EXSC 530 Exam #2
Define, describe and discuss the primary anatomic structures of the heart
- Right and left atria (RA, LA): top, receiving chambers - Right and left ventricles (RV, LV): bottom, pumping chambers -Arteries and arterioles: Carry blood away from the heart -Capillaries: Exchange of O2, CO2, and nutrients with tissues -Veins and venules: Carry blood toward the heart Epicardium: outer covering; prevents friction Myocardium: muscular; blood supply via coronary arteries •can change shape; slow-twitch fibers (type I); LV is larger •CONTRACTS ALL TOGETHER/AT ONCE •The heart has its own circulatory network, the coronary circulation •Cardiac muscle fibers connected by intercalated discs Endocardium: protects lining of chambers and valves. •Heart muscle has single nuclei, z-discs, contractile proteins (actin and myosin), endomysium is the connective tissue, and is shorter than skeletal muscle. •Ca+ source comes from sarcoplasmic reticulum and extracellular Ca+ BLOOD VESSELS: Arteries: -Swell with systole and recoil with diastole and contain high pressure -sympathetic stimulation (veins) - The arterial system consists of high-pressure tubing that propels oxygen-rich blood to tissues, no gaseous exchange occurs. Capillaries: •Arterioles branch and form smaller and less muscular vessels called metarterioles that contain 6% of total blood volume. •single layer cell •Two factors trigger precapillary sphincter relaxation to open more capillaries: (allow or disallow blood to capillaries) 1.) Driving force of increased local BP plus intrinsic neural control 2. )Local metabolites produced in exercise Veins: -With sympathetic stimulation veins are able to continue to augment venous return under low pressure Venous Return: -allow blood to flow in only one direction toward the heart -Without valves, blood would stagnate in extremity veins; people would faint every time they stood up because of reduced venous return and diminished cerebral blood flow.
Q5: VO2 max values declines steadily after age 25 at a rate of about ______ per decade. A. 1% B. 5% C. 10% D. 25%
C. 10%
Q5: The Borg's rating of perceived exertion (RPE) scale has value ranged from 6 to 20. This corresponds roughly to a heart rate range of ______________________. A. 70 to 150 bpm B. 110 to 150 bpm C. 60 to 200 bpm D. 106 to 200 bpm
C. 60 to 200 bpm
DIASTOLIC BLOOD PRESSURE
•Indicates the ease that blood flows from the arterioles into the capillaries •Typically stays the same throughout exercise intensity.
Extrinsic Control of Blood Flow
•Parasympathetic Influence (Not overall major regulatory factor) • • •
Identify the factors that regulate local blood flow during exercise
#1.) Vasodilation (in skeletal muscle) - Blood flow increased to meet metabolic demands of active tissue.- #2.) Vasoconstriction (to visceral organs and inactive tissues) -SNS vasoconstriction •When sitting down doing nothing blood vessels are vasoconstricted •SYmpathetic activity dictates whether or not it's vasoconstricted/ vasodialated. •Extrinsic vs. Intrinsic control of blood flow (peripheral circulation)
Discus several explanations for the sudden rise in blood lactate concentration during incremental exercise. (essay question)
(1) low muscle oxygen (2) accelerated glycolysis due to epinephrine and norepinephrine (3) recruitment of fast muscle fibers (4) a reduced rate of lactate removal • There is a low O2 level in the blood •slow-twitch to fast-twitch fibers [perform high force activity] •LDH converts pyruvate to lactate and has a greater affinity. •LDH isozyme in fast fibers promotes lactic acid formation. Then, NADH produced faster than it is shuttled into the mitochondria and excess NADH in cytoplasm converts pyruvic acid to lactic acid •The result is a reduced rate of lactate removal from the blood. •Lactate WITH H+ ions causes fatigue -Lactic acid is removed more rapidly with light exercise in recovery. Optimal intensity is ~30-40% VO2 max
Max Intensity & the Sprinter
-% anaerobic decreases over time while % aerobic increases -ATP resynthesis from phosphocreatine breakdown -ATP resynthesis from glycogen metabolism -fatigue is caused by running out of PC! and the accumulation of metabolites. unlike marathon runners who fatigue from low GLYCOGEN levels!
PROLONGED EXERCISE
-% anaerobic decreases while % aerobic increases. -The ability to supply energy by aerobic metabolism is a key factor in success in middle- and long-distance events. -A high capacity for oxidative metabolism is a prerequisite for success in endurance events - endurance athletes contain a high proportion of type I fibers -muscle and liver carbohydrate stores are depleted which causes fatigue - development of hypoglycemia ( slows the brain, due to low glycogen levels) may contribute to fatigue.
