Transcript Chapter 33
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 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 Over the 2nd intercostal space 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 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 The electrocardiogram (ECG) 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) 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) 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 Tachycardia HR above 100 bpm Bradycardia HR below 60 bpm Fibrillation Uncoordinated heart contractions