PET3380 Exam II Study Guide 1 What are the expected training effects from aerobic exercise on HR SV and Q HR heart rate max heart rate does not change but overall heart rate decreases lower HR at rest SV stroke volume SV eventually hits a plateau with max at about 40 aerobic capacity 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 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 QRS complex ventricular depolarization o S T segment ventricular repolarization if there is depression in this S T segment it is a good predictor of an upcoming heart attack because you aren t getting enough O2 to the heart o T wave ventricular repolarization o Q T interval ventricular depolarization and repolarization 3 Understand these relationships at rest during sub maximal and maximal exercise Q depends on rate of pumping and how much blood is ejected from heart with 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 HR x S each stroke Q VO2 a vO2 diff Q P R also Q MAP TPR Darcy s Law MAP mean arterial pressure TRP total peripheral resistance increasing resistance decreases Q VO2 Q x a vO2 diff Fick equation increasing Q or a vO2 difference would increase VO2 a b c d 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 to the kidneys and visceral organs is greatly reduced to make available about 600 mL of oxygen each minute to be used by the active muscles blood flow to the sin greatly increases during light and moderate exercise in response to the rise in core body temperature during max blood flow to the skin is restricted to active muscles cerebral and cardiac blood flow also increases during exercise so these vital organs can receive the oxygen they need two factors cause this blood flow redistribution hormonal vascular regulation and local metabolic conditions 5 What is venous return What factors influence venous return venous return the flow of blood back to the heart through the venous circuit the output of the heart depends on venous return during exercise venous return is pulsitile factors affecting venous return o venoconstriction decrease volume capacities o one way 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 they compress veins and assist in pushing blood back to the heart o lungs pressure and muscle composition respiratory pump action rhythmic pattern of breathing also provides a mechanical pump that increases venous return by alternating changes in thoracic and abdominal pressures 6 Describe the immediate acute adjustments made by the heart and circulatory system to allow for physical activity Give neural and hormonal mechanisms Give changes from rest to sub maximal to heavy maximal exercise two factors increase SV 1 increasing amount of blood in ventricle before systole increase end diastolic volume and 2 decreasing the amount of blood left in the ventricles at the end of systole decrease end systolic volume Frank Starling Law increasing EDV in left ventricle causes a stretch of ventricular myocardium which enhances contractility as well as SV adaptations to aerobic training o at rest o submaximal exercise o at maximal exercise resting HR reduces but the resting Q does not differ between trained and untrained individuals so it is the SV that is elevated at rest for trained individuals for a trained person HR is lower at a given workload VO2 max but SV will be greater at a given workload Q will be the same between trained and untrained people trained individual achieves larger Q during exercise because of a larger stroke volume than that of an untrained person HR max does not change with training 7 Define cardiac output EXPLAIN How cardiac output is measured Fick method cardiac output the amount of blood pumped by the heart during a one minute period maximal value reflects functional capacity of cardiovascular system depends on heart rate rate of pumping and stroke volume quantity of blood ejected with each stroke cardiac output Q HR SV Fick principle Q VO2 a v O2 difference 100 o used to calculate cardiac output o a v O2 difference average difference between oxygen content of arterial and mixed venous blood mL per 100 mL of blood o VO2 volume of oxygen consumed in one minute mL min 8 Give the mechanisms controlling stimulation in the heart rate prior to and during activity extrinsic controls accelerate heart in anticipation before exercise begins and then rapidly adjust to intensity of physical effort changes made by nerves that directly supply myocardium and chemical messengers neurotransmitters and hormones that circulate the blood o sympathetic influence causes the heart to beat faster tachycardia o parasympathetic influence causes the heart rate to be reduced bradycardia intrinsic controls the heart maintains its own rhythm has spontaneous activity muscle nerves of heart can be excited o see question 2 at rest
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