Biological Systems - MYP 4&5 Biology Notes PDF

MYP 4&5 BIOLOGY 2023-2024 Title Biological Systems Timeframe 7 UNIT 4...

MYP 4&5 BIOLOGY 2023-2024 Title Biological Systems Timeframe 7 UNIT 4 Orientation in space and time Global Context: Systems Key Concept: Function. Environment. Related Concept: Biological systems are maintained by the form and function of structures that allow the exchange and Statement of Inquiry: interaction between organisms and their environment. Factual What structures do larger organisms have in order to efficiently exchange nutrients, gases, and waste with their environment? Conceptual How does perceiving and responding to changing conditions of their environment Inquiry Questions contribute to the survival of organisms? Debatable To what extent can we assume an organism truly reaches homeostatic balance when all systems are constantly interacting with each other and the environment? DISCLAIMER The following booklet is a collage of the theoretical content of the following sources: ▪ Biology for the IB MYP 4&5: By Concept. Davis & Deo. Hodder Education. 2015. ISBN: 9781471841705 ▪ Cambridge IGCSE Biology Study and Revision Guide 2 nd Edition. Hayward. Hodder Education. 2016. ISBN: 9781471865138 ▪ Oxford IB Study Guides: Biology for the IB Diploma. Allot. Oxford University Press. 2014. ISBN: 9780198393511 ▪ IB Biology Course Book: Oxford IB Diploma Programme. Allot and Mindorff. Oxford University Press. 2014. ISBN: 9780198392118. ▪ Oxford IB Course Preparation: Biology for IB Diploma Programme Course Preparation. Bkerat. Oxford University Press. 2018. IBN:978019842350-8. (1) Biological System When a group of cells with similar structure work together to perform shared functions, a tissue is born. An organ is a structure made up of a group of tissues working together to perform specific functions. And finally, an organ system is what we call a group of organs with related functions working together to perform body functions. Thus, our orientation in time and space is founded on the relationship between the different cells, tissue, and organs in our body, which work together to make us function as a whole organism. Although organs consist of multiple tissue types, many organs are composed of the main tissue that is associated with the organ’s major function and other tissues that play supporting roles. The main tissue may be unique to that specific organ. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 1  Figure 1 - Levels of organization within a biological system, such as the human body. Source: https://slideplayer.com/slide/1074437 2/ For example, the main tissue of the heart is the cardiac muscle, which performs the heart’s major function of pumping blood and is found only in the heart. The heart also includes nervous and connective tissues that are required for it to perform its major function. Additionally, the nervous tissues control the beating of the heart, and connective tissues make up heart valves that keep blood flowing in just one direction through the heart. A. Vital Organs The human body contains five organs that are considered vital for survival. They are the heart, brain, kidneys, liver , and lungs. If any of the five vital organs stops functioning, the death of the organism is imminent without medical intervention. 1. The heart is located in the centre of the chest, and its function is to keep blood flowing through the body. Blood carries substances to cells that they need and also carries away wastes from cells. 2. The brain is located in the head and functions as the body’s control centre. It is the seat of all thoughts, memories, perceptions, and feelings. 3. The two kidneys are located in the back of the abdomen on either side of the body. Their function is to filter blood and form urine, which is excreted from the body. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 2  4. The liver is located on the right side of the abdomen. It has many functions, including filtering blood, secreting bile that is needed for digestion , and producing proteins necessary for blood clotting. 5. The two lungs are located on either side of the upper chest. Their main function is exchanging oxygen and carbon dioxide with the blood. Figure 2 - Diagram of human anatomy to locate the five organs described above: heart, brain, kidneys, liver, and lungs. Source: https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/10%3A_Introduction_to_the_Human_Body/10.4 %3A_Human_Organs_and_Organ_Systems B. Twelve (12) Human Organ System Functionally related organs often cooperate to form whole organ systems. There are twelve human organ systems, with a clear distinction between the male and female reproductive systems. The purpose of the twelve body systems is to maintain homeostasis see note #1: Note #1 – Recap! Homeostasis is any self-regulating process by which biological systems tend to maintain stability while adjusting to conditions that are optimal for survival. If an organism is uncapable of maintaining homeostasis, then it will perish. In simpler terms, homeostasis is the delicate balance that holds the entire machinery of live together – all metabolic functions. To further understand homeostasis, we need to break down its definition into two parts: (1) stability of biological systems; and (2) optimal conditions for survival. 1. Integumentary system Organs of the integumentary system include the skin, hair, and nails. The skin is the largest organ in the body. It encloses and protects the body and is the site of many sensors’ receptors. The skin is the body’s first defence against invaders (i.e., pathogens), and it also helps regulate body temperature and eliminate wastes in sweat. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 3  2. Skeletal system The skeletal system consists of bones, joints, teeth. The bones of the skeletal system are connected by tendons, ligaments, and cartilage. Functions of the skeletal system include supporting the body and giving it shape. Along with the muscular system, the skeletal system enables the body to move. The bones of the skeletal system also protect internal organs, store calcium, and produce red and white blood cells. 3. Muscular system The muscular system consists of three different types of muscles. (1) Skeletal muscles, which are attached to bones by tendons and allow for voluntary movements of the body. (2) Smooth muscle tissues control the involuntary movements of internal organs, such as the organs of the digestive system, allowing food to move through the system. Smooth muscles in blood vessels allow vasoconstriction and vasodilation and thereby help regulate body temperature. (3) Cardiac muscle tissues control the involuntary beating of the heart, allowing it to pump blood through the blood vessels of the cardiovascular system. 4. Nervous system The nervous system includes the brain and spinal cord, which make up the central nervous system, and nerves that run throughout the rest of the body, which make up the peripheral nervous system. The nervous system controls both voluntary and involuntary responses of the human organism and also detects and processes sensory information. 5. Endocrine system The endocrine system is made up of glands that secrete hormones into the blood, which carries the hormones throughout the body. Endocrine hormones are chemical messengers that control many body functions, including metabolism, growth, and sexual development. The master gland of the endocrine system is the pituitary gland, which produces hormones that control other endocrine glands. Some of the other endocrine glands include the pancreas, thyroid gland, and adrenal glands. