TOPIC 6: HUMAN HEALTH AND PHYSIOLOGY

TOPIC 6: HUMAN HEALTH AND PHYSIOLOGY

6.2 Transport System/Circulatory Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart. State that the coronary arteries supply heart muscle with oxygen and nutrients. Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).

6.2 Transport System/Circulatory Explain the relationship between the structure and function of arteries, capillaries and veins. State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets. State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.

6.2 Transport System/Circulatory Our circulatory system provides a delivery and pick-up service for the whole body. The heart/blood/blood vessels make the most efficient transport system in our body by dropping off substances we need to cells, and taking away their waste. If all the blood vessels within an adult human were laid out, the length from end to end would be 60 MILES!

6.2 Transport System/Circulatory The Human Heart Size of clenched fist Side by side pumps On a complete journey, blood will pass through the heart twice On diagrams, the right/left are switched, as if the heart is inside of you. Right side pump receives deoxygenated blood from all over the body and pumps it to the lungs to pick up more oxygen Blood on this pathway to the lungs is on a pulmonary circulation. (Pulmonary = Lungs)

6.2 Transport System/Circulatory Left side pump receives oxygenated blood from the lungs and pumps it to cells all over the body Blood on the pathway to your body is on a systemic circulation. On a complete journey, blood will pass through the heart twice Blood that is pumped out from the heart makes this circuit through the following range of blood vessels: 1. Large Artery to pump blood away from the heart 2. Smaller artery branches 3. Arterioles (smallest arteries) 4. Capillary bed (where diffusion happens) 5. Venules (smallest veins) 6. Larger veins 7. A large vein to take blood back to the heart

Pulmonary Circulation Blood coming back to the heart is carbon dioxide heavy and needs to go to the lungs to drop off the waste and pick up oxygen. 1. Deoxygenated blood comes back to the heart through the superior and inferior vena cava. 2. This blood is returned into the right atrium. 3. Once the blood collects here, the right atrioventricular valve contracts pushing the blood into the right ventricle. 4. By increased pressure, the right semilunar valve opens forcing the blood to enter the pulmonary arteries. The right atrioventricular valve stays closed to prevent backflow

5. Blood now in the pulmonary artery goes away from the heart and towards the lungs. Remember, the blood has more CO2 than O2 at this point. 6. As the blood nears the lungs, it travels from a large artery into smaller and smaller arteries called arterioles, then into capillary beds. (capillaries are so small that often only one RBC can fit through at a time) The smaller the vessel the better - easier exchange/diffusion of CO2 and O2 in lungs. 7. Once the exchange is finished at the lungs, the blood comes back to the heart (with lots of O2) through larger and larger veins until the largest vein takes our blood into the left atrium.

Systemic Circulation Blood leaving the heart is oxygen heavy and needs to go to the rest of the body/cells to drop it off and pick up carbon dioxide. 1. Oxygenated blood enters the left atrium 2. Valves in the right/left atrium contract in unison, so the left atrioventricular valve opens at the same time the right one does. 3. Blood enters the left ventricle, semilunar valve opens. 4. By increased pressure, the left semilunar valve opens forcing the blood to enter the aorta. The right atrioventricular valve stays closed to prevent backflow

5. Blood is now in the largest artery of the body - the aorta. Aorta has many branches that leads to all tissues in the body. One of the first branches from the aorta allows blood to enter the coronary arteries (supplies heart muscle itself) 6. Blood goes to cells to drop off O2 and pick up CO2 7. Once the exchange is finished in the cells, the blood comes back to the heart (with lots of CO2) through larger and larger veins until the largest vein takes our blood into the right atrium. Each complete circuit around the body includes both the systemic route and pulmonary route - a complete circuit takes no longer than a minute.

6.2 Transport System/Circulatory Control of Heart Rate Heart tissue is made of a special type of muscle that is different from other muscles in our bodies. Cardiac muscle is unique because it contracts and relaxes without stimulation from the nervous system. Cardiac muscle spontaneously contracting and relaxing is known as myogenic muscle contraction. Myogenic activity of the heart needs to be controlled in order to keep the timing of the contractions unified. Natural myogenic contractions are started by your built-in pacemaker.

The pacemaker is actually a mass of tissue in the walls of the right atrium known as the sinoatrial node (SA node). The SA node sends out an "electrical" signal to initiate the contraction of both atria (right/left atrium). For a person with a resting heart rate of 72 beats/ minute, the signal from the SA node is sent out every 0.8 seconds. Also in the right atrium, there is the atrioventricular node (AV node) which receives the signal from the SA node, waits approx 0.1 seconds and then sends out another signal that results in the ventricles contracting. This explains why both atria, and then later, both ventricles contract together!

SA node both atria contract AV node 0.1 second delay http://www.youtube.com/watch?v=oz1_tawcuww both ventricles contract

6.2 Transport System/Circulatory During times of increased body activity (exercise) the heart rate needs to increase above the resting heart rate. This is because there is an increased demand for O2 for cell respiration and a need to get rid of excess CO2 during exercise. When exercise begins, your brain (medulla in the brain stem) chemically senses the increase in CO2 and sends a chemical to the cardiac nerve to increase heart rate. This signal is then sent to the SA node. It doesn't change HOW the heart beats, just the TIMING. Chemicals can also influence heart rate - Adrenalin! Causes SA node to 'fire' more frequently.

6.2 Transport System/Circulatory Arteries/Veins/Capillaries Artery Vein Capillary Take blood away from heart (has yet to reach a capillary) Thick walled High internal pressure (directly connected to ventricles) Take blood to the heart (collect blood from capillaries) Thin walled Low internal pressure (blood flow slow after coming out of capillary beds) but larger internal diameter In-between type of blood vessel deals directly with diffusion of O2/CO2 Super thin - wall is 1 cell thick Low internal pressure (capillary beds are a network No internal valves Has internal valves No internal valves No exchanges No exchanges All exchanges/diffusion occurs (small enough to efficiently allow molecules in and out of blood)

6.2 Transport System/Circulatory Components of Blood Component plasma erythrocytes leucocytes platelets Description liquid portion of blood red blood cells - carry oxygen and carbon dioxide white blood cells - phagocytes and lymphocytes cell fragments - assist in blood clotting

Transport of Blood What is transported Nutrients Oxygen Carbon Dioxide Hormones Antibodies Urea Heat What it is/does glucose, amino acids, etc reactant needed for aerobic cell respiration waste product of aerobic cell respiration transported from gland to target cells protein molecules involved in immunity nitrogenous waste - filtered out of blood by kidneys skin arterioles - can change diameter in order to gain or lose heat