Cardio-Vascular system

Cardio-Vascular system

• Also called as circulatory system
• A closed system of the heart and blood vessels
• The heart pumps blood
• Blood vessels allow blood to circulate to all parts of the body
• The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products

​

Heart

• Cone-shaped organ about the size of a closed fist
• In the mediastinum
• Extends from the level of the second rib to about the level of the sixth rib
• Slightly left of the midline
• Heart is bordered:
• Laterally by the lungs
• Posteriorly by the vertebral column
• Anteriorly by the sternum

​

• Rests on the diaphragm inferiorly

​

Heart

Chambers of the Heart

• Atria – two superior chambers
• “Receiving chambers”
• Blood from veins enters atria
• Ventricles – two inferior chambers
• “pumping chambers”
• Thick muscular walls to increase force of pumping action
• Left > right
• Separated by interventricular septum

​

Valves of the Heart

• Permit blood flow in one direction during circulation
• Atrioventricular valves (AV valves)
• Also cuspid valves
• Between atria and ventricles
• Semilunar (SL valves)
• Between R ventricle and pulmonary arteries and L ventricle and aorta

​

Atrioventricular Valves

• Tricuspid valve
• Btwn R atrium and ventricle
• 3 flaps of endocardium
• Connected to ventricular papillary muscle via chordae tendinae
• Bicuspid valve
• Btwn L atrium and ventricle
• Also called mitral valve
• Two flaps of endocardium

​

Semilunar Valves

• Pulmonary semilunar valve
• Btwn R ventricle and pulmonary trunk
• Aorta semilunar valve
• Btwn L ventricle and aorta

Chambers & Valves

The Heart

• Humans have a four chambered heart surrounded by a fluid filled membrane known as the pericardium.
• The right and left side of the heart are separated by a wall of muscle called the septum.

Atria

• The heart contains two thin walled upper chambers known as atria.
• The atria collect blood from the veins.

​

Ventricles

• The heart contains two thick walled lower chambers called ventricles.
• The ventricles receive blood from the atria and pump it out of the heart.

​

Heart Valves

• The heart contains valves that control the flow of blood.
• Valves are located between the atria and the ventricles known as atrioventricular valves.
• Valves are also located between the ventricles and the arteries known as semi-lunar valves.

​

Covering layers of heart

• Pericardium – a double-walled sac around the heart composed of:
1. A superficial fibrous pericardium
2. A deep two-layer serous pericardium
1. The parietal layer lines the internal surface of the fibrous pericardium
2. The visceral layer or epicardium lines the surface of the heart
1. Pericardial space: between parietal and visceral layer
• Filled with 10-15mL of pericardial fluid
• Decreases friction

​

Covering layers of heart

• The Function of the Pericardium:
• Protects and anchors the heart
• Prevents overfilling of the heart with blood
• Allows for the heart to work in a relatively friction-free environment

​

Pericardial Layers of the Heart

Chapter 18, Cardiovascular System

19

Figure 18.2

Heart Wall

• 3 layers –
• Epicardium
• Myocardium
• Endocardium
• Epicardium – outer layer
• Epicardium = visceral layer of serous pericardium
• Myocardium – thick, contractile layer composed of cardiac muscle cells
• Intercalated disks contain many gap junctions
• Allow cardiac muscle cells to function as a single unit
• Endocardium – interior of cardiac wall
• Endothelial tissue
• Provides smooth lining for inner side of heart
• Covers valves of heart.

Path of Blood

• Oxygen depleted blood enters the right side of the heart through the inferior/superior vena cava.
• Blood enters the right atrium and the atrium contracts.
• The atrioventricular (tricuspid) valve opens and blood enters the right ventricle.
• The right ventricle contracts.
• The (pulmonary) semilunar valve opens and blood enters the pulmonary artery.

​

Path of Blood

• The pulmonary artery carries the oxygen depleted blood to the lungs where the carbon dioxide is dropped off and oxygen is picked up.
• Oxygen rich blood now travels back to the left side of heart through the pulmonary vein.
• Blood enters the left atrium and the left atrium contracts. 

​

Path of Blood

• The atrio-ventricular (bicuspid) valve opens and blood enters the left ventricle.
• The left ventricle contracts. 
• The (aortic) semi-lunar valve opens and the oxygen rich blood enters the aorta.
• The aorta carries the oxygenated blood to the entire body.

