Ex Phys Test 4 PDF

Cardiovascular system - Regulation of pH during strenuous activity becomes difficult due to - Increased co2 production - Increased lactate formation - Decreases in blood pH accompany increases in blood lactate concentration - Ventilatory...

Cardiovascular system - Regulation of pH during strenuous activity becomes difficult due to - Increased co2 production - Increased lactate formation - Decreases in blood pH accompany increases in blood lactate concentration - Ventilatory threshold - At initial exercise intensities, ventilation increases linearly with O2 consumption (Ve=Vo2) - At some intensities, Ve increases faster than Vo2 (ventilatory threshold) - the rate of breathing increases exponentially faster than the rate of oxygen uptake - Ventilatory threshold approximates lactate threshold - Lactate threshold: lactate accumulates faster than the body can remove it - Acid buffering by bicarbonate produces additional co2 (pulmonary ventilation) - The need to breathe more to buffer the acid produced from anaerobic glycolysis - Purpose of the cardiovascular system - Transport blood - Transport nutrients - Generate pressure for gradients - How does the cardiovascular system maintain blood pressure - Negative feedback loops - Vasoconstriction and vasodilation - Altering cardiac output - Important equations - CO(cardiac output)=HR(heart rate) xSV (stroke volume) - MAP(mean arterial pressure)=COxSVR(systematic vascular resistance) - Systematic circulation of the cardiovascular system - skeletal muscle - Skin - GI tract - Liver - Kidney - Brain - Blood distribution - At rest - 5 total liters - Heart: 350mL - Lungs: 450mL - Arteries: 700mL - Capillaries: 300mL  - Veins: 3200mL - Order blood travels through the heart - Superior vena cava and inferior vena cava - Right atrium - Right ventricle - Pulmonary artery - Pulmonary veins (now oxygenated) - Left atrium - Left ventricle - Aorta - The heart - Weighs 9-11 oz - Resting heart rate: 60-100bpm (40 million beats/year) - Pumps: - 70mL for each beat (stroke volume) - CO=5L/min (average resting cardiac output) - 1800 gallons a day - Structure of the heart - Atria: collecting chambers - Ventricles: pumping chambers - Atrioventricular valves: separate chambers - Vena cavas: return blood to the heart - Aorta: distributes blood to body and brain - Pulmonary artery: blood to lung from the heart - Semilunar valves: prevent blood from flowing back into heart between contractions (aortic valve and pulmoary valve) - Pulmonary veins: from lung to the heart - Phases of the heart - Diastole: all chambers are relaxed, and blood flows into the heart - Atrial systole, ventricular diastole: atria contract and push blood into the ventricles - Atrial diastole, ventricular systole: atria relax, ventricles contract pushing blood out of the heart - Systole is a higher number because positive force is created to pump Cardiovascular system Pt2 - Cardiac muscle - Myocardium - Single nucleus in each fiber - Branches between fibers - Intercalated discs at ends - Strong a coordinated rhythmic contractions - Intrinsically stimulated and propagated - Pathway of electrical conduction  - SA node - AV node - Bundle of his - Right and left bundle branches - Purkinje fibers - The hearts blood supply - Own circulatory system: coronary circulation that arises from aorta - Normal blood flow to myocardium at rest: 200-250mL/min - Blood flow to heart occurs during diastole - Coronary blood flow is determined by O2 demand - Coronary circulation - From aorta: - Right coronary artery - Left coronary artery - Left atrium - Left ventricle - Right ventricle - Into right atrium: - Blood leaves left ventricle via coronary sinus and drains into right atrium - Blood leaves right ventricle via anterior cardiac veins and drain directly into the right atrium - Myocardial oxygen supply and use - Heart requires about 5% of total blood flow - At rest, myocardial O2 extraction is greater than muscle O2 extraction - At max exercise, myocardial O2 extraction is nearly 100% - Increase in myocardial blood flow caused by: - Increase in myocardial metabolism dilates coronary vessels - Increased O2 requires increased flow - Increase in aortic pressure during exercise forces a greater volume of blood into coronary circulation - Flow of blood through coronary arteries is faster during diastole - Cardiac/myocardial metabolism - 3x the oxidative capacity of skeletal muscle (more mitochondria) - Relies heavily on free fatty acid metabolism at rest - Oxidizes (uses) a large amount