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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

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

10. 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

11. 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

12. 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

13. 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

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

15. 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

16. 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

17. Questions… When the body is not receiving enough O 2, what will happen to EPO levels? –They increase to create more RBC to carry O 2 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

18. 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

19. 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

20. Blood Clotting STEPS: 1.Platelets adhere to the damaged region and become sticky  release clotting factors 2.Clotting factors cause Prothrombin (inactive) to become Thrombin (active) 3.Thrombin causes Fibrinogen (plasma protein) to become fibrin (active form) 4.Fibrin forms threads that help seal the damaged area up Slide 19 of 23

21. 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

22. 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

23. 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

24. 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