Middle Distance Events
-& anaerobic decreases while % aerobic increases. -Energy supply for sudden acceleration to running speed at the onset of a race: provided by ATP and PCr stores in the muscle -More than 2 minutes: main source of energy from oxidative metabolism. -accumulation of lactate within the muscle causes fatigue. Hydrogen ion accumulation in the cell may cause fatigue by.... • Inhibiting reactions of anaerobic glycolysis • Interfering directly with the contractile mechanism
Regulation of Stroke Volume
-ANS plays important role in HR regulation #1.) Strength of the ventricular contraction (myocardial contractility) •Enhanced by: - Direct sympathetic stimulation of heart - Circulating epinephrine and norepinephrine •Extrinsic regulation! •Parasympathetic: ventricles allow blood to be ejected. •Has little/no effect on myocardial contractility!! •Innervate SA & AV nodes, do not innervate ventricles. •SV isn't innervated w/ parasympathetic activity b/c there is no innervation of vagus nerve fibers!!!!! •Comes from sympathetic activity •Increased Ca+ availability= Increased contractility=Increased SV #2.) End-diastolic volume (EDV) - Preload •Volume of blood in the left ventricle at the end of diastole •Intrinsic Regulation! •Greater EDV results in a more forceful contraction •Increased contractility of heart=Increased SV •The more blood in the LV gives you more contraction •The heart can do more efficient work,easier work for the heart (ex: rubber band) #3.) Aortic blood pressure - Afterload •The tension, force, or stress (aortic pressure) in the LV wall after the onset of shortening •In order to eject blood, the pressure generated by the left ventricle must exceed the pressure in the aorta. Therefore, aortic pressure or mean arterial pressure (afterload) represents a barrier to ejection of blood from the ventricles. •SV is thus inversely proportional to afterload. •Afterload is worse than increase in Preload
Define graded exercise test.
-Incremental tests that can be maximal or submaximal -Gold standard measure of cardiorespiratory fitness (Open-circuit spirometery) -Tests use incremental changes in workload until peak exertion/exhaustion is reached. -VO2max is determined using exercise that activate the body's large muscle groups -Cardiorespiratory fitness measured using: - Treadmill - Cycle ergometer - Stepping bench -Specificity for patients and athletes
Explain in detail why there is an abrupt increase in ventilation leading to and increase RER> 1.0 (essay question)
-It signifies the highest work rate or oxygen consumption at which the energy demands exceed circulatory ability to sustain aerobic work. -CO2 is the biproduct of breaking down fats and CHO's and causes hyperventilation -Extra CO2 comes from lactic acid -Sodium bi-carbonate acts as a buffer to break down lactic acid.
Discuss the mechanisms of muscular fatigue due to the accumulation of lactate in blood and skeletal muscle during high intensity exercise. (essay question)
-Lactate doesn't cause muscle fatigue -muscle soreness is caused by damage to muscle that leads to inflammation and an increase in H+ ions from lactate that stimulates a burning sensation. elevated H+ concentration on the contractile mechanism: •Inhibition of the SR ATPase, reducing Ca2+ reuptake and Ca2+ release • inhibition of Ca2+ binding to troponin C, reducing crossbridge activation •Inhibition of crossbridge actomyosin ATPase and ATP hydrolysis •Reduce the force per cross-bridge •Reduce the force generated at a given Ca++ concentration
Define mean arterial pressure
-MAP = Q x Total Vascular Resistance -MAP=DBP+1/3(SBP-DBP) [used to actually calc] -Average pressure during a cardiac cycle - Determines the rate of blood flow through the systemic circuit. -combines systole and diastole -Not simply average of SBP and DBP because diastole generally lasts longer than systole
Differentiate between maximal oxygen consumption and peak oxygen consumption
-Max O2 Consumption-plateau -Peak O2 Consumption- point right before VO2 max plateaus
Define myocardial oxygen consumption
-Oxygen consumption by the heart -Double Product= SBP x HR (Index of relative work of the heart) -The higher the #, the more O2 being consumed -Increases linearly with exercise intensity -point at which patients feel chest pain.
BETA-BLOCKADE
-Reduce heart rate, contractility, and blood pressure. -Compete with epinephrine and norepinephrine for beta adrenergic receptors in the heart -Will lower heart rate during submaximal and maximal exercise
Cardiovascular response at the completion of dynamic resistance exercise (concentric knee extension) with varying loads. Mean arterial pressure and heart rate response during a set of dynamic exercise to failure
-Resistance exercise results in a dec SV due to dec EDV and/or inc ESV ( high intrathoracic pressure, mechanical occulusion of vein inc afterload). -HR lower during strength exercise than during endurance exercise. Increase in proportion to the muscle mass used.
Functions of the CVS & The 4 Components
-Transport O2 and nutrients to tissues - Removal of CO2 wastes from tissues - Regulation of body temperature 1.) A pump that provides continuous linkage with the other three components 2.) A high-pressure distribution circuit 3.) Exchange vessels 4.) A low-pressure collection and return circuit - The right side of the heart pumps blood through the pulmonary circulation -The left side of the heart delivers blood to the systemic circulation.
Obtain a functional understanding of the Fick equation.
-VO2 = Q x a-vO2 difference -VO2 = HR x SV x a-vO2 difference -depends on blood flow and oxygen extraction -linear relationship between work rate and VO2 -Cardiac output is highly correlated with VO2 max -represents Oxygen Consumption
Identify the common measures taken during a graded exercise test
-Work rate increases every 2-3 minutes and the optimal test length is from 6 to 15 minutes.
Q5: Which of the following exercise test protocols yield the lowest VO2 max value in healthy, untrained collegeaged adults? A. Arm ergometer test B. Cycle egometer test C. Step test D. Treadmill Test
A. Arm ergometer test
#6.) For healthy, untrained persons, at what percentage of the individual's maximal capacity for aerobic metabolism does blood lactate begin to accumulate and rise in an exponential fashion? A. At about 55% B. At about 75% C. At about 85% D. At about 95%
A. At about 55%
Q4: The excess ventilation (VE) during increasing intensity of exercise is primarily due to a rather sudden increase in CO2 production which results directly from buffering of lactate using sodium bicarbonate. A. True B. False
A. True
#5.) Which of the following is true about VO2 during exercise? A. VO2 increases linearly with work rate. B. VO2 is an indicator of glycolytic ATP production. C. VO2 drops sharply just prior to fatigue. D. None of the above are true.
