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Exercise 37
Human cardiovascular physiology
Cardiac cycle
Concepts to memorize: The two atria contract simultaneously The two ventricles contract
simultaneously Diastole
The relaxation period Systole
The contraction period
Steps of the cardiac cycle
The heart is in diastoleHeart 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
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
The pressure in the aorta and pulmonary arteries increase
The semilunar valves close The ventricles relax
The cardiac sounds (lub-dup pause) 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 valvesIt happens at the end of the systole
The cardiac sounds
MurmursIt represents a turbulent blood flowIt 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
Auscultation of the mitral valveOver the 5th intercostal spaceIn line with the middle of the clavicle
Auscultation of the tricuspid valveOver the sternum
Cardiac cycle
Auscultation of the pulmonary valveOver the 2nd intercostal spaceAt left sternal margin
Auscultation of the aortic valveOver the 2nd intercostal spaceAt the right sternal margin
The pulse
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 rateIt is the same as the heart rateNormal: 60-100 bpm
The pulse
Pulse rhythm Pulse amplitude Superficial pulse points
Common carotid arteryTemporal arteryFacial arteryBrachial arteryRadial artery
The pulse
Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery
The blood pressure
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 readingnormal:120 mm Hg
The blood pressure
Diastolic pressureReflects the pressure in the arteries
during ventricular relaxationIt is the second readingNormal: 80 mm Hg
The blood pressure
Sounds of KorotkoffIndicates 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
Venous pressure Normal: 30-90 mm Hg They are affected by muscle activity,
deep pressure, breathing, etc
The blood pressure
Pulse Pressure (PP)Systolic pressure – diastolic
pressure Mean arterial pressure (MAP)
MAP=diastolic pressure+PP/3
Effects of various factors on blood pressure
BP=CO * PR Factors that increase PR:
Constriction of arteriesIncreased blood viscosityIncreased blood volumeHardening of the arteries walls
Effects of various factors on blood pressure
Factors that increase BP: Age Weight Drugs Exercise Emotions, etc
Skin color
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)
Conduction of impulses through the heart Generation of electrical impulses Detection of the electrical impulses on the body’s
surface Electrocardiograph
The electrocardiogram (ECG)
Deflection wavesThe 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 contractionThe T wave indicates ventricular
repolarization; third wave
An Electrocardiogram
The electrocardiogram (ECG)
Intervals- Always include at least one wavePR 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)
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
TachycardiaHR above 100 bpm
BradycardiaHR below 60 bpm
FibrillationUncoordinated heart contractions