IB Biology Review

1. IB Biology Review Circulatory System

2. Why do we need blood circulation? • Move blood around the body to • Bring oxygen to cells • Take away carbon dioxide • Take away other metabolic waste • Bring metabolic reactants (sugar) • Bring water • Bring hormones • Bring antibodies • Bring nutrients • Distribute heat • Basically, to keep our bodies doing what they do!

3. What are the components of the circulatory system? • Heart • Arteries • Veins • Capillaries • Remember Arteries Away from heart • Arteries have oxygenated blood • Veins have deoxygenated blood

4. A Closer Look at the Heart

5. Identify the structures of the heart. 1 15 14 2 13 3 12 4 11 5 6 10 7 8 9

6. Be able to draw something like this. Pulmonary veins Atrioventricular valves Semilunar valves

7. The Path of Blood through the Heart • Deoxygenated blood comes from body through superior and posterior vena cava • Enters right atrium • Goes through atrioventricular valve • Enters right ventricle, pumped into pulmonary artery • Passes through semilunar valve • Gets oxygen from lungs • Enters left atrium via pulmonary veins • Goes through atrioventricular valve • Enters left ventricle, pumped into aorta • Passes through semilunar valve • Blood goes to rest of the body

8. How Blood Gets Oxygen • (2) Goes from right ventricle to pulmonary artery • (3) Goes to lungs • (4) Comes through pulmonary vein to left atrium • (5) Goes to left ventricle • (6) Goes through aorta • (7) (8) To body!

9. Which arteries help out the heart? • Coronary arteries supply heart muscle with • Oxygen • Nutrients

10. How does the heart know when to pump? • The heart beats by itself (myogenic) • The SA node sends an electrical signal to the walls of the atria • This causes them to contract (think about when you get electrocuted, your hand snaps back because your muscles contract) • SA signal reaches the AV node, which delays the signal • AV node sends signal to ventricles, which contract • Atrioventricular valves snap shut • After blood leaves ventricles, semilunar valve closes to prevent back flow

11. Composition of Blood • Blood is made of • Plasma • Erythrocytes (red blood cells) • Leucocytes (white blood cells) • Phagocytes • Lymphocytes • Platelets

12. IB Exam Question 1. Which vessel carries deoxygenated blood? (1 mark) A. The pulmonary artery B. The coronary artery C. The aorta D. The pulmonary vein • Correct answer: A

13. IB Exam Question 2. What is the function of the right ventricle? (1 mark) A. Pumping blood into the pulmonary artery B. Pumping blood into the pulmonary vein C. Pumping blood into the aorta D. Pumping blood into the coronary artery • Correct answer: A

14. IB Exam Question 3. Draw a labelled diagram to show the internal structure of the heart.(6 marks) • Award [1] for each of the following structures clearly drawn and labelled correctly in a diagram of the heart. • left and right ventricle; • left and right atria; • atrioventricular valves; • semilunar valves; • aorta and vena cava; • pulmonary artery and pulmonary vein; • ventricle wall thicker than atria; • left ventricle wall thicker than right ventricle wall; • Do not award marks for a diagram with only the ventricles or atria. However, it is not necessary to show the cordae tendinae.

15. IB Exam Question 4. Explain the relationship between the structure and function of arteries, veins and capillaries.(8 marks) ([3 max] for information on arteries) • thick wall / elastic fibres to help withstand the high(er) pressure; • outer fibrous coat prevents artery from rupturing under the high pressures; • valves in aorta and pulmonary artery to prevent back flow into ventricles in diastole; • layers of (smooth) muscle to allow arteries to contract / elastic recoil; • allows the pressure to be altered (vasoconstriction and vasodilation); ([3 max] for information on veins) • thinner wall (than arteries) since pressure low(er); • very little muscle since not needed for constriction; • valves to prevent back flow between pulses; ([3 max] for information on capillaries) • no muscle / elastic tissue since pressure very low; • endothelial layer one cell thick to allow permeability / diffusion of chemicals / tissue fluid; • no valves since pressure very low;

16. IB Exam Question 5. Outline the control of the heartbeat in terms of myogenic muscle contractions, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline). • The heart beats by itself (myogenic) • SA node (pacemaker) in the heart muscle produces an electrical signal across nerves throughout walls of atria to begin cycle • This nerve impulse causes the atria to contract • SA signal reaches atrioventricular (AV) node which delays the electrical signal • Electrical signal spreads across nerves, causing ventricles to contract • Atrioventricular valves snap shut • After ventricles are emptied, semilunar valves close • Under certain circumstances, adrenaline carries messages from the brain to pacemaker telling the pacemaker to speed up the beating of the heart

17. IB Exam Question 6. State four substances that are transported by blood.(4 marks) • Nutrients • Oxygen • Carbon dioxide • Hormones • Antibodies • Urea • Heat