The Circulatory System Do you remember when you

The Circulatory System

• Do you remember when you were little and had an earache and your parents gave you medicine to take? Were you confused as to how the medicine would get from your mouth to your ear? • As you got older, you were probably made aware of the transportation system within your body called the circulatory system. The main purpose of the circulatory system is to transport materials within an organism. • Remember in the digestion activity there was a connection between the circulatory system and the digestive system within the small and large intestine. • Also, do you recall from the last activity that the alveoli and capillaries exchanged gases within the lungs? • These links are necessary so that materials like proteins, carbohydrates, fats, oxygen and medicine can be transported to all the cells of the body.

• https: //www. youtube. com/watch? v=9 fxm 85 F y 4 s. Q • Start at 5: 35

• Not all circulatory systems are the same. • Some unicellular organisms lack a circulatory system because their cell is in constant contact with the external environment and materials can pass directly across the cell membrane. • Recall that plants too have a transport system that involves xylem and phloem cells. • Some animals have an open circulatory system. • More complex multicellular animals have a closed circulatory system.

Open Circulatory System • An open circulatory system lacks blood vessels. There is no separation of blood from the other interstitial fluid. • The contraction of one or more hearts pushes blood throughout the different cavities in the organism's body. • In addition, the contraction of muscles assists the movement of blood. The blood carrying nutrients and oxygen bathes each cell directly. Insects, snails, and crustaceans have an open circulatory system.

Closed Circulatory System • In a closed circulatory system, blood is confined in vessels. • A heart pumps blood throughout the body, but the blood remains separate from the interstitial fluids. • Each blood vessel branches off into smaller vessels so that tissues and cells can receive the nutrients and oxygen they need. • Earthworms, fish, and humans have a closed circulatory system.

Human Circulatory System • The human circulatory system is a closed system that cycles blood through three different cycles: • Cardiac Circulation: Blood moves within the heart muscle. • Pulmonary Circulation: Blood travels to the lungs and then back to the heart. • Systemic Circulation: Blood travels from the heart to the rest of the body and then returns to the heart.

The Heart • The heart is a four chambered muscular pump located on the left side of your chest that receives blood and then pumps it out to the rest of the body. • The upper chambers are called the atria and are divided into the left and right atrium. • The lower chambers are called the ventricles and are divided into a left ventricle and a right ventricle. • The septum divides the heart vertically into the left and right sides. • In addition, the heart contains four valves that regulate the movement of blood within the four chambers. • The valves also ensure that blood will flow in only one direction. • The diagram below of a cross section of the heart illustrates the chambers, valves and blood vessels related to the heart.

Questions 1. Which is a more efficient circulatory system: a closed system or an open system? Explain. 2. What happens to blood when it enters the lungs? 3. The heart is not symmetrical in shape. Why is the left side thicker than the right side? 4. Explain the blood flow within the three cycles of the human circulatory system.

Answers 1. A closed system is more efficient because it transports materials at a faster rate. Also, open circulatory systems usually do not transport oxygen which is only effective for smaller organisms. In addition, in an open system blood cells transporting waste materials and useful materials are mixed together. 2. When blood enters the lungs, carbon dioxide leaves the red blood cell and oxygen then binds to hemoglobin. The colour of blood changes from blue, deoxygenated blood, to red, oxygenated blood.

3. The left side of the heart is more muscular than the right side. The right ventricle pumps blood to the lungs which are relatively close to the heart, therefore it does not require much force. However, the left ventricle pumps blood to the rest of the body, head, legs, arms, etc. which requires a greater amount of force. 4. Cardiac circulation involves blood flowing into the heart tissue and cells. Pulmonary circulation involves blood flowing into the lungs and back to the heart. Systemic circulation involves blood flowing to all parts of the body and then returning to the heart.

The Cardiac Cycle • The heart works in a continuous cycle of relaxation and contraction. The cycle consists of diastole and systole. • Diastole occurs when the heart is at rest and pressure is low. Blood flows into all four chambers as the pulmonary valve and aortic valve remain closed. This phase ends when the atria contract.

• Systole begins with the contraction of the ventricles and the blood pressure is high. This contraction forces blood out of the heart and into the lungs or out through the aorta. This occurs when both the aortic valve and pulmonary valve are open and the tricuspid and mitral valve are closed.

Animation of a Pumping Heart • http: //www. sumanasinc. com/webcontent/ani mations/content/human_heart. html • This is broken down into stages

Heart Beat • The beating of the heart is controlled by a nerve impulse that is located in the wall of the right atrium called the sinoatrial node (SA node). • The SA node is also referred to as the natural pace maker. You are probably familiar with the “lub-dub” sound that your heart makes when it is beating. • Those familiar sounds arise from the opening and closing of the four valves within the heart. • The “lub” sound is produced when the tricuspid and mitral valves open and close. • The “dub” sound occurs when the pulmonary and aortic valve open and close.

Heart Rate • An electrocardiogram (ECG) is a test that measures the electrical activity of the heart. • The ECG can detect irregular heartbeats, irregularities in shape and size of the chambers and any damage to the heart. • A normal resting heart rate is 70 beats per minute with a consistent and even rhythm.

• Elite athletes will have a resting heart rate which is lower. You can also measure your heart rate at pulse points in your neck, wrists and behind the knee. • As you know, your heart rate can fluctuate throughout the day. Exercise elevates your heart rate, while reading or sleeping generally lowers your heart rate. Sometimes emotions of fear, happiness, surprise, and love can alter the heart rate as well. Drugs and medications can raise the heart rate to levels that can result in death.

Try This! • Locate a pulse point on your body and count the number of times your heart beats in 10 seconds. • Once you have completed that multiply the number by six and you will have determined your resting heart rate. • Record that number.

Homework • Read pages 242 – 243 and 250 - 263