A. VO2 increases linearly with work rate.
Q5: Which of the following trained individuals should have the highest VO2 max values? A. cross country skiers B. 400-meter sprinters C. Weight lifters D. Rowers E. Swimmers (100-meters)
A. cross country skiers
#1.) After the first few minutes of constant-load, submaximal exercise, VO2 reaches steady state, indicating that A. the ATP demand is being met aerobically. B. levels of lactic acid in the blood are very high. C. the exercise can be continued indefinitely without fatigue. D. the oxygen uptake is not sufficient to meet the ATP demand
A. the ATP demand is being met aerobically.
#5.) Blood flow to the skin during maximal exercise intensity usually: A. Increases B. Decreases C. does not change
B. Decreases
#3.) The product of heart rate and diastolic blood pressure provides a good estimate of myocardial workload. A. True B. False
B. False
Q4: Lactate itself is directly responsible for muscular fatigue during high intensity of exercise. A. True B. False
B. False
Q5: Criteria for reaching a true VO2 max: Blood lactate levels rise above 2 mmol per liter of blood. A. True B. False
B. False
Q5: Which of the following variables are typically included during a maximal exercise test on a treadmill? A. Measurement of heart rate, blood lactate, RPE, skeletal muscle mitochondrial density B. Measurement of blood pressure, heart rate, blood lactate, RPE, and VO2. C. Measurement of heart rate, blood pressure, blood lactate, body temperature, and VO2. D. Measurement of blood pressure, blood lactate, blood glucose, body temperature and VO2.
B. Measurement of blood pressure, heart rate, blood lactate, RPE, and VO2.
#7.) Most of the increase in mean arterial blood pressure that occurs during large muscle, dynamic, incremental exercise is due to A. an increase in diastolic blood pressure B. an increase in systolic blood pressure C. both an increase in diastolic and systolic blood pressure
B. an increase in systolic blood pressure
#2.) During moderate-intensity (65% VO2 max) exercise, the percent of ATP derived from carbohydrates is ___________ the percent ATP from fats. A. less than B. equal to C. greater than
B. equal to
Q4: During the "rapid" portion of the oxygen debt (or EPOC), the excess VO2 is due to A. high body temperature. B. gluconeogenesis. C. restoration of muscle CP and blood and muscle oxygen stores. D. elevated blood levels of epinephrine and norepinephrine.
C. restoration of muscle CP and blood and muscle oxygen stores.
Describe the types of carbohydrates and fats used during increasing intensities of exercise and during prolonged exercise of moderate intensity.
CHO's: -muscle glycogen (high-intensity/ first hour) primary source. -liver glycogen (low-intensity/ long duration) used as muscle glycogen declines -Initial muscle glycogen content is strongly related to endurance performance. FATS: -Intramuscular triglycerides (high-intensity) -Plasma FFA (low-intensity) •Prolonged, low-intensity exercise- Shift from carbohydrate metabolism toward fat metabolism. • Fats cannot be broken down by the Krebs Cycle •Pyruvate is a precursor for malate and oxalo-acetate.
Discuss in detail mechanisms for a shift toward and increase in CHO metabolism and decrease in fat metabolism as exercise intensity increases. (essay question)
Crossover Concept: -Due to the Recruitment of fast muscle fibers and Increasing blood levels of epinephrine Recruitment of fast muscle fibers: •Abundance of glycolytic enzymes but few mitochondrial and lipolytic enzymes • Higher glycogen content and phosphocreatine content • Higher myosin ATPase activity • Higher power output Increasing blood levels of epinephrine: • Increase glycogenolysis by increasing phosphorylase activity, which will increase rate of glycolysis and lactate production • Inhibition of fat metabolism from increased production of lactate.
#6.) During maximal intensity of aerobic exercise such as running, how much of the cardiac output is redirected to the skeletal muscles? A. 15 to 20% B. 40 to 50% C. 55 to 65% D. 80 to 85%
D. 80-85% (?)
#9.) Other than the active muscle mass, which organ receives the greatest redistribution of the blood flow during moderate intensity of cycling exercise A. Kidney B. Brain C. Liver D. Skin E. None of the above
D. Skin
Q6: At exercise intensity above 60% VO2 max, an increase in cardiac output is due to: A. increase in stroke volume only B. increase in stroke volume and decrease in heart rate C. decrease in stroke volume and increase in heart rate D. increase in heart rate only E. increase in both stroke volume and heart rate
D. increase in heart rate only
Max HR
Direct method: •total exhaustion; all out fatigue Indirect method: •more common, estimated based on age Max HR=208 - 0.7 x (age) +/- 12bpm •decrease of HRmax of 3 to 5% per decade •Large variation in individuals of the same age group.
