BTEC_Level_3_Nationals_Applied_Science_Student_Boo..._----_(Pg_32--36).pdf

Getting started...

Getting started Principles and Applications of Science II This unit builds on Unit 1, where you learned about cells and tissues. It is very important that scientists, science technicians, medical personnel, teachers, nursery nurses and others have an understanding of the human body and its organ systems. This knowledge can be used in many ways, including to assess and treat illnesses, and to help prevent disease. It is essential that you understand the body’s structure and function in terms of organs and organ systems, and how they all work together to maintain a steady internal environment known as homeostasis. List any organs and organ systems you can think of, and briefly note the importance of each system. When you have completed this unit, see if you can add more to your list. B Organs and systems Blood is responsible for transporting: ▸▸ oxygen from the lungs to body cells for aerobic respiration ▸▸ carbon dioxide from respiring cells back to the lungs to be exhaled The cardiovascular system ▸▸ nutrients from the intestines to body cells ▸▸ urea (waste product) from the liver to the kidney to be In this section you will learn about the structure and function of the heart, the blood vessels and the events of the cardiac removed cycle. You will also investigate the effect of caffeine on the ▸▸ hormones from the endocrine glands to their target cells heart rate in Daphnia, more commonly known as water fleas. ▸▸ heat from respiring tissue to organs to maintain body temperature or to the skin to be lost. Many cells in a multicellular organism are not in direct contact with their surroundings. This means that the organism Blood is also responsible for regulating: cannot rely on diffusion alone to supply the cells of all its ▸▸ body temperature organs with the nutrients and oxygen it needs to survive. The ▸▸ pH of body tissues cardiovascular system, also known as the circulatory system, ▸▸ volume of fluid in circulation. allows blood to circulate around the body to transport and supply the essential nutrients that multicellular organisms Blood also protects us because it contains: need in order to maintain homeostasis and to survive. ▸▸ platelets that cause clotting, to prevent bleeding and entry of pathogens The cardiovascular system consists of the heart, blood vessels and blood (see Figure 5.11). It is responsible for not ▸▸ leukocytes that defend us against infection. only transporting nutrients and oxygen but also hormones Copyright © 2017. Pearson Education, Limited. All rights reserved. and cellular waste throughout the body. Link Blood is a tissue and it always flows in blood vessels. Go to Unit 20: Biomedical Science, Section A, to find The components that make up human blood are more information about the structure and function of erythrocytes, leukocytes, thrombocytes and plasma. erythrocytes, leukocytes and thrombocytes. Key terms Characteristic features of blood Cardiac cycle – a complete heartbeat from the generation of the beat to the beginning of the next beat. vessels Erythrocytes – red blood cells, containing Blood is always in blood vessels, either arteries, arterioles, haemoglobin, that transport oxygen around the body. capillaries, venules or veins. The vessels form a closed Leukocytes – white blood cells, of which there are transport system which starts and finishes at the heart. many different types. We refer to the mammalian circulation system as double Thrombocytes (platelets) – component of blood circulation because we have two separate circulations. The involved in blood clotting. blood flows from the heart to body tissues and back to the heart. This is known as systemic circulation. In a separate Annets, F, Hartley, J, Hocking, S, Llewellyn, R, & Meunier, C 2017, BTEC Level 3 Nationals Applied Science Student Book 2, Pearson Education, Limited, Harlow. Available from: ProQuest Ebook Central. [28 September 2024]. Created from coulsdon-ebooks on 2024-09-28 21:24:47. 21 M05 BTEC National Applied Science Student B2 XXXXX.indd Page 21 09/05/17 9:10 pm f-0313 /122/PE02858/BTEC_Applied_Science/NA/SE/Applied_Science/G1/XXXXXXXXXX/Layout/Inte...  Tissue capillaries Venules Arterioles Aorta Artery Vein Pilmonary LUNG artery LUNG Pulmonary RIGHT LEFT HEART HEART Artery vein Vein Arterial circulation Venous circulation Venules Tissue capillaries Arterioles ▸▸ Figure 5.11 The cardiovascular system structure: heart, blood and blood vessels circulation known as pulmonary circulation, blood flows carry the blood to the organs in the body. They contain from the heart to the lungs to expel carbon dioxide and less elastic tissue and more smooth muscle than larger take in oxygen and then it returns back to the heart. elastic arteries. Arteries then divide into smaller arterioles. These vessels contain smooth muscle cells wrapped Key terms around the endothelium. These eventually become capillaries. Systemic circulation – parts of the