-1-
LECTURE NOTES
IN
CARDIOVASCULAR PHYSIOLOGY
BRIEF OUTLINE
SN TOPIC
1. Cardiovascular system, components, functions, pulmonary & systemic circulation,
innervation of the heart and blood vessels.
2. Physical characteristics & functional significance of cardiac structure, specialised
conductive tissues, pericardium
3. Biophysics of the heart, cardiac action potential, all or none principles.
4 Electrocardiography, vectors, electrical axis
5 Cardiac cycle: meaning, components, atrial, ventricular pressures waves.
6 Haemodynamics
7 Cardiac rates, rhythm, arrhythmias, ventricular hypertrophy, heart blocks and
cardiac arrest.
9 Cardiac output: meaning, determinant, measurement, cardiac index & cardiac
reserve
10 Cardiovascular tree, lymphatic circulation, venous and central pressure
11 Cardiovascular regulatory mechanism: Local and Systemic circulation
12 Systolic, diastolic, pulse and mean arterial pressure. Measurement of blood
pressure
13 Fetal and regional circulation
14 Cardiovascular adjustment in health & diseases: exercise, haemorrhage, shock,
hypertension.
Recommended textbooks
Essentials of medical physiology by K. Sembulingam
Review of Medical Physiology by Ganong
Guyton & Hall Textbook of Medical Physiology
Human physiology: the mechanism of body function by Vander et al.,
, -2-
CARDIOVASCULAR PHYSIOLOGY
OVERVIEW OF THE CARDIOVASCULAR SYSTEM
The cardiovascular system (CVS) is basically a closed vehicle transport system. This
system provides a mechanism by which blood in vessels circulates through body tissues. In
circulating blood, the CVS provides a link between the external environment and tissues. By
this, the CVS supply oxygen and digested nutrients from the gastrointestinal tract (GIT) to
body tissues and also removes carbon-dioxide and other wastes from tissues for excretion
either through the lungs, kidneys, skin etc. It also regulates blood pressure. As blood circulate
through the tissues, hormones, antibodies and other defense components are distributed as
needed for homeostasis, and circulating blood also assist in temperature regulation.
The cardiovascular system is composed of the heart and blood vessels. The heart is
an incessant muscular pump almost the size of a clenched fist, it pumps blood through a
series of vessels (aorta, artery, arterioles, capillaries, venules, veins and vena cavae), the
most smallest of which is the capillaries and are suitable for exchange between blood and
body tissues. The cardiovascular system is also called the circulatory system. The circulatory
system is divided into the systemic (major or greater) circulation and the pulmonary (minor or
lesser) circulation. The third circulation is called the lymphatic circulation which drains the
interstitial space of excess fluid as lymph.
The systemic circulation is operates under high pressure, it starts from the left
ventricles pumping oxygenated blood through the aorta, other systemic vessels back to the
right atrium via the vena cava.
The pulmonary circulation starts from the right ventricles which pumps deoxygenated
blood though the pulmonary artery into the lungs, from the lungs pulmonary veins carry the
oxygenated blood into the left atrium.
The Heart
Heart is made up of three layers of tissues: 1. Outer pericardium 2. Middle myocardium
3. Inner endocardium. Pericardium is the outer covering of the heart. It is made up of two
layers: i. Outer parietal pericardium ii. Inner visceral pericardium.
The space between the two layers is called pericardial cavity or pericardial space and it
contains a thin film of fluid.
i. Outer Parietal Pericardium forms a strong protective sac for the heart. It helps also
to anchor the heart within the mediastinum. It is made up two layers: a). Outer fibrous layer
and b). Inner serous layer. The Fibrous layer is formed by thick fibrous connective tissue. It
is attached to the diaphragm and it is continuous with tunica adventitia (outer wall) of the
blood vessels, entering and leaving the heart. it protects the heart from over stretching.
Serous layer is formed by mesothelium, together with a small amount of connective tissue.
, -3-
Mesothelium contains squamous epithelial cells which secrete a small amount of fluid, which
lines the pericardial space. This fluid prevents friction and allows free movement of heart
within pericardium, when it contracts and relaxes. The total volume of this fluid is only about
25 to 35 mL.
ii. Inner Visceral Pericardium lines the surface of myocardium. It is made up of
flattened epithelial cells. This layer is also known as epicardium.
