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Cardiovascular Regulation

Cardiovascular Regulation. Exercise Physiology McArdle, Katch, and Katch, 4 th ed. Regulation of the Cardiovascular System. Heart Rate Regulation. Blood Flow Regulation. Heart Rate Regulation.

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Cardiovascular Regulation

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  1. Cardiovascular Regulation Exercise Physiology McArdle, Katch, and Katch, 4th ed.

  2. Regulation of theCardiovascular System Heart Rate Regulation Blood Flow Regulation

  3. Heart Rate Regulation • The heart has both intrinsic (situated within the heart) and extrinsic (originating outside the heart) regulation. • Many myocardial cells have unique potential for spontaneous electrical activity (intrinsic rhythm). • In normal heart, spontaneous electrical activity is limited to special region. • Sinoatrial node serves as pacemaker.

  4. Intrinsic Regulation of HR • Sino atrial node: pacemaker

  5. Intrinsic Regulation • Depolarization muscle membrane creates an action potential or electrical impulse • Impulse travels through the heart in an established pathway • SA node →across atria →AV node →AV bundle →left & right bundle branches → Purkinjie fibers → Ventricles

  6. Normal Route of Depolarization S-A Node  Atria  A-V Node  Bundle of His  Purkinje Fibers  Ventricles

  7. Intrinsic Heart Rate • SA node rate approximately 90 bpm • Parasympathetic innervation slows rate • referred to as parasympathetic tone • training increases parasympathetic tone

  8. Electrocardiogram • The ECG is recorded by placing electrodes on the surface of the body that are connected to an amplifier and recorder. • Each wave in the shape of the ECG is related to specific electrical change in heart. • Purposes of ECG to monitor heart rate and diagnose rhythm.

  9. Electrocardiogram Each wave of ECG related to specific electrical change in the heart • P wave - atrial depolarization • QRS complex - ventricular depolarization • masks atrial repolarization • T wave - ventricular repolarization

  10. ECG Arrhythmias • PACs- premature atrial contraction • PVCs- premature ventricular contraction • Ventricular fibrillation- cardiovert

  11. Extrinsic Regulation of HR • Neural Influences override intrinsic rhythm • Sympathetic: catecholamines • Epinephrine • Norepinephrine • Parasympathetic • Acetylcholine • Cortical Input • Peripheral Input

  12. Neural Regulation of HR • Sympathetic influence • Epinephrine  ↑HR (tachycardia) and ↑ contractility • Norepinephrine  general vasoconstrictor • Parasympathetic influence • Acetylcholine→↓HR (bradycardia) • Endurance (aerobic) trg. increases vagal dominance

  13. Cardiac Accelerator Nerves Sympathetic Fibers • Innervate SA node & ventricles • Increase heart rate • Increase contractility • Increase pressure

  14. Vagus Nerve Parasympathetic Nerve • Innervates SA node & AV node • Releases acetylcholine • Slows heart rate • Lowers pressure

  15. Cortical Influences on Heart Rate • Cerebral cortex impulses pass through cardiovascular control center in medulla oblongata. • Emotional state affects cardiovascular response • Cause heart rate to increase in anticipation of exercise

  16. Peripheral Influences on HR Peripheral receptors monitor state of active muscle; modify vagal or sympathetic • Chemoreceptors • Monitor pCO2, H+, pO2 • Mechanoreceptors • Heart and skeletal muscle mechanical receptors • Baroreceptors

  17. Peripheral Influence on HR • Baroreceptors in carotid sinus and aortic arch. • ↑ pressure → ? HR & contractility • ↓ pressure → ? HR & contractility

  18. Blood Flow Regulation • During exercise, local arterioles dilate and venous capacitance vessels constrict. • Blood flow is regulated according to Poiseuille’s Law: Flow = pressure  resistance.

  19. Blood Flow Regulation • Flow = pressure gradient x vessel radius4 vessel length x viscosity • Blood flow Resistance Factors • Viscosity or blood thickness • Length of conducting tube • Radius of blood vessel

  20. Blood Flow Regulation • 1 of every 30 or 40 capillaries is open in muscle at rest • Opening “dormant” capillaries during exercise • Increases blood flow to muscle • Reduces speed of blood flow • Increases surface area for gas exchange

  21. Local Factors Resulting in Dilation • ↓ tissue O2 produces potent vasodilation in skeletal and cardiac muscle • Increased temperature • Elevated CO2 • Lowered pH • Increased ADP • Nitric Oxide (NO) • Ions of Mg+2 and K+ • Acetylcholine

  22. Blood Flow Neural Factors • Sympathetic nerves (adrenergic): norepinephrine general vasoconstrictor • Sympathetic nerves (cholingergic): acetylcholine vasodilation in skeletal and cardiac muscle.

  23. Blood Flow Humoral Factors • Sympathetic nerves to adrenal medulla causes release of epinephrine & norepinephrine into blood (humor).

  24. Blood Flow Humoral Factors Sympathetic Nerves to Adrenal Medulla  epi & norepi in blood  vasoconstriction except in skeletal muscle

  25. Neural Factors of Flow Control

  26. Integrated Response

  27. Regulation from Rest to Exercise • Rapid increase in heart rate, SV, cardiac output • due to withdrawal of parasympathetic stimuli • increased input from sympathetic nerves • Continued increase in heart rate • temperature increases • feedback from proprioceptors • accumulation of metabolites

  28. Integrated Response in Exercise

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