​

Pathway of Blood Through the Heart and Lungs

• Right atrium 🡪 tricuspid valve 🡪 right ventricle
• Right ventricle 🡪 pulmonary semilunar valve 🡪 pulmonary arteries 🡪 lungs
• Lungs 🡪 pulmonary veins 🡪 left atrium
• Left atrium 🡪 bicuspid valve 🡪 left ventricle
• Left ventricle 🡪 aortic semilunar valve 🡪 aorta
• Aorta 🡪 systemic circulation

Chapter 18, Cardiovascular System

25

Pathway of Blood Through the Heart and Lungs

Chapter 18, Cardiovascular System

26

Figure 18.5

Blood Flow

27-27

Blood Vessels: The Vascular System

Slide 11.23

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Taking blood to the tissues and back to the heart
• Arteries
• Arterioles
• Capillaries
• Venules
• Veins

The Vascular System

Slide 11.24

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 11.8b

Structure of Blood Vessels

• Tunica adventitia - outermost layer
• Fibrous connective tissue
• Holds vessels open; prevents tearing of vessels walls during body movements
• Larger in veins than arteries
• Tunica media – middle layer
• Smooth muscle and elastic CT
• Helps vessels constrict and dilate
• Larger in arteries

​

Structure of Blood Vessels

• Tunica intima – innermost layer
• Composed of endothelium
• Semilunar valves present in veins
• One cell thick in capillaries

​

Types of Blood Vessels

• There are three types of blood vessels in mammalian circulation: arteries, veins and capillaries.
• Together they form a network of blood vessels throughout the organism that transport blood.

Arteries

• Arteries are blood vessels that carry oxygen rich blood away from the heart. (except pulmonary artery)
• The walls of arteries are very thick layers of connective tissue and muscle fibres and are therefore able to withstand the pressure of blood pumped from the heart.
• The walls are also elastic to allow for increased blood flow.
• Paired – left and right artery of the same name

​

Arterioles

• Arteries decrease in size to become arterioles which are composed of smooth muscle and elastic fibre.
• Blood flows through arteries into smaller and smaller vessels known as arterioles.
• The arterioles finally connect to the capillaries.

​

Aorta

Systemic Arteries

• Arch of aorta
• Subclavian (L and R)
• Brachiocephalic
• common carotid (L and R)
• Axillary (L and R)
• Brachial (L and R)
• Radial
• Ulnar

• Thoracic aorta
• Abdominal aorta
• Common iliac
• External iliac
• Femoral
• Popliteal
• Posterior tibial
• Anterior tibial
• Dorsal pedis

Veins

• Veins are blood vessels that carry oxygen poor blood from the body back to the right side of the heart. (except pulmonary vein)
• The walls of the veins are composed of smooth muscles. Pressure in the veins is low so they rely on skeletal muscles to aid in venous blood flow.
• Most large veins have the same names as the arteries

​

Veins

• Veins contain valves that ensure blood flows in one direction only. In other words, they prevent the backward flow of blood.
• Sometimes these valves are damaged and the pooling blood causes the veins to bulge and the result is varicose veins.

​

Systemic Veins

• Superior vena cava
• Inferior vena cava
• External jugular
• Internal jugular
• Brachiocephalic (L and R)
• Subclavian (L and R)
• Cephalic
• axillary

• Basilic
• Median basilic
• Median cubital
• Common iliac
• External iliac
• Femoral
• Popliteal
• Great saphenous
• Small saphenous

Capillaries

• Capillaries are the smallest blood vessels with walls that are composed of a single layer of cells.
• Exchange of materials between the blood and the body cells occurs in the capillaries. The single layer of cells is ideal for diffusion of nutrients and gases.

Differences Between Blood Vessel Types

Slide 11.26

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Walls of arteries are the thickest
• Lumens of veins are larger
• Skeletal muscle “milks” blood in veins toward the heart
• Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue

Movement of Blood Through Vessels

Slide 11.27

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Most arterial blood is pumped by the heart
• Veins use the milking action of muscles to help move blood

Figure 11.9

Blood circulation

• 4 types –
• Systemic circulation
• Pulmonary circulation
• Coronary circulation
• Portal circulation

Systemic Circulation

• the system of blood vessels that carries oxygenated blood from LV of heart to the tissues of the body and deoxygenated blood back to the heart (RA).
• The pathway between the left and right sides of the heart.
• Left ventricle 🡪 aorta 🡪 arteries 🡪 arterioles 🡪 capillaries 🡪 venules 🡪 veins 🡪 vena cava 🡪 heart (right atrium)