of lactate during intense exercise - Myocardial blood supply - Myocardium has limited anaerobic capacity, so it depends on O2 supply - Tissue hypoxia can stimulate myocardial blood flow - Causes angina - Exercise can be used to evaluate adequacy of myocardial blood flow - Blood clots - In the heart: thrombus - Lungs: pulmonary embolism - Legs: deep vein thrombosis  - Brain: stroke - Regular exercise reduces risks of blood clots Blood flow and pressure - Blood vessels - Arteries - Thick outer wall - Small lumen - Muscular - Made of elastic fibers - Vein - Thin wall - Less muscle and elastin - Large lumen - Capillary - Very small lumen - Single-cell wall - Large surface area to volume ratio - The arterial system - High pressure tubing that propels oxygen rich blood to tissues - Arteries - Made of elastin and collagen - Elastic and not compliant - Connected to capillaries through arterioles - Arterioles - Smooth muscle - Dilates and constricts to direct blood flow to approprate tissues - Arteries do not change size, arterioles do - Capillaries - Contains a small amount of blood at rest - Very narrow, allows one RBC through at a time - 1 cell thick to allow nutrients to cross the membrane easily - 2000-3000 capillaries per mm of muscle - Very large capillary density in the cardiac muscle - Venous system - Contains 65% of total blood during rest - Increase in venous tone can rapidly redistribute blood from peripheries to central region (venous return) - Blood reservoir, but an active one - Veins - Receive blood from capillaries and return it to the heart - Compliant and not elastic - Surrounded by smooth muscle  - Contain valves - Skeletal muscle pump - Muscular contractions squeeze veins to keep them moving toward the heart - Varicose veins - Valves in the veins fail or become weak or damaged - Blood is not returned to the heart as efficiently - Needs to do regular rhythmic exercises to keep the skeletal muscles pumps active and returning blood back to the heart - Gravity on blood flow - If standing too long, blood will pool in the legs which decreases venous return - Fainting can occur if decrease in VR, decrease in SV, decrease in BP, and increase in HR - Active cool down after exercise keeps the skeletal muscle pumps working - Blood - Hematocrit - Value of RBCs - 40-45% of blood volume - Anemia - Decreased RBC - Iron deficiency - Folate or B12 deficiency - Polycythemia - Too many RBCs - Dehydration - Erythropoietin - Plasma - Serum - 55-60% of total blood volume - Volume varies with - Hydration level - Training status - Altitude - Temperature - Osmolarity helps regulate blood volume - Hormonal control by sodium - Blood pressure - Force that circulating blood exerts on arterial walls - Average pressure: mean arterial pressure (MAP) - Heart remains in diastole longer than systole - Turbulent flow makes the noise we listen for - When is BP too high for an assessment: 160/100 - Hypertension can cause - Stroke - Blindness  - Atherosclerosis - Heart attack - Kidney failure - Benefits of exercise training - Decreased BP - Decreased inflammation - Increased baroreflex sensitivity - Decreased cardiovascular risk - Increased autonomic function - Increase in cardiorespiratory capacity Electrical activity in the heart - Resting membrane potential - Na and K channels are closed - Sodium potassium pump pumps k into the cell and Na out - Intrinsic regulation of heart rate - SA node - Pacemaker of the heart - Made of specialized muscle in the posterior right atrium - Spontaneously depolarizes and reploarizes to provide a sinus rhythm - 60-100bpm - The impulse from the SA node then spreads across the atria from one fiber to the next until it reaches the AV node - AV node - At the junction of the right atria and ventricle - Receives and transmits signals from the atria - Can serve as a pacemaker if the SA node fails (much slower bpm) - Transmits signal to the bundle of his - Electrical activity of the heart - P-wave: atrial depolarization - PR-interval: transmission from atria to ventricles - QRS complex: ventricular depolarization - Largest because ventricles are larger and need more contractile force - ST-segment: interval between wentricular depolarization and repolarization - T wave: ventricular repolarization - Extrinsic regulation of heart rate - Cardiovascular control center - Venterolateral medulla - Anticipatory response to exercise - Increase in SNS - Increase in HR - Increase in BP - During exercise - Parasympathetic nervous system withdraws  - SNS is stimulated - Feed forward