CARDIOVASCULAR%20SYSTEM

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CARDIOVASCULAR SYSTEM

• Dr.Vindya Rajakaruna
• MBBS (COLOMBO)

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CVS consists of

• Heart
• Blood vessels

heart?arteries ?arterioles ? ? veins?venule
s ?capillaries
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What is the function of CVS

• Circulate blood throughout entire body for
• Transport of oxygen to cells
• Transport of CO2 away from cells
• Transport of nutrients (glucose) to cells
• Movement of immune system components (cells,
  antibodies)
• Transport of endocrine gland secretions

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Heart

• The heart is a cone-shaped, muscular organ
• An adult human heart weighs between 200 and 425
  grams (7 and 15 ounces) and is slightly larger
  than a fist.
• The heart is located between the lungs in the
  middle of the chest, behind and slightly to the
  left of the sternum and in front of the spine

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• A double-layered membrane called the pericardium
  surrounds the heart like a sac.
• Layers of the heart wall
• Three layers of tissue form the heart wall. The
  outer layer of the heart wall is the epicardium,
  the middle layer is the myocardium, and the inner
  layer is the endocardium.

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Epicardium

• The epicardium is the outer layer of the wall of
  the heart. It is composed of connective tissue (
  mainly Adipose Tissue) covered by epithelium.
• Coronary vessels and cardiac nerves
• The epicardium is also known as the visceral
  pericardium
• Provides an outer protective layer for the heart.

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Cardiac Muscle/Myocardium
Intercalated Disc
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• Myocardium is the muscular middle layer of the
  wall of the heart. It is composed of
  spontaneously contracting cardiac muscle fibers
  which allow the heart to contract.
• Stimulates heart contractions to pump blood from
  the ventricles and relaxes the heart to allow the
  artria to receive blood.

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Endocardium

• The endocardium is the inner layer of the heart.
  It consists of epithelial tissue and connective
  tissue.
• Lines the inner cavities of the heart, covers
  heart valves and is continuous with the inner
  lining of blood vessels.
• Purkinje fibers are located in the endocardium.
  They participate in the contraction of the heart
  muscle.

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Pericardium

• The pericardium is the fluid filled sac that
  surrounds the heart and the proximal ends of the
  aorta, vena cava, and the pulmonary artery.
• Pericardial Membranes
• The pericardium is divided into two
  layersFibrous Pericardium - the outer fibrous
  sac that covers the heart.
• Serous Pericaridum The membranous covering on
  the outside

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• The serous pericardium is divided in to
• Parietal Pericardium
• Visceral Pericardium

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Functions of Pericardium

• Keeps the heart contained in the chest cavity.
• Prevents the heart from over expanding when blood
  volume increases.
• Limits heart motion.

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Chambers of the heart

• The human heart has four chambers. The upper
  chambers are called the left and right atria, and
  the lower chambers are called the left and right
  ventricles.
• A wall of muscle called the septum separates the
  left and right atria and the left and right
  ventricles.

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• The two atria are thin-walled chambers that
  receive blood from the veins the right atrium
  receives deoxygenated blood from systemic veins,
  while the left atrium receives oxygenated blood
  from the pulmonary veins.
• The two ventricles are thick-walled chambers that
  forcefully pump blood out of the heart.

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• Differences in thickness of the heart chamber
  walls are due to variations in the amount of
  myocardium present, which reflects the amount of
  force each chamber is required to generate.
• The left ventricle is the largest and strongest
  chamber

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Valves

• Valves are flap-like structures that allow blood
  to flow in one direction. The heart has two kinds
  of valves, atrioventricular and semilunar valves.
  

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Atrioventricular Valves

• The atrioventricular valves are thin structures
  that are composed of endocardium and connective
  tissue. They are located between the atria and
  the ventricles.
• Mitral Valve
• Tricuspid Valve

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Semilunar Valves

• The semilunar valves are flaps of endocardium and
  connective tissue reinforced by fibers which
  prevent the valves from turning inside out.
• They are shaped like a half moon, hence the name
  semilunar (semi-, -lunar).