​

Pulmonary circulation

• Includes the system of blood vessels that carries deoxygenated blood from RV to the lungs and oxygenated blood back to the heart (LA).
• The blood pathway between the right side of the heart, to the lungs, and back to the left side of the heart.
• Right ventricle 🡪 pulmonary artery trunk 🡪 pulmonary arteries 🡪 lungs 🡪 pulmonary veins 🡪 heart (left atrium)
• Purification of the blood

​

​

Coronary Circulation�

• Coronary circulation is the functional blood supply to the heart muscle itself
• Blood in the heart chambers does not nourish the myocardium
• The heart has its own nourishing circulatory system
• Coronary arteries
• Cardiac veins
• Blood empties into the right atrium via the coronary sinus

​

Coronary Circulation: Arterial Supply

Chapter 18, Cardiovascular System

51

Figure 18.7a

Coronary Circulation: Venous Supply

Chapter 18, Cardiovascular System

52

Figure 18.7b

Portal circulation

• The portal system is the system of veins comprising the hepatic portal vein and its tributaries.
• The portal venous system is responsible for directing blood from parts of the gastrointestinal tract & spleen to the liver. Substances absorbed in the small intestine travel first to the liver for processing before continuing to the heart.
• It also includes venous drainage from the spleen and pancreas.
• The hepatic portal vein is a blood vessel that conducts blood from the gastrointestinal tract and spleen to the liver. This blood is rich in nutrients that have been extracted from food, and the liver processes these nutrients; it also filters toxins that may have been ingested with the food. The blood leaves the liver to the heart in the hepatic veins.

• The hepatic portal vein is usually formed by the combination of the superior mesenteric, inferior mesenteric, gastric, and splenic veins.

Conduction System of The Heart

Slide 11.13a

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Heart has Intrinsic conduction system �consisting of special junctional tissues. (Hence, Heart muscle cells contract, without nerve impulses, in a regular, continuous way).
• These specialized tissues generate & conduct the electrical cardiac impulses all over the heart.

​

Conduction System of The Heart

Slide 11.13b

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Four structures composed of modified cardiac muscle

• Sinoatrial node (SA Node)
• Atrioventricular node (AV Node)
• Atrioventricular bundle (Bundle of His) with its right & left branches
• Purkinje fibers

Slide 11.14b

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 11.5

Conduction System of the Heart

• Sinoatrial Node (SA Node)
• Pacemaker of the heart – generates impulses
• 100s of cells in the R atrium near the opening of the superior vena cava.
• Sends impulses to AV node
• Atrioventricular Node (AV Node)
• Small mass of cardiac muscle tissue
• Left lower border of R atrium
• Receives impulses from SA node & sends to Bundle of His.
• When SA node fails to generate impulse, AV node generates impulses.

Conduction System of the Heart

• Atrioventricular Bundle
• Also called as Bundle of His
• Bundle of specialized cardiac muscle fibers originating in the AV node
• Branches into R and L branches eventually becoming Purkinje fibers
• Extend into the walls of the ventricles and papillary muscles

Heart Physiology: Sequence of Excitation

• Sinoatrial (SA) node generates impulses about 75 times/minute
• Atrioventricular (AV) node delays the impulse approximately 0.1 second
• Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)
• AV bundle splits into two pathways in the interventricular septum (bundle branches)
• Bundle branches carry the impulse toward the apex of the heart
• Purkinje fibers carry the impulse to the heart apex and ventricular walls

​

Chapter 18, Cardiovascular System

63

Chapter 18, Cardiovascular System

64

Figure 18.14a

The Heart: Cardiac Conduction System

• Group of structures that send electrical impulses through the heart

​

• Sinoatrial node (SA node)
• Wall of right atrium
• Generates impulse
• Natural pacemaker
• Sends impulse to AV node

​

• Atrioventricular node (AV� node)
• Between atria just above ventricles
• Atria contract
• Sends impulse to the bundle of His

​

​

• Bundle of His
• Between ventricles
• Two branches
• Sends impulse to Purkinje fibers

