PHYSIOLOGY OF CARDIOVASCULAR SYSTEM FOR NURSES

1. Physiology of Cardiovascular System
Dr.Hisham Darayseh

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Functions of the Circulatory
System
 Transportation:
 Respiratory:
 Transport 02 and C02.
 Nutritive:
 Carry absorbed digestion products to liver and
to tissues.
 Excretory:
 Carry metabolic wastes to kidneys to be
excreted.

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Functions of the Circulatory
System (continued)
 Regulation:
 Hormonal:
 Carry hormones to target tissues to produce
their effects.
 Temperature:
 Divert blood to cool or warm the body.
 Protection:
 Blood clotting.
 Immune:
 Leukocytes, cytokines and complement act
against pathogens.

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Components of Circulatory
System
 Cardiovascular System (CV):
 Heart:
 Pumping action creates pressure head needed to push blood
through vessels.
 Blood vessels:
 Permits blood flow from heart to cells and back to the heart.
 Arteries, arterioles, capillaries, venules, veins.
 Lymphatic System:
 Lymphatic vessels transport interstitial fluid.
 Lymph nodes cleanse lymph prior to return in venous blood.

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Atrioventricular and Semilunar
Valves
 Atria and ventricles are separated into 2 functional
units by a sheet of connective tissue by AV
(atrioventricular) valves.
 One way valves.
 Allow blood to flow from atria into the ventricles.
 At the origin of the pulmonary artery and aorta are
semilunar valves.
 One way valves.
 Open during ventricular contraction.
 Opening and closing of valves occur as a result of
pressure differences.

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Atrioventricular and Semilunar
Valves

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 The Circuit of Blood
Flow
Right half of heart
receives and pumps
deoxygenated blood
Left half receives
and pumps
oxygenated blood
Blood returning from
the systemic
circulation
(deoxygenated)
enters the right atria
via two large veins:
superior and inferior
venae cavae

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Blood Flow Through the
Heart
 Blood follows this sequence through the
heart: superior and inferior vena cava
→ right atrium → tricuspid valve →
right ventricle → pulmonary semilunar
valve → pulmonary trunk and arteries
to the lungs → pulmonary veins leaving
the lungs → left atrium → bicuspid
valve → left ventricle → aortic
semilunar valve → aorta → to the body

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Path of blood through the heart

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Pulmonary vs. Systemic
Circulation
 Pulmonary circulation: the flow of blood from the right
ventricle through the pulmonary artery to the lungs, where
carbon dioxide is exchanged for oxygen, and back through the
pulmonary vein to the left atrium.
 Systemic circulation: the flow of blood from the left ventricle
to the aorta which leads to smaller arteries, arterioles, and
finally capillaries. carbon dioxide diffuse out of the cell into the
blood, and oxygen in the blood diffuses into the cell. Blood then
moves to venous capillaries, and then to inferior vena cava and
superior vena cava, through which the blood re-enters the heart
at the right atrium

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Cardiac Cycle
 Refers to the repeating pattern of contraction
and relaxation of the heart.
 Systole:
 Phase of contraction.
 Diastole:
 Phase of relaxation.
 If heart rate is 70/min then cardiac cycle is less
than 1 second≈0.8 sec
 Systole :0.4 sec
 Diastole: 0.4 sec

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 Is volume of blood pumped/min by
each ventricle
 Heart Rate (HR) = 70 beats/min
 Stroke volume (SV) = blood
pumped/beat by each ventricle
 Average is 70-80 ml/beat
 CO = SV x HR
 Cardiac output in man at rest is about
5.5L
Cardiac Output (CO)
14-4

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 EDV(end diastolic volume) is workload
(preload) on heart prior to contraction
 SV is directly proportional to preload & contractility
 Strength of contraction varies directly with EDV
 Total peripheral resistance = afterload which
slow down ejection from ventricle
 SV is inversely proportional to peripheral resistance
 Ejection fraction is SV/ EDV (~80ml/130ml=62%)
 Normally is 60%; useful clinical diagnostic tool
Regulation of Stroke
Volume
14-10

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Heart Sounds
 Closing of the AV and
semilunar valves.
 Lub (first sound):
 Produced by closing of the
AV valves during
isovolumetric contraction.
 Dub (second sound):
 Produced by closing of the
semilunar valves when
pressure in the ventricles
falls below pressure in the
arteries.

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Conducting Tissues of the Heart
(continued)

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Conducting Tissues of the Heart
 Electrical impulses spread through myocardial
cells through conducting tissues .
 Impulses cannot spread to ventricles directly
because of fibrous tissue.
 Conduction pathway:
 SA node.(SinoAtrial Node)
 AV node.(AtrioVentricular Node)
 Bundle of His.
 Purkinje fibers.
 Stimulation of Purkinje fibers cause both
ventricles to contract simultaneously.