Pacemaker is structure in the heart that generates the impulses for heart beat. It is
formed by pacemaker cells called P cells. Sinoatrial (SA) node forms the pacemaker in
human heart.
Heart Chambers: In man, the heart is a four chambered muscular pump; it consists of
the right and the left atrial, the right and the left ventricles. The left atrium receives oxygenated
blood from the lungs and the left ventricles pumps it to all parts of the body via the aorta for
the supply of oxygenated blood to the tissues.
The right atrium receives deoxygenated blood from all parts of the body via the vena
cavae and the right ventricle pumps it to the lungs for oxygenation via the pulmonary artery.
Right and left atria are separated from one another by a fibrous septum called inter-atrial
septum. Right and left ventricles are separated from one another by inter-ventricular septum.
The upper part of this septum is a membranous structure, whereas the lower part of it is
muscular in nature.
The left chamber starts the systemic circulation or the major circulation and it has
thicker walls than the right ventricles, this is because it requires greater force to overcome the
high aortic pressure. The right chamber of the heart starts the pulmonary circulation or the
lesser circulation.
The third circulation is called lymphatic circulation. The lymphatic circulation starts
from the interstitial spaces as lymph, it is carried via the lymphatic vessels and empties into
the systemic circulation via the thoracic duct and the right lymphatic duct, from here they enter
the left and right subclavian veins and then emptied into the left and right jugular veins of their
respective sides.
Cardiac valves: Guarding the openings between the atrial and ventricles are atrio-
ventricular valves (A-V) valves. The right valve has 3 cups and it is called the tricuspid valve
while the left A-V valve has two cups and it is called the bicuspid valve or mitral valve. AV
valves open when the pressure in the atrial exceeds the ventricular pressure and closed when
the reverse occurs. The AV values are held in place during ventricular contraction to avoid
bulging into the atrium during systole by the papillary muscles. The papillary muscles are
attached to the chordae tendineae at the apex of the heart. Also guarding the exits from the
ventricles and the aorta are semi-lunar valves, they have three cups and shaped like a half
, -4-
moon. They usually open when the pressure in the ventricles exceeds that in their connecting
vessels. Cardiac valves prevent back flow of blood by allowing one directional flow.
Nerve supply (innervation) to the heart
The heart receives a rich supply of sympathetic and parasympathetic nerve fibers
(vagus nerves). The sympathetic postganglionic fibers innervate the entire heart and release
norepinephrine, whereas the parasympathetic fibers terminate mainly on special cells found in
the atria and release primarily acetylcholine. The receptors for norepinephrine on cardiac
muscle are mainly beta-adrenergic. The receptors for acetylcholine are of the muscarinic type.
Blood Supply to the heart
The blood being pumped through the heart chambers does not exchange nutrients and
metabolic end products with the myocardial cells. The heart like the cells of all other organs,
receive their blood supply via arteries called coronary artery that branch from the aorta. This
forms the coronary blood flow. The coronary arteries form 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.
ACTIONS OF THE HEART
The action of the heart are classified into four types: 1. Chronotropic action
2. Inotropic action 3. Dromotropic action 4. Bathmotropic action.
Chronotropic action is the frequency of heartbeat or heart rate. It is of two types:
i. Tachycardia or increase in heart rate ii. Bradycardia or decrease in heart rate.
Inotropic action is the force of contraction of heart. It is of two types: i. Positive
inotropic action or increase in the force of contraction ii. Negative inotropic action or
decrease in the force of contraction.
Dromotropic action is the velocity of conduction of impulse through heart. It is of two
types: i. Positive dromotropic action or increase in the velocity of conduction and ii. Negative
dromotropic action or decrease in the velocity of conduction.
Bathmotropic action is the excitability of cardiac muscle. It is also of two types:
i. Positive bathmotropic action or increase in the excitability of cardiac muscle and ii. Negative
bathmotropic action or decrease in the excitability of cardiac muscle.
PROPERTIES OF CARDIAC MUSCLES
The properties of cardiac muscles include:
Excitability is defined as the ability of a living tissue to give response to a stimulus in
the form of action potential.
