Regulation Notes EXSC 530 001
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This 10 page Class Notes was uploaded by Natalie Lopez on Saturday September 12, 2015. The Class Notes belongs to EXSC 530 001 at University of South Carolina - Columbia taught by Dr. Chen in Summer 2015. Since its upload, it has received 32 views. For similar materials see The Physiology of Muscular Activity in Physical Education at University of South Carolina - Columbia.
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Date Created: 09/12/15
0 Three primary adjustments must occur for maintaining rhythmic exercise 0 Autonomic Nervous System adjustments to increase LVcardiac output I Unit is Lmin it s a rate I HR X SV I beatsmin X mLbeat mLmin 9 Lmin o Redistribution of augmented cardiac output 0 Increased venous return to the heart in exact proportion to the increase in LV output 0 Key Results increased cardiac output and mean arterial pressure Parasympathetic nervous system 0 Pre and postganglionic fibers release ACh at effector cells Sympathetic nervous system 0 Postganglionic fibers release NE at organs and heart binding to alpha receptors in organs and beta receptors in heart 0 Postganglionic fibers release ACh to kidneys and cause Epi and NE to be released Cholinergic Receptors 0 Will find muscarinic receptors ACh is released bind to muscarinic receptors and inhibit cardiac muscle Adrenergic Receptors 0 Bl heart once NE binds increases HR and strength of contraction o 32 Coronary arteries once NE binds dilates coronary arteries Regulation of Heart Rate 0 Regulated Intrinsically and Extrinsically Intrinsic Regulation of Heart Rate 0 Has specialized conductive cells that will depolarize on its own 0 SA Node 9 AV Node 9 AV Bundle 9 Purkinje Fibers I SA 60100 bpm depolarized o What is intrinsic HR 100 bpm Extrinsic Regulation Neural Control ANS o Innervation of nerve fibers 0 Most important control Hormonal Control 0 Chemical messengers that circulate in the blood 0 Secondary control In atria will find both nerve fibers In ventricles will find only sympathetic nerve fibers Cardiovascular center Medulla o Sympathetic nerve fibers 0 Innervate SA node and AV node myocardium ventricles Cardioinhibitory center 0 Parasympathetic nerve fibers Vagus Nerves o Innervate most heavily in SA and AV nodes Changes in parasympathetic sympathetic activity can cause heart rate to increase or decrease Parasympathetic and Sympathetic Influence o A decrease in parasympathetic vagal tone to the heart can elevate heart rate 0 An increase in parasympathetic activity vagal tone to the heart can decrease heart rate 0 A decrease in sympathetic activity to heart can decrease heart rate 0 An increase in sympathetic activity to heart can decrease heart rate Parasympathetic Influence at REST o Resting heart rate is primarily controlled by parasympathetic activity Medulla Cardioinhibitory center Parasympathetic nerve fibeers SA and AV nodes Neurotransmitter Acetylcholine Receptor muscarinic receptors at SA and AV nodes 0 Heart Rate Causes slower depolarization and conduction speed 9 decreased HR From Sitting to Walking 0 We know HR goes up70 to 100 bpm o What happens to Parasympathetic activity I Decrease stimulation Sympathetic Influence During Exercise 0 Medulla Cardioacceleratory center Sympathetic nerve fibers SA and AV nodes Neurotransmitter NE Receptor Bl at SA and AV nodes Heart Rate Causes faster depolarization and conduction speed Increased heart rate 0000 0000 Extrinsic Regulation of Heart Rate Endocrine System Hormonal I Medulla Caridoacceleratory center I Sympathetic nerve fibers Adrenal Medulla I Hormones Catecholamines 80 Epi 20 NE 0 Produce same effects as neurotransmitter I Receptor Bl receptors at SA and AV node I Heart Rate causes faster depolarization and conduction speed Increased heart rate Regulation of Stroke Volume I Strength of the ventricular contraction myocardial contractility 0 Enhanced by I Direct sympathetic stimulation of heart I Circulating epinephrine and norepinephrine I Enddiastolic volume EDV Preload I Aortic BP afterload Extrinsic Regulation of Stroke Volume Parasympathetic Influence I Medulla I Parasympathetic nerve fibers SA and AV nodes I Neurotransmitter I Receptor I Myocardial contractility parasympathetic activity has little or no effect on myocardial contractility Sympathetic Influence During Exercise I Medulla Cardioacceleratory center I Sympathetic nerve fibers myocardiumventricles I NeurotransmitterHormone NE 80 Epi 20 NE I Receptor Bl receptors in myocardiumventricles I Myocardial contractility increased calcium availability gt increased contractility gt increase in stroke volume EDV Preload I EDV amount of blood that is remaining