​

• Purkinje fibers
• Lateral walls of ventricles
• Ventricles contract

27-65

27-66

HEART PHYSIOLOGY

Cardiac cycle

Cardiac Cycle

• It is the sequence of events which occurs during one complete heart beat.
• In each cardiac cycle, heart contracts & relax alternately, leading to pressure difference & flow of blood from higher pressure to lower pressure.
• Total time required for one cardiac cycle is 0.8 sec
• Systole = contraction of heart muscle
• Diastole = relaxation of heart muscle

​

Events of Cardiac cycle

• Both atria & ventricles undergo systolic & diastolic phases, hence one cardiac cycle is divided into 4 phases –
• Atrial Systole – Contraction of atrium – 0.1 sec
• Atrial Diastole – Relaxation of atrium – 0.7 sec
• Ventricular Systole – Contraction of ventricles – 0.3 sec
• Ventricular Diastole – Relaxation of ventricles – 0.5 sec

Atrial events

• These include atrial systole & atrial diastole.
• Atrial systole occurs for 0.1 sec followed by atrial diastole for 0.7 sec.
• During atrial systole, atria contract & pour their blood into respective ventricles.
• Right atrium contracts
• Tricuspid valve opens
• Blood fills right ventricle
• Left atrium contracts
• Bicuspid valve opens
• Blood fills left ventricle

​

Atrial events

• During atrial diastole, atria relax & the blood from SV & IV fill the RA & the blood from PV fills the LA.
• After this, they again contract to perform atrial systole.

Ventricular events

• As the atrial systole ends, the ventricular systole begins & continues for 0.3 sec & is followed by ventricular diastole for 0.5 sec.
• The ventricular events can be studied in different periods such as-
• Isometric ventricular contraction period (0.05)
• Rapid & slow ejection period(0.25)
• Prodiastolic period (0.04)
• Isometric ventricular relaxation period (0.08)
• Rapid & slow inflow period (0.28)
• Last rapid filling period (0.1)

​

Ventricular events

• Isometric ventricular contraction period – As ventricular systole starts, both the AV valves close synchronously. This produces first heart sound. At this time SL valves are also closed & hence the ventricular pressure is increasing without any decrease in its volume. This period is Isometric ventricular contraction period. This period remains for 0.05 sec.
• This period starts with closure of AV valves & ends with opening of SL valves.

Ventricular events

• Rapid & slow ejection period – After 0.05 sec, the SL valves open & due to ventricular systole, blood is ejected out into respective arteries. This is rapid ejection period (0.15 sec). Later on, as the volume decreases, the intraventriclar pressure declines & blood is poured out with slow speed. This is called as slow ejection period (0.1 sec)
• Prodiastolic period – After ventricular systole, blood tries to rush back into respective ventricles. But, this is suddenly stopped by the closure of SL valves. This produces 2^nd heart sound, indicating the end of ventricular systole. The interval between start of ventricular diastole & closure of SL valves is known as Prodiastolic period (0.04 sec)

Ventricular events

• Isometric ventricular relaxation period – After Prodiastolic period, the ventricles undergo relaxation (even atria). During this period (0.08) both SL & AV valves are closed & both atria & ventricles are in diastolic condition. Thus, intra-ventricular pressure is minimum & heart is relaxing.
• Rapid & slow inflow period (0.28) – The Isometric ventricular relaxation period ends with opening of AV valves & since ventricles are relaxing, rapid flow of blood from atria to ventricles starts. This is known as rapid inflow period – 3^rd heart sound is heard on echophone at this time. After this slow inflow of blood continues.

• Last rapid filling period (0.1) – When ventricular diastole is about to end, the atrial systole has already started & it overlaps for 0.1 sec. During this period, because of active contraction of atria, filling of ventricles start rapidly. This is called as rapid filling period & 4^th heart sound is heard at this time on echophone.

Heart Sounds

• Heart sounds (lub-dup) are associated with closing of heart valves
• First sound occurs as AV valves close and signifies beginning of systole (contraction)
• Second sound occurs when SL valves close at the beginning of ventricular diastole (relaxation)

Chapter 18, Cardiovascular System

79

Heart Sounds

• First heart sound or “lubb”
• Atrioventricular valves and surrounding fluid vibrations as valves close at beginning of ventricular systole
• Second heart sound or “dupp”
• Results from closure of aortic and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer
• Third & fourth heart sound (occasional)
• Caused by turbulent blood flow into ventricles and detected near end of first one-third of diastole

The Heart: Heart Sounds

• One cardiac cycle – two heart sounds (lubb and dubb) when valves in the heart snap shut
• Lubb – First sound
• When the ventricles contract, the tricuspid and bicuspid valves snap shut
• Dubb – Second sound
• When the atria contract and the pulmonary and aortic valves snap shut

27-81

Significance of heart sounds

• The intensity & duration of heart sounds indicate functioning of myocardium.
• First sound “Lubb” indicates proper functioning of AV valves & beginning of ventricular systole
• Second sound “Dubb” indicates proper functioning of Semi lunar valves & end of ventricular systole & beginning of ventricular diastole.