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 4  6. Cardiovascular/cardiovascular system The Cardiovascular system includes the heart, blood, and three types of blood vessels: arteries, veins, and capillaries. The heart pumps blood, which travels through the blood vessels. The main function of the cardiovascular system is transport. Oxygen from the lungs and nutrients from the digestive system are transported to cells throughout the body. Carbon dioxide and other waste materials are picked up from the cells and transported to organs such as the lungs and kidneys for elimination from the body. The cardiovascular system also equalizes body temperature and transports endocrine hormones to cells in the body where they are needed. 7. Urinary/excretory system The urinary system includes the pair of kidneys, which filter excess water and a waste product called urea from the blood and form urine. Two tubes called ureters carry the urine from the kidneys to the urinary bladder, which stores the urine until it is excreted from the body through another tube named the urethra. The kidneys also produce an enzyme called renin and a variety of hormones. These substances help regulate blood pressure, the production of red blood cells, and the balance of calcium and phosphorus in the body. 8. Respiratory system Organs and other structures of the respiratory system include the nasal passages, lungs, and a long tube called the trachea, which carries air between the nasal passages and lungs. The main function of the respiratory system is to deliver oxygen to the blood and remove carbon dioxide from the body. Gases are exchanged between the lungs and blood across the walls of capillaries lining tiny air sacs (alveoli) in the lungs. 9. Lymphatic system The lymphatic system is sometimes considered to be part of the immune system. It consists of a network of lymph vessels and ducts that collect excess fluid (called lymph) from extracellular spaces in tissues and transport the fluid to the bloodstream. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 5  The lymphatic system also includes many small collections of tissue, called lymph nodes, and an organ called the spleen, both of which remove pathogens and cellular debris from the lymph or blood. In addition, the thymus gland in the lymphatic system produces some types of white blood cells (lymphocytes) that fight infections. 10. Digestive system The digestive system consists of several main organs — including the mouth, esophagus, stomach, and small and large intestines — that form a long tube called the gastrointestinal (GI) tract. Food moves through this tract where it is digested, its nutrients absorbed, and its waste products excreted. The digestive system also includes accessory organs (such as the pancreas and liver) that produce enzymes and other substances needed for digestion but through which food does not actually pass. 11. Reproductive system The human reproductive system includes the male reproductive system which functions to produce and deposit sperm; and the female reproductive system which functions to produce egg cells, and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation. In addition to differences in nearly every reproductive organ, there are numerous differences in typical secondary sex characteristics. Figure 3 - Illustration of the 11 human organ system. All taken from the same source: https://heathernelsonmassage.files.wordpress.com/2014/08/the-human-body-organs-system.jpg 12. Immune system The environment consists of numerous pathogens, which are agents, usually microorganisms, that cause diseases in their hosts. A host is the organism that is invaded and often harmed by a pathogen. Pathogens include bacteria, protists, fungi, and other infectious organisms. We are constantly exposed to pathogens in food and water, on surfaces, and in the air. Mammalian immune systems evolved for protection from such pathogens; they are composed of an extremely diverse array of specialized cells and soluble molecules that Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 6  coordinate a rapid and flexible defence system capable of providing protection from a majority of these disease agents. Although each of the twelve human body systems could be described in more detail, only the digestive system, Cardiovascular system, respiratory system, endocrine system, and nervous system will be further described in the unit’s following chapters/sections. Additionally, the immune system will be thoroughly analysed in unit Disease and Global Health. The information of the chapter above taken from the following sources: Website Libretexts. “10.4: Human Organs and Organ Systems.” Biology LibreTexts, Libretexts, 13 Dec. 2021, https://bio.libretexts.org/Bookshelves/Human_Biology/Book:_Human_Biology_(Wakim_and_Grewal)/10:_Introduction_to_the_Human_B ody/10.4:_Human_Organs_and_Organ_Systems. “Human Reproductive System.” Wikipedia, Wikimedia Foundation, 21 Dec. 2021, https://en.wikipedia.org/wiki/Human_reproductive_system. Libretexts. “42: The Immune System.” Biology LibreTexts, Libretexts, 3 Sept. 2021, https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book:_General_Biology_(OpenStax)/7:_Animal_Structure_and_ Function/42:_The_Immune_System. Until here, you can now do the following formative questions at the end of the unit: 1 & 2. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 7 (2) Digestive system The purpose of the alimentary tract/canal is two-fold. First, to break down foods into their basic components, a process referred to as digestion. Second, to carry out the absorption of the basic components into the body. Digestion consists of mechanical breakdown of foods into smaller particles via the action of the teeth, and via contractions of the muscles along the alimentary tract. In addition, digestion relies on chemical breakdown of the macronutrients - protein, fat, and carbohydrate - from their more complex molecular structures into their basic components. So, for protein these are amino acids, for fat these are fatty acids, and for carbohydrates this is mainly glucose (monosaccharide). Figure 4 - Quick illustration between the distinction of mechanical/physical breakdown vs. chemical breakdown. Source: https://www.pinterest.pt/pin/397090892129861302/ Chemical breakdown is carried out by so-called digestive enzymes produced by various cells and tissues along the alimentary tract. In biochemical terms, digestive enzymes function as catalysts. All reactions catalysed by digestive enzymes represent hydrolysis. Lipases acts on fats, proteases act on peptides/proteins, and amylase acts on starch (polysaccharide). Chemical digestion by digestive enzymes occurs in all major parts of the alimentary tract, except for the colon or large intestine. Thus, it occurs in the mouth, stomach, and small intestine. Figure 5 - Quick diagram of the three main digestive enzymes and their act on the three macromolecules. Source: https://www.blendspace.com/lessons/VUCPcE9FachHaA/enzyme Table 1 - Detailed information regarding the three main digestive enzymes: amylase; protease; and lipase. Enzyme Site of action Special conditions Substrate digested End products Amylase Mouth, duodenum Slightly alkaline Starch (branched glucose) Maltose, glucose Protease Stomach, Acid in stomach, alkaline Protein Amino acids duodenum in duodenum Lipase Duodenum Alkaline Fat Fatty acids and glycerol Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 8 By the end of the stomach digestion is complete and absorption starts at the beginning of the small intestine. Absorption is a process where