heart is resting, the pressure within the blood vessels is called as the
diastolic blood pressure (80 mm Hg).
The blood pressure is expressed as BP = 120/80 mm Hg.The difference between the systolic and diastolic pressure is called pulse
pressure.The average of blood pressure levels is called mean blood pressure. Its normal value is 40 mm Hg but becomes more
in case of hypertension. Pulse pressure is lower in case of kids.
Measurement of blood pressure
Both systolic and diastolic bloodpressuresarereadily measuredin humanbeingswiththeuseofadevicecalledsphygmomanometer,
in terms of height in millimeters of a column of mercury.An inflatable cuff containing a pressure gauge is wrapped around the upper
arm, and a stethoscope is placed in a spot on the arm just below the cuff where the brachial artery lies.
The cuff is then inflated with air to a pressure greater than systolic blood pressure.The high pressure in the cuff is transmitted through
the tissue of the arm and completely compresses the artery under the cuff, thereby preventing blood flow through the artery.The air

13. in the cuff is then slowly released, causing the pressure in the cuff and on the artery to decrease.When cuff pressure has decreased
to a value just below the systolic pressure, the artery opens slightly and allows blood flow for a brief time at the peak of systole.
During this interval, the blood flow through the partially compressed artery occurs at a very high velocity because of the small
opening and the large pressure difference across the opening. The high-velocity blood flow is turbulent and, therefore, produces
vibrations called Korotkoff’s sounds that can be heard through the stethoscope.Thus, the pressure at which sounds are first heard
as the cuff pressure decreases is identified as the systolic blood pressure.
As the pressure in the cuff decreases further, the duration of blood flow through the artery in each cycle becomes longer. When the
cuff pressure reaches the diastolic blood pressure, all sound stops because flow is now continuous and nonturbulent through the
open artery.Therefore, diastolic pressure is identified as the cuff pressure at which sounds disappear.
The sounds heard during measurement of blood pressure are not the same as the heart sounds described earlier, which are due to
closing of cardiac valves.
bLood circuLation
In human there are two circuits of blood circulation for
greater efficiency and to completely prevent the mixing of
oxygenated and deoxygenated blood. Usually it is called
double circulation.
Double circulation is the passage of same blood twice in
the heart through separate pathways for completing one
cycle. It consists of pulmonary circulation and systemic
circulation.
Pulmonary circulation is the movement of blood
from the heart, to the lungs, and back to the heart again.
Deoxygenated blood is pumped out of the right ventricle of
the heart into the pulmonary trunk, then to the pulmonary
arteries and into the lungs via pulmonary veins, oxygenated
blood is then drained into the left atrium. Blood is then
circulated in the systemic circulation.The flow of oxygenated
blood from the left ventricle to all parts of the body and deoxygenated blood from various body parts to the right atrium is called
systemic circulation.
The advantage of double circulation is that the blood can be sent to the lungs to pick up oxygen and then returned to the
heart to be pumped again before travelling around the body.The blood therefore is pumped through the capillary bed (which slows
it down and reduces its pressure) then receives another pump before it enters another capillary bed. Double circulatory systems are
therefore high pressure system. In this type of circulation there is no mixing of the oxygen rich blood and oxygen poor blood in the
heart. Oxygenated blood carries more oxygen to different body parts as well as more CO2 is carried with deoxygenated blood for the
removal through lungs.
diSorderS of circuLatory SySteM
High blood pressure
The maintenance of a normal systolic blood pressure is important for health. Any value above 150 mm Hg in an otherwise healthy
adult means high blood pressure or hypertension.
Hypertension is categorised according to its causes. Hypertension of unknown cause is diagnosed as primary hypertension;
secondary hypertension has identifiable causes.
There are two main causes of high blood pressure :
thickening or hardening of the arteries due to deposition of cholesterol (– arteriosclerosis).
kidney disease (– nephritis).
Treatment comprises of a well balanced programme of mild exercise followed by rest. Beverages containing caffeine and excessive
salt need to be avoided.Smoking must be stopped because tobacco constricts the smaller vessels raising blood pressure.A substance
reserpine obtained from the roots of a herb called Rauwolfia helps in reduction of blood pressure.