LECTURE NOTES
IN
CARDIOVASCULAR PHYSIOLOGY
BRIEF OUTLINE
SN TOPIC
1. Cardiovascular system, components, functions, pulmonary & systemic circulation,
innervation of the heart and blood vessels.
2. Physical characteristics & functional significance of cardiac structure, specialised
conductive tissues, pericardium
3. Biophysics of the heart, cardiac action potential, all or none principles.
4 Electrocardiography, vectors, electrical axis
5 Cardiac cycle: meaning, components, atrial, ventricular pressures waves.
6 Haemodynamics
7 Cardiac rates, rhythm, arrhythmias, ventricular hypertrophy, heart blocks and
cardiac arrest.
9 Cardiac output: meaning, determinant, measurement, cardiac index & cardiac
reserve
10 Cardiovascular tree, lymphatic circulation, venous and central pressure
11 Cardiovascular regulatory mechanism: Local and Systemic circulation
12 Systolic, diastolic, pulse and mean arterial pressure. Measurement of blood
pressure
13 Fetal and regional circulation
14 Cardiovascular adjustment in health & diseases: exercise, haemorrhage, shock,
hypertension.
Recommended textbooks
Essentials of medical physiology by K. Sembulingam
Review of Medical Physiology by Ganong
Guyton & Hall Textbook of Medical Physiology
Human physiology: the mechanism of body function by Vander et al.,
, -2-
CARDIOVASCULAR PHYSIOLOGY
OVERVIEW OF THE CARDIOVASCULAR SYSTEM
The cardiovascular system (CVS) is basically a closed vehicle transport system. This
system provides a mechanism by which blood in vessels circulates through body tissues. In
circulating blood, the CVS provides a link between the external environment and tissues. By
this, the CVS supply oxygen and digested nutrients from the gastrointestinal tract (GIT) to
body tissues and also removes carbon-dioxide and other wastes from tissues for excretion
either through the lungs, kidneys, skin etc. It also regulates blood pressure. As blood circulate
through the tissues, hormones, antibodies and other defense components are distributed as
needed for homeostasis, and circulating blood also assist in temperature regulation.
The cardiovascular system is composed of the heart and blood vessels. The heart is
an incessant muscular pump almost the size of a clenched fist, it pumps blood through a
series of vessels (aorta, artery, arterioles, capillaries, venules, veins and vena cavae), the
most smallest of which is the capillaries and are suitable for exchange between blood and
body tissues. The cardiovascular system is also called the circulatory system. The circulatory
system is divided into the systemic (major or greater) circulation and the pulmonary (minor or
lesser) circulation. The third circulation is called the lymphatic circulation which drains the
interstitial space of excess fluid as lymph.
The systemic circulation is operates under high pressure, it starts from the left
ventricles pumping oxygenated blood through the aorta, other systemic vessels back to the
right atrium via the vena cava.
The pulmonary circulation starts from the right ventricles which pumps deoxygenated
blood though the pulmonary artery into the lungs, from the lungs pulmonary veins carry the
oxygenated blood into the left atrium.
The Heart
Heart is made up of three layers of tissues: 1. Outer pericardium 2. Middle myocardium
3. Inner endocardium. Pericardium is the outer covering of the heart. It is made up of two
layers: i. Outer parietal pericardium ii. Inner visceral pericardium.
The space between the two layers is called pericardial cavity or pericardial space and it
contains a thin film of fluid.
i. Outer Parietal Pericardium forms a strong protective sac for the heart. It helps also
to anchor the heart within the mediastinum. It is made up two layers: a). Outer fibrous layer
and b). Inner serous layer. The Fibrous layer is formed by thick fibrous connective tissue. It
is attached to the diaphragm and it is continuous with tunica adventitia (outer wall) of the
blood vessels, entering and leaving the heart. it protects the heart from over stretching.
Serous layer is formed by mesothelium, together with a small amount of connective tissue.
, -3-
Mesothelium contains squamous epithelial cells which secrete a small amount of fluid, which
lines the pericardial space. This fluid prevents friction and allows free movement of heart
within pericardium, when it contracts and relaxes. The total volume of this fluid is only about
25 to 35 mL.
ii. Inner Visceral Pericardium lines the surface of myocardium. It is made up of
flattened epithelial cells. This layer is also known as epicardium.