Shoveling Snow: •Higher SBP, RPP then treadmill •More vasoconstriction •Dec Preload •Dec Venous Return •No aerobic exercise Treadmill: •Higher HR, VO2 than shoveling snow
Dynamic (Isotonic): •Higher cardiac output, HR, SV than static Static (Isometric): •Higher peripheral resistance, SBP,DBP, MAP than dynamic
Q5: Maintaining a minimal VO2 max is important because VO2 max below the _____________ is associated with sedentary lifestyle and increased risk of death from all causes. A. 90th percentile B. 60th percentile C. 55th percentile D. 33rd percentile E. 20th percentile
E. 20th percentile
Describe the cardiovascular responses to incremental exercise, submaximal (steady state) exercise and prolonged exercise.
Incremental Exercise: •Heart rate and cardiac output- Increases linearly with increasing work rate and Reaches plateau at 100% VO2 max •Blood pressure- Mean arterial pressure increases linearly and Systolic BP increases / Diastolic BP remains fairly constant •Double product (Rate-pressure product)- Increases linearly with exercise intensity and Indicates the work (pumping capacity) of the heart. -RPP=SBP+HR -MAP inc as intensity inc -MAP=DBP+1/3(SBP-DBP) -Double Product is an INDIRECT index of MVO2 Prolonged Exercise: •Cardiac output is maintained • Gradual decrease in stroke volume • Gradual increase in heart rate • Cardiovascular drift: associated w/ dehydration. If you're biking at the same intensity, HR inc while SV dec, cardiac output is the SAME. Part of cardiac output goes to the skin too cool it off. • Decrease SV - Increase Skin blood flow - Decrease Plasma volume (sweating) - Decrease Venous return •HR to compensate (to maintain cardiac output)
Indicate the influence of each of the following factors on VO2 max.: mode of exercise, heredity, state of training, gender, body composition and age (end of lecture)
Mode of exercise: • Influences muscle mass activated •Highest on treadmill •Specificity and skill are very influential in many modes Heredity: •50% of VO2 max •Large variation in change in VO2 max with training •21 genes play a role change in VO2 max with training Gender: •Differences may be due to Muscle mass and Hemoglobin concentration •Women achieve scores on average 15 − 30% lower than men. Age: •VO2max declines after age 25 by ~ 1% per year. •At age 55, it averages about 27% below values for 20-year olds. Body size and composition: • Express VO2 max relative to body mass •More accurate: per kg of fat-free mass Health and Disease: •Healthy individuals men had higher VO2 max •Diseased individuals men had higher VO2 max or equal to women.
AVO2 Difference
REST - Arterial O2 content - mixed venous O2 content - Oxygen content of arterial blood = 20 ml O2•dL-1 - Oxygen content of venous blood =15 ml O2•dL-1 - Typical a-vO2 difference = 5 ml O2•dL-1 MAXIMAL - Oxygen content of arterial blood • a-vO2 difference = 20 ml O2•dL-1 - Oxygen content of venous blood • a-vO2 difference = 5 ml O2•dL-1 - Typical a-vO2 difference : • 15 ml O2•dL-1
Outline cardiac output distribution to major body tissues during rest and aerobic exercise
REST: •typical 5-L cardiac output distributes as follows: - One fifth flows to muscle tissue (4 to 7 mL/min/100 g muscle). - Major portion of remaining blood flows to digestive tract, liver, spleen, brain, and kidneys receive major portions of the remaining blood. •Liver, kidneys receive ~50% • Skeletal muscle receives ~15% to 20% AEROBIC EXERCISE: •Cardiac output increases due to inc HR and inc SV •Exercising muscles receive 80% to 85% of Q (50 to 75 ml / 100 g muscle) - Decreased blood flow to less active organs Liver, kidneys, GI tract
[Cardiovascular Regulation and Control] Understand the regulation of cardiac output at rest and during exercise
REST: PARASYMPATHETIC: •Neurotransmitter at effector organs is Acetylcholine Effects mediated: CHOLINERGIC RECEPTORS- -Muscarinic receptors-Activation; inhibition of cardiac muscle -Nicotinic receptors- Excitation • Decrease GI motility, Relax bronchial smooth muscles, Increase sweating, relax uterine smooth muscle EXERCISE: SYMPATHETIC: •Neurotransmitter at effector organs: Norepinephrine Effects mediated: ADRENERGIC RECEPTORS- -Alpha (α) adrenergic receptors -A1-location: skin, skeletal muscle, mucosae, abdominal viscera, kidneys; Constricts blood vessels. -A2-location: Membrane of adrenergic axon terminals (nerves) and blood platelets; Mediates inhibition of NE release and promotes blood clotting -Beta (β) Adrenergic receptors -Β1-location: HEART; Increases heart rate and strength of contraction -Β2-location:CORONARY ARTERIES; Dilates coronary arteries -Β3-location: ADIPOSE TISSUE; Stimulates lipolysis by fat cells
Hemodynamics
Resistance depends upon: - Length of the vessel - Viscosity of the blood - Radius of the vessel •Resistance = Length x Viscosity/ Radius ^4
Describe, graphically, the change in oxygen uptake during the transition from rest to steady state exercise, and then recovery from exercise. Identify the oxygen deficit, oxygen requirement, and oxygen debt (excess post-exercise oxygen uptake).