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• The semilunar valves are located between the
  aorta and the left ventricle and between the
  pulmonary artery and the right ventricle.
• Aortic Valve
• Pulmonary Valve

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Function of the Heart

• Right Side of the Heart
• The right side of the heart receives
  de-oxygenated blood from the body tissues (from
  the upper- and lower-body via the Superior Vena
  Cava and the Inferior Vena Cava, respectively)
  into the right atrium.

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• This de-oxygenated blood passes through the
  tricuspid valve into the right ventricle.
• This blood is then pumped under higher pressure
  from the right ventricle to the lungs via the
  pulmonary artery

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• Left-Hand Side of the Heart
• The left-hand side of the heart receives
  oxygenated blood from the lungs (via the
  pulmonary veins) into the left atrium.
• This oxygenated blood then passes through the
  bicuspid valve into the left ventricle.

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• It is then pumped to the aorta under greater
  pressure
• This higher pressure ensures that the oxygenated
  blood leaving the heart via the aorta is
  effectively delivered to other parts of the body
  via the vascular system of blood vessels (incl.
  arteries, arterioles, and capillaries).

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The Vessels

• Functions
• Distribution of blood
• Exchange of materials with tissues
• Return of blood to the heart
• Structure
• Most have the same basic structure
• 3 layers surrounding a hollow lumen

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• Arteries and veins are composed of three tunics
• tunica interna
• tunica media
• tunica externa
• Capillaries are composed of endothelium.

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Tunica Intima

• innermost smooth layer
• simple squamous epithelium
• continuous with the endocardium
• present in all vessels

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Tunica Media

• layer of smooth muscle - circular arrangement
  contains elastin
• supplied by sympathetic division of the ANS
• depending on bodys needs lumen is narrowed
  (vasoconstriction) or widened (vasodilation)

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Tunica Externa (Adventitia)

• thin layer of Connective Tissue
• elastic collagen fibres

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Types of Vessels

• Arteries carry blood away from the heart
• Veins carry blood towards the heart
• Capillaries the most important part of the
  vascular system site of exchange of materials

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• Elastic Arteries
• Thick-walled arteries near the heart the aorta
  and its major branches.
• Large lumen allows low-resistance conduction of
  blood.
• Contain lots of elastin in all three tunics.
• walls stretch and recoil to propel blood
• Withstand and regulate large blood pressure
  fluctuations.

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• Muscular (distributing) arteries
• medium sized vessels
• tunica media more smooth muscle less elastin
• major area of vaso-constriction dilation
  to regulate blood flow

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• Arterioles (diameter of 0.3 mm or less)
• - smallest arteries lead to capillary beds.
• - close to capillaries - single layer of muscle
  spiralling around the endothelial lining
• - regulates blood flow to capillary

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• Capillaries
• Smallest vessels diameter just large enough for
  a red blood cell
• walls consist of tunica intima only
• (i.e. layer of endothelium)
• thinness facilitates exchange of
• materials

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• Venules
• Are formed when capillary beds unite.
• They merge to create veins.
• Veins
• Thin tunica media and a thick tunica externa
  consisting of collagen fibers and elastic
  networks.
• Capacitance vessels (blood reservoirs) that
  contain 65 of the blood supply.

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Circulation
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Pulmonary Circulation

• Deoxygenated (used) blood is pumped out of the
  right ventricle.
• It travels through the pulmonary valve into the
  pulmonary artery, leaving the heart.
• Deoxygenated (used) blood reaches the lungs.
  Here, carbon dioxide is removed from the blood
  and oxygen is added to it.
• The fresh blood leaves the lungs.

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• Fresh blood enters the left atrium through the
  pulmonary vein.
• Then, it is pumped through the mitral valve into
  the left ventricle.
• This ends the pulmonary circulation.

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Systemic Circulation

• Oxygenated (fresh) blood is pumped out of the
  left ventricle.
• It travels through the aortic valve into the
  aorta, leaving the heart.
• Oxygenated (fresh) blood reaches the head and the
  body (gut, kidney, muscles), where the oxygen in
  it is used and replaced by carbon dioxide.

