“Little Cowboy”

1. “Little Cowboy”

2. Homeostasis and The Heart Tissues and Organs Depend on Appropriate Blood Flow (Perfusion) Supply = Demand

3. Starling’s Law: Intrinsic Control of Heart • Venous Return determines “stretch” of cardiac myocytes: • Venous Return = Stretch • Stretch = Force and Rate • Known as Preload • Exercise Increases Venous Return / Preload / Force & Rate

4. Extrinsic Control: Baroreceptor Reflex • Baroreceptors: Sense stretch in artery walls(Stretch = Pressure) • Aorta • Internal Carotid Artery • Afferent Signals to Cardioregulatory Centers: Medulla Oblongata

5. Perfusion homeostasis by addressing pressure problems: Pressure Increases Inhibition Of Pressure Signals Heart Rate Decreases

6. Baroreceptor Reflex… • Efferent Signals from Autonomic Nervous System: • Parasympathetic: Decrease HR • Sympathetic: Increase HR • Adrenal: Increase HR • How do you think pressure affects perfusion of vital tissues?

7. Decreased CO Threatens Vital Organs • Cardiac Response: • Increase HR (to compensate for decreased pressure/SV) • Vascular Response: • Direct more of the total blood volume to vital tissues • Away from less vital tissues

8. Extrinsic Control: Chemoreceptor Reflexes • Increased Metabolism produces more CO2, acids, and Temp: • Chemoreceptors (mostly in the medulla oblongata) initiate: • SNS stimulation: Rescues from “metabolic buildup” by HR • PSNS stimulation: Slows the heart when CO2, acids and temp recover

9. Exercise = Preload • Working muscles “squeeze” more blood back to heart • Increased Venous Return = Increased Preload • Starling Law is important in initial increases in Exercise CO

10. Exercise Stimulates SNS • Cardioregulatory centers + SNS: • Stimulate SA Node to increase HR • Stimulate Adrenal Medulla to release Norepinepherine, which increases HR • Increase contractility and SV • Increase myocardial blood flow

11. Exercise increases CO2, H+ and Temperature • Chemoreceptors stimulate SNS and adrenal medulla • Increase HR and SV

12. Exercise Applications: • Vital Organs: Heart, Lungs, Brain (Kidney) • How does Exercise affect the “Priority” of blood flow to “vital organs”? • What TWO tissues during exercise have high priority for perfusion? (become vital organs)

13. Vital Tissues during Exercise: • Working Muscles • Larger muscles = more blood volume = greater venous return • Skin (cooling) • Brain • Heart • Lungs

14. Meeting the Demand: More “Vital Organs” • Cardiac Response: • Increased CO by Increased SV * HR • Preserving Blood flow to “HLB” • Vascular Response: • Redistributing blood flow from less vital tissues…more later

15. Think About This: • Explain the difference between an “athlete’s” heart and an non-athlete’s heart: • Address Cardiac Output and Heart rate at rest and exercise.

16. Athlete vs. Non-Athlete • Ventricle Volume and Mass • Max SV • = Max HR • Max CO • Resting HR • Resting SV • = Resting CO

17. More Thinking: • How do you think cardiac output is affected in paraplegic athletes? • What are the dominant muscles? Where? • Would swimmers be similar?

18. Upper Body Athletes: • Smaller Active Muscle Mass = Venous Return • SV • = HR • CO At Maximum Exercise

19. Summarize: The Heart • Functions of the Heart: • Blood Pressure = Perfusion • Directing Blood: Lungs / Body • Anatomy – Location • Location / Orientation • Chambers / Valves • Tissues: Epicardium, myocardium, endocardium

20. Summary: • Anatomy, cont: • Coronary Arteries • Pericardium • Blood Flow Through Heart • Beginning at Right Atria… • Relative O2 contents • Cardiac Myocytes: • Anatomy and Action Potentials

21. Summary: • Conduction System of Heart: • SA, AV nodes, AV bundles, bundle branches, purkinje fibers • ECG • Cardiac Cycle: • Atrial systole - diastole • Ventricular systole and diastole • Heart Sounds / Murmurs

22. Summary: • Regulation of Cardiac Output • Intrinsic Regulation: • Starling’s Law • Extrinsic Regulation: • SNS, PSNS, Endocrine • Exercise and Homeostasis: • Perfusion to “VITAL ORGANS” • Intrinsic and Extrinsic Controls