circulatory system concerned with the transport of oxygen to, and carbon Capillaries dioxide from, the heart to body cells. Capillaries allow the exchange of materials between Pulmonary circulation – parts of the circulatory blood and the body’s cells via tissue fluid. These are tiny system concerned with the transport of oxygen to, vessels with very thin walls consisting of only one layer and carbon dioxide from, the heart to lungs. of endothelium cells. This thin wall reduces the diffusion distance for the materials being exchanged. The lumen of Copyright © 2017. Pearson Education, Limited. All rights reserved. Arteries and arterioles a capillary is very narrow, with a diameter that is the same Arteries carry blood away from the heart. The blood leaves size as a red blood cell. The small diameter allows only one the ventricles of the heart and enters thick elastic arteries erythrocyte through at one time. This ensures that the red under high pressure. The artery lumen is small and arteries blood cell has to squeeze through the capillaries which have thick walls that contain collagen, a fibrous protein, help it release the oxygen. Capillaries spread throughout to help maintain the shape and volume of the arteries tissues, forming capillary networks, and it is here where under pressure. Artery walls also contain elastic tissue to the plasma of blood, rich with nutrients and oxygen, is enable them to continuously expand and recoil to keep forced out through small gaps in the capillary walls. This the blood under pressure. This expansion and recoiling fluid that is forced out is known as tissue fluid and it also is what you will feel as your pulse where an artery passes carries away the waste from cellular activity. Capillaries link near the surface of the skin. Arteries also contain smooth arterioles to venules. muscle that contracts, enabling the artery lumen to narrow if needed. Arteries are lined with smooth endothelium Venules and veins tissue, reducing the friction as the blood flows through the Capillaries become slightly larger and form venules, lumen. As blood flows further from the heart, these large which also have small diameters. Venules join to elastic arteries become smaller muscular arteries which make veins. Veins have a large lumen and their walls Annets, F, Hartley, J, Hocking, S, Llewellyn, R, & Meunier, C 2017, BTEC Level 3 Nationals Applied Science Student Book 2, Pearson Education, Limited, Harlow. Available from: ProQuest Ebook Central. [28 September 2024]. 22 Principles and Applications of Science II Created from coulsdon-ebooks on 2024-09-28 21:24:47. M05 BTEC National Applied Science Student B2 XXXXX.indd Page 22 09/05/17 9:10 pm f-0313 /122/PE02858/BTEC_Applied_Science/NA/SE/Applied_Science/G1/XXXXXXXXXX/Layout/Inte...  Learning aim B UNIT 5 are thinner than arteries. Veins have thinner layers of muscle can flatten veins. This also helps force the blood Principles and Applications of Science II collagen, smooth muscle and elastic tissue as they do back to the heart. not need to constrict and recoil. Veins have valves to Table 5.8 states the role of the major blood vessels found help prevent the back flow of blood as it makes its way in the body. back to the heart. The action of the surrounding skeletal ▸▸ Table 5.8 Roles of the major blood vessels Blood vessel Artery or vein Role Vena cava Vein To deliver deoxygenated blood from the body into the right atria of the heart. Pulmonary vein Vein To deliver oxygenated blood from the lungs into the left atria of the heart. To transport deoxygenated blood away from right ventricle in the heart to the lungs to collect Pulmonary artery Artery oxygen. Aorta Artery To transport oxygenated blood away from left ventricle in the heart to the rest of the body. Coronary Artery Artery To supply the cardiac muscle with its own supply of oxygen. P a u se po i n t Explain the structure and function of blood and the vessels it travels in. Hint Close the book and list the components of blood and all the blood vessels. Extend Think about the differences between the components and the vessels and why their structure is important for their function. Structure and function of the heart aorta pulmonary artery Your heart is about the size of your fist when it is clenched left atrium and it has a mass of about 300 g. It is in the thoracic cavity between the lungs and behind the sternum, enclosed in a fibrous bag made from inelastic connective tissue vena cava coronary artery called the pericardium. The heart is a muscular double pump divided into two halves, each of which contain two Copyright © 2017. Pearson Education, Limited. All rights reserved. chambers. left ventricle right atrium The wall of the heart is made from mainly myocardium, which consists of cardiac muscle. Cardiac muscle contracts to make your heart beat. The coronary arteries seen in right ventricle Figure 5.12 lie on the surface of the heart. They carry oxygenated blood to the heart muscle itself. ▸▸ Figure 5.12 External