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BIOS 162-a Review: Cardiovascular II

BIOS 162-a Review: Cardiovascular II. September 26, 2011. Important Regulated Variable: Mean Arterial Pressure (MAP). MAP = Diastolic Pressure + 1/3 (Systolic Pressure – Diastolic Pressure). Systolic pressure. Diastolic pressure. Feedback mechanism for mean arterial pressure. Sensor:

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BIOS 162-a Review: Cardiovascular II

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  1. BIOS 162-a Review: Cardiovascular II September 26, 2011

  2. Important Regulated Variable: Mean Arterial Pressure (MAP) • MAP = Diastolic Pressure + 1/3 (Systolic Pressure – Diastolic Pressure) Systolic pressure Diastolic pressure

  3. Feedback mechanism for mean arterial pressure Sensor: Stretch receptors in arteries Stimulus: decrease in MAP

  4. Feedback mechanism for mean arterial pressure Integrating center: Brainstem Set point: 100 mmHg Afferent pathway: Afferent neurons Sensor: Stretch receptors in arteries Stimulus: decrease in MAP

  5. How much can the set point vary?

  6. Feedback mechanism for mean arterial pressure Integrating center: Brainstem Set point: 100 mmHg Efferent pathways Neurons Endocrine Afferent pathway: Afferent neurons Effectors Sensor: Stretch receptors in arteries Stimulus: decrease in MAP

  7. How to change MAP? • MAP = Cardiac Output x Total Peripheral Resistance Heart Rate Stroke Volume Arteriolar Resistance

  8. Feedback mechanism for mean arterial pressure Integrating center: Brainstem Set point: 100 mmHg Efferent pathways Neurons Endocrine Afferent pathway: Afferent neurons Effectors Sensor: Stretch receptors in arteries Arteries Heart Increased Heart Rate Increased Stroke Volume Increased Resistance - Stimulus: decrease in MAP

  9. More Detailed: Control of Heart Rate • Neural • Sympathetic/parasympathetic activity at SA and AV node • Endocrine • Epinepherine from the adrenal gland

  10. More Detailed: Control of Stroke Volume • Neural • Sympathetic activity increases contractility

  11. More Detailed: Control of Arteriolar Resistance • Note: resistance is directly proportional to diameter of blood vessel! • Neural • Increase in sympathetic activity (epinepherine/norepinepherine) • Endocrine • Local (vasodilation): metabolites, decreased oxygen, NO, prostaglandins, EDHF • Systemic (vasoconstriction): vasopressin, angiotensin II

  12. Hypertension • Increased blood volume • Blood glucose and change in osmotic pressure • Renal dysfunction • Increased total peripheral resistance • Atherosclerosis

  13. Quiz!

  14. Why might women have lower hematocrit than men? • Low hematocrit = anemia • Blood loss can lead to low hematocrit when blood cell production can’t keep up: menstrual cycle • Nutritional deficiencies?

  15. What is the problem with “blood doping”? • Increases risk of abnormal blood clotting • Enlargement of spleen • Can damage bone marrow, may lead to leukemia

  16. Explain why my ankle would swell after a sprain? How does the swelling go down after it heals? • Swell: normally, proteins can’t get through blood vessels. This provides osmotic pressure to keep fluid in blood vessels. When damage occurs (ankle sprain), immune cells release cytokines that increase permeability of blood vessels (to allow in macrophages). But, proteins can move in too, changing osmotic gradient. • Decrease swelling: ice (causes vasoconstriction), lymphatic vessels (return interstitial fluid to circulatory system)

  17. Swelling of the feet may be an indication of what? • Right heart failure leads to build up of fluid in the systemic organs, especially the feet

  18. Why might a soldier standing at attention eventually faint? • Skeletal muscle pump, which requires contraction of skeletal muscles, moves blood back to heart. Without contraction (as in during standing at attention), blood cannot get back to heart and therefore to brain.

  19. Someone with AV block would have a heart rate that is the same as/higher/lower than someone without AV block • Lower: Partial AV block Complete AV block

  20. Indicate which is atrial/ventricular defibrillation, and the concerns associated with each? Atrial: less concerning, because only ~15% of cardiac output comes from atrial contraction. However, concern for blood clotting Ventricular: more concerning, most cardiac output provided here. Describe how a heart would look during ventricular defibrillation?

  21. Describe the abnormal heart sounds, and what causes each? • Normal heart sounds: lub=AV valve closing, dub=semilunar valves closing • S3: tensing of chordae tendineae (indicates excessive volume in ventricles in adults, normal in children) • S4: Atrium contracting against a stiffening ventricle • Murmur: insufficient valve closing

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