digested food molecules (small enough) are taken in through the wall of the small intestine into the bloodstream, being subsequently distributed throughout the body. Figure 6 - Digestion and absorption of monosaccharides: membrane transport. Source: http://astarbiology.com/aqa/digestion-and-absorption/ The villi present in the small intestine are finger-like projections that increase the surface area for absorption. The surface area of the villi is further increased by the presence of microvilli. Inside each villus are blood capillaries that absorb amino acids and glucose. Figure 7 - Illustration of the folding of the small intestine. (a) A section of the small intestine. (b) A zoomed-in While glucose can stay in the section of the wall of the small intestine, allowing for a detail view of the villi. (c) A detail depiction of a villus. (d) An epithelial cell with a clear visualization of microvilli. bloodstream, amino acids are Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 9 directly taken in by muscle cells and converted into glycogen (storage). However, if glucose levels are higher than the energy demands, glucose will be taken up by tissues and converted into fat (storage). The absorption of nutrients at the level of the small intestine occurs without energy by the process of diffusion. Diffusion is the movement of molecules from higher to lower concentration. The villi and microvilli allow for an increase rate of diffusion of nutrients to the bloodstream, thus wherever metabolic processes require energy (cellular respiration). Figure 8 - Illustration of the processes of digestion include six activities: ingestion, propulsion, mechanical or physical digestion, chemical digestion, absorption, and defecation. Source: https://microbenotes.com/physiology-of-digestion/. The chapter above was complemented with information taken from the following sources: Lecture Kersten, Sander. “MOOC 1 and 2”. HNH-32206 Food Components and Health, October 2017 Until here, you can now do the following formative questions at the end of the unit: 3 -10. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 10 (3) Cardiovascular system The organs of the body are composed of tissues whose cells are alive. This means they need glucose oxygen and other nutrients to perform their various jobs and produce waste in the process. However, the cells of the body occupy fixed positions, far from the source of food, oxygen, and water. Therefore blood, containing vital nutrients and oxygen, must be carried to each cell in the body. The Cardiovascular system is a system of blood vessels with a pump (the heart) and valves to make sure the blood flows one way. A. Blood vessels Blood vessels are intrinsically associated with the heart, lungs and with the kidneys (urinary/excretory system). There are three types of blood vessels. Arteries carry blood at high pressure away from the heart. Veins carry blood from the capillaries back to the heart, under low pressure. And capillaries supply nutrients and oxygen to the cells by diffusion; as well as carry away waste products from the cells. Each type of blood vessels shows a specific structure that relates to its function. Figure 9 - Sections of the three types of blood vessels. Source: http://igbiologyy.blogspot.com/2013/05/71- arteries-veins-and-capillaries.html B. The heart The heart of mammals is a double pump that pushes blood first to the lungs under low pressure and then to the rest of the body under high pressure. This double circulation system helps to maintain blood pressure, making circulation efficient: ▪ Blood passes through the heart twice for each complete circulation of the body. ▪ The right side of the heart collects deoxygenated blood (illustrated always in blue) from the body and pumps it to the lungs. ▪ The left side collects oxygenated blood (illustrated always in red) from the lungs and pumps it to the body. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 11  TIP! “LORD” → Left Oxygenated Right Deoxygenated In terms of structure, the heart has four chambers. The (1) right and (2) left atria receive blood from the veins and squeeze it into the ventricles. The (3) right and (4) left ventricles receive blood from the atria and squeeze it into arteries. ▪ The wall of the left ventricle is much thicker than the wall of the right ventricle because it needs to build up enough pressure to move the blood to all the main organs. ▪ The walls of the atria are much thinner than those of ventricles. This is because the contraction of the atria needs to be powerful enough only to move blood down into the ventricles, while the ventricles are moving blood around the body and through all the Figure 10 - Illustration of the heart's anatomy. Source: organs. https://simple.wikipedia.org/wiki/Heart#/media/File:Diagram_of_the_human_heart_(cropped).svg In general, blood flows into the heart from a vein, goes into an atrium, then a ventricle, and out through an artery. The heart contains valves to prevent the blood flowing backwards: ▪ The right side has a tricuspid valve (a valve with three flaps) ▪ The left side has a bicuspid valve (a valve with two flaps) Both sides have semi-lunar valves (at the entrances to the pulmonary artery and aorta). C. Double circulation system The heart is a muscular organ. Its function is to pump blood. The right-side pumps blood through the pulmonary circuit, while the left side pumps blood through the systemic circuit. A septum separates the right and left sides. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 12 Pulmonary circulation is the movement of blood from the heart to the lungs for oxygenation, then back to the heart again. 1. Deoxygenated blood from the body leaves the systemic circulation when it enters the right atrium through the superior and inferior venae cava. 2. The blood is then pumped through the tricuspid valve into the right ventricle. 3. From the right ventricle, blood is pumped through the pulmonary valve and into the pulmonary artery. 4. The pulmonary artery splits into the right and left pulmonary arteries and travel to each lung. 5. At the lungs, the blood travels through capillary beds on the alveoli where gas exchange occurs, removing carbon dioxide and adding oxygen to the blood. 6. The oxygenated blood then leaves the lungs through pulmonary veins, which returns it to the left atrium, completing the pulmonary circuit. Figure 11 - Schematic representation of the double circulation system of humans. Deoxygenated blood is represented in blue. Oxygenated blood is represented in red. Source: https://tamarasbiologylessons.weebly.com/transport-in-animals.html Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 13 As the pulmonary circuit ends, the systemic circuit begins. Systemic circulation is the movement of blood from the heart through the body to provide oxygen and nutrients to the tissues of the body while bringing deoxygenated blood back to the heart. 7. Oxygenated blood enters the left atrium from the pulmonary veins. The blood is then pumped through the mitral valve into the left ventricle. 8. From the left ventricle, blood is pumped through the aortic valve and into the aorta, the body’s largest artery. 9. The aorta arches and branches into major arteries to the upper body before passing through the diaphragm, where it branches further into several arteries which supply the lower parts of the body. 10. The arteries branch into smaller arteries, arterioles, and finally capillaries. 10.1. Gas and nutrient exchange with the tissues occurs within the capillaries that run through the tissues. 