Rest to Steady State: -ATP through anaerobic system -ATP-PC System -Glocolysis -when steady state is reached, switches to aerobic metabolism. [ Aerobic gylcolysis, beta oxidation, Krebs Cycle, ETC] -Your body isn't using O2 during the first 3 mins. If you don't use O2 to break down CHO's and fat you have to use Creatine Phosphate (the anaerobic system) which is why the first few mins of exercise is anaerobic. Recovery From Exercise: -if you immediately stop w/ no cool-down, HR is still high & you still breathe hard b/c your body is trying to make up the O2 deficit from the beginning. Our body doesn't return to rest immediately b/c of EPOC. -only ~20% elevated O2 consumption used to "repay" O2 deficit -EPOC is bigger than O2 deficit -Rapid Component: •resynthesizes ATP & PC • Replenishing muscle and blood O2 stores -Slow Component: •increases metabolic rate, helps to contribute to burn calories when you stop exercising. E % NE are the cause of HR and heavy breathing. •Elevated heart rate and breathing = ↑ energy need • Elevated body temperature = ↑ metabolic rate •Elevated epinephrine and norepinephrine = ↑ metabolic rate •Conversion of lactic acid to glucose (gluconeogenesis)
{Exercise Metabolism] Discuss the relationship between exercise intensity/duration and the bioenergetic pathways that are most responsible for the production of ATP during various types of exercise.
Rest to exercise: • ATP production increases immediately. •O2 rises but doesn't increase instantly •O2 deficit- lag in O2 uptake in the •In the transition from rest to light or moderate exercise, oxygen uptake increases rapidly, generally reaching a steady state within 1 to 4 minutes. •Endurance-trained individuals reach steady rate more rapidly, with a smaller oxygen deficit, than sprint-power athletes, cardiac patients, older adults, or untrained individuals -trained subjects have a better developed aerobic bioenergetic capacity. Aerobic ATP production system activated earlier and it results in less production of lactate and H+.
Outline the circulatory responses to various types of exercise at submaximal (absolute and relative) and maximal intensity of exercise HR SV Cardiac Output VO2 (Absolute) VO2 (Relative)
Resting Submaximal Value Max Value 72bpm 137bpm 180bpm 70 ml/beat 102 ml/beat 106 ml/beat 5 L/min 14 L/min 19 L/min 0.245 L/min 1.57 L/min 2.45 L/min 3.5 ml/kg/min 22 ml/kg/min 35 ml/kg/min
Contrast cardiovascular and metabolic dynamics during upper body vs. lower body exercise
Upper Body: •Same VO2 will have the same cardiac output •MVO2 is higher because heart works harder •results in max O2 consumption ~20 to 30% lower than lower-body exercise •Higher O2 consumption for a given submax workload (Lower mechanical efficiency and Muscular effort to stabilize torso) •SV is lower; HR is higher • INC HR, BP, & TPR. •Increase in AFTERLOAD •More pressure •puts more strain on the heart •Must squeeze harder to get blood out. BP will be higher. • More Vasoconstriction Lower Body: •Same VO2 will have the same cardiac output • Increase in PRELOAD •Not much pressure •"Frank Starling Mechanism" •More Vasodialation •More muscle mass activity, muscle pump, venous return, and EDV than upper, leading to INCREASED SV -When O2 uptake reqired to perfrom a submax workload is the same (same absolute energy expenditure) cardiac output is simiar for upper and lower body exercises. However, the mechanism to achieve the required inc in cardiac output is not the same. -SV is lower during upper-body exercise compared to lower body exercise. Upper-body exercise results in a lower SV and a higher HR at any submax workload. . -Upper body exercise puts more strain on the relatively smaller upper-body musculature for any submax exercise level. Added strain augments peripheral feedback to the medulla. -The inc sympathetic stimulation occurs during upper-body exercise is responsbile for INCREASED HR, BP, & TPR.
List the factors that regulate fuel selection during different types of exercise.
• Intensity and Duration of Exercise • Diet and Feeding During Exercise • Exercise Training • Muscle fiber type composition • Hormones • Prior exercise • Environmental factors
RECOVERY AFTER EXERCISE
• Restoration of the muscle PCr and ATP levels • Removal of accumulated lactate • Restoration of normal pH • Recovery of muscle glycogen stores
SKIN CIRCULATION
• function of sympathetic innervation is to alter blood flow to the skin for body temperature regulation. •A1 receptors •mostly extrinsic regulation •During exercise, sympathetic centers controlling cutaneous blood flow are inhibited •Produces vasodilation in cutaneous arterioles •Warm blood from the body core can be shunted to the skin surface for heat dissipation. •Local vasodilator metabolites have little effect on cutaneous blood flow. •Decrease sympathetic activity controlling BF. Decrease vasoconstriction.
McArdle's Syndrome:
•A Genetic Error in Muscle Glycogen Metabolism • Cannot synthesize the enzyme phosphorylase • Inability to break down muscle glycogen • Patients complain of exercise intolerance and muscle pain. •CHO availability limits fat oxidation even during steady state exercise in patients with this.
SKELETAL MUSCLE CIRCULATION
•A1 & B2 receptors •Skeletal muscle gets more blood flow by opening more sphincters (Intrinsic Regulation) This is how the problem is solved. •Major control is Intrinsic Regulation At Rest... - Blood flow to muscle is primarily regulated by its sympathetic innervation. -α1: vasoconstriction / increased resistance / decreased blood flow -Vasoconstriction predominates During Exercise... -Β2: vasodilation / decreased resistance / increased blood flow -Blood flow controlled primarily by local metabolites -Lactate and adenosine
BLOOD FLOW TO THE HEART AND BRAIN
•At rest, the myocardium uses ~75% of O2 • Cerebral blood flow increases during exercise by ~25-30% compared with the resting flow •Increase BF is precisely matched to the increase in VO2 in that particular organ. -Blood flow to active tissues increases in proportion to their metabolic activity -Brain BF inc; % dec; b/c inc in cardiac output -inc in skin BF b/c it releases body heat to maintain body temp. It DECREASES at max level b/c the blood goes to the heart and other muscles instead
Cerebral Circulation
•BF mostly due to local metabolites (local O2) •Little sympathetic innervation •Most important factor: cerebral PCO2 • Vasodilation of cerebral arterioles •Result in an increased blood flow to assist in removing excess CO2.