​

ECG

• Electrocardiogram
• It is the graphical recording of electrical changes in the heart during cardiac cycle.
• Instrument used – Electrocardiograph.
• In clinical practice, ECG is recorded by placing electrodes on the arms & legs (Limb leads) & six positions on the chest (chest leads).
• The electrocardiograph amplifies the heart’s electrical activity & produces different tracings on the graph paper

​

Electrocardiogram

• A normal ECG consists of 3 different waves-
• P wave corresponds to depolarization of SA node
• QRS complex wave corresponds to ventricular depolarization
• T wave corresponds to ventricular repolarization
• Atrial repolarization record is masked by the larger QRS complex

Electrocardiogram

• Pattern
• P wave
• Atria depolarization
• QRS complex
• Ventricle depolarization
• Atria repolarization
• T wave:
• Ventricle repolarization

Electrocardiogram

• P wave (0.2 mV, 0.08 sec) is a small upward wave, representing atrial depolarization (excitation followed by contraction), which spreads from SA node through out both atria.
• QRS complex (1.8 mV, 0.06 sec), begins as large downward wave, continues as large upright triangular wave & ends as a downward wave.
• The QRS complex represent the onset of ventricular depolarization, as the electrical impulses spreads through the ventricles.

Electrocardiogram

• T wave (0.4 mV, 1.12 sec) is a dome shaped upward deflection, which indicates the ventricular repolarization (relaxation) & starts just before ventricles begin to relax.
• The repolarization of atrium is not evident in ECG, bcoz, it is buried under QRS complex.

Significance of ECG

• ECG is a diagnostic tool to assess cardiac functions. It gives information about the following–
• Heart rate, & rhythm & conduction of cardiac impulses.
• Position of heart in the chest cavity.
• Relative size of cardiac chambers & muscle.
• Type of conduction blockade
• Site, duration & extent of ischemic damage to the myocardium.
• Extra systoles or Arrthymias

Electrocardiography

Figure 18.16

Electrocardiogram (ECG) can trace conduction

of electrical signals through the heart

Aberrant ECG patterns indicate damage

Alterations in Electrocardiogram

Heart Excitation Related to ECG

Figure 18.17

Cardiac Output

Slide 11.18

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Cardiac output (CO)
• Amount of blood pumped out by heart (both RV & LV) in one minute
• CO = heart rate x stroke volume
• Stroke volume
• Volume of blood pumped out by heart (both ventricles) in one cardiac cycle or heart beat.
• 70 ml per beat

Cardiac output, cont.

• CO = HR x SV
• 5040 ml/min = 72 beats/min x 70 ml/beat
• Normal cardiac output = 5 litres/min
• Hence, almost entire blood supply passes through heart once per minute.
• CO varies with demands of the body.

The Heart: Regulation of Heart Rate

Slide 11.20

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Stroke volume usually remains relatively constant
• Starling’s law of the heart – the more that the cardiac muscle is stretched, the stronger the contraction
• Changing heart rate is the most common way to change cardiac output

Regulation of Heart Rate

Slide 11.21

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Increased heart rate
• Sympathetic nervous system
• Crisis
• Low blood pressure
• Hormones
• Epinephrine
• Thyroxine
• Exercise
• Decreased blood volume

The Heart: Regulation of Heart Rate

Slide 11.22

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Decreased heart rate
• Parasympathetic nervous system
• High blood pressure or blood volume
• Decreased venous return
• In Congestive Heart Failure the heart is worn out and pumps weakly. Digitalis works to provide a slow, steady, but stronger beat.

Cardiac Output Regulation

Slide 11.19

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 11.7

Pulse

Slide 11.35

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• Pulse – pressure wave of blood
• Monitored at “pressure points” where pulse is easily palpated

Figure 11.16

Blood Pressure

• Force/Lateral pressure exerted by the blood on the inner walls of blood vessels.
• Highest in arteries
• Lowest in veins

​

• In clinical practice, usually BP is measured

in large arteries.

