Study

1. CARDIOVASCULAR SYSTEM
• INTRODUCTION
• The cardiovascular system (circulatory system)
consists of three basic components:
1. The heart serves as the pump
2. The blood vessels which are the series of
distributing and collecting tubes
3. The blood serves as the transport medium
within which materials being transported are
dissolved or suspended

2. Functions of cardiovascular system
• The function of cardiovascular system is to supply
oxygen, nutrients and other essential substances
to the tissues of the body and to remove
metabolic end products (e.g. carbon dioxide)
from the tissues.
Heart
• Heart is a muscular organ situated in between the
two lungs in the mediastinum.
• It is made up of two atria and two ventricles.
• Musculature is more and thick in the ventricles
than in the atria.

3. Right side of the heart
• Right atrium has got the pacemaker known as
sinoatrial node that produces cardiac impulses and
atrioventricular node that conducts impulses to the
ventricles.
• It also has two large veins:
 Superior vena cava that returns the
deoxygenated(venous) blood from the head, neck
and upper limbs, and

4. Inferior vena cava that returns the deoxygenated
blood from the lower parts of the body.
• Right atrium communicates with the right
ventricle through the tricuspid valve.
• Deoxygenated blood from the right atrium enters
the right ventricle through this valve
• From the right ventricle, pulmonary artery arises
through which deoxygented blood is pumped into
the lungs
• In the lungs, the deoxygenated blood gets
oxygenated and is returned to left atrium as
arterial blood through pulmonary veins

5. Left side of the heart
• Left atrium communicates with the left ventricle
through the mitral valve (bicuspid valve).
• Left atrium empties oxygenated blood into the left
ventricle through this valve.
• From left ventricle, the systemic aorta arises through
which oxygenated blood is pumped through out the
body.

6. Arterial system
• Comprises the aorta, arteries and arterioles

7. Venous System
• From capillaries venous system starts and it
includes venules, veins and vena cavae.
• Capillaries end in venules
• Venules are continued as veins
• Veins lead in to superior and inferior vena
cava

8. DIVISIONS OF CIRCULATION
Blood flows through two divisions of circulatory system:
1. Systemic circulation and
2. Pulmonary circulation
Systemic circulation is also known as greater circulation
• Blood pumped from left ventricle passes through a
series of blood vessels of arterial tree or arterial system
and reaches the tissues.
• After the capillaries , blood enters venous system and
returns to right atrium of the heart.
• From right atrium, blood enters the ventricle
• Therefore, through the systemic circulation, oxygenated
blood or arterial blood is supplied from heart to tissues
and venous blood returns to the heart from tissues

9. Pulmonary circulation is also called lesser
circulation
• Blood is pumped from right ventricle to lungs
through pulmonary artery
• Exchange of gases occurs between blood and
alveoli of lungs through pulmonary capillary
membrane
• Oxygenated blood returns to left atrium
through the pulmonary veins
• Therefore, left side of the heart contains
oxygenated or arterial blood and the left side
of the heart contains venous blood.

10. CARDIAC MUSCLE CONDUCTION
1. Excitability
 Definition: the ability of tissue to give
response to a stimulus is called excitability
• In case of muscle , the response is the
development of action potential
• This is followed by shortening of muscle
fibres.

11. • The heart has a specialised excitatory structure
from which the discharge of impulse is generated
• This specialised structure is called Pacemaker
• From this, the impulses spread to other parts
through the specialised conductive system
Pacemaker
• Pacemaker is defined as the part of the heart
from which the impulses for the heart beat are
produced normally.

12. • Even though, other parts of the heart like AV
node, atria and ventricle can produce the
impulses, SA node is called the Pacemaker
because the rate of production of impulse
(rhythmicity) is more here.
Spread of Impulses from SA node
• The heart has got specialised conductive
system by which impulses from SA node
spreads to the different parts of the heart

13. • The specialised conductive system is formed by
the modified muscle fibres and include the
following components:
Internodal pathway – between sinoatrial node
and atrioventricular node.
Atrioventricular node (AV node)
Bundle of His
Branch of bundle of His
Purkinje fibres

14. Rhythmicity of other parts of the heart
• Though the SA node is the pacemaker in the
mammalian heart, other parts of the heart also
have the property of rhythmicity:
SA node…………………………….. 70 to 80/ minute
AV node ……………………………. 40 to 60 / minute
Atrial muscle …………………….. 40 to 60 / minute
Ventricular muscle…………………..20 to 40/minute

15. • Potassium channels remain open for a longer
time, causing efflux of more amount of
potassium ions.
• This leads to the development of more
negativity beyond the level of RMP.
• This exists only for a short while.
• Then, the slow depolarisation start again
leading to the development of pacemaker
potential which triggers the next AP.

16. 3. Conductivity
• In human heart, the impulses produced by the
SA node are transmitted to the cardiac muscle
by means of specialised conductive system.
Conductive System in Human Heart
• SA is situated in the right atrium just below
the opening of the superior vena cava.
• AV is situated in the right portion of intraatrial
septum.

17. • Impulses from SA node are conducted to AV node
by means of atrial fibres via:
Anterior internodal fibres of Bachman
Wenckebach and
Posterior internadal fibres of Thorel
• All these fibres converge towards the AV node
and interdigitate with fibres of AV node.
• From AV node, the bundle of HIS arises and
divides into right and left branches.