Right atrium
Deoxygenated blood
Right ventricle
Through pulmonary arch for
oxygenation, deoxygenated
blood enters into
Pulmonary
circulation
Lungs
Left atriumOxygenated blood
Left ventricle
Fig.: Double circulation
Systemic
circulation
Through aorta
oxygenated blood
enters into
Body part except
lungs for
deoxygenation
Deoxygenated blood
(through coronary sinus,
inferior vena cava and
superior vena cava) enters

14. Low blood pressure
A fall in systolic blood pressure below the normal range in an adult is called low blood pressure or hypotension. A reading
below 100 mm is an indication of a weak circulation.
atherosclerosis /coronary artery disease (cad)
It is the deposition of lipids (cholesterol) on the wall lining of arteries called atheromatous or atherosclerotic plaque. These
plaques may completely block the artery. Such plaques, if formed in the coronary artery, reduce the blood supply to the heart and
may result in heart attack or stroke.
arteriosclerosis
It is the hardening and thickening of the arteries due to the deposition of calcium salts with the cholesterol. Such artery
loses the property of distension and its walls may rupture, resulting in the formation of clot or thrombosis in the coronary artery
leading to heart attack and even death.
Heart block
It is a condition in which the sinus node is normal but the impulses are interrupted at any point along the conducting system of the
heart.Thus impulses do not follow the normal conduction pathway.Two common types of heart block are :
AV block– : It occurs at the atrioventricular node. The impulses from the SA node do not reach the AV node.
Bundle branch block :– It involves one of the branches of the bundle of His.
angina pectoris
Sclerosis of the coronary arteries can cause pain in the chest. This anginal pain usually starts in the centre of the chest and
spreads down the left arm. The chest pain may be associated with restlessness, fear or anxiety, a pale skin, profuse sweating and
vomiting (all because of increase adrenergic discharge).The pain lasts for only a few moments.
coronary thrombosis
A clot may form in the lumen of a coronary artery, it is called coronary thrombosis. Therefore, a large portion of the heart
muscle is deprived of blood and the patient develops a ‘heart attack’.Anticoagulant drugs like TPA (tissue plasminogen factor) and
streptokinase helps to prevent the formation and extension of blood clots if given within 4 hours of attack.
Heart failure (congestive heart failure)
It is a collection of signs and symptoms that occur when the heart fails to pump an adequate cardiac output. Heart failure is not the
same as cardiac arrest (when the heart stops beating) or heart attack (when the heart muscle is suddenly damaged by inadequate
blood supply).
Heart attack
Heart attack, also called myocardial infarction (MI), refers to a sudden event in which a portion of the heart muscle stops working
because it no longer receives blood, usually due to a blockage in the coronary artery. Generally, a heart attack occurs when plaque
(fat, cholesterol, and calcium) builds up and then ruptures in the coronary artery, creating a place where a blood clot can form
(thrombus).
Signs of heart attack :– chest pain; pain or discomfort in the upper body (arms, back, neck, jaws or stomach); shortness
of breath (usually occurs at the same time as chest pain); cold sweat; nausea or vomiting and light headedness.
Controllable risk factors– : High cholesterol; cigarette smoking; excess weight; sedentary lifestyle; stress; high blood
pressure; diabetes and certain drugs, such as oral contraceptives for women who smoke.
rheumatic heart disease (rHd)
The patient may have an acute rheumatic fever, joint pains and infection of throat. Rheumatic fever may cause permanent
damage of one or more valves (mitral or aortic semilunar valves), pericarditis and myocarditis. Its causative factor is Streptococcus
bacteria.

15. congenital heart diseases
Defects or diseases of the heart from the birth are known as congenital heart diseases and are due to some error in the development
of the heart. It is possible that some of these defects may be due to an infectious disease like rubella (German measles) in the
mother or administration of some harmful drugs during first three months of pregnancy.A small number of cases of congenital heart
diseases are associated with chromosomal abnormalities.
ebstein’s disease
It is a congenital downward displacement of the tricuspid valve into the right ventricle.
fibrillation
Fibrillation is a condition in which the heart muscle is contracting very rapidly but in an uncoordinated fashion. There are atrial and
ventricular fibrillation. Ventricular fibrillation is immediately life threatening unless it can be stopped by defibrillation. A machine
called a defibrillator is used to do this.
cardiac arrest
It is the complete stoppage of the heart beat (sudden and complete loss of cardiac-function).
ischaemia
It is inadequate flow of blood to a part of the heart caused by obstruction to its blood supply.
