PET3380 Exam II Study Guide 1 What are the expected training effects from aerobic exercise on HR SV and Q HR heart rate SV stroke volume o Max heart rate does not change but overall heart rate decreases lower HR at rest o SV eventually hits a plateau with max at about 40 aerobic capacity o With training you can increase your max SV because the myocardium becomes stronger and contraction can generate more force so the ventricles can hold more blood Q cardiac output blood pumped by the heart in liters per minute o Increases with training 2 How are the electrical impulses passed through the heart What are the physiological events associated with the beat of the heart SA node atria AV node AV bundle Purkinje fibers ventricles SA node depolarizes and repolarizes to provide the innate stimulus for heart action which is why it is sometimes called the pacemaker sets the heart beat Impulses start at the SA node and spread through the atria to a spot near the tricuspid valve called the AV node A short delay occurs after that to allow the atria to contract and propel blood into the ventricles Following the AV node comes the AV bundle also referred to as the bundle of His This bundle spreads farther into the Purkinje fibers which form distinct bundle branches that penetrate the right and left ventricles o These fibers transmit impulses about 6 times faster than normal ventricular fibers Physiological events o Can use an electrocardiogram to find these physiological signs o P wave atrial depolarization o P R interval measures time takes impulse SA bundle branches 0 1 0 2 sec o If 0 32 sec something is wrong o QRS complex ventricular depolarization get more force for more blood to body o S T segment ventricular repolarization enough oxygen o T wave ventricular repolarization o Highly trained aerobic capacity has a dramatic QRS complex because they can A depression indicates upcoming heart attack because the heart isn t receiving o If this doesn t repolarize right and pre mature ventricular contraction tachycardia cannot pump out enough blood to sustain life o Q T interval ventricular depolarization and repolarization 3 Understand these relationships at rest during sub maximal and maximal exercise Q HR x SV o Q depends on rate and how much blood is ejected from heart with each stroke o At rest Q is 5 6 L min o With training HR will decrease and SV with increase to maintain Q o During submaximal exercise all values will increase SV increase at the onset of exercise to accommodate the blood flow redistribution HR will increase with the increasing intensity SV is the greatest contributor to the increase in Q o During maximal exercise HR will increase exponentially after 50 60 of VO2 max SV will increase greatly until 40 of VO2 max reaches plateau Since HR is still increasing so will Q o An increase in a vO2 difference during exercise is due to an increase in the amount of O2 taken up and used for production of ATP by skeletal muscle Q VO2 a vO2 diff Q P R o Q MAP TPR o MAP mean arterial pressure o TPR total peripheral resistance o Increasing resistance decreases Q o With exercise Resistance decreases to increase blood flow to the muscles This is controlled by the diameter of the vessels o Blood pressure decreases throughout the circulatory system Starts 100 at the heart and reaches almost 0 once it gets back to the right atrium VO2 Q x a vO2 diff o Fick equation o Increasing Q or a vO2 difference would increase VO2 o VO2 will increase as intensity increases At rest VO2 250 ml min During exercise 3200 ml min How increase blood flow o VO2 max is a great measure of cardiovascular health as this is the amount of oxygen the body heart can supply to the working muscles o A V O2 difference represents the gas exchange to the tissues The greater this difference means that the muscles are being more efficient at using oxygen 4 What is blood flow redistribution and which tissues are affected HOW Blood flow redistribution blood flow from one organ to another by vasoconstriction in one inactive muscle and vasodilation in the other active muscle Important during exercise because muscles needing blood are provided with more blood from organs that do not need as much blood flow during exercise During exercise blood flow o Kidneys and visceral organs is greatly reduced o 600 mL of oxygen available each minute to be used by the active muscles 80 of cardiac output to working muscles skin o Increase to cerebral and cardiac so these vital organs can receive the oxygen they need Two factors cause this blood flow redistribution o Hormonal vascular regulation local metabolic conditions At rest working muscles get only 15 of cardiac output while organs get 80 o This switches during exercise Blood flow o To the heart increase during exercise not only through but to the myocardium o To the lungs more blood through the lungs and to the respiratory muscles o To the brain by volume it will increase due to cardiac output but percentage wise it stays the same to the active muscles o To skin increases during light moderate exercise but during maximal blood is shunted The body strives to maintain internal core temp for organs Initially it drops but then it increases past resting levels in order to dissipate heat and maintain core temperature change happens within minutes Hypothalamus thermostat In the event of dehydration the blood flow to the skin would reduce in order to eliminate excess water loss o To visceral organs reduced to make available for active muscles 5 What is venous return What factors influence venous return Venous return the flow of blood back to the heart through the venous circuit o The output of the heart depends on venous return o Greatest factor in increasing blood volume and Q by increasing EDV thereby increasing SV Since the system is a closed loop the amount that leaves the ventricles will always equal the amount that returns through the right atrium the more blood returning means more blood gets pumped out Factors affecting venous return o Unidirectional valves pressure and gravity composition In veins prevent back flow especially to the lower extremities o Muscle pumps mechanical process squeezes vessels As muscles contract compress veins and assist in pushing blood back to heart o Respiratory pump diaphragm lungs inflation o Rhythmic pattern of breathing also provides a mechanical pump that increases venous return by alternating changes in thoracic and abdominal pressures o Venoconstriction reflexive
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