10.2. Metabolic waste and carbon dioxide diffuse out of the cell into the blood, while oxygen and glucose in the blood diffuses out of the blood and into the cell. 11. The deoxygenated blood continues through the capillaries which merge into venules, then veins, and finally the venae cava, which drain into the right atrium of the heart, through the pulmonary circulation to be oxygenated. The information for the chapter above was taken from the following source: Website Libretexts. “17.2D: Systemic and Pulmonary Circulation.” Medicine LibreTexts, Libretexts, 14 Aug. 2020, https://med.libretexts.org/Bookshelves/Anatomy_and_Physiology/Book:_Anatomy_and_Physiology_(Boundless)/17:_Cardiovascular_System:_The _Heart/17.2:_Circulation_and_Heart_Valves/17.2D:_Systemic_and_Pulmonary_Circulation. Until here, you can now do the following formative questions at the end of the unit: 11 - 21. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 14 (4) Respiratory system A. Ventilation The process of gaseous exchange involves the passage of gases such as oxygen into and carbon dioxide out of cells or a transport system. First air needs to be in contact with the gaseous exchange surface – the alveoli in the lungs of mammals. Ventilation refers to the flow of air into and out of the alveoli Figure 12 - Respiratory system's anatomy. Source: https://visualsonline.cancer.gov/details.c fm?imageid=7235 The composition of inspired and expired air can be seen in the table below, Table 2 -The composition of inspired and expired air in percentages Gas Inspired Expired Purpose air/% air/% Nitrogen 79 79 Not used or produced by body processes. Used up in the process of respiration, but the system is not very Oxygen 21 16 efficient, so only a small proportion of the oxygen available is absorbed from the air. Carbon 0.04 4 Produced in the process of respiration. dioxide Water Variable Saturated Produced in the process of respiration; moisture evaporates vapour from the surface of the alveoli Ventilation of the lungs (breathing) ensures there is always fresh air entering the alveoli, which means there is always a difference in oxygen concentration – concentration gradient – between the alveolar air and the blood. Ventilation is possible due to the movement of the ribcage alongside the intercoastal muscles. The Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 15 movement of the ribcage is brought about by the contraction of two sets of intercoastal muscles that are attached to the ribs. The external intercostal muscles are attached to the external surface of the ribs; the intercostal muscles are attached to the internal surface Figure 13 - Labelled representation of the movement of the internal and external Figure 14 - Lateral (left) and anterior (right) view of the location of the intercostal muscles during breathing/ventilation. intercostal muscles. Source: https://quizlet.com/gb/389326337/ap-inspiration-expiration-and-pause- Source: https://shiangyingdotcom.wordpress.com/2014/03/06/how-are- diagram/ you-breathing/ B. Gas exchange Gas exchange occurs in the lungs between alveolar air and the blood of the pulmonary capillaries. Gas exchange occurs through diffusion. Blood that is low in oxygen concentration and high in carbon dioxide concentration undergoes gas exchange with air in the lungs. The air in the lungs has a higher concentration of oxygen than that of oxygen-depleted blood and a lower concentration of carbon dioxide. This concentration gradient allows for gas exchange during cellular respiration. Figure 15 - Illustration of the respiratory system: gas exchange between the oxygenated blood (red circuit) and the deoxygenated blood (blue circuit). Source: https://sequencewiz.org/2020/08/12/gas- exchange-within-the-body-dont-rush-to- get-rid-of-carbon-dioxide/ Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 16 Gas exchange during ventilation occurs primarily through diffusion. For the diffusion rate to be efficient, the exchange surface must: ▪ Be thin – a short distance for gases to diffuse. ▪ Have a large surface area - for gases to diffuse over. ▪ Have a good ventilation with air – this creates and maintains a concentration gradient. ▪ Have a good blood supply – to transport oxygen to respiring tissues and bring carbon dioxide from those tissues. The chapter above was complemented with information taken from the following sources: Website “Oxygen & Carbon Dioxide: Gas Exchange and Transport in Animals.” Biology 1520, 23 Mar. 2020, organismalbio.biosci.gatech.edu/nutrition- transport-and-homeostasis/gas-exchange-in-animals/#:~:text=The air in the lungs in a mixture of gases. Until here, you can now do the following formative questions at the end of the unit: 22 - 27. (5) Nervous System As with other higher vertebrates, the human nervous system has two main parts: the central nervous system (the brain and spinal cord) and the peripheral nervous system (the nerves that carry impulses to and from the central nervous system). Each main part is then further broken down into sub-parts. Figure 16 - Diagram of all parts that make up the human nervous system. Source: https://www.researchgate.net/figure/The-central-nervous-system-CNS-and- peripheral-nervous-system-PNS-source_fig1_317485174 Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 17  A. Nerves A reflex is an automatic and involuntary response to a stimulus. The nervous system is responsible for conducting stimuli from sensory receptors to the brain and spinal cord and conducts impulses back to other parts of the body, generating this response. Neurons, also called nerve cells, are basic cells of the nervous system and they are responsible for the entire response chain of a reflex. Bundles of fibres from neurons are held together by connective tissue and form nerves. A typical neuron has a cell body containing a nucleus and two or more long fibres. Impulses are carried along one or more of these fibres, called dendrites, to the cell body. The impulse is then carried away from the cell body through the axon. The impulse leaves the neuron through the axon terminal via synapses. A synapse is the site of transmission of electric nerve impulses between two neurons or between a neuron and a gland or muscle cell (effector). A sensory neuron transmits impulses from a receptor, such as those in the eye or ear, to a more central location in the nervous system, such as the spinal cord or brain. Figure 17 - Illustration of a neuron, also known as a nerve cell. Source: https://www.google.com/imgres?imgurl=https%3A%2F%2Fwww.nichd.nih.gov A motor neuron transmits impulses from a central area %2Fsites%2Fdefault%2Ffiles%2F2018-10%2Fnervous- system.jpg&imgrefurl=https%3A%2F%2Fwww.nichd.nih.gov%2Fhealth%2Fto of the nervous system to an effector, such as a muscle. pics%2Fn Additionally, sensory neurons can be of several types: ▪ Thermoreceptors respond to changes in temperature. ▪ Photoreceptors respond to changes in light. ▪ Chemoreceptors respond to changes in chemicals associated with odours, tastes, and dissolved substances in the blood. ▪ Mechanoreceptors respond to changes in pressure or touch. ▪ Sonoreceptors respond to changes in sounds Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 18  B. Reflex arc A reflex arc is a neurological and sensory mechanism that controls a reflex, an immediate response to a particular stimulus. The primary components of the reflex arc are the sensory neurons (or receptors) that receive stimulation and in turn connect to other nerve cells that activate muscle cells (motor neurons, or effectors), which perform the reflex action. The simplest arrangement of a reflex arc consists of the sensory neurons, a relay neuron (or adjustor), and a motor neuron - together, these units form a functional group. Sensory neurons carry input from the receptor (afferent impulses) to a central interneuron, which contacts a motor neuron. The motor neuron carries efferent impulses to the effector, which produces the response. A good example of a reflex arc is one’s reflex to touching something hot, such as a hot pot: 1. The response begins at the fingers, where sensory neurons, such as thermoreceptors, are stimulated by the high temperature they sense. 