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Electrical Activity of the Heart
 SA node: sinoatrial
node
 Functions as the
pacemaker of the heart.
 Spontaneous
depolarization
(pacemaker potential)
 AV node: conducts
the normal electrical
impulse from the atria
to the ventricles
 Bundle of His:
transmits the electrical
impulses from the AV
node to the point of
the apex of the heart

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Factors affecting heart rate
 Autonomic nervous system
 Sympathetic: incease heart rate
 Parasympathetic: decrease heart rate
 Circulating hormons: Adrenaline,noradrenalin,thyroxine…
 Drugs
 Exercise
 Emotional state
 Age and gender
 temerature

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Electrocardiogram (ECG/EKG)
 The body is a good conductor of electricity.
 Tissue fluids have a high [ions] that move in
response to potential differences.
 Electrocardiogram:
 Measure of the electrical activity of the heart
per unit time.
 Potential differences generated by heart are conducted
to body surface where they can be recorded on
electrodes on the skin.
 Does NOT measure the flow of blood through
the heart.

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ECG Leads
 Bipolar leads:
 Record voltage between
electrodes placed on wrists
and legs.
 Right leg is ground.
 Unipolar leads:
 Voltage is recorded between
a single “exploratory
electrode” placed on body
and an electrode built into
the electrocardiograph.
 Placed on right arm, left arm,
left leg, and chest.
 Allow to view the changing
pattern of electrical activity
from different perspectives.

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ECG
 P wave:
 Atrial
depolarization.
 QRS complex:
 Ventricular
depolarization.
 Atrial
repolarization.
 T wave:
 Ventricular
repolarization.

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 Role is to direct
the flow of
blood from the
heart to the
capillaries, and
back to the
heart.
Systemic Circulation
 Arteries.
 Arterioles.
 Capillaries.
 Venules.
 Veins.

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Blood Vessels (continued)
 Most of the blood volume is contained in the
venous system.
 Venules:
 Formed when capillaries unite.
 Very porous.
 Veins:
 Contain little smooth muscle or elastin.
 Capacitance vessels (blood reservoirs).
 Contain 1-way valves that ensure blood flow to the heart.
 Skeletal muscle pump and contraction of
diaphragm:
 Aid in venous blood return of blood to the heart.

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Capillaries
The smallest of a body's blood
vessels and are part of the
microcirculation. They are
only 1 cell thick. These
microvessels, connect
arterioles and venules, and
enable the exchange of water,
oxygen, carbon dioxide, and
many other nutrient and waste
chemical substances between
blood and surrounding tissues

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Blood Pressure (BP)
 Blood Pressure: is the pressure exerted by circulating blood
on the walls of blood vessels.
 During each heartbeat, blood pressure varies between a
maximum (systolic) and a minimum (diastolic) pressure.
measured by mm Hg with reference to atmospheric pressure
≈760 mm Hg
 The maximum pressure in the aorta and large arteries is called
systolic pressure while the heart is contracted
 The minimum pressure called diastoilc pressure while the heart
is relaxed
 If BP is 120/70 then ,systolic BP is 120mmHg,diastolic BP is 70
mmHg
 the arterial BP is needed to push blood through arterioles
capillaries and veins in order achieve blood flow

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Factors that control Blood Pressure (BP)
 It is controlled mainly by HR, SV, & peripheral
resistance
 An increase in any of these can result in increased
BP
 Baroreceptors are found in the wall large blood
vessels
 Sympathatic nervous system activity raises BP via
arteriole vasoconstriction & by increased cardiac
output.
 Kidney plays role in BP by regulating blood volume &
thus stroke volume 14-54

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Factors affecting Blood Pressure
 Size of arteries
 Viscosity of blood
 Autonomic nervous
system(adrenalin,noradrenaline.
 Emotional state
 Drugs
 Smokoing
 obesity

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Lymphatic System
 3 basic functions:
 Transports interstitial (tissue) fluid back to
the blood.
 Transports absorbed fat from small
intestine to the blood.
 Provides immunological defenses against
microbes.

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Lymphatic System (continued)
 Lymphatic capillaries:
 Closed-end tubules that
form vast networks in
intercellular spaces.
 Lymph:
 Fluid that enters the
lymphatic capillaries.
 Lymph carried from
lymph capillaries, to
lymph ducts, and then
to lymph nodes.
 Lymph nodes filter the
lymph before returning
it to the veins.

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Spleen Functions

1-Phagocytosis and destruction of
old and abnormal Red Blood Cells
and other old cells like white blood cells
,platelets,

2-Storage of blood: Contains about
350ml of blood and can rapidly return
most of it to circulation in cases of
bleeding

3-Immune response: contains T and
B lymphocytes important in killing
microbes

4-Erythropoesis in fetus : Red Blood
Cells production during fetal life

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