VENOUS RETURN
•EDV depends on amount of blood coming form system, back up to the heart (Venous Return) •Venous return increased by: - Venoconstriction •Via SNS / smooth muscle •Reduce the volume capacity of the veins to store blood •Innervates nerve fibers in smooth muscle •64% of blood in venous side •The venous system has great capacity to hold blood volume b/c veins have little vascular smooth and are very elastic/ balloon-like. - Skeletal muscle pump •1-way valve that helps maintain venous return to the heart by preventing retrograde blood flow even under low pressure, especially in lower extremities. •Muscle contraction pushes blood back up •When muscles contract during exercise, they compress veins and push blood back to the heart •Between contractions blood refills the veins and the process is repeated. Blood is prevented from flowing away. - Respiratory pump •During inspiration, pressure w/i the thorax (chest) decreases and abdominal pressure increases. Creates flow of venous blood from abdominal region to thorax and promotes venous return. •Changes in thoracic pressure pull blood toward heart
Extrinsic Regulation of the Heart
•Neural: nerves that directly supply the myocardium and override the myocardium's inherent rhythm. • Hormonal: chemical messengers that circulate in the blood CARDIOACCELEATORY & CARDIOINHIBITORY
List the criteria that indicate attainment of a true VO2 max during graded exercise testing.
•Oxygen consumption plateaus during the last minutes of a graded exercise test despite an increase in exercise intensity. •Heart rate within 10 beats of the age predicted maximal heart rate [208 - (0.7 x age)] •Blood lactate levels above 8 mmol per liter of blood (mmol/L) •RER increases to 1.15 or higher •RPE > 17
CARDIOINHIBITORY
•Parasympathetic nerve fibers •via vagus nerve •slows HR by inhibiting SA and AV node •innervate SA & AV nodes. •Ach is released at the ending of nerve fibers and binds to muscarinic receptors at AV & SA nodes. •SLOWER depolarization & conduction speed & DECREASED heart rate. •Changes in parasympathetic activity can cause HR to increase or decrease. A decrease in parasympathetic tone to the heart can elevate HR. Increase in parasympathetic activity causes an slowing of HR. •From rest to 100 bpm (parasympathetic) when you begin to slightly jog there is a decrease in parasympathetic activity and an increase in sympathetic activity. •The parasympathetic activity predominates as rest when HR is less than 100 bpm. •Increase in HR from resting to 100 bpm is cause by a decrease in parasympathetic activity •When exercise begins/ at onset of exercise, or if exercise is at a low intensity, primary due to withdrawal of vagal tone/ consistent decrease in parasympathetic, resulting in an increase in HR. •AV & SA nodes responsible for increase in HR
SYSTOLIC BLOOD PRESSURE
•Pressure generated as blood is ejected from the heart during ventricular systole •Tells us how hard the heart is working to pump blood. •Linearly related to increasing exercise intensity for aerobic dynamic exercise.
Intrinsic Control of Blood Flow
•Sympathetic Influence •Autonomic Nervous System (ANS) •Endocrine System (Hormonal) •innervates smooth muscle in arteries and arterioles •Increase in Sympathetic activity= Increase Vasoconstriction METABOLIC HYPOTHESIS: -Increase production of metabolic bi-products when you exercise. -Example: CO2, H+, Lactate and Adenosine -The greater the level of metabolic activity, the greater the production of vasodilator metabolites: vasodilation of arterioles which decreases resistance and increased blood flow to meet the increased demand of O2. -Some factors automatically vasodialiate -Some will cause nitric oxide to be released, but many directly act to relax smooth muscle. -Will override anything that will cause vasoconstriction (allow more BF to tissue)
CORONARY CIRCULATION
•Sympathetic innervation: β2 receptors (minor role) •Controlled almost entirely by local metabolites •Most important factors: hypoxia (lack of O2 conc) and adenosine ( bi-product of ATP breakdown) •End result is vasodilation of the coronary arterioles •Increase in sympathetic activity (NE binds to B2 receptors)
CARDIOACCELEATORY:
•Sympathetic nerve fibers •via cardiac accelerator nerves • increases HR by stimulating SA and AV node •SA & AV nodes innervated by NE •Binds to B1 receptor at SA & AV nodes •Causes FASTER depolarization & conduction speed/ INCREASES heart rate. •Hormonal regulation is a secondary factor •Primary factor is sympathetic/ parasympathetic stimulation •Hormones are Catacholamines: 80% E and 20% NE •Takes longer to activate this sytem •NE & EPI produce the same effects as NE released by sympathetic nerves. Enhances HR but SLOWER acting effect on cardiac function. •Carries impulses to SA, AV nodes
Describe, graphically, the changes in oxygen uptake and blood lactate during and incremental (graded) exercise test. Identify the lactate threshold and maximal oxygen uptake (VO2 max).