New MCQs
1. Pacemaker is situated in heart
(a) in the wall of right atrium
(b) on inter auricular septum
(c) on inter ventricular septum
(d) in the wall of left atrium.
2. Right atrium receives blood from
(a) pulmonary aorta
(b) pulmonary veins
(c) inferior vena cava
(d) superior and inferior vena cava.
3. First heart sound is
(a) ‘lubb’ due to closure of AV valves
(b) ‘lubb’ due to closure of spiral valves
(c) ‘dupp’ due to closure of AV valves
(d) ‘dupp’ due to closure of spiral valves
4. Papillary muscles occur in
(a) ventricles
(b) auricles
(c) atrioventricular valves
(d) pulmonary valves.
5. What happens when the pacemaker becomes non-
functional?
(a) Only auricles contract rhythmically.
(b) Only ventricles contract rhythmically.
(c) Cardiac muscles do not undergo co-ordinated rhythmic
movements.
(d) Auricles and ventricles contract rhythmically.
6. If vagus nerve to heart is cut the heart beat will
(a) decrease (b) increase
(c) remain normal (d) stop.
7. T wave of ECG represents
(a) ventricular depolarisation
(b) ventricular repolarisation
(c) depolarisation of atria
(d) auricular repolarisation.
8. Hardening of the wall of small arteries is known as
(a) thrombosis (b) arteriosclerosis
(c) atherosclerosis (d) myocardial infarction.
9. The heart murmur is due to
(a) coronary thrombosis
(b) defective leaky valve
(c) arterial pulse
(d) ill developed atrium.
10.Heart pumps blood more forcefully in older persons than
younger ones due to
(a) decrease in oxygen content of blood
(b) decrease in elasticity of arteries
(c) fall in nutrient content of blood
(d) increase in elasticity of arteries.

16. Exam Section
1. Doctors use stethoscope to hear the sounds produced during
each cardiac cycle.The second sound is heard when
(a) AV node receives signal from SA node
(b) AV valves open up
(c) Ventricular walls vibrate due to gushing in of blood from
atria
(d) Semilunar valves close down after the blood flows into
vessels from ventricles. (AIPMT 2015)
2. What is the stroke volume of an adult human heart?
(a) 50 mL (b) 70 mL
(c) 90 mL (d) 100 mL
(West Bengal 2015)
3. Identify the correct statement regarding cardiac activity.
(a) Normal activities of the human heart is regulated
intrinsically, hence, it is neurogenic.
(b) A special neural centre in the medulla oblongata can
moderate the cardiac function through the CNS.
(c) Parasympathetic neural signals increase the rate of heart
beat.
(d) Adrenal medullary hormones can increase cardiac
output.
(e) The end of a T-wave marks the end of diastole.
(Kerala PMT 2014)
4. Read the statements A and B and select the correct option
Statement A : Atherosclerosis is a disease characterized
by the thickening of arterial walls.
Statement B : Deposition of cholesterol and triglycerides
in the arterial walls causes atherosclerosis.
(a) Statement A is correct, B is wrong.
(b) Both the statements are correct but not related to each
other.
(c) Both the statements are correct and B is the reason
for A.
(d) Both the statements are wrong.
(Karanataka CET 2013)
5. Ventricular diastole occurs due to a/an
(a) organ system (b) cell organelle
(c) tissue (d) organ.
(AIIMS 2012)
6. The frequency of heart beat in our body is maintained by
(a) AV Node (b) SA Node
(c) Node of Ranvier (d) Chordae tendineae
(Karnataka CET 2012)
7. ‘Bundle of His’ is a part of which one of the following organs
in humans?
(a) Brain (b) Heart
(c) Kidney (d) Pancreas
(AIPMT Prelims 2011)
8. Given below is the ECG of a normal human. Which one of
its components is correctly interpreted below?
