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Exercise 37
Human cardiovascular
physiology
Cardiac cycle
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Concepts to memorize:
The two atria contract simultaneously
The two ventricles contract
simultaneously
Diastole
 The
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relaxation period
Systole
 The
contraction period
Steps of the cardiac cycle
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The heart is in diastole
 Heart pressure is low
The blood flows passively from the
pulmonary and systemic system into
the atria
The AV valves open
The blood flows into the ventricles
The atria contracts to force the residual
blood into the ventricles
Cardiac cycle
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The ventricular pressure increases
The ventricular systole begins
 The atria are in diastole and begin to
be filled
The AV valves close
The semilunar valves open
The blood flows into the aorta and the
pulmonary arteries
Cardiac cycle
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The pressure in the aorta and
pulmonary arteries increase
The semilunar valves close
The ventricles relax
The cardiac sounds
(lub-dup pause)
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First heart sound (S1- lub)
 Represents the closing of the AV
valves
 It happens at the beginning of the
systole
Second heart sound (S2- dup)
 It represents the closing of the
semilunar valves
 It happens at the end of the systole
The cardiac sounds
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Murmurs
 It represents a turbulent blood flow
 It is found when blood flows through
narrow openings (stenosis)
 Also found when there is backflow of
blood (regurgitation) because of
defected valves (insufficiency)
Cardiac cycle
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Auscultation of the mitral valve
 Over the 5th intercostal space
 In line with the middle of the clavicle
Auscultation of the tricuspid valve
 Over the sternum
Cardiac cycle
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Auscultation of the pulmonary valve
 Over the 2nd intercostal space
 At left sternal margin
Auscultation of the aortic valve
 Over the 2nd intercostal space
 At the right sternal margin
The pulse
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It is palpation of the pressure wave that
travels along the arteries
The pressure wave causes the
expansion of the arterial wall
Parameters detected by the pulse
palpation:
Pulse rate
 It is the same as the heart rate
 Normal: 60-100 bpm
The pulse
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Pulse rhythm
Pulse amplitude
Superficial pulse points
 Common carotid artery
 Temporal artery
 Facial artery
 Brachial artery
 Radial artery
The pulse
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Femoral artery
Popliteal artery
Posterior tibial artery
Dorsalis pedis artery
The blood pressure
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It is the pressure that the blood causes
to the wall of the vessels
It is reported in millimeters of mercury
(mm Hg)
Arterial pressure:
Systolic pressure
 Reflects the pressure in the arteries
during ventricular ejection
 It is the first reading
 normal:120 mm Hg
The blood pressure
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Diastolic pressure
 Reflects the pressure in the arteries
during ventricular relaxation
 It is the second reading
 Normal: 80 mm Hg
The blood pressure
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Sounds of Korotkoff
 Indicates the resumption of blood
flow into the forearm when the
pressure to occlude the artery is
gradually released
 First sound heard is the systolic
pressure
 The disappearance of the Korotkoff
indicates the diastolic pressure
The blood pressure
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Venous pressure
Normal: 30-90 mm Hg
They are affected by muscle activity,
deep pressure, breathing, etc
The blood pressure
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Pulse Pressure (PP)
 Systolic pressure – diastolic pressure
Mean arterial pressure (MAP)
 MAP=diastolic pressure+PP/3
Effects of various factors on
blood pressure
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BP=CO * PR
Factors that increase PR:
 Constriction of arteries
 Increased blood viscosity
 Increased blood volume
 Hardening of the arteries walls
Effects of various factors on
blood pressure
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Factors that increase BP:
Age
Weight
Drugs
Exercise
Emotions, etc
Skin color
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It indicates local circulatory dynamics
Factors that influence skin color
 Oxygen supply (cyanosis)
 Temperature (cold, warm)
 Hormones (thyroid hormones)
 Autonomic nervous system
• Fight or flight reaction
Collateral blood flow
Electrocardiogram (ECG)
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Conduction of impulses through the heart
Generation of electrical impulses
Detection of the electrical impulses on the body’s
surface
Electrocardiograph
The electrocardiogram (ECG)
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Deflection waves
 The P wave accompanies the depolarization of
the atria
• First wave, small and precedes atrial
contraction
The electrocardiogram (ECG)
 The
QRS complex appears as the
ventricles depolarize
• Second wave, large and precedes
ventricular contraction
 The T wave indicates ventricular
repolarization; third wave
An Electrocardiogram
The electrocardiogram
(ECG)
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Intervals- Always include at least one wave
 PR interval (PQ)
• From the beginning of P wave to the start of
QRS
• Represents atrial depolarization and
conduction through AV node
 QT interval
• From the Q wave to the end of T wave
• Ventricular depolarization, contraction and
repolarization
The electrocardiogram
(ECG)
 ST
interval
• From the end of the QRS to the end of the T
wave
• Represents the spread of impulse to the
ventricles (ventricular contraction) +
ventricular repolarization
An Electrocardiogram
The electrocardiogram
(ECG)
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Segments
 From the end of one wave to the start of the
next one
 ST segment
• From the end of QRS to the beginning of T
wave
• Represents the spread of the impulse to the
ventricles (ventricular contraction)
The electrocardiogram
(ECG)
 PR
segment
• From the end of P wave to the beginning of
QRS complex
• Represents the spread of the impulse to the
atria (atrial contraction)
An Electrocardiogram
The electrocardiogram
(ECG) abnormalities
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Tachycardia
 HR above 100 bpm
Bradycardia
 HR below 60 bpm
Fibrillation
 Uncoordinated heart contractions