• Systolic pressure (110 – 140 mm of Hg)
• Is the maximum pressure exerted by blood

during ventricular systole

​

• Diastolic pressure (70 – 90 mm of Hg)
• Is the minimum pressure exerted by blood

during ventricular diastole

​

• Reported as the systolic number over the diastolic number (120/80 mm of Hg)

Blood Pressure

• The force of blood on the arteries’ walls = blood pressure
• Blood pressure decreases when the heart relaxes, but there must always be some pressure to keep the blood flowing
• Doctors measure blood pressure with a sphygmomanometer by 3 methods
• Palpatory method
• Auscultatory method
• Oscillatory method

​

Measuring Arterial Blood Pressure

Slide 11.37

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

Figure 11.18

More cells constriction of blood

vessel walls

Regulation of Blood Pressure

• BP is regulated by 3 different process –
• 1. Autonomic nervous system regulation
• Baroreceptor reflex
• Chemoreceptor reflex
• 2. Chemical regulation
• 3. Hormonal regulation
• Renin-Angiotensinogen-Aldosterone system
• Adrenaline & Nor-adrenaline
• Anti-diuretic hormone
• Atrial Natriuretic peptide

Baroreceptor reflex

• Baroreceptors are present in carotid sinus & aortic arch
• Sensitive to changes in blood pressure & sends impulses to Cardiac centre of medulla oblongata.
• The cardiac center in turn responds and sends impulses back to heart through sympathetic & parasympathetic nerves

Baroreceptor Reflex

Chemoreceptor reflex

• Chemoreceptors are sensitive to change in concentration of chemicals such as Oxygen, Carbon dioxide & Hydrogen.
• Located nearby to baroreceptors such as carotid bodies & aortic bodies present at carotid sinus & arch of aorta respectively.
• They responds to the changes in concentration of these chemicals in blood & sends impulses to cardiac center & respiratory center.

• During Hypoxia, Hypercapnia & acidosis, BP is decreased & the chemoreceptors sends impulses to cardiac center, which in turn causes sympathetic stimulation leading to vasoconstriction & increase in cardiac output & hence increase in BP.

Chemoreceptor Reflex-pH

Baroreceptor and Chemoreceptor�Reflexes

Chemical regulation

• The inorganic salts present in the blood maintains the BP.
• Sodium, Potassium & Calcium ions
• Increase in sodium ions leads to increase in BP
• Increase in potassium ions leads to decrease in BP.
• Increase in calcium ions leads to increase in BP

​

Hormonal regulation

• Hormones provide long term regulation of BP by –
• Altering cardiac output
• Changing peripheral vascular resistance
• Adjusting total blood volume
• Adrenaline & Nor-Adrenaline – these are produced by adrenal medulla gland. They increase pumping action of heart (HR & FOC) & bring about the vasoconstriction of arteries in skin & abdominal organs leading to increase in BP.

• Anti-diuretic hormone – is produced by hypothalamus & stored & released from posterior pituitary gland.
• ADH causes vasoconstriction of blood vessels & also decrease the loss of water & salts through urine (so blood volume is increased) leading to increase in BP.

• Atrial-Natriuretic peptide – is released by the cells of atrium of heart.
• ANP lowers the BP by causing vasodilatation & promoting loss of water & salts through urine.

Renin-Angiotensinogen-Aldosterone system

• It is the main regulating system of BP in long term.
• Due to decrease in blood volume, sodium levels, the BP decreases.
• Decrease in BP stimulates Juxta-Glomerular cells of kidney to secrete an enzyme called as Renin.
• The increased levels of renin in blood leads to conversion of Angiotensinogen (a plasma protein produced by liver) into Angiotensin-I.
• As blood flows through the lungs, an enzyme called as Angiotensin converting enzyme (ACE)in lung capillaries converts inactive Angiotensin-I into active Angiotensin-II.

​

• This angiotensin-II has multiple targets.
• 1. Angiotensin –II acts on adrenal cortex gland to increase the secretion of Aldosterone.
• The aldosterone increases the reabsorption of sodium & water in renal tubules leading to increase in blood volume & BP.
• 2. Angiotensin –II directly acts on smooth muscles in the walls of arteries to cause vasoconstriction & rise in BP.