2. The same thermoreceptors are activated by the ‘extreme heat’, initiating a signal called a nerve impulse/action potential, along the length (axon) of the sensory neuron (itself). 3. When the nerve impulse reaches the end of the sensory neuron (axon terminal, synapse), it causes chemicals called neurotransmitters to be released from the sensory neuron. 4. The released neurotransmitters float across the synaptic cleft between neurons, reaching neighbouring neurons; allowing the nerve impulse to continuous throughout all neighbouring neurons (step 2. – 4.). Figure 18 - Illustration of an impulse travelling through a synapse. Source: https://socratic.org/questions/how- do-impulses-travel-across-a- synapse Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 19  The nerve impulse ‘extreme heat’ travels continuously, rapidly, automatically, and nonstop along all of the sensory neurons in the peripheral nervous system (PNS) through one’s hand, up one’s arm, and to one’s spinal cord (central nervous system, CNS). Because the spinal cord is part of the CNS, it has the ability to command one’s body without one having to use one’s brain to think about making a decision. 5. In the spinal cord, the ‘extreme heat’ nerve impulse reaches the relay neurons, that relay/pass the nerve impulse from the sensory neurons to the motor neurons. 6. The motor neurons synapse with each other, extending the spinal cord and down along the arm and the hand. 7. The motor neurons synapse with muscle cells in one’s arm and hand, passing the nerve impulse, which causes both to contract, and one pulls one’s arm and hand away from the hot pot. Figure 19 - Simple illustration of a reflec arc when one touches a hot object. Source: https://www.examrace.com/Study-Material/Medical-Science/Physiology/Reflex- Action.html The information of the chapter above was taken from the following sources: Websites “Reflex Arc.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/reflex-arc. “Human Nervous System.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/human-nervous-system. “Synapse.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/synapse. “Neuron.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., https://www.britannica.com/science/neuron. Until here, you can now do the following formative questions at the end of the unit: 28 - 32. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 20 (6) Endocrine system The endocrine system is a complex network of glands and organs. It uses hormones to control and coordinate your body's metabolism, energy level, reproduction, growth and development, and response to injury, stress, and mood. The following are integral parts of the endocrine system: 1. Hypothalamus secretes hormones that stimulate or suppress the release of hormones in the pituitary gland, in addition to controlling water balance, sleep, temperature, appetite, and blood pressure. 2. Pineal body produces the hormone melatonin, which helps the body know when it's time to sleep. 3. Pituitary gland controls many functions of the other endocrine glands. 4. Thyroid and parathyroid. The thyroid plays an important role in the body's metabolism. The parathyroid glands play an important role in the regulation of the body's calcium balance. 5. Thymus produces white blood cells that fight infections and destroy abnormal cells. 6. Adrenal gland works hand-in-hand with the hypothalamus and pituitary gland; releases corticosteroid hormones and epinephrine that maintain blood pressure and regulate metabolism. 7. Pancreas plays a role in digestion; and produces the hormones insulin and glucagon, which regulate levels of blood sugar. 8. Ovary produces the hormones estrogen and progesterone, responsible for secondary reproductive characteristics and regulating women’s menstrual cycle and Figure 20 - Illustration of endocrine system's glands. Source: libido. https://en.wikipedia.org/wiki/Endocrine_system 9. Testis produce testosterone and sperm, responsible for secondary reproductive characteristics and regulating men’s libido. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 21  A. Chemical messengers - Hormones Hormones and neurotransmitters are two types of chemicals signalling molecules (chemical messengers) produced by animals. They are responsible for the behaviour and attitudes of the organism. A hormone is a product of living cells, which circulates in fluids like blood or sap, and produces a specific, usually stimulatory effect on the activity of cells, remote from its point of origin. Therefore, hormones are chemical messengers that aid the communication between different parts of the body by sending chemical signals from one to the other. By the contact of a hormone, growth, and development of cells and tissues, initiation and maintenance of sexual development, food metabolism, body temperature, and mood can be affected. Since hormones are extremely powerful molecules, a few hormones may have a major effect on the body. Hormones are destroyed after their action. Therefore, they are not reusable. In animals, they are directly released into the bloodstream by endocrine glands and circulate through the body until the target tissue or organ is found. Some of the endocrine glands found in the body are pituitary gland, pineal gland, pancreas, liver, thymus, thyroid gland, adrenal gland, ovary, and testis Hormones can be either proteins, lipids, or cholesterol-based molecules. Figure 21 - Brief differences between hormones and neurotransmitters, both chemical Neurotransmitters are proteins. The main messengers of the body. Source: http://www.differencebetween.net/science/health/difference-between-hormones-and- difference between hormones and neurotransmitters/ neurotransmitters is that hormones are Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 22 produced in endocrine glands and are released into the blood stream where they find their targets of action at some distance from its origin. Whereas neurotransmitters are released into the synaptic gap by a terminal of a stimulated presynaptic nerve cell, transmitting a nerve signal to its neighbouring postsynaptic nerve cell. The information of the chapter above was taken from the following sources: Websites Panawala, Lakna. “Difference Between Hormones and Neurotransmitters.” Research Gate, June 2017. “Anatomy of the Endocrine System.” Johns Hopkins Medicine, https://www.hopkinsmedicine.org/health/wellness-and-prevention/anatomy-of-the- endocrine-system#:~:text=The endocrine system is a,Hypothalamus. Until here, you can now do the following formative questions at the end of the unit: 33 - 34. B. Plant Hormones – Tropism A tropism is a biological phenomenon, indicating growth or turning movement of a biological organism, usually a plant, in response to an environmental stimulus. In tropisms, this response is dependent on the direction of the stimulus. They can commonly be either positive (towards the stimulus) or negative (away from it). Tropisms are usually named for the stimulus involved: ▪ Phototropism, movement or growth in response to lights or colours of light ▪ Hydrotropism, movement or growth in response to water; in plants, the root cap senses differences in water. ▪ Aerotropism, growth of plants towards or away from a source of oxygen. ▪ Gravitropism, sometimes referred to as geotropism, movement or growth in response to gravity. Tropisms occur in three sequential steps. First, there is a detection of a stimulus. Next, signal transduction occurs, producing a specific response-protein, a hormone in this case. And finally, the directional growth response occurs. Auxin is a plant hormone that regulates growth, particularly by stimulating cell elongation in stems. Phototropism occurs due to the action of auxin: 1. Auxin is equally distributed in all cells. 