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• Deoxygenated blood is collected through the vena
  cava into the right atrium and is pumped through
  the tricuspid valve into the right ventricle.
• This ends the systemic circulation.

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Diffusion

• The exchange of molecules between cells and blood
  occurs at the capillary level.
• Capillaries are very small blood vessels with
  very thin walls.
• Oxygen and nutrients diffuse from the blood into
  the cell and carbon dioxide and waste diffuse
  from the cell into the blood.

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Cardiac Cycle

• The cardiac cycles refers to the repeating
  pattern of contraction and relaxation of the
  heart
• The phase of contraction is called systole and
  the phase of relaxation is called diastole

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• The right and left atria contract almost
  simultaneously , followed by contraction of the
  right and left ventricles 0.1 to 0.2 seconds
  later
• During the time when both the atria and
  ventricles are relaxed, the venous return of
  blood fills the atria
• The build up of pressure that results causes the
  AV valves to open and blood flow from atria to
  ventricles

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• The ventricles are about 80 filled with blood
  even before the atria contract
• Contraction of atria adds the final 20 to the
  end diastolic volume , which is the total volume
  of blood in the ventricles at the end of diastole
• Contraction of the ventricles in systole ejects
  about 2/3 of the blood they contain ( Stroke
  volume ) leaving 1/3 of blood in the ventricles
  as end systolic volume.

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Pressure changes during cardiac cycle

• When the heart is in diastole, pressure in the
  systemic arteries is about 80mmHg
• During systole pressure in the systemic arteries
  is about 120mmHg.

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Electrical Conductivity System of the Heart
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• The heart is the pump responsible for maintaining
  adequate circulation of oxygenated blood around
  the vascular network of the body.
• It is a four-chamber pump, with the right side
  receiving deoxygenated blood from the body at low
  pressure and pumping it to the lungs (the
  pulmonary circulation) and the left side
  receiving oxygenated blood from the lungs and
  pumping it at high pressure around the body (the
  systemic circulation).

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Electrical Circuitof the Heart
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The S-A Node

• The S-A Node is the most important element in the
  electrical circuit of the heart.
• It starts the cardiac cycle by periodically
  generating action potentials without any external
  stimulation. (Therefore, it is said to be
  autorhythmic.)
• It is also known as the pacemaker of the heart.

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Location of SA node

• In the right atrium
• Near the opening of the superior vena cava

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Conducting Tissues of the Heart

• Action potentials that originate in the SA node
  spread to adjacent myocardial cells of the right
  and left atria through the gap junctions between
  these cells
• Since myocardium of the atria is separated from
  the myocardium of the ventricles by fibrous
  skeleton of the heart , however the impulse
  cannot be conducted directly from atria to the
  ventricles

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• Therefore specialized conducting tissue (
  modified myocardial cells) need for electrical
  conduction of the heart
• These specialized myocardial cells form the AV
  node, Bundle of His ( Atrioventricular bundle)
  and Purkinje fibers
• Once the impulse has spread through atria , it
  passes to the AV node, which located on the
  inferior portion of the interatrial septum from
  there impulse continues through the bundle of His
  , beginning at the top of the interventricular
  septum

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• The bundle of His divides in to right and left
  bundle branches , which are continuous with the
  Purkinje fibers with in the ventricular walls
• Stimulation of Purkinje fibers causes both
  ventricles to contract simultaneously and eject
  blood into the pulmonary and systemic
  circulation.

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The A-V Node

• The most important function of the A-V node is to
  regulate the timing of the ventricular
  contraction by delaying the action potentials.
• The delayed action potentials are spread over the
  ventricles to cause a contraction.

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The Electrical Cycle

• 1.The S-A Node generates an action potential.
• 2. The action potential propagates in the atria
  and causes a contraction. It is also transmitted
  to the AV Node.
• 3.The action potential is delayed at the A-V Node.