view of the heart Key terms they sit above the two lower chambers called ventricles. Ventricles are thicker walled chambers. Deoxygenated Pericardium – a fibrous membrane that surrounds and blood flows into the right atrium from the vena cava protects the heart. (a main vein); at the same time the left atrium receives Myocardium – the middle and thickest layer of the oxygenated blood from the lungs via the pulmonary heart wall, composed of cardiac muscle. vein. From here the blood flows into the lower ventricles through atrioventricular valves. The atrioventricular The heart is divided into four chambers. The two upper valve between the left atria and left ventricle is known chambers are called the atria. They have thin walls and as the bicuspid valve. The tricuspid is the valve between Annets, F, Hartley, J, Hocking, S, Llewellyn, R, & Meunier, C 2017, BTEC Level 3 Nationals Applied Science Student Book 2, Pearson Education, Limited, Harlow. Available from: ProQuest Ebook Central. [28 September 2024]. Created from coulsdon-ebooks on 2024-09-28 21:24:47. 23 M05 BTEC National Applied Science Student B2 XXXXX.indd Page 23 09/05/17 9:10 pm f-0313 /122/PE02858/BTEC_Applied_Science/NA/SE/Applied_Science/G1/XXXXXXXXXX/Layout/Inte...  the right atrium and right ventricle. These valves are thin blood to a number of arteries to supply the body cells flaps of tissue attached to the ventricles via tendinous with oxygen. At the base of both of these arteries there are chords to stop the valves from turning inside out. When semi-lunar valves that prevent back flow of blood into the the ventricles are full of blood and ready to contract, the ventricle when they relax. valves close to stop the back flow of blood into the atrium. The heart is divided into the right and left side and the Key terms ventricles are separated by a wall of muscle called the Atria – two top chambers of the heart. septum. This stops the oxygenated and deoxygenated Ventricle – two bottom chambers of the heart. blood coming into contact with each other. Vena cava – a large vein carrying deoxygenated blood When the ventricles contract, deoxygenated blood flows into the heart. upwards out of the right ventricle into the pulmonary Atrioventricular valve – the structure found between artery, where the blood is transported to the lungs to the atrial and ventricular chambers of the heart to collect oxygen. prevent back flow. Oxygenated blood leaving the left ventricle flows into the Septum – the dividing wall between the right and left aorta. This is a major artery that carries the oxygenated sides of the heart. P a u se po i n t Label the structure of the heart. Hint Use the internet to find an unlabelled diagram of the heart, and see what you can label. Extend Draw a flow diagram of the cardiac cycle. Include the functions of all the structures. The heart muscle is described as myogenic, because it from the atria to the apex (bottom of the septum in the can initiate its own contraction and contracts and relaxes ventricle). At the apex, the Purkinje fibres spread through rhythmically, even without stimulation from the nervous the walls of the ventricles and, as the excitation spreads system. At the top of the right atrium there is a patch upwards through the muscle tissue, the ventricles contract of tissue, commonly known as a pacemaker, called the simultaneously. The ventricles contract from the base sinoatrial node (SAN). It is this node that generates the upwards and this pushes the blood up into the arteries. electrical activity and initiates a wave of excitation at This is known as ventricular systole. When the ventricles regular intervals. relax, semi-lunar valves at the base of the aorta and pulmonary artery prevent any blood flowing back into Copyright © 2017. Pearson Education, Limited. All rights reserved. The wave of excitation quickly spreads over the walls the heart. of the atrium. As it spreads along the muscle tissue membrane, it causes the muscle cells in both atria to contract simultaneously. This is known as atrial systole. The excitation cannot, however, spread directly to the Key terms ventricle because there is non-conducting tissue in the Sinoatrial node (SAN) – a patch of tissue found in the base of the atria. The wave of excitation is picked up by right atrium that generates the electrical activity and the atrioventricular node (AVN) located in the top of initiates a wave of excitation at regular intervals. the septum separating the two ventricles. The wave of Atrioventricular node (AVN) – a patch of tissue excitation is delayed here, which allows the atria time to located in the top of the septum that picks up the wave complete its contraction and for the blood to flow through of excitation from the atria. the atrioventricular valves into the ventricle before they start to contract. Bundle of His – a collection of heart muscle cells specialised for electrical conduction. The AV node stimulates the bundle of His, a bundle of Purkinje fibres – specialised conducting fibres found in conducting tissue made from Purkinje fibres. These fibres the heart. line the interventricular septum and carry the excitation Annets, F, Hartley, J, Hocking, S, Llewellyn, R, & Meunier, C 2017, BTEC Level 3 Nationals Applied Science Student Book 2, Pearson Education, Limited, Harlow. Available from: ProQuest Ebook Central. [28 September 2024]. 