Human cardiovascular physiology Exercise 37 Human cardiovascular physiology

Cardiac cycle The relaxation period The contraction period 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 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 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 valves It happens at the end of the systole

The cardiac sounds 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 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 Auscultation of the pulmonary valve Over the 2nd intercostal space At left sternal margin Auscultation of the aortic valve 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 It is the same as the heart rate Normal: 60-100 bpm

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

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

The blood pressure 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 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 Narrow pulse pressure (>30mm Hg) = aortic stenosis, constrictive pericarditis, tachycardia

Effects of various factors on blood pressure 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 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

Electrocardiogram

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

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

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

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

ECG - Intervals ST interval From the end of the QRS to the end of the T wave ST segment + T wave Decreased conduction through atriaspread out P wave PR segment = conduction through the AV node PR intervalincreased conduction through AV node (sympathetic stimulation for example)decrease PR interval; decreased conduction through AV node increased PR interval ST segment = Plateau of the ventricular action potential

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