18. • These branches run on either side of the
intventricular septum and give off Purkinje
fibres which spread all over the ventricular
myocardium.
Velocity of Conduction of Impulses at
different parts of the Conductivity System
Atrial muscle fibre………………….. 0.3 metre/sec
Internodal fibre………………………1.0 metre/sec
AV node………………………………… 0.05 metre/sec

19. • These branches run on either side of the
intventricular septum and give off Purkinje
fibres which spread all over the ventricular
myocardium.
Velocity of Conduction of Impulses at
different parts of the Conductivity System
Atrial muscle fibre………………….. 0.3 metre/sec
Internodal fibre………………………1.0 metre/sec
AV node………………………………… 0.05 metre/sec

20. Bundle of His.……………………… 0.12 metre/sec
Purkinje Fibres …………………… 4.0 metre/ sec
Ventricular muscle fibres …… 0.5 metre/sec
• Therefore, the velocity for conduction of
impulses is maximum in Purkinje fibres and it
is minimum at AV node.

21. 4. Contractility
• The ability to shorten the length(contraction)
after receiving a stimulus is called
Contractility.
• The different contractile properties are:
All or none law
Staircase phenomenon
Summation of subliminal stimulus

22. Refractory period
This is the period in which the muscle does
not show any response to stimulus.
It is of two types:
1. Absolute refractory period and
2. Relative refractory period.

23. CARDIAC CYCLE
1.Definition
• Each heart beat consists of two major periods
called SYSTOLE and DIASTOLE
• During Systole, there is contraction of the cardiac
muscle and pumping of blood from the heart.
• During Diastole, there is relaxation of cardiac
muscle and filling of blood.
• Various changes occur in different chambers of
the heart during each heart beat.

24. • These changes are repeated during every heart
beat in a cyclic manner.
• Therefore, the cardiac cycle is defined as the
succession of coordinated activities which take
place during every heart beat.
2. Divisions of Cardiac Cycle
• The events of cardiac cycle are classified into two
divisions:
Systole and
Diastole

25. 3. Subdivisions of Cardiac
• The subdivisions of the systole and diastole
are:
Systole Time(sec)
1. Isometric contraction……………… 0.05
2. Ejection period ………………………. 0.22
0.27

26. Diastole Time (sec)
1. Protodiastole……………………………….. 0.04
2. Isometric relaxation……………………..0.08
3. Rapid filling ………………………………… 0.11
4. Slow filling ………………………………….. 0.19
5. Atrial systole ………………………………. 0.11
0.53
Total duration of cardiac cycle is 0.27 + 0.53 =0.8sec

27. 4. Description of each event of cardiac cycle
• For the search of better understanding, the
description of events of cardiac cycle is
commenced with atrial systole.
Atrial Systole
• Duration of atrial systole is 0.11 sec .
• This is also called second rapid filling stage or
presystole.
• It is considered as the last phase of ventricular
diastole.

28. • During this period, only a small amount i.e.
10% of blood is forced into the ventricles.
Summary
• Atria contract and a small amount of blood
enters the ventricles.
Isometric Contraction
• It lasts for 0.05 sec.
• All the valves are closed

29. • Ventricles undergo isometric contraction.
• And pressure in the ventricles is increased
sharply.
• This type of contraction is called Isometric
Contraction or Isovolumetric contraction.
Ejection Period
• Duration of ejection period is 0.22 sec.
• Due to the opening of the semilunar valves and
contraction of ventricles, blood is ejected out of
both ventricles.

30. • This period is of two stages:
1st stage is called rapid ejection period ( large
amount of blood is rapidly ejected from both
ventricles)
2nd stage is called the slow ejection period
(blood is pumped out with much less force)
Protodiastole
• Lasts 0.04 sec

31. • Due to ejection of blood, pressure in aorta and
the pulmonary artery increases and pressure
in ventricles drops.
• When the intraventricular pressure becomes
less than the pressure in aorta and pulmonary
artery, the semilunar valves are closed.
• During this period no change occurs.
• Therefore, protodiastole indicates only the
end of systole and beginning of diastole .

32. Isometric Relaxation Period
• Duration of isometric relaxation is 0.08 sec.
• All the valves of the heart are closed.
• Both the ventricles relax as closed cavities
without any change in volume or length of the
muscle fibre.
• Therefore, this is called Isometric or
Isovolumetric relaxation period.
• There is a fall in intraventricular pressure.

33. • The atrioventricular valve open.
• This leads to filling of ventricles.
Rapid Filling
• Duration is 0.11 sec.
• When AV valves are opened, there is a sudden
rush of blood into ventricles.
• So, this period is called the First rapid filling
period.
• About 70% of filling takes place during this phase.

34. Slow Filling
• Duration is 0.19 sec
• After sudden rush of blood, the ventricular
filling becomes slow.
• Therefore, it is called the slow filling ( it is also
called diastasis).
• About 20 % of filling occurs in this phase.

35. Atrial Systole
• After slow filling period, the atria contract
and, the cycle is repeated.
• The atrial systole is also called the last rapid
phase and, a small quantity of the blood
enters the ventricles from atria.
• About 10 % of filling takes place during this
period.

36. THE END