24 Principles and Applications of Science II Created from coulsdon-ebooks on 2024-09-28 21:24:47. M05 BTEC National Applied Science Student B2 XXXXX.indd Page 24 09/05/17 9:10 pm f-0313 /122/PE02858/BTEC_Applied_Science/NA/SE/Applied_Science/G1/XXXXXXXXXX/Layout/Inte...  Learning aim B UNIT 5 The cardiac cycle ▸▸ Wave QRS indicates excitation of the ventricles, when Principles and Applications of Science II they begin to contract and therefore represents One whole cardiac cycle takes about 0.8 seconds. ventricular systole. 1 Both atria relax and fill with blood from the pulmonary ▸▸ Wave T shows diastole, when the heart chambers are vein and vena cava. This is atrial diastole. relaxing. 2 The atria contract and force the atrioventricular (AV) The shape of an ECG can indicate that there is a valves open. Blood flows into the ventricles and they problem with the heart muscle. It can detect various fill up; this is ventricular diastole. arrhythmias: 3 The AV valves close when the pressure in the ventricles ▸▸ Tachycardia is a condition where the heart rate is very rises above the pressure in the atria to prevent the fast and over 100 beats per minute. Here the P waves backflow of blood into the atria. are evenly spread but are closer together than they 4 The ventricle walls contract and increase pressure in should be. the ventricles. This forces the semi-lunar valves to open and the blood flows into the pulmonary artery ▸▸ Bradycardia is a condition where the heart rate is very and aorta. slow and under 60 beats per minute. Here the P waves are evenly spread but further away from each other 5 When the pressure in the aorta and pulmonary artery than they should be. rises, the semi-lunar valves close to prevent backflow of blood into the ventricles. ▸▸ Ventricular fibrillation is a very serious condition where the contraction of ventricles is not controlled or coordinated. The ventricles fibrillate/quiver and the Assessment practice 5.5 heart pumps little or no blood, it can cause cardiac 1 Describe the cardiac cycle. Ensure that you arrest. Here there are no identifiable P, QRS or T waves mention the action of the valves. on the ECG, and the heart rate is very fast. 2 Explain why the sinoatrial node is commonly ▸▸ Sinus arrhythmia is a normal variation in the beating of referred to as a pacemaker. your heart. It occurs when your heart rate cycles with your breathing. When you breathe in, your heart rate 3 Explain why the ventricles contract from the speeds up and when you breathe out, your heart rate apex upwards. slows back down. Here there is a normal P wave but they are not evenly spread. Electrocardiograms ▸▸ Flat line is where the ECG shows no electrical activity of the heart. An electrocardiogram (ECG) can be used to monitor the electrical activity of the heart. Some of the electrical activity that is generated by the heart spreads through Assessment practice 5.6 tissue surrounding the heart and to the skin. During an 1 Describe the shape of an electrocardiogram. ECG a number of sensors are attached to the skin, they Copyright © 2017. Pearson Education, Limited. All rights reserved. pick up this electrical excitation and convert it into a 2 Explain why the QRS peak is larger than the P trace, as shown in Figure 5.13, that can be interpreted by wave. a medical professional. R A normal ECG The effect of caffeine on T P heart rate Q S Many different drugs can have an effect on the rate of your heart beat. Caffeine makes your heart ‘beat’ faster ▸▸ Figure 5.13 Electrocardiogram trace showing a normal ECG by increasing the electrical activity of the SAN. It also affects the ventricles, leading to an increase in the rate of A healthy trace consists of a series of waves and has a contraction and relaxation of each heartbeat. As well as particular shape. The waves are labelled P, Q, R, S and T. beating faster, a larger volume of blood can be pumped These waves indicate different information: out every time the heart beats. Two or three cups of strong ▸▸ Wave P shows excitation of the atria, when they begin coffee or tea contain enough caffeine to increase human to contract and therefore represents atrial systole. heart rate by 5–20 beats/min. Annets, F, Hartley, J, Hocking, S, Llewellyn, R, & Meunier, C 2017, BTEC Level 3 Nationals Applied Science Student Book 2, Pearson Education, Limited, Harlow. Available from: ProQuest Ebook Central. [28 September 2024]. Created from coulsdon-ebooks on 2024-09-28 21:24:47. 25 M05 BTEC National Applied Science Student B2 XXXXX.indd Page 25 09/05/17 9:10 pm f-0313 /122/PE02858/BTEC_Applied_Science/NA/SE/Applied_Science/G1/XXXXXXXXXX/Layout/Inte...