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• 4.The action potential is transmitted to the
  ventricles and causes a contraction.

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The Electrocardiogram

• The electrocardiogram (ECG) is a standardized way
  to measure and display the electrical activity of
  the heart.

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• The P Wave Depolarization of the atria
• The QRS Complex Depolarization of the ventricles
• The T Wave Repolarization of the ventricles
• From one P Wave to the next P wave duration
  equals to a cardiac cycle

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Cardiac Out Put
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What is Cardiac Out Put ?

• The pumping ability of the heart
• Cardiac out put is equal to the volume of blood
  pumped per minute by each ventricle
• Cardiac out put Stroke volume Cardiac
• 
  rate
• ( ml/min) (ml/beat)
  (beats/min)

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Factors Regulate Cardiac Rate

• Autonomic nervous system
• In the complete absence of neural influences the
  heart will continue to beat according to the
  rhythm set by the SA node
• With influence of the ANS cardiac rate changes
• The activity of autonomic innervation of the
  heart is coordinated by the cardiac center in the
  medulla oblongata

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Factors Regulate the Stroke Volume

• End diastolic volume ( Volume of blood in the
  ventricles at the end of diastole immediately
  before contraction )
• Peripheral resistance ( The resistance to blood
  flow in the arteries)
• Contractility ( Strength of ventricular
  contraction )

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• When the End diastolic volume is more the Stroke
  volume also increases
• When the contractility is more the Stroke volume
  also increases
• But when the peripheral resistance is more the
  Stroke volume decreases

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Factors affecting End Diastolic Volume

• Controlled by the factors that affect the Venous
  return ( Return of blood to the heart via veins)
• Mainly depends on the total blood volume and the
  venous pressure
• Total blood volume depends on the balance between
  water loss and the water gain

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• Venous pressure highest in venules (10mmHg) and
  lowest at the junction of superior vena cava with
  right atrium (0mmHg)
• In addition to the pressure difference, venous
  return to the heart is aided by
• Sympathetic nerve activity , which stimulates
  the smooth muscle contraction in the venous walls
• The skeletal muscle pump, which squeezes veins
  during muscle contraction

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• The pressure difference between the thoracic and
  abdominal cavities, which promotes the flow of
  venous blood back to the heart.

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Exchange of Fluid between Capillaries and Tissues
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What is Osmotic Pressure ?

• The ability to take the water in to a solution
• by osmosis
• Greater the solute concentration greater the
  osmotic pressure

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What is Hydrostatic Pressure?

• The pressure created by the liquid atoms in side
  the solution

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• Filtration results due to the pressure
  differences within the capillaries and the tissue
  fluid
• This hydrostatic pressure, which is exerted
  against the inner capillary wall, is equal to
  37mmHg at the arteriolar end of systemic
  capillaries and drops to about 17mmHg at the
  venular end of the capillaries

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• The net filtration pressure is equal to the
  hydrostatic pressure of the blood in the
  capillaries minus the hydrostatic pressure of
  tissue fluid out side the capillaries which
  opposes the filtration.

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• Glucose, comparably sized organic molecules,
  inorganic salts and ion are filtered along with
  water through the capillary channels
• The concentration of these substances in tissue
  fluid are thus the same as in plasma
• The protein concentration of tissue fluid ,
  however is less than the protein concentration of
  plasma
• This difference is due to the restricted
  filtration of proteins through the capillary pores

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• The osmotic pressure exerted by plasma proteins ,
  called the colloid osmotic pressure of the plasma
  is greater than the colloid osmotic pressure of
  tissue fluid
• The difference between these two pressures is
  called the oncotic pressure
• Usually the colloid osmotic pressure of tissue
  fluid is very low ( can be neglect )and the
  colloid osmotic pressure of the plasma is about
  25mmHg

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Venular End
Arteriolar End
HP 37mmHg OP 25mmHg
HP 17mmHg
OP 25mmHg
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Net Fluid Movement
Tissue Fluid
Osmotic Pressure of Tissue Fluid
Hydrostatic Pressure of Tissue Fluid
Osmotic Pressure of Blood Plasma
Hydrostatic Pressure of Blood Plasma
Blood Vessel
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• Fluid Movement
• ( HPc OPt) ( HPt OPc)

Fluid In
Fluid Out
HPc Hydrostatic Pressure in the capillary OPt
Osmotic Pressure in the tissue fluid HPt -
Hydrostatic Pressure in the tissue fluid OPc -
Osmotic Pressure in the capillary
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Blood Flow
Blood Flow
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Why blood flow occur?