reaction - Parasympathetc influence - Transported by vagus nerve - Acetylcholine neurotransmitter - Many PsNS neurons in the atria - When activated, the PsNS causes the heart rate to slow - Dominant activation at rest - The initial increase in heart rate at the start of exercise is caused by decreased parasympathetic stimulation - Sympathetic influence - Many SNS neurons in the atria and ventricles - Catecholamines are the transmitters - Released by the adrenal gland - Causes heart rate to increase via epinephrine - Causes increase in contractility - Dominant during exercise Cardiac Output - CO=HRxSV - HR - RPP=HRxSBP - Rate pressure product is closely related to myocardial VO2 - Correlation between RPP and angina/ECG abnormalities is useful for cardiac patients - Chronotropic effect: causes a change in heart rate - Stroke volume - Amount of blood ejected by the heart during a contraction - SV=EDV-ESV - End diastolic volume: amount of blood in the ventricle before contraction - End systolic volume: amount of blood in the ventricle after contraction - Ejection fraction: % of blood ejected with each beat - SV/EDV=EF - Heart failure - Preserved ejection fraction - Heart cant fill during diastole - Walls of the heart become too thick - Not enough blood, low stroke volume - Reduced ejection fraction - Heart cant pump during systole - Walls of heart are too thin, cant pump, low stroke volume - Frank-starling mechanism - Increase in contractility occurs with an increase in end diastolic volume - Caused by increased VR and preload)  - Inotropic effect: causes a change in contractility Cardiovascular responses to exercise - During aerobic exercise - Heart rate increase due to - PsNS withdrawal - SNS stimulation of the SA node - SV increase due to - Increased contractility from epinephrine - Increases venous return from skeletal muscle pumps and venoconstriction - Cardiac output increases because of an increase in HR and VR - SBP and MAP increase - DBP will only change a little (bad if high during exercise) - During recovery, SBP will decrease below resting values - Post exercise hypotension - Meeting O2 demand - Each component of the fick equation increases to meet the greater O2 demand of physical activity - VO2-HRxSVxa-VO2diff - Redistribution of blood flow - The amount of blood needed by different tissues changes during exerice - Blood is directed by: - Vasoconstriction - Decreased blood flow to areas with low demand - Vasodilation - Increased blood flow to areas with high demand - SNS activity leads to vasoconstriction - Vasodilation in area of high activity is caused by - Metabolic products (H, K, Po4, adenosine) - Nitric oxide released by endothelial cells cause relaxation of vascular smooth muscle - Blood flow to the skin - Exercise onset - Decreased blood flow to skin in order to supply the active muscle - increase/continuation of exercise - Increased blood flow to the skin to maintain body temperature - Max intensity exercise - Decreased blood flow to the skin to supply active muscle - Cardiovascular drift - Increase in heartrate is observed due to extended duration of constant-wrokload sub-maximal exercise - Potential reasons - Decrease in plasma volume  - Decrease in SV because of increased blood to the skin, which causes an increase in HR - Heart rate increases to maintain cardiac output - Acute response to resistance exercise - Intense or isometric contractions cause a sharp increase in blood pressure - This can increase the workload on the heart - Cardiac adaptations to training - Endurance training - Eccentric LV hypertrophy - Increase in left ventricular volume, mass, and thickness - Increased capillary density and circulation - Increased blood volume and total RBCs and hemoglobin - Strength training - Concentric LV hypertrophy - Significant increase in left ventricular mass and thickness - Produces minimal improvement in cardiovascular function - Combination of resistance and endurance exercises produces optimal results on cardiovascular function Physiologic core concepts - Structure-function - Capillaries have a thin wall and a large surface area to volume ratio to increase diffusion - Homeostasis - bicarbonate buffering during intense exercise to maintain blood pH - Flow down gradients - Blood flows through the heart via pressure gradients - Cell to cell communication - Acetylchlioine and cathelomines regular heart rate through the SNS and PNS - Interdependence - Cardiovascular system and pulmonary system work together to pump oxygenated blood throughout the body