•VO2 max is the point where O2 consumption doesn't increase with further increase in intensity. maximal oxygen uptake (VO2 max) is reached •VO2 max is influenced by the ability of cardiorespiratory system to deliver oxygen to the muscle and the ability of muscles to use oxygen and produce ATP aerobically • Trained individuals have a higher VO2 max **Oxygen uptake increases linearly until no further increase in VO2 with increasing work rate: Lactate threshold: •Point of intensity where lactate increases quickly. •After threshold, switch to more anaerobic glycolysis to make ATP. •Lactate is produced from fast glycolysis •Appears at ~50-60% VO2 max in untrained subjects •LT & VO2 max are the best performance predictors. •Also called: Anaerobic Threshold
NITRIC OXIDE
•Vasodilator •Constant exercise allows for the release of NO •Promotes smooth muscle relaxation •Results in vasodilation and increased blood flow •Decreases vascular resistance •Produced in the endothelium or arterioles •Increases muscle blood flow
3 primary adjustments must occur for maintaining rhythmic exercise
#1.) ANS adjustments to increase LV output #2.) Redistribution of augmented cardiac output #3.) Increased venous return to the heart in exact proportion to the increase in LV output. Key results: increased cardiac output and mean arterial pressure
ARTERIAL BLOOD PRESSURE
-Blood pressure is the force exerted by blood against the arterial walls -Catheter insertion is the most direct way to measure BP
[Part II Acute Cardiovascular Responses to Exercise] Graphs of... BP-linear inc w/ exercise intensity O2 consumption-inc linearly w/ exercise intensity. TPR (total preipheral resistance)- dec w/ inc of exercise intensity AOD (oxygen difference)- same at O2 consumption
-The increase in SBP is mediated through the increase in cardiac output. -DBP is typically constant/ changes little. Vasodialation in the vasculature of the active muscle is balanced by vasoconstriction (GI tract) in other vascular beds!
Q6: What is the recently developed equation (more accurate) in predicting maximal heart rate?
208 - 0.7 x age
#8.) The arterial-venous oxygen difference A. increases as a function of exercise intensity during aerobic exercise B. does not change during aerobic exercise C. decreases as the aerobic exercise intensity increases
A. increases as a function of exercise intensity during aerobic exercise (?)
#3.) The primary fuel source during high-intensity (85% VO2 max) exercise is A. muscle glycogen. B. blood glucose. C. muscle triglycerides. D. plasma FFA.
A. muscle glycogen.
Q4: After the first few minutes of constant-load, submaximal exercise, VO2 reaches steady state, indicating that A. the ATP demand is being met aerobically. B. levels of lactic acid in the blood are very high. C. the exercise can be continued indefinitely without fatigue. D. the oxygen uptake is not sufficient to meet the ATP demand.
A. the ATP demand is being met aerobically.
Compare heart rate and blood pressure responses to arm and leg work at the same oxygen uptake. Know the factors that might explain the observed differences
At the same oxygen uptake, arm work results in higher: - Heart rate due to higher sympathetic stimulation - Blood pressure due to vasoconstriction of large inactive muscle mass #1.) There is a higher VO2 in ARMS at submax intensity #2.) VO2 max for LEGS is higher here than ARMS b/c there is more muscle mass •ARM exercise requires inc O2 consumption than leg exercise at any submax power output throughout the comparison range. •20-30% lower in arms •It is inefficient doing an armogometer ( you use more energy), you have to use more muscle; it's much harder. •MVO2 is myocardial O2 consumption •Double Product is an INDIRECT index of MVO2
#2.) During a graded exercise test on a treadmill, diastolic blood pressure in healthy participants increases with exercise intensity. A. True B. False
B. False
METABOLIC RESPONSES TO SHORT-TERM, INTENSE EXERCISE
First 1-5 seconds of exercise... • ATP through ATP-PC system Intense exercise longer than 5 seconds... • Shift to ATP production via glycolysis Events lasting longer than 45 seconds... • ATP production through ATP-PC, glycolysis, and aerobic systems • 70% anaerobic/30% aerobic at 60 seconds • 50% anaerobic/50% aerobic at 2 minutes
Steady-state HR
•takes 2 to 3 min at submax exercise intensity •HR plateaus b/c you've reached max O2 consumption
There is an inverse relationship between a given energy system's max rate of ATP production and the total ATP amount it is capable of producing over a long period of time.
Phosphogen energy system primarily supplies ATP for high-intensity exercise of short duration, the glycolytic system for mod-to-high intensity intensity exercises.
State the typical VO2 max values for various sedentary, active, and athletic populations.
Women: sedentary-40 active-45-55 athletic-55+ Men: sedentary-45 active-55-65 athletic-65+
Factors that affect Venous Return
#1.) Venal Constriction #2.) Respiratory Pump- breathin pushes blood to chest ragion #3.) Muscle Pump- contraction of veins to push blood up. Has the higher venous return
#4.) Energy to run a maximal 400-meter race (i.e., 50 to 60 seconds) comes from A. aerobic metabolism exclusively. B. mostly aerobic metabolism with some anaerobic metabolism. C. a combination of aerobic/anaerobic metabolism, with most of the ATP coming from anaerobic sources. D. the ATP-CP system exclusively.