(a) Complex QRS - one complete pulse
(b) Peak T - initiation of total cardiac contraction
(c) Peak P and peak R together - systolic and diastolic blood
pressures
(d) Peak P- initiation of left atrial contraction only.
(AIPMT Mains 2011)
9. Cardiac muscle is found in
(a) myocardium (b) epicardium
(c) endocardium (d) all of these. (Odisha 2011)
10.Which one of the following is the correct pathway for
propagation of cardiac impulse ?
(a) SA node → AV node → Bundle of His → Purkinje fibres.
(b) AV node → Bundle of His → SA node → Purkinje fibres.
(c) SA node → Purkinje fibres → AV node → Bundle of His.
(d) Purkinje fibres → AV node → SA node → Bundle of His.
(WB-JEE 2011)
11.The volume of blood each ventricle pumps out during a cardiac
cycle is about
(a) 70 mL (b) 5000 mL
(c) 7 L (d) 1200 mL
(e) 40 mL. (Kerala PMT 2011)
12.In a typical heart, If EDV is 120 mL of blood and ESV is 50 mL
of blood, the stroke volume (SV) is
(a) 120 – 50 = 70 mL (b) 120 + 50 = 70 mL
(c) 120 × 50 = 6000 mL (d) 120 ÷ 50 = 2.4 mL.
(Karnataka CET 2011)
13.Pulmonary vein carries
(a) deoxygenated blood (b) oxygenated blood
(c) mixed blood (d) none of these.
(AFMC 2010)
14.Heart of heart is
(a) SA node (b) AV node
(c) bundle of His (d) Purkinje fibres.
(BHU 2010)

17. 15.Bundle of His is a network of
(a) muscle fibres distributed throughout the heart walls
(b) muscle fibres found only in the ventricle wall
(c) nerve fibres distributed in ventricles
(d) nerve fibres found throughout the heart. (BHU 2010)
16.In order for the blood to flow from right ventricle to left ventricle
in mammalian heart, it must flow through
(a) right ventricle, pulmonary arteries, lungs, pulmonary veins,
left atrium
(b) right ventricle, pulmonary veins, lungs, pulmonary arteries,
left atrium
(c) right ventricle, right atrium, lungs, pulmonary veins, left
atrium
(d) right ventricle, systemic aorta, lungs, pulmonary veins, left
atrium (DU MET 2010)
17.The cardiac cycle in normal subject is about
(a) 0.5 second (b) 0.8 second
(c) 1.0 second (d) 1.2 seconds. (WB-JEE 2010)
18.Chordae tendineae are found in
(a) atria of heart (b) ventricles of heart
(c) joints of legs (d) joints of hands
(e) ventricles of brain. (Kerala PMT 2010)
19.Blood enters the heart because muscles of the
(a) atrium contracts (b) atrium relaxes
(c) ventricle relaxes (d) ventricle contracts.
(Odisha 2009)
20.How many double circulations are normally completed by the
human heart, in one minute?
(a) Eight (b) Sixteen
(c) Seventy two (d) Thirty six.
(Karnataka CET 2006)
21.An artery is a vessel that carries blood
(a) away from the heart
(b) towards the heart
(c) which is deoxygenated without any exception
(d) none of the above (Odisha 2007)
22.Which chamber of the human heart has the thickest muscular
wall?
(a) left auricle (b) left ventricle
(c) right auricle (d) right ventricle.
(Karnataka CET 2005)
23.During ventricular systole
(a) oxygenated blood is pumped into the pulmonary artery and
deoxygenated blood is pumped into the artery
(b) oxygenated blood is pumped into the aorta and
deoxygenated blood is pumped into the pulmonary vein
(c) oxygenated blood is pumped into the pulmonary vein and
deoxygenated blood is pumped into the pulmonary artery
(d) oxygenated blood is pumped into the aorta and
deoxygenated blood is pumped into the pulmonary artery.
(Karnataka CET 2003)
24.The valves which allow blood to flow from the ventricles into
the arteries and not in the opposite direction are
(a) AV valve (atrio ventricular valve) and semilunar valve
(b) bicuspid and tricuspid valves
(c) semilunar valve and tricuspid valve
(d) aortic valve and Mitral valve.