• Due to the pressure difference of two vessel ends

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Vascular resistance to blood flow

• The rate of blood flow to an organ is related to
  the resistance to flow in the small arteries and
  arterioles that serve the organ
• Vasodilatation decreases resistance and increases
  the flow, where as vasoconstriction increases the
  resistance and decreases the flow

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Factors affecting the resistance

• Length of the blood vessel When the length is
  more resistance also increase
• Viscosity of blood when the viscosity increases
  resistance also increases
• Radius of the blood vessel when the radius is
  more resistance is less

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What is Total Peripheral resistance?

• The sum of all the vascular resistances within
  the systemic circulation is called the Total
  Peripheral Resistance

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Regulation of blood flow

• Regulation by Sympathetic nervous system
• Cardiac out put -
• Vascular resistance in
• a. Brain -
• b. Skeletal muscles - ..
• c. GI tract - .
• d. Skin -
• e. Heart - .

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• Regulation by Parasympathetic nervous system
• Vascular resistance
• GI Tract -
• External genitalia - .
• Salivary Glands -

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By endothelium secretary factors

• Vasodilators
• Nitric oxide
• Bradykinin
• Prostacyclin

• Vasoconstrictors
• Endothelin 1

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Myogenic control

• When the vascular blood pressure is high the
  vessels constrict and reduce the blood flow to
  the tissues
• When the vascular blood pressure is low the
  vessels dilate and increase the blood flow to the
  tissues

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Metabolic control

• When the Oxygen concentration decreases due to
  increased metabolic rate and when the Carbon
  Dioxide concentration increases local
  vasodilatation occurs and increase the blood flow
  to the tissues

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Regulation of Blood Flow and Pressure by Kidneys

• By Anti Diuretic Hormone ( ADH )
• By Aldosterone
• By Atrial Natriuretic Factor ( ANF )
• By Renin Angiotensin system

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By Anti Diuretic Hormone ( ADH )

• When blood plasma osmolality ( osmotic pressure /
  thickness ) increases it detects by
  osmoreceptors in hypothalamus and stimulate the
  posterior pituitary to secrete ADH
• ADH stimulate water reabsorption from the
  filtrate during the urine formation and thereby
  increase the fluid volume in the plasma as well
  as the pressure

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By Aldosterone

• Aldosterone secreted by Adrenal Cortex stimulates
  the reabsorption of salt
• Retention of salt indirectly promotes retention
  of water
• Which will lead to increase the pressure and
  volume of blood

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By Atrial Natriuretic Factor ( ANF )

• ANF is produced by the atria of the heart and
  promoting salt and water excretion in the urine
• By that it reduces the blood volume as well as
  the pressure

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By Renin Angiotensin system

• When blood flow and pressure reduce in renal
  artery a group of cells in kidney secretes an
  enzyme called Renin in to blood
• This renin leads to activation of Angiotensin
  which can increase vasoconstriction of arteries
  and thereby increase the pressure

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• It also leads to secretion of aldosterone which
  leads to salt and water retention by kidneys and
  increase the volume of blood

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Blood Supply to the Heart

• Coronary arteries supply blood to the heart
• Contraction of the myocardium squeezes the
  coronary arteries
• Unlike blood flow in all other organs, flow in
  the coronary vessels thus decreases in systole
  and increases in diastole
• Myocardium contains large amount of Myoglobin
  which stores Oxygen during diastole and releases
  during systole

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• In this way, the myocardial cells can receive a
  continuous supply of oxygen even though coronary
  blood flow is temporarily reduced during systole