2. In order to bend towards the light, auxin is actively pumped (active transport/ATP) OUT of the cells that are closest to the light source. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 23  3. Auxin accumulates in the spaces between the cells, creating a concentration gradient. 4. Auxin diffuses into the cells that are farthest from the light (passive transport). 5. The increased auxin levels activate genes that code for a specific enzyme. 6. The enzyme causes the cell walls of the cells farthest from the light to elongate. 7. The elongation of cells from the light causes the plant to bend towards the light. Figure 22 - Positive phototropism in plant shoots is a result of auxin accumulating on the shaded side of a shoot. Source: https://www.savemyexams.co.uk/igcse/biology/edexcel/19/revision-notes/2-structure--function-in-living-organisms/2-10-co-ordination--response/2-10-4-the-role- of-auxin-in-phototropism/ The information of the chapter above was taken from the following sources: Websites “Tropism.” Wikipedia, Wikimedia Foundation, 2 July 2022, https://en.wikipedia.org/wiki/Tropism. “The Role of Auxin in Phototropism (2.10.4): EDEXCEL IGCSE Biology Revision Notes 2019.” Save My Exams, https://www.savemyexams.co.uk/igcse/biology/edexcel/19/revision-notes/2-structure--function-in-living-organisms/2-10-co-ordination-- response/2-10-4-the-role-of-auxin-in-phototropism/. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 24 (7) The Immune system The immune system fights germs and foreign substances on the skin, in the tissues of the body and in bodily fluids such as blood. The immune system is made up of two parts: the innate, (general) immune system and the adaptive (specialized) immune system. These two systems work closely together and take on different tasks A. Innate vs. adaptive immune system The innate immune system is the body's first line of defence against germs entering the body. It responds in the same way to all germs and foreign substances, which is why it is sometimes referred to as the "nonspecific" immune system. It acts very quickly: For instance, it makes sure that bacteria that have entered the skin through a small wound are detected and destroyed on the spot within a few hours. The innate immune system has only limited power to stop germs from spreading, though. The innate immune system consists of Protection offered by the skin and mucous membranes Protection offered by the immune system cells (defence cells) and proteins The adaptive immune system takes over if the innate immune system is not able to destroy the germs. It specifically targets the type of germ that is causing the infection. But to do that it first needs to identify the germ. This means that it is slower to respond than the innate immune system, but when it does it is more accurate. It also has the advantage of being able to "remember" germs, so the next time a known germ is encountered, the adaptive immune system can respond faster. This memory is also the reason why there are some illnesses you can only get once in your life, because afterwards your body becomes “immune.” It may take a few days for the adaptive immune system to respond the first time it comes into contact with the germ, but the next time the body can react immediately. The second infection is then usually not even noticed or is at least milder. The adaptive immune system is made up of: T lymphocytes in the tissue between the body's cells B lymphocytes, also found in the tissue between the body's cells Antibodies in the blood and other bodily fluids Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 25  A. White blood cells Many cells work together as part of the innate (non-specific) and adaptive (specific) immune system. Leukocytes (white blood cells) are immune system cells involved in defending the body against infectious disease and foreign materials. The innate leukocytes include the phagocytes, mast cells, eosinophils, basophils, neutrophil, and natural killer cells. These cells identify and eliminate pathogens and are important mediators in the activation of the adaptive immune system. ▪ Macrophages are a type of white blood cell that engulf and destroy bacteria (phagocytosis), foreign particles, and dying cells to protect the body. They bind to pathogens and internalize them in a phagosome, which acidifies and fuses with lysosomes to destroy the contents. ▪ Mast cells are a type of white blood cells that mediate inflammatory responses such as hypersensitivity and allergic reactions by releasing histamines. ▪ Eosinophils are a variety of white blood cells and one of the immune system components responsible for combating multicellular parasites and certain infections in vertebrates. ▪ Basophils are a type of phagocytic immune cell that has granules. Inflammation causes basophils to release histamine during allergic reactions. Figure 23 - Comic representation of the main function of B-cells and T-cells. Source: A lymphocyte is a type of white blood cell that is part of the https://askabiologist.asu.edu/b-cell adaptive immune system. There are two main types of lymphocytes: B cells and T cells. ▪ The B-cells are the type of cells that produce antibodies to fight bacteria and viruses. These antibodies are Y-shaped proteins that are specific to each pathogen and can lock onto the surface of an invading cell and mark it for destruction by other immune cells. ▪ The T-cells destroy the body's own cells that have themselves been taken over by viruses or that have become cancerous. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 26  The chapter above was complemented with information taken from the following sources: Websites “Components of the Immune System.” Healio, www.healio.com/hematology-oncology/learn-immuno-oncology/the-immune-system/components-of-the-immune-system. “B-Cells vs T-Cells: Learn the Difference & Types of T-Cells.” Cancer Treatment Centers of America, 10 Nov. 2021, https://www.cancercenter.com/what-are-b-cells-vs- t-cells. “Lymphocyte.” Genome.gov, https://www.genome.gov/genetics-glossary/Lymphocyte. Until here, you can now do the following formative questions at the end of the unit: 35 -37. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 27  Formative Questions, Unit 4 – Biological Systems This set of questions comprises IB DP Biology standard level questions for students’ maximization of understanding and application of knowledge within the topic. 1. Compare and contrast the location and function of the five vital organs. 2. Outline the main function of each of the 12 body systems 1. Integumentary 7. Urinary 2. Skeletal 8. Respiratory 3. Muscular 9. Lymphatic 4. Nervous 10. Digestive 5. Endocrine 11. Reproductive 6. Cardiovascular 12. Immune 3. Compare and contrast the site of action, substrate digested and end products of the three main enzymes: amylase; protease and lipase 4. Distinguish between digestion and absorption 5. Draw and label the gastrointestinal tract 6. Celiac disease is an immune reaction to eating gluten, a protein found in many cereals. The diagram shows the arrangement of normal villi and villi affected by celiac disease in the small intestine. a. Outline the functions of the villi in the small intestine b. Explain the consequences of celiac disease for absorption of digested nutrients. 