Cv System1


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The structure of the heart, how it is controlled and the effects of exercise.

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Cv System1

  1. 1. The Cardiovascular System Structure and Function
  2. 2. What is the Point? <ul><li>Structure? </li></ul><ul><li>The Cardiovascular system is comprised of the Heart and Blood Vessels. </li></ul><ul><li>Function? </li></ul><ul><li>To supply the body with oxygen and nutrients and remove waste products (e.g. carbon dioxide and lactic acid). </li></ul>
  3. 4. The Cardiac Cycle <ul><li>The heart pumps blood around the body </li></ul><ul><ul><li>2 types of circulation </li></ul></ul><ul><ul><ul><li>Pulmonary - to the lungs </li></ul></ul></ul><ul><ul><ul><li>Systemic - to the rest of the body </li></ul></ul></ul><ul><li>One complete cardiac cycle takes 0.8 seconds </li></ul><ul><ul><ul><li>Systole (contraction) - 0.3 secs </li></ul></ul></ul><ul><ul><ul><li>Diastole (relaxation) - 0.5 secs </li></ul></ul></ul>
  4. 5. The Heart’s Conduction System <ul><li>Systole </li></ul><ul><li>Unconscious stimulation from cardiac centre in the medulla oblongata sends impulse to sinoatrial (SA) node located in the right atrium. </li></ul><ul><li>This spreads the impulse across both atria. </li></ul><ul><li>The atrioventricular (AV) node where the impulse is delayed for 0.1 secs. </li></ul><ul><li>This sends the impulse through the Bundle of His to the base of the ventricles where it is sent across the ventricles through the Purkinje fibres (0.06 secs). </li></ul><ul><li>Muscle tissue of ventricles repolarise. </li></ul><ul><li>Atrial Systole – Blood pumped from atria into the ventricles. </li></ul><ul><li>Atrial Diastole – Ventricles filled with blood. </li></ul><ul><li>Ventricular Systole – Blood pumped from ventricles into the pulmonary artery (right/pulmonary) and aorta (left/systemic). </li></ul><ul><li>Ventricular Diastole – Atria fill with blood from pulmonary vein (left) and vena cava (right). </li></ul>
  5. 6. Electrocardiograms (ECGs) <ul><li>The electrical sequence of the heart’s cardiac cycle </li></ul><ul><li>P wave - atrial contraction </li></ul><ul><li>P-R interval - transmission of impulse to ventricles </li></ul><ul><li>QRS - ventricle contraction </li></ul><ul><li>ST &T wave -ventricular repolarisation </li></ul><ul><li>Q-T interval -ventricle depolarisation and repolarisation </li></ul>
  6. 7. Control of the Heart <ul><li>Neural control </li></ul><ul><li>Cardiac Control Centre (Medulla Oblongata) </li></ul><ul><li>Hormonal Control </li></ul><ul><li>Intrinsic Control </li></ul>
  7. 8. Neural Control <ul><li>Autonomic control </li></ul><ul><ul><ul><li>Sympathetic accelerator nerve (speed up) </li></ul></ul></ul><ul><ul><ul><li>Parasympathetic vagus nerve (slow down) </li></ul></ul></ul><ul><li>Effected by … </li></ul><ul><ul><ul><li>Proprioceptors (in muscles) </li></ul></ul></ul><ul><ul><ul><li>Baroreceptors (changes in blood pressure) </li></ul></ul></ul><ul><ul><ul><li>Chemoreceptors (in muscles and aorta/carotid arteries - changes in Ph) </li></ul></ul></ul><ul><ul><ul><li>Thermo receptors (changes in temperature) </li></ul></ul></ul>
  8. 9. Hormanal and Intrinsic Control <ul><li>Hormonal </li></ul><ul><ul><ul><li>Adrenaline released from pituitary gland speeds up the heart and increases the force it contracts. </li></ul></ul></ul><ul><li>Intrinsic - Starling's Law </li></ul><ul><ul><ul><li>An increase in venous return to the heart results in increased heart rate and force of contraction </li></ul></ul></ul>
  9. 10. <ul><li>Measures </li></ul><ul><li>Heart Rate </li></ul><ul><li>Maximum Heart Rate </li></ul><ul><li>Cardiac Output </li></ul><ul><li>Stroke Volume </li></ul><ul><li>Blood Pressure </li></ul><ul><li>Definitions </li></ul><ul><li>The number of times the heart contracts in a minute </li></ul><ul><li>220 - age in years </li></ul><ul><li>the amount of blood pumped out of the heart per minute (ml) </li></ul><ul><li>the amount of blood ejected by the left ventricle per ventricular contraction </li></ul><ul><li>blood flow x resistance </li></ul><ul><li> systolic 120 </li></ul><ul><li> diastolic 80 </li></ul>
  10. 11. The Cardiovascular System and Exercise <ul><li>Immediate effects </li></ul><ul><ul><ul><li>‘ fight or flight’ release of adrenaline in anticipation of action </li></ul></ul></ul><ul><ul><ul><li>muscle & chemoreceptors detect rise in waste products both leading to increased heart rate . </li></ul></ul></ul><ul><ul><ul><li>if continued get an increase in temperature and venous return also causing an increase in heart rate . </li></ul></ul></ul><ul><li>During exercise </li></ul><ul><ul><ul><li>heart rate increases in proportion to exercise intensity so that cardiac output matches the body’s demands. </li></ul></ul></ul><ul><li>After exercise </li></ul><ul><ul><ul><li>still get elevated heart rate levels in order to replenish energy stores and remove waste products (CO 2 /lactic acid) </li></ul></ul></ul>
  11. 12. Homework <ul><li>Describe how the conduction system of the heart controls the cardiac cycle. </li></ul><ul><li>(5 Marks) </li></ul><ul><li>For next lesson </li></ul>