(Karnataka CET 2003)
25.Heart sound which is longer is
(a) lubb
(b) dup
(c) both equal
(d) sometimes (a) and sometimes (b).
(Punjab 2001)
Assertion & Reason
The following questions consist of two statements each :assertion
(A) and reason (R). To answer these questions, mark the correct
alternative as directed below :
(a) If both A and R are true and R is the correct explanation
of A.
(b) If both A and R are true but R is not the correct explanation
of A.
(c) If A is true but R is false.
(d) If both A and R are false.
1. Assertion (A) : The enlarged Q and R waves indicate
myocardial infarction.
Reason (R) : The QRS complex represents ventricular
repolarisation.
2. Assertion (A) : Pulse rate per minute can be counted to
know the heart beat.
Reason (R) : Each heart beat sends one pulse along the
arteries.
3. Assertion (A) : Wall of ventricles are thicker than the
auricles.
Reason (R) : Chordae tendineae are attached to cone
shaped projections of the ventricular wall known as papillary
muscles.
4. Assertion (A) : Closed circulatory system is less efficient
than open circulatory system.
Reason (R) : The blood flow is slow in closed circulatory
system than in open circulatory system.
5. Assertion (A): AV bundle is essential for the conduction
of cardiac impulse.
Reason (R) : The AV node picks up the wave of contraction
propagated by SA node.
6. Assertion (A): Cardiac output rises during exercise.
Reason (R) : Cardiac output helps in less nutrient
consumption.

18. Short Answer Type Questions
1. Match column A with column B.
Column A Column B
(a) SA node (i) Tricuspid valve
(b) Human heart (ii) Sphygmomanometer
(c) Ebstein’s disease (iii) 0.8 sec
(d) Blood pressure (iv) Pacemaker
(e) Cardiac cycle (v) Myogenic
2. (i) Define cardiac cycle?
(ii) Why does the left ventricle possess thicker wall than the
right ventricle?
(iii) Who is considered as “Father of Electrocardiography”?
(iv) Name four valves of heart.
(v) What is atherosclerosis?
3. Fill in the blanks
(i) Pulmonary vein drains the blood into ______ atrium.
(ii) First heart sound is caused by the closure of ________
and _______ valve.
(iii) In arteriosclerosis _______ salts precipitate with the
_______ to form plaques.
4. Differentiate between pulmonary and systemic circulation.
5. Why SA node is called pacemaker of heart?
ANSWER KEY
New MCQs
1. (a) 2. (d) 3. (a) 4. (a) 5. (c)
6. (b) 7. (b) 8. (b) 9. (b) 10. (b)
Exam Section
1. (d) 2. (b) 3. (d) 4. (c) 5. (c)
6. (b) 7. (b) 8. (a) 9. (a) 10. (a)
11. (a) 12. (a) 13. (b) 14. (a) 15. (b)
16. (a) 17. (b) 18. (b) 19. (b) 20. (c)
21. (a) 22. (b) 23. (d) 24. (a) 25. (a)
Assertion & Reason
1. (c) 2. (a) 3. (b) 4. (d) 5. (b)
6. (c)
Short Answer Type Questions
1. (a) – (iv), (b) – (v), (c) – (i), (d) – (ii), (e) – (iii)
2. (i) A regular sequence of three events : auricular systole,
ventricular systole and joint diastole or complete cardiac
diastole (relaxation of both auricles and ventricles) during
the completion of one heart beat is known as cardiac cycle.
(ii) Left ventricle pumps blood to whole body whereas right
ventricle pumps blood to lungs which are placed near the
heart,so left ventricle’s wall has to be thicker as it needs extra
pressure to pump the blood to whole body.
(iii) Einthoven (got Nobel Prize in 1924 for discovery of ECG).
(iv) (a) Bicuspid valve
(b) Tricuspid valve
(c) Aortic semilunar valve
(d) Pulmonary semilunar valve.
(v) Atherosclerosis refers to deposition of lipids (cholesterol) on
the wall lining the lumen of arteries.This deposition is called
atherosclerotic plaque. This decreases the area of lumen of
artery and flow of blood is reduced. In extreme cases these
plaques may block the artery completely.