7. Which part of the body secretes amylase, lipase and endopeptidase for use in the digestion of food? a. Mouth b. Pancreas c. Stomach d. Small intestine Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 28 8. Which products are formed by the action of the enzymes protease and amylase? 9. Describe the processes involved in absorbing different nutrients across the cell membrane of villus epithelium cells lining the small intestine. 10. Explain how the small intestine moves, digests, and absorbs food. 11. What is a property of arteries? a. Arteries have elastic walls. b. Arteries have valves. c. All arteries carry oxygenated blood. d. Arteries receive blood from the atria. 12. What blood flow does the right semilunar valve prevent? a. Backflow of blood to the right atrium during ventricular contraction b. Blood flowing from the aorta back into the heart when the ventricle is filling c. Blood flowing from the pulmonary artery to the right ventricle when the heart is relaxing d. Blood flowing from the right atrium to the vena cava when the right atrium contracts 13. Explain the differences between the results shown for vein and artery. 14. The diagram shows the human heart. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 29  After a red blood cell picks up oxygen in the lungs, which sequence shows the path it could take when passing through the heart during its circuit of the body? a. I → II → III → IV b. II → I → IV → III c. IV → III → I → II d. IV → III → II → I 15. Which feature of capillaries distinguishes them from arteries and veins? a. Narrow diameter b. Valves to prevent backflow c. Thick muscular walls d. Elastic tissue 16. Which vessel carries deoxygenated blood away from the heart? a. Aorta b. Pulmonary artery c. Vena cava d. Pulmonary vein 17. The diagram shows red blood cells and undifferentiated tissue cells. [Source: © International Baccalaureate Organization 2017] Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 30 Diffusion of oxygen from blood cells to tissue cells is represented by arrow 3 in the diagram. What molecules are shown diffusing by arrow 1 and arrow 2? 18. In which blood vessel connected to the heart does blood have the lowest carbon dioxide concentration? a. Pulmonary vein b. Vena cava c. Pulmonary artery d. Coronary vein 19. Describe how increased capillary density could affect the aerobic capacity of muscle. 20. Which is a valid comparison between arteries and veins? 21. Outline the 11 steps of the double circulation system of the heart 22. Distinguish between ventilation and gas exchange 23. Which process results in the exchange of gases across the membrane of pneumocytes? a. Active transport b. Simple diffusion Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 31  c. Facilitated diffusion d. Mass flow 24. Explain the process of gas exchange taking place in the alveoli. 25. Outline the process of inspiration in humans. 26. Outline how ventilation in humans ensures a supply of oxygen. 27. Which conditions are correct for inspiration? 28. Outline the difference between a sensory neuron and a motor neuron 29. Outline the different types of sensory neurons 30. Define reflex arc 31. Explain how a reflex arc occurs in steps. 32. Define neurotransmitter 33. Define hormone 34. Compare and contrast hormonal and nervous communication 35. Distinguish between the innate and adaptive immune system 36. Explain the role of cells in the defence against infectious diseases 37. Outline the role of lymphocytes in defence against disease. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 32  MARKSCHEME of Formative Questions 1. Organ Location Function Heart Centre of chest keep blood flowing through the body, thus carry oxygen and glucose towards cells and waste away from cells Brain Head Body’s control centre and where memory is stored Kidneys Back of abdomen on either Filter blood and form urine side Liver Right side of abdomen filtering blood, secreting bile that is needed for digestion , and producing proteins necessary for blood clotting. Lungs Either side of upper chest exchanging oxygen and carbon dioxide with the blood 2. a. Integumentary: first defence against invaders (i.e., pathogens), and it also helps regulate body temperature and eliminate wastes in sweat b. Skeletal: supporting the body and giving it shape; also protect internal organs, store calcium, and produce red and white blood cells. c. Muscular system: skeletal muscles allow for movement of voluntary organs; smooth muscle controls the involuntary movements of internal organs: cardiac muscle controls the involuntary beating of heart d. Nervous: controls both voluntary and involuntary responses of the human organism and also detects and processes sensory information. e. Endocrine system: made up of glands that secrete hormones into the blood, which carries the hormones throughout the body. f. Cardiovascular system: transport – of oxygen from lungs into cells, of carbon dioxide from cells into lungs; also equalizes body temperature and transports endocrine hormones g. Urinary: which filter excess water and a waste product called urea from the blood and form urine h. Respiratory: to deliver oxygen to the blood and remove carbon dioxide from the body i. Lymphatic; remove pathogens and cellular debris from the lymph or blood. j. Digestive: digestion and absorption of nutrients k. Reproductive: to produce and deposit sperm and/or egg cells Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 33  l. Immune: detection, destruction and protection against pathogens 3. Enzyme Site of action Substrate digested End products Amylase Mouth, Starch (branched Maltose, glucose duodenum glucose) Protease Stomach, Protein Amino acids duodenum Lipase Duodenum Fat Fatty acids and glycerol 4. Digestion consists of mechanical breakdown of foods into smaller particles via the action of the teeth, and via contractions of the muscles along the alimentary tract. Absorption is a process where digested food molecules (small enough) are taken in through the wall of the small intestine into the bloodstream, being subsequently distributed throughout the body. 5. 6. IB DP question, your answer should include as much as possible: Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 34  a. a. increase the surface area for absorption; b. absorption of digested foods/nutrients c. absorption of mineral ions/vitamins b. a. (celiac disease/gluten causes) much smaller villi/flattened villi/smaller surface area (of villi) / no villi b. (smaller villi leads to) less efficient/less/slower/poor absorption OR nutrients/energy lost / fatigue/malnutrition may result c. (celiac sufferers) must eat a gluten-free diet / WTTE Note that this question requires an explain not an outline. 