C. a combination of aerobic/anaerobic metabolism, with most of the ATP coming from anaerobic sources.
Q6: Compared to moderate intensity of exercise, blood flow to the skin during maximal intensity usually: A. does not change B. increases C. decreases
C. decreases
Kidneys & Splanchnic Circulation
•A1 receptors here •Increases sympathetic activity causing NE to be released at the nerve endings (binding to α1 receptors) causing vasoconstriction of the blood vessels within inactive tissue, such as intestinal tract, liver, kidneys •Helps to divert blood away from these regions temporarily and ensuring that more blood reaches the muscles. •As you sit (do nothing) there is some sympathetic activity, causing some vasoconstriction to help maintain BP.
RELATIONSHIPS AMONG PRESSURE, RESISTANCE, AND FLOW
•Directly proportional to pressure at the two ends of the system: 1.) Provided by heart contraction 2.) Blood flows from region of high pressure (LV, arteries) to region of low pressure (veins, RA) •Inversely proportional to resistance: force that opposes flow Blood Flow: - Directly proportional to the pressure difference between the two ends of the system - Inversely proportional to resistance Pressure - Proportional to the difference between MAP and right atrial pressure (change in Pressure)
Define cardiovascular drift and the cardiovascular dynamics associated with this phenomenon.
•Gradual time-dependent downward drift in stroke volume and increase in heart rate -Associated with increase of core temperature and dehydration during prolonged aerobic exercise •Associated w/ dehydration. If you're biking at the same intensity, HR inc while SV dec, cardiac output is the SAME. Part of cardiac output goes to the skin too cool it off.
[Part I: Acute Cardiorespiratory Responses to Exercise] Describe various cardiovascular responses to large muscle, rhythmic, aerobic exercise
•Increases linearly with increased work rate and plateaus near VO2 max •At exercise intensities up to 40-60 % VO2max, increase in cardiac output is facilitated by increase in HR and SV. • Thereafter, the increase results almost solely from the continued increase in HR •Maximal cardiac output is a function of body size and aerobic fitness. SV and cardiac output for women: lower than men (due to smaller body size) • Cardiac output decreases with age b/c max HR decreases.
Explain "central command" in cardiovascular regulation during exercise.
•Initial signal to "drive" cardiovascular system comes from higher brain centers, Due to centrally generated motor signals. •Fine-tuned by feedback from: -Heart mechanoreceptors -Muscle chemoreceptors: Sensitive to muscle metabolites (K+,lactic acid) -Muscle mechanoreceptors: Sensitive to force and speed of muscular movement -Baroreceptors: Sensitive to changes in arterial blood pressure •EX: HR increases before running a race (nerves) •Advantage: allows more O2 and blood flow.
Be able to define maximal oxygen consumption and its physiologic significance
•Maximal rate at which oxygen can be taken up, distributed and utilized by the body during vigorous level of exercise. •Most widely recognized measure of cardiorespiratory (aerobic) fitness •L x min-1 (non-wt bearing activities)and ml x kg-1 x min-1 (comparing diff body sizes) •VO2 max decreases w/ age •If your VO2 max is below 20th percentile, risk of death increases. •92 ml x kg-1 x min-1 is the highest Vo2 max. [cross country skiiers]
Stroke Volume
•Volume of blood ejected from the left ventricle per heart beat •SV = EDV - ESV •Rest: 60 to 70 ml / beat •Maximal Exercise: 90 to 110 ml / beat • Ejection Fraction=(SV / EDV) x 100% (Percent of EDV pumped out of the left ventricle) During Upright Exercise: •Increases linearly up to 40 to 60 % of VO2 max •Supine SV much higher versus standing (Supine EDV > standing EDV ) because there is a greater gravity effect when standing, therefore lower SV.
Understand the concept of cardiac cycle
•repeating pattern of contraction and relaxation of the heart. •Why SV plateaus • Consists of an active phase (cardiac contraction) called systole, and relaxation phase is diastole •During exercise, both systole and diastole are shorter •Systole - Contraction phase - Systole is shorter than diastole - Ejection of blood: ~2/3 blood is ejected from ventricles per beat • Diastole - Relaxation phase - Filling with blood - longer during rest b/c there is more time for the heart to fill w/ blood.
Wt. Training
•With high intenisty resistance training, BP can barely reach 480/350 mmHg. Very high pressures are more commonly seen when performing a VALSALVE MANEUVER to aid heavy lifts. •The maneuver occurs when a person tries to exhale while the mouth, nose, and glottis are closed. Causes great INC in intrathoracic pressure. Much of the subsequent BP inc results from the body.
Intrinsic Regulation of the Heart
•cells can generate action potential •Spontaneous rhythmicity: special heart cells generate and spread electrical signal via gap junctions. •Pacemakers generate action potential that allows the heart to beat on it's own. •SA NODE is the highest rate of depolarization, therefore it is our pacemaker. •beats 100 times/minute by itself.
Protein Sources During Exercise
•leucine, isoleucine, and valine are the branch chain amino acids used for energy. •Only a small contribution (~2%) to total energy production during exercise • Enzymes that degrade proteins (proteases) are activated in long-term exercise -Rate and capacity of ATP production are inversely related.
Explain the rate-pressure product and rationale for its use in clinical exercise physiology
−Index of relative work of the heart − Provides a convenient estimate of myocardial workload (oxygen uptake) − Excellent correlations between MVO2 and RPP − RPP = SBP X HR − Increases linearly with exercise intensity − Point at which patients feel chest pain.
