Exercise 37 Human cardiovascular physiology Cardiac cycle Concepts

Exercise 37 Human cardiovascular physiology

Cardiac cycle ¢ ¢ Concepts to memorize: The two atria contract simultaneously The two ventricles contract simultaneously Diastole l The ¢ relaxation period Systole l The contraction period

Steps of the cardiac cycle The heart is in diastole l 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 The ventricular pressure increases ¢ The ventricular systole begins l 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 (S 1 - lub) l Represents the closing of the AV valves l It happens at the beginning of the systole ¢ Second heart sound (S 2 - dup) l It represents the closing of the semilunar valves l It happens at the end of the systole ¢

The cardiac sounds ¢ Murmurs l It represents a turbulent blood flow l It is found when blood flows through narrow openings (stenosis) l Also found when there is backflow of blood (regurgitation) because of defected valves (insufficiency)

Cardiac cycle Auscultation of the mitral valve l Over the 5 th intercostal space l In line with the middle of the clavicle ¢ Auscultation of the tricuspid valve l Over the sternum ¢

Cardiac cycle Auscultation of the pulmonary valve l Over the 2 nd intercostal space l At left sternal margin ¢ Auscultation of the aortic valve l Over the 2 nd intercostal space l At 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 rate l It is the same as the heart rate l Normal: 60 -100 bpm ¢

The pulse Pulse rhythm ¢ Pulse amplitude ¢ Superficial pulse points l Common carotid artery l Temporal artery l Facial artery l Brachial artery l Radial 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 l Reflects the pressure in the arteries during ventricular ejection l It is the first reading l normal: 120 mm Hg ¢

The blood pressure ¢ Diastolic pressure l Reflects the pressure in the arteries during ventricular relaxation l It is the second reading l Normal: 80 mm Hg

The blood pressure ¢ Sounds of Korotkoff l Indicates the resumption of blood flow into the forearm when the pressure to occlude the artery is gradually released l First sound heard is the systolic pressure l 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) l Systolic pressure – diastolic pressure ¢ Mean arterial pressure (MAP) l MAP=diastolic pressure+PP/3 ¢

Effects of various factors on blood pressure BP=CO * PR ¢ Factors that increase PR: l Constriction of arteries l Increased blood viscosity l Increased blood volume l Hardening 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 l Oxygen supply (cyanosis) l Temperature (cold, warm) l Hormones (thyroid hormones) l 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 ¢

Electrocardiogram

ECG - Waves P wave represents the depolarization of the atria • First wave, small and precedes atrial contraction ¢ QRS complex ventricular depolarization; second wave l Precedes ventricular contraction ¢ T wave indicates ventricular repolarization; third wave ¢

ECG - Segments Flat Lines ¢ PR segment l From the end of P wave to the beginning of QRS complex l Represents the conduction through the AV node ¢

ECG - Segments ¢ ST segment l From the end of QRS to the beginning of T wave l Represents the plateau of the ventricular action potential

ECG - Intervals Always include at least one wave ¢ PR interval (PQ) l P wave + PR segment ¢ QT interval l From the Q wave to the end of T wave l QRS complex + ST segment + T wave ¢

ECG - Intervals ¢ ST interval l From the end of the QRS to the end of the T wave l ST segment + T wave

The electrocardiogram (ECG) abnormalities Tachycardia l HR above 100 bpm ¢ Bradycardia l HR below 60 bpm ¢ Fibrillation l Uncoordinated heart contractions ¢