7. B 8. D 9. IB DP question, your answer should include as much as possible: a. «simple» diffusion of nutrients along/down a concentration gradient b. example of simple diffusion, eg: fatty acids c. facilitated diffusion of nutrients involves movement through channel proteins d. example of nutrient for facilitated diffusion eg: fructose e. active transport of nutrients against a concentration gradient / involving protein pumps f. example of active transport, eg: (iron) ions/glucose/amino acids g. endocytosis / by means of vesicles h. example of nutrient for endocytosis, eg: cholesterol in lipoprotein particles 10. IB DP question, your answer should include as much as possible: a. contraction of muscle «layers»/peristalsis helps move food OR circular muscle contraction prevents backward movement of food Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 35  OR longitudinal muscle contraction moves food along gut b. peristalsis/muscle contractions mix food with intestinal enzymes c. enzymes digest macromolecules into monomers Accept an example for mp c d. pancreatic enzymes/amylase/lipase/endopeptidase «chemically» digest food in«lumen of» small intestine e. «pancreatic» amylase digests starch OR lipases digest lipids/fats/triglycerides OR endopeptidases/dipeptidases digest proteins/polypeptides f. f. bile/bicarbonate secreted into the small intestine creates favorable pH for enzymes OR bile emulsifies fat g. some final digestion into monomers is associated with epithelial cells/epithelium «of small intestine» h. villi/microvilli increase surface area for better absorption i. villi absorb products of digestion/monomers/mineral «ions»/vitamins j. glucose/amino acids enter blood «capillaries» OR lipids enter lymph vessels/lacteals k. absorption involves active transport/diffusion/facilitated diffusion l. different nutrients are absorbed by different transport mechanisms 11. A 12. C 13. IB DP question, your answer should include as much as possible: a. veins have thinner walls (than arteries); b. veins sustain lower (blood) pressure (than arteries); c. when stretched, veins become longer (than arteries); d. veins have less muscle/elastic (fibre in their) walls (than arteries); Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 36  e. veins have lower elasticity/recover less/remain more stretched (than arteries after weights removed); Accept inverse for arteries in all cases. Do not accept a listing of numerical values without explanation 14. B 15. A 16. B 17. C 18. A 19. IB DP question, your answer should include as much as possible: a. increases amount of blood taken to the muscle b. increases the delivery of oxygen/glucose/nutrients for aerobic respiration c. increases the removal of carbon dioxide/wastes OR increased gas exchange 20. C 21. This answer is as detailed as possible, but you were just required to outline: 1. Deoxygenated blood from the body leaves the systemic circulation when it enters the right atrium through the superior and inferior venae cava. 2. The blood is then pumped through the tricuspid valve into the right ventricle. 3. From the right ventricle, blood is pumped through the pulmonary valve and into the pulmonary artery. 4. The pulmonary artery splits into the right and left pulmonary arteries and travel to each lung. 5. At the lungs, the blood travels through capillary beds on the alveoli where gas exchange occurs, removing carbon dioxide and adding oxygen to the blood. 6. The oxygenated blood then leaves the lungs through pulmonary veins, which returns it to the left atrium, completing the pulmonary circuit. 7. Oxygenated blood enters the left atrium from the pulmonary veins. The blood is then pumped through the mitral valve into the left ventricle. 8. From the left ventricle, blood is pumped through the aortic valve and into the aorta, the body’s largest artery. 9. The aorta arches and branches into major arteries to the upper body before passing through the diaphragm, where it branches further into several arteries which supply the lower parts of the body. 10. The arteries branch into smaller arteries, arterioles, and finally capillaries. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 37  11. The deoxygenated blood continues through the capillaries which merge into venules, then veins, and finally the venae cava, which drain into the right atrium of the heart, through the pulmonary circulation to be oxygenated. 22. Ventilation of the lungs (breathing) ensures there is always fresh air entering the alveoli, which means there is always a difference in oxygen concentration – concentration gradient – between the alveolar air and the blood. Gas exchange occurs in the lungs between alveolar air and the blood of the pulmonary capillaries. Gas exchange occurs through diffusion. 23. B 24. IB DP question, your answer should include as much as possible: a. O2 diffuses into blood and CO2 diffuses out from blood b. blood entering the alveoli is high in CO2/low in O2 OR air in alveolus is high in O2/low in CO2 c. diffusion (in either direction) take place due to concentration gradients d. concentration gradients maintained by ventilation/blood flow e. large surface area created by many alveoli/spherical shape of alveoli for more efficient diffusion f. rich supply of capillaries (around alveoli) allows efficient exchange g. type I pneumocytes are thin to allow easy diffusion/short distances h. gases must dissolve in liquid lining of alveolus in order to be exchanged i. type II pneumocytes secrete surfactants to reduce surface tension/prevent lungs sticking together j. type II pneumocytes create moist conditions in alveoli 25. IB DP question, your answer should include as much as possible: a. diaphragm and external intercostal muscles contract b. diaphragm moves down/becomes flatter OR external intercostals raise the ribcage/move the ribcage up/out c. muscles/diaphragm/intercostals increase volume of thorax/expand the thorax OR muscles/diaphragm/intercostals decrease pressure in the thorax d. as volume «of thorax/lungs» increases the pressure decreases Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 38  e. air enters «lungs» due to decreased pressure/higher pressure outside body f. air flows to lungs through trachea and bronchi/bronchioles Accept thoracic cavity or chest cavity in place of thorax in any part of the answer. Do not allow “oxygen” instead of air in mpe or mpf. 26. IB DP question, your answer should include as much as possible: a. ventilation is exchange of gases between lungs and air. b. during inhalation diaphragm contracts AND lowers. Both needed. c. external intercostal muscles contract, raising ribs upwards and outwards d. increase in volume AND decrease in pressure within thoracic cavity e. air drawn into alveoli bringing fresh supply of oxygen f. oxygen concentration in alveolar sacs is higher than in blood capillaries g. «oxygen concentration gradient» causes oxygen to diffuse out of alveoli into red blood cells in capillaries 27. A 28. A sensory neuron transmits impulses from a receptor, such as those in the eye or ear, to a more central location in the nervous system, such as the spinal cord or brain. A motor neuron transmits impulses from a central area of the nervous system to an effector, such as a muscle. 29. Thermoreceptors respond to changes in temperature. Photoreceptors respond to changes in light. Chemoreceptors respond to changes in chemicals associated with odours, tastes, and dissolved substances in the blood. Mechanoreceptors respond to changes in pressure or touch. Sonoreceptors respond to changes in sounds 30. A reflex arc is a neurological and sensory mechanism that controls a reflex, an immediate response to a particular stimulus. 31. Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 39  1. The response begins at the fingers, where sensory neurons, such as thermoreceptors, are stimulated by the high temperature they sense. 2. The same thermoreceptors are activated by the ‘extreme heat’, initiating a signal called a nerve impulse/action potential, along the length (axon) of the sensory neuron (itself). 3. When the nerve impulse reaches the end of the sensory neuron (axon terminal, synapse), it causes chemicals called neurotransmitters to be