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Regulation of Coronary Blood Flow

• When the metabolism of myocardium increases ,
  there are local accumulation of carbon dioxide
  together with depletion of oxygen
• These changes act directly on vascular smooth
  muscles and cause relaxation of muscles which
  leads to vasodilatation
• There fore blood flow to the myocardium increases

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• Other than this sympathetic nervous system
  stimulates the vasodilatation during exercise

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• During resting vasoconstriction of coronary
  arteries occur

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Blood Flow to the Brain

• When the brain is deprived of Oxygen for just a
  few seconds, a person looses consciousness
  irreversible brain injury may occur after a few
  minutes
• For this reason, the cerebral blood flow is held
  remarkably constant at about 750ml per minute.
  This amounts to about 15 of the total cardiac
  out put at rest

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• Cerebral blood flow not normally influenced by
  sympathetic nerve activity ( Autoregulation )
• Only when the arterial pressure rises to about
  200mmHg do sympatheic nerves cause a significant
  degree of vasoconstriction in the cerebral
  circulation
• This vasoconstriction helps to protect small,
  thin walled arterioles from bursting under the
  pressure, and thus helps to prevent
  cerebrovascular accidents

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• When the blood pressure falls, the cerebral
  arteries automatically dilate when the pressure
  rises , they constrict.
• The cerebral vessels are also sensitive to the
  carbon dioxide concentration of arterial blood
• When the carbon dioxide rises due to inadequate
  ventilation, the cerebral arterioles dilate.
• Conversely when the arterial carbon dioxide falls
  below the normal level arterial constriction
  occurs

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Blood Flow to the Skin

• Blood flow through the skin is adjusted to
  maintain deep body temperature at about 37C.
• These adjustments are made by constriction and
  dilatation of arterioles
• When temperature is low, sympathetic nerves
  stimulate cutaneuos vasoconstriction cutaneuos
  blood flow is decreased, so that less heat will
  be lost from the body

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• Skin can tolerate an extremely low blood flow in
  cold weather because its metabolic rate decreases
  when the environment temperature decreases

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• As the temperature warms, cutaneous arterioles in
  the hands and feet dilate as a result of
  decreased sympathetic nerve activity

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• Continued warming causes dilatation of arterioles
  in other areas of the skin
• If the resulting increase in cutaneous blood
  flow is not sufficient to cool the body, sweat
  gland stimulations stimulated.

Perspiration helps to cool the body as it
evaporates from the surface of the skin
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Skin blood flow with relative conditions

• Exercise Pre exercise state, the sympathetic
  nervous system activation reduces the blood flow
  to the skin
• During the exercise due to the heat generating
  in the body vasodilatation in the cutaneuos
  vessels occur together with vasodilatation in the
  exercising muscles

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• During fear reaction Vasoconstriction in the
  skin along with activation of sweat glands can
  produce pallor and cold sweat

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• When you are shy cutaneous blood flow to the
  face increased by vasodilatation and you become
  blushed.

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Blood Pressure
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• The pressure of arterial blood is regulated by
  the blood volume, total peripheral resistance and
  the cardiac rate
• An increase of any of these, if not compensated
  for by a decrease in another variable, will
  result in an increased blood pressure.

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• Blood pressure can regulate by the kidneys, which
  control the blood volume and thus stroke volume
  and by the sympathetic nervous system
• Increase activity of sympathetic nervous system
  can raise blood pressure by stimulating
  vasoconstriction of arterioles (thus increasing
  the peripheral resistance ) and by promoting an
  increased cardiac out put.

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• Sympathetic stimulation can also affect blood
  volume indirectly by stimulating constriction of
  renal blood vessels and thus reducing urine out
  put.

