Illinois State University The Cardiovascular System The Cardiovascular System Cardiovascular Control During Exercise Chapter 11 and 12

Illinois State University Heart Structure and Blood Flow n The atria receive blood into the heart; the ventricles eject blood from the heart. Atria Ventricles

Illinois State University The Myocardium n Because the left ventricle must produce more power than other chambers, its myocardium is thicker due to hypertrophy.

Illinois State University Cardiac Conduction n Cardiac tissue is capable of autoconduction. n It initiates its own pulse without neural control.

Illinois State University Cardiac Conduction n The sinoatrial (SA) node is the heart’s pacemaker, establishing the pulse and coordinating activity throughout the heart.

Illinois State University Extrinsic Control of Heart Activity n Heart rate and contraction strength can be altered by the autonomic nervous system or the endocrine system.

Illinois State University Electrocardiography (ECG) n The ECG is a recording of the heart’s electrical functioning. n An exercise ECG may reveal underlying cardiac disorders. p q r s t

Illinois State University Cardiac Function n The cardiac cycle: Relaxation = diastole.Relaxation = diastole. Contraction = systole.Contraction = systole. ECG waves: P, QRS, T.ECG waves: P, QRS, T. n Stroke volume.

Illinois State University Cardiac Function n Ejection fraction from left ventricle (60% at rest). n Cardiac output ( L. min -1 )

Illinois State University Vascular System: n Arteries. n Arterioles. n Capillaries. n Venules. n Veins.

Illinois State University Venous Return n Blood returns to the heart through the veins, assisted by: Breathing. Breathing. Muscle pump. Muscle pump. Valves. Valves. n Valsalva Manuever

Illinois State University Distribution of Blood n Activity dictates distribution. n Vasoconstriction. n Vasodilation.

Illinois State University Blood Pressure (NHLBI, 2003) PressureNormal Pre- hypertension Stage I Hypertension Stage II Hypertension Systolic < > 160 Diastolic < > 100 Treatment Otherwise healthy NoneNone Diuretics for most, possibly other drugs Two-drug combo; usually one is a diuretic With other diseases None Medically treat diseases Multiple medications

Illinois State University Blood n Blood and lymph are the substances that transport materials to and from body tissues. n Fluid from plasma enters tissues, becoming interstitial fluid.

Illinois State University Blood n Most interstitial fluid returns to the capillaries, but some enters the lymphatic system as lymph, eventually returning to the blood.

Illinois State University Blood n Blood is about 55% to 60% plasma and 40-45% formed elements including RBCs, WBCs, etc. n Hematocrit – ration of blood cells to total blood volume.

Illinois State University Blood n Oxygen is primarily transported bound to the hemoglobin in red blood cells. n As blood viscosity increases, so does resistance to flow.

Illinois State University Total Peripheral Resistance n TPR = length x viscosity ______________ ______________ (Radius) 4 (Radius) 4

Illinois State University Response to Exercise n As exercise intensity increases, HR increases.

Illinois State University Exercise n The heart ejects blood more often, thus speeding up circulation.

Illinois State University Response to Exercise n Stroke volume also increases, so the amount of blood ejected with each contraction increases. n Increases in HR and SV increase cardiac output.

Illinois State University Response to Exercise n More blood is forced out of the heart during exercise then when at rest, and circulation speeds up.

Illinois State University Response to Exercise n This insures that adequate supplies of the needed materials - oxygen and nutrients - reach the tissues and that waste products, which build up much more rapidly during exercise, are quickly cleared away.

Illinois State University Major Changes in Blood During Exercise n The a-vO 2 difference increases. n Increased extraction of oxygen from the blood for use by the active muscles.

Illinois State University Major Changes in Blood During Exercise n Plasma volume decreases during exercise. n Water is forced into tissues by increased blood pressure. n Water also evaporates.

Illinois State University Major Changes in Blood During Exercise n Hemoconcentration occurs as plasma fluid (water) is lost. n Although the actual number of red blood cells might not increase, the relative number of red blood cells per unit of blood increases, which increases O 2 carrying capacity.

Illinois State University Major Changes in Blood During Exercise n pH levels drops from resting values of 7.4 to 7.0 or lower. n Muscle pH decreases even further. n The decrease in pH results primarily from increased blood lactate accumulation with increasing exercise intensity.