3. (i) left (ii) bicuspid, tricuspid
(iii) calcium, cholesterol.
4.
Pulmonary circulation Systemic circulation
(i) It consists of flow of
deoxygenated blood from
right ventricle to the lungs
and flow of oxygenated
blood from lungs to the
left atrium.
It consists of flow of
oxygenated blood from left
ventricle to all parts of body
and deoxygenated blood
from different parts to right
atrium.
(ii) Blood flow is for a short
distance.
Blood flow is for a longer
distance.
5. The SA node is located in the wall of right auricle slightly
below the opening of the superior vena cava. It has a unique
property of self excitation. It is capable of initiating impulses
which then can stimulate the heart muscles to contract and
thus establishes the basic rhythm at which the heart beats.
So it is aptly called as pacemaker of heart.


19. Prakhar Goel
Student of APEX
One year classroom Program.
He is studying MBBS in Maulana
Azad Medical college Delhi.
Siddhant Rathore
CBSE : 91.6%
Student of APEX
ree year classroom Program.
He is studying Mechanical
Engineering in BITS Goa.
Dhwani Jain
Student of APEX
ree year classroom Program.
She is studying Chemical
Engineering in NUS Singapore.
Selected in NUS
National University of Singapore: 1st Rank in Asia
AIPMT AIR 427(GE)
Prerna Kashyap
CBSE : 96%
Student of APEX
Two year classroom Program.
She is studying in NIT Kurukshetra.
IIT-Main AIR 521(GE)
Apeksha Garg
CBSE : 96%
Student of APEX
One year classroom Program.
Vibhav Singh
CBSE : 96%
Student of APEX
One year classroom Program.
M-95, C-98, P-95 B-98, C-97, P-95
School : Cambridge Indirapuram
School : Amity Noida
Student of APEX
Four year classroom Program.
She is studying in Delhi Technical
Univercity(DTU) .
IIT-Main Score: 186
School : DPS Noida
School : Ryan Noida
STAR PERFORMERS OF THE YEAR
Arindham Roy
CBSE : 95%
Student of APEX
Two year classroom Program.
He is studying in NIT Patna.
IIT-Main Score : 158
School : Cambridge Indirapuram
BITS SCORE: 329
Sharvi Tomar
CBSE : 95.4%
Shubham Mukharjee
Student of APEX
One year classroom Program.
He is studying in IIT Guahati.
IIT(Adv.)AIR 1823(GE)
Shaurya Tomar
CBSE : 93.2%
Student of APEX
Four year classroom Program.
He is studying in Thapar
Institute Patiyala.
IIT-Main Score : 149
School : DPS Noida
Rishab Gupta
CBSE : 92.8%
Student of APEX
Four year classroom Program.
He is studying in Government
Engineering College Bilaspur.
IIT-Main Score :158
School : KV Noida
CBSE TOPPERS
68% Selections in IIT-Main
Selections in IIT-Advanced56%
60%Selections in AIPMT
Shreya
CBSE : 94%
Student of APEX
Twor year classroom Program.
Sharvi Tomar
CBSE : 95.4%
Student of APEX
Four year classroom Program.
M-95, C-96, P-95 M-95, C-95, P-91
School : DPS Noida School : Modern school Noida
Shaurya Tomar
CBSE : 93.2%
Student of APEX
Four year classroom Program.
M-95, C-97, P-92
School : DPS Noida
Pranjal Singh
CBSE : 90.4%
Student of APEX
Two year classroom Program.
Areesha
CBSE : 91%
School : Genesis global school
Deepti
CBSE : 88%
Aarushi
CBSE : 88%
School : St. Teresa Indirapuram School : Ralli Int. schoolSchool : St. Francis Indirapuram
Student of APEX
One year classroom Program.
Student of APEX
Four year classroom Program.
Student of APEX
Two year classroom Program.
Apex topper scored
96%
marks in Board Exam.
100%
students got more
than 85% marks in
Board Exam.
.......and many more
Unmatched results in IITJEE & Medical consistently
Near Jaipuriya Mall
Call for Free Demo classes @ 9990495952
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SCHOOL: DPS Indirapuram