• 3. Angiotensin-II can directly act on renal tubules to increase the reabsorption of sodium & water leading to increase in blood volume & BP.
• 4. Angiotensin-II can also stimulate sympathetic nervous system.
• 5. Angiotensin-II can also increase the secretion of ADH from posterior pituitary gland, leading to increase in reabsorption of sodium & water which leads to increase in blood volume & BP

Cardiovascular disorders

• Hypertension,
• Hypotension,
• Arteriosclerosis,
• Atherosclerosis,
• Angina pectoris,
• Myocardial infarction,
• Congestive heart failure,
• Cardiac arrhythmias

Hypertension

• Is the persistent increase in BP.
• Systolic BP=140 mm of Hg or more
• Diastolic BP = 90 mm of Hg or more
• Two types
• 1. Primary or Essential Hypertension
• 2. Secondary Hypertension
• Primary Hypertension – it is persistently elevated BP, for which exact cause is not known. It may be due to stress, high fat diet, increased sodium level, increased blood volume or genetic reasons.

• Secondary hypertension – is the secondary rise in BP due to presence of some other primary disorders such as renal diseases, pheochromocytoma, Cushing's syndrome, hyperthyroidism, aldosteronism etc.
• Hypotension – generally called as acute fall in BP due to excessive blood loss or cardiovascular disorders. The systolic BP is less than 100 mm Hg & diastolic is less than 60 mm Hg.

• Arteriosclerosis – is the thickening of the walls of arteries & loss of elasticity. Generally occurs in old age, due to which lumen of arteries become narrow leading to reduced flow of blood.
• Atherosclerosis – is a type of arteriosclerosis, in which fatty substance especially cholesterol & triglycerides accumulate in the walls of medium & large sized damaged arteries.
• The causes for damage to arteries include – smoking, carbon monoxide, high BP for long term, DM or genetic factors. After damage, series of deposition of platelets, cholesterol, triglycerides occurs forming atherosclerotic plaque, which narrows the artery & produces ischemic heart diseases.

• Angina pectoris – is a clinical pain syndrome felt at chest region, which radiates to left arm, neck & jaws.
• It occurs due to myocardial ischemia i.e. low blood supply to heart through coronary artery. This may be due to obstruction or narrowing of coronary artery.
• The causative factors include – obesity, smoking, high cholesterol levels, atheromatus plaque, spasm of coronary smooth muscle etc.

• Myocardial infarction – is more serious than ischemia, commonly called as Heart attack.
• It is the death of part of myocardium due to reduced blood supply for long term.
• It occurs due to myocardial ischemia
• Congestive cardiac failure – is the failure/inability of heart to pump sufficient amount of blood into the arteries. This is due to less force of contraction of heart leading to less cardiac output.
• It is of two types – Right ventricular failure & Left ventricular failure.

• Cardiac arrhythmia –

is abnormal/irregular heart beats. There is absence of normal rhythm in heart beat.

It may be due to abnormal generation & conduction of cardiac impulses.

If the heart beat is more than 100 per min, it is termed as Tachycardia & if it is less than 60 per min, it is called as Bradycardia

Questions

• Explain the conducting system of heart. Add a note on ECG. (10)
• Write the significance of heart sounds (2)
• Explain cardiac cycle (5)
• Explain the various events of cardiac cycle. Add a note on Glaucoma (10)
• Explain ECG. Mention the different waves of ECG (5)
• Write a note on Renin- Angiotensin system (5)
• Define cardiac arrhythmia & Congestive cardiac failure (2)
• Explain coronary circulation (2)
• With the help of neat labeled diagram, describe the internal anatomy of heart. Add a note on heart sounds (10)

​

• Explain the role of renin –angiotensin system in BP regulation (5)
• Draw a neat labeled diagram of internal anatomy of heart (5)
• Define Blood pressure. Discuss the various factors that regulate BP (5)
• Define hypertension (2)
• Define cardiac cycle (2)
• Define CCF & Myocardial infarction (2)
• ECG (2)
• Describe the structure & functions of conducting system of heart. (5)

​

​

• Define hypertension & hypotension (2)
• Define & label deflection waves of normal ECG (2)
• Explain ECG with diagram. Enumerate different events of cardiac cycle (5)
• How is BP maintained (5)
• Write the significance of heart beat (2)
• What is cardiac cycle. Explain the various events of cardiac cycle. Add a note on heart sounds. (10)
• Explain ECG. Mention the significance of each wave. (5)
• Define Angina pectoris & atherosclerosis (2)
• Heart sounds (2)

​