Pacemaker is structure in the heart that generates the impulses for heart beat. It is
formed by pacemaker cells called P cells. Sinoatrial (SA) node forms the pacemaker in
human heart.
Heart Chambers: In man, the heart is a four chambered muscular pump; it consists of
the right and the left atrial, the right and the left ventricles. The left atrium receives oxygenated
blood from the lungs and the left ventricles pumps it to all parts of the body via the aorta for
the supply of oxygenated blood to the tissues.
The right atrium receives deoxygenated blood from all parts of the body via the vena
cavae and the right ventricle pumps it to the lungs for oxygenation via the pulmonary artery.
Right and left atria are separated from one another by a fibrous septum called inter-atrial
septum. Right and left ventricles are separated from one another by inter-ventricular septum.
The upper part of this septum is a membranous structure, whereas the lower part of it is
muscular in nature.
The left chamber starts the systemic circulation or the major circulation and it has
thicker walls than the right ventricles, this is because it requires greater force to overcome the
high aortic pressure. The right chamber of the heart starts the pulmonary circulation or the
lesser circulation.
The third circulation is called lymphatic circulation. The lymphatic circulation starts
from the interstitial spaces as lymph, it is carried via the lymphatic vessels and empties into
the systemic circulation via the thoracic duct and the right lymphatic duct, from here they enter
the left and right subclavian veins and then emptied into the left and right jugular veins of their
respective sides.
Cardiac valves: Guarding the openings between the atrial and ventricles are atrio-
ventricular valves (A-V) valves. The right valve has 3 cups and it is called the tricuspid valve
while the left A-V valve has two cups and it is called the bicuspid valve or mitral valve. AV
valves open when the pressure in the atrial exceeds the ventricular pressure and closed when
the reverse occurs. The AV values are held in place during ventricular contraction to avoid
bulging into the atrium during systole by the papillary muscles. The papillary muscles are
attached to the chordae tendineae at the apex of the heart. Also guarding the exits from the
ventricles and the aorta are semi-lunar valves, they have three cups and shaped like a half
, -4-
moon. They usually open when the pressure in the ventricles exceeds that in their connecting
vessels. Cardiac valves prevent back flow of blood by allowing one directional flow.
Nerve supply (innervation) to the heart
The heart receives a rich supply of sympathetic and parasympathetic nerve fibers
(vagus nerves). The sympathetic postganglionic fibers innervate the entire heart and release
norepinephrine, whereas the parasympathetic fibers terminate mainly on special cells found in
the atria and release primarily acetylcholine. The receptors for norepinephrine on cardiac
muscle are mainly beta-adrenergic. The receptors for acetylcholine are of the muscarinic type.
Blood Supply to the heart
The blood being pumped through the heart chambers does not exchange nutrients and
metabolic end products with the myocardial cells. The heart like the cells of all other organs,
receive their blood supply via arteries called coronary artery that branch from the aorta. This
forms the coronary blood flow. The coronary arteries form 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.
ACTIONS OF THE HEART
The action of the heart are classified into four types: 1. Chronotropic action
2. Inotropic action 3. Dromotropic action 4. Bathmotropic action.
Chronotropic action is the frequency of heartbeat or heart rate. It is of two types:
i. Tachycardia or increase in heart rate ii. Bradycardia or decrease in heart rate.
Inotropic action is the force of contraction of heart. It is of two types: i. Positive
inotropic action or increase in the force of contraction ii. Negative inotropic action or
decrease in the force of contraction.
Dromotropic action is the velocity of conduction of impulse through heart. It is of two
types: i. Positive dromotropic action or increase in the velocity of conduction and ii. Negative
dromotropic action or decrease in the velocity of conduction.
Bathmotropic action is the excitability of cardiac muscle. It is also of two types:
i. Positive bathmotropic action or increase in the excitability of cardiac muscle and ii. Negative
bathmotropic action or decrease in the excitability of cardiac muscle.
PROPERTIES OF CARDIAC MUSCLES
The properties of cardiac muscles include:
Excitability is defined as the ability of a living tissue to give response to a stimulus in
the form of action potential.
