Circulation: Components and Control

1. Circulation: Components and Control Vessels, Blood, Blood Pressure, Regulation, Heart Disease, Clotting AP Biology Unit 6

2. Blood Flow through Vessels • Arteries (and arterioles) • Thick, muscular walls • Walls also contain collagen and elastic fibers (make them stretchable) • Can be constricted or dilated Slide 2 of 23

3. Blood Flow through Vessels • Veins (and venules) • Thinner walls • one-way valves to prevent blood from flowing backwards • Blood in veins is moved by the contractions of skeletal muscles around them (“milking”) Slide 3 of 23

4. Blood Flow through Vessels • Capillaries • Thin walls (usually one cell layer thick) • Permeable to water, ions, other small molecules • Blood flows slowly through them (red blood cells often have to travel single file) • Every cell in the body is close to at least 1 capillary Slide 4 of 23

5. Capillaries • Capillaries must exchange materials between the blood and the interstitial fluid • Blood pressure and osmotic pressure drive the movement of molecules into and out of capillaries • Blood pressure forces water and solutes out (on the artery side) • Osmotic pressure (due to the proteins left in the capillaries) causes water to flow back into the capillaries by osmosis Slide 5 of 23

6. Question… • How does the structure of each type of vessel support its function? • Arteries– thick walls can withstand pressure from heart pumping blood • Veins- valves help prevent backflow since the heart is too far away to provide forward pressure (to push the blood back to the heart) • Capillaries- very thin walls allow for easy exchange with the interstitial fluid Slide 6 of 23

7. Blood Pressure • Blood pressure = the force being applied to the blood vessel walls (from blood). • 2 phases of the cardiac cycle • Systole = when the heart muscle is contracting • Diastole = when the heart muscle is relaxed (between contractions) Slide 7 of 23

8. Blood Pressure • Systolic Pressure = pressure in arteries when heart contracts • Diastolic Pressure = pressure in arteries between contractions Slide 8 of 23

9. Question… • Giraffes need higher blood pressure. Why? • Since they are taller, they need more pressure to get the blood all the way to the top of their bodies Slide 9 of 23

10. Control of Circulation • Heart rate is controlled by • Nerve impulses sent to SA and AV Nodes • Hormones (adrenaline/epinephrine) • Body temperature • Oxygen requirements due to exercise Slide 10 of 23

11. Control of circulation • The opening of sphincters leading to capillary beds is controlled by • Nerve impulses • Hormones • By controlling these sphincters, blood can be directed to specific parts of the body under stressful conditions Slide 11 of 23

12. Control of Circulation • The Lymphatic System also plays a role in controlling circulation • Maintains fluid levels so blood pressure can remain constant • Lymph = fluid (like interstitial fluid, high in water and other nutrients) • Filters body fluids before allowing them to flow back into the circulatory system • Fluids flow out and into capillaries via blood pressure and osmotic pressure Slide 12 of 23

13. Question… • From what part of the Digestive System did lymph flow from? • Small intestines (lacteals in the villi) Slide 13 of 23

14. Components of blood • Plasma • Water, nutrients, proteins, ions, etc. • Cellular Components • Red blood cells (carry oxygen) • White blood cells (immune function) • Platelets (clotting) Slide 14 of 23

15. Differentiation of Blood Cells • Blood cells (RBC, WBC and platelets) all develop from stem cells in the red bone marrow. • Erythropoietin (EPO) is a hormone that promotes the production of erythrocytes (RBC) • Synthesized in the kidneys Slide 15 of 23

16. Questions… • When the body is not receiving enough O2, what will happen to EPO levels? • They increase to create more RBC to carry O2 • If a patient is anemic (low iron levels in the blood), why might the doctor prescribe synthetic EPO? • Iron is the central part of hemoglobin that carries oxygen in RBC Slide 16 of 23

17. Question… • How would taking synthetic EPO help with athletic performance? • Having more red blood cells would improve oxygen transport abilities  more endurance Slide 17 of 23

18. Blood clotting • Platelets begin the clotting reaction • damage in the blood vessel wall exposed collagen fibers • Platelets stick the collagen release substances to make other platelets sticky • Clotting factors = released by platelets to activate enzymes needed for clotting Slide 18 of 23

19. Blood Clotting • STEPS: • Platelets adhere to the damaged region and become sticky release clotting factors • Clotting factors cause Prothrombin (inactive) to become Thrombin (active) • Thrombin causes Fibrinogen (plasma protein) to become fibrin (active form) • Fibrin forms threads that help seal the damaged area up Slide 19 of 23

20. Cardiovascular Disease • Atherosclerosis = narrowing of arteries due to plaque build up • plaque deposits as a result damage to the vessel lining • Plaque desposits narrow the pathway for blood to flow • If the plaque is ruptured it will also cause clotting to occur– blocks pathway of blood Slide 20 of 23

21. Cardiovascular t Disease • Atherosclerosis can lead to heart attack or stroke • Heart attack – blockage in the arteries that supply the heart with blood • Stroke = blockage in an artery in the brain Slide 21 of 23

22. Heart Disease and Cholesterol • Cholesterol travels in the blood (plasma) • Low Density Lipoproteins (LDLs) are associated with cholesterol deposits in arteries = “bad” cholesterol • High Density Lipoproteins (HDLs) appear to reduce cholesterol deposition = “good” cholesterol • What seems to matter is the ratio of HDL to LDLs in your blood Slide 22 of 23

23. Cholesterol and lifestyle choices • While there is a genetic component to cholesterol levels, lifestyle choices also influence it • Exercise increases HDL levels • Smoking increases LDL and lowers HDL levels Slide 23 of 23