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Baroreceptor Reflex

• To maintain blood pressure within limits
  specialized receptors are needed
• Baroreceptors are stretch receptors located in
  aortic arch and in the carotid sinuses
• An increase in pressure causes the walls of these
  arterial regions to stretch ,increasing the
  frequency of action potentials along the sensory
  nerve fibers

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• A fall in pressure below the normal range, by
  contrast , causes a decrease in the frequency of
  action potentials produce by these sensory nerve
  fibers
• Sensory nerve activity from baroreceptors ascends
  to vasomotor control center and the cardiac
  center in medulla oblongata
• These centers control the blood pressure via
  autonomic nervous system
• Vasomotor center control vasoconstriction and
  vasodilatation and hence helps to regulate the
  total peripheral resistance

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• The cardiac center regulates the cardiac rate
• Baroreceptor reflex is activated whenever blood
  pressure increases or decreases .
• The reflex is more sensitive to decrease in
  pressure than to increase in pressure
• And is more sensitive to sudden changes of
  pressure than the gradual changes of pressure

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What will happen in following situation ?
Lying Down
Standing
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• When a person goes from a lying to a standing
  position there is a shift of 500 to 700ml of
  blood from the veins of the thoracic cavity to
  veins in the lower extremities (the pooling area)
• This pooling of blood leads to reduction of the
  venous return and there by reduction of cardiac
  out put which leads to reduction of blood
  pressure

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• This fall in blood pressure is almost immediately
  compensated by the baroreceptor reflex
• Inhibition of parasympathetic activity and the
  stimulation of sympathetic activity by vasomotor
  center and the cardiac center produces an
  increase of cardiac rate and the vasoconstriction
  , which help to maintain the adequate blood
  pressure upon standing

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What will happen in following situation ?
Lying Down
Standing
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Atrial Stretch Reflexes

• Atrial stretch receptors located in the atria of
  the heart
• These receptors are activated by increased venous
  return to the heart
• This inhibit the ADH release, resulting in the
  excretion of larger volumes of urine and a
  lowering of blood volume

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• Promote secretion of ANF ,which lowers the blood
  volume by increasing urinary salt and water
  excretion by and by antagonizing the actions of
  angiotensin
• Other than these stimulate reflex tachycardia

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Measurement of Blood Pressure

• Blood Pressure- measurement of the force exerted
  by blood against the walls of the arteries
• Systolic blood pressure- the pressure in the
  large arteries when the heart is contracted
• Diastolic Blood pressure- the pressure in the
  large arteries when the heart is relaxed

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Steps for Measuring  Blood Pressure 

• Seated for 5 minutes
• Patient Position
• Expose Upper arm
• Center of upper arm at heart level

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• Cuff applied 1 inch above crease at elbow
• Locate brachial artery
• Palpate radial pulse
• Inflate cuff until pulse disappears   

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• Let air out
• Place stethoscope on brachial artery
• Pump up cuff to 20-30 above point of obliteration
  
• Let air out at 2 mmHg per second
• Note the pressures 1st and 5th Korotkoff sounds
  can be heard

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Korotkoff Sounds

• First Phase
• A clear tapping sound onset of the sound for two
  consecutive beats is considered systolic
• Second Phase
• The tapping sound followed by a murmur
• Third Phase
• A loud crisp tapping sound

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• Fourth Phase
• Abrupt, distinct muffling of sound, gradually
  decreasing in intensity
• Fifth Phase
• The disappearance of sound, is considered
  diastolic blood pressure- two points below the
  last sound heard

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Mechanism

• Initially ,the cuff is usually inflated to
  produce a pressure greater than the systolic
  pressure, so that the artery is pinched off and
  silent.
• The pressure in the cuff is read from an attached
  meter called sphygmomanometer.

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• A value is then turned to allow the release of
  air from the cuff, causing a gradual decrease in
  cuff pressure.
• When cuff pressure is equal to the systolic
  pressure, the first Korotkoff sound is heard as
  blood started to pass through the opening of
  constricted vessel
• Korotkoff sound will continue to be heard at
  every systole as long as the cuff pressure
  remains greater than the diastolic pressure

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• When cuff pressure becomes equal to or less than
  the diastolic pressure , the sounds disappear,
  because the artery is completely open and blood
  flows smoothly