in the left ventricle when the heart is relaxed I Call it a diastole phase Left Ventricular EndDiastolic Volume I Volume of blood in the left ventricle at the end of diastole o Preload I The relationship between preload and developed tension I FrankStarling Mechanism 0 Greater EDV results in a more forceful contraction I Graph explained o The increase in EDV results in lengtheningstretching of cardiac fibers which improves the force of the contraction 0 Increase in the length of cardiac fibers increases the number of myosin cross bridges interactions with the actin resulting in increased force production tension 0 Increased contractility of the heart increased stroke volume Aortic Blood Pressure Afterload o The tension force or stress aortic pressure in the LV wall after the onset of shortening 0 Resistance to LV ejection of blood 0 In order to eject the blood the pressure in the LV must exceed the pressure in the aorta o Aortic pressure MAP represents a barrier to ejection of blood from the ventricles o SV inversely proportional to afterload Factors that regulate cardiac output 0 CO HR x SV 0 HR affected by parasympathetic and sympathetic nerves 0 Stroke volume affected by contraction strength EDV and MAP I Contraction strength affected by FrankStarling Stretch Central Command Theory 0 Initial signal to drive cardiovascular system comes from higher brain centers 0 Finetuned feedback from 0 Heart mechanoreceptors 0 Muscle chemoreceptors 9 sensitive to muscle metabolites K lactic acid 0 Muscle mechanoreceptors 9 Normal CV Responses to acute rhythmic exercise 0 Three primary adjustments must occur for maintaining rhythmic exercise 0 ANS adjustments to increase LV output 0 Redistribution of augmented cardiac output 0 Increased venous return to the heart in exact proportion to the increase in LV output 0 Key results increased cardiac output and mean arterial pressure Distribution of Cardiac Output Regulation of Local Blood Flow During Exercise 0 Vasodilation in skeletal muscle 0 Blood flow increased to meet metabolic demands of active tissue 0 Vasoconstriction to visceral organs and inactive tissues 0 SNS vasocontriction Extrinsic vs Intrinsic control of blood flow peripheral circulation Extrinsic Regulation Peripheral Circulation Parasympathetic Influence 9 not overall major regulatory factor Sympathetic Influence 9 o ANS major regulatory factor I SNS innervated smooth muscle in the arteries and arterioles I vasomotor tone 0 Increase sympathetic increase vasoconstriction o Decrease sympathetic decrease vasoconstriction passive vasodilation I Alpha 1 receptors 0 Serve in the skin skeletal muscle kidneys etc o Constrict blood vessels I Beta 2 receptors 0 Serves coronary arteries 0 Dilates blood vessels Intrinsic Regulation Resulting from metabolic activity tissues produce various metabolites C02 H Lactate and Adenosine Many act directly to relax vascular smooth muscle but some may act by causing vascular endothelial cells to release nitric oxide The greater the activity the greater the production of vasodilator metabolites o Vasodilation of arterioles which decreases resistance and increased blood flow to meet the increased demand of 02 These factors override any extrinsic factor 0 A1 mediated vasoconstriction 0 When at rest A1 is dominant during exercise a lot more metabolites and such so they are overridden Nitric Oxide Important vasodilator Produced in endothelium or arterioles Promotes smooth muscle relaxation o Resulting in vasodilation and increased blood flow 0 Decreased vascular resistance One of several involved in blood flow regulation during exercise increases muscle blood flow Used in some medications such at nitroglycerin and related heart drugs causing vasodilation by stimulating NO release Kidneys and Splanchnic Circulation At onset of exercise o Increases sympathetic activity causing NE to be released at the nerve endings binding to A1 causing vasoconstriction of the blood vessels within inactive tissue such as intestinal tract liver kidneys o Helps to divert blood away from these regions temporarily and ensuring that more blood reaches the muscles Coronary Circulation 0 Sympathetic innervation 32 receptors 0 Minor role 0 Controlled almost entirely by local metabolites 0 Most important factors hypoxia and adenosine o Vasodilation of the coronary arterioles Skin Circulation 0 Principal function of sympathetic innervation alter blood flow to the skin for body temperature regulation 0 During exercise sympathetic centers controlling cutaneous blood flow are inhibited o Produces vasodilation in cutaneous arterioles 0 Warm blood from the body core can be shunted to the skin surface for heat dissipation 0 Local vasodilator metabolites have little effect on cutaneous blood flow Skeletal Muscle Circulation 0 Vascular smooth muscle in the arterioles 0 A1 and 32 receptors 0 At Rest 0 Blood flow to muscle is primarily regulated by sympathetic innervation 0 A1 9 vasoconstriction increased resistance increased blood flow 0 Vasoconstriction predominates 0 During Exercise o 32 vasodilation decreased resistance increased blood flow 0 Blood flow controlled primarily by local metabolites overrides A1 0 Ex Lactate and adenosine Venous Return 0 EDV Dependent on venous return 0 Venous return increased by 0 Venoconstriction 9 constriction of the veins activated by the sympathetic nerve fibers 0 Skeletal muscle pump 0 Respiratory pump 0 ALL increase EDV 9 SV Venoconstriction o The venous system carries about 65 of the blood 0 They have little vascular smooth muscle and are very elastic and balloonlike 0 Via SNS smooth muscle 0 Reduce the volume capacity of the veins to store blood Respiratory Pump 0 Changes in thoracic pressure pull blood towards the heart 0 Pressure gradient difference when breathing in chest rises and pressure in chest decreases because it expands and abdominal pressure increases 0 This creates a flow of venous blood from abdominal region into the thorax and promotes venous return Skeletal Muscle Pump 0 Ways to provide a milking action similar to heart action compress vein 0 Muscular Contractions o Oneway valve 0 Wall of some veins contain one way valves that help maintain venous return to the heart by preventing retrograde blood flow even under low pressure especially in lower extremities ACUTE CARDIOVASCULAR RESPONSE TO EXERCISE PT 1 Exercise Categories 0 Shortterm light to moderate submaximal steady state aerobic exercise 0 1020 min no more than 30 o Steady state means no changes in intensity 0 Longterm moderate to heavy submaximal steady state aerobic exercise 0 An hour or more 0 Incremental aerobic exercise to maximum 0 Will bring your body through each stage until maxing out Heart Rate o It varies in most 6080 bpm 0 Lower does not mean more fit always 0 Magnitude of HR response 0 Age posture food intake stress smoking type of activity BV medications Assessment of HR 0 Good indicator of exercise intensity 0 HR monitors handgrip sensors 0 EKG o Auscultation 0 Bell of stethoscope o Palpation 0 Pulse taken at radialcarotid artery with fingers Steady State HR 0 HR reaches a point of plateau 0 HR will rise to circulatory demands 0 Adjustments takes about 23 minutes 0 If intensity increases HR does as well 0 INSERT GRAPH Heart Rate During Incremental Aerobic Exercise 0 Changing the intensities 0 Graph shows walking then walking up hill joggingrunning up hill 0 HR increases linearly with work rate 0 Levels off at V02 max Max Heart Rate 0 Direct 0 Max can be achieved in an allout effort to the point of volitional fatigue 0 Indirect 0 Max HR can be estimated from age since measurement requires a max exercise effort 0 Number decreases with age 0 Max HR 220age o More accurate 20807xage 0 Based on decrease of HR max of 35 per decade Stroke Volume 0 Volume of blood ejected from the left ventricle per heart beat mlbeat 0 Difference between the blood volume in the LV after filling and the blood volume after systole 0 During systole most not all blood ejected o SV EDVESV o 1004060SV o In active untrained individuals 0 Rest 9 6070 mLbeat o Maximal Exercise 90110 mL beat Assessment of Stroke Volume 0 More difficult to measure than HR 0 Some clinically used cardiovascular diagnostic techniques have made it possible to determine exactly how SV changes with exercise 0 Doppler echocardiography o Radionuclide techniques Ejection Fraction 0 Percent of EDV pumped out of the left ventricle o SVEDV 100 o 60mL100mL 06 100 60 0 Clinical index of heart contractile function 0 Normally averages 60 in healthy active young adults Arteriovenous Oxygen Difference Maximal Oxygen Uptake V02 max 0 Maximal amount of oxygen that can be consumed and utilized by the body during vigorous level of aerobic exercise 0 Aka aerobic power 0 Most valid measure of aerobic fitness 0 Expressed as Lmin ml kgmin 0 Lmin 0 Used for nonweightbearing activities I Swimming biking etc 0 Used for caloric expenditure Mlkgmin 0 To compare fitness levels between two people Aerobic Fitness Classifications Graded Exercise Tests GXT 0 Used to test VOZmax 0 Done on treadmill bike stepping bench o Treadmill bc use upper and lower body and produces largest voZ max value 0 615 minutes 0 Used to max out cardiovascular system o If goes to 3040 bad test Arterioles have a lot more smooth muscle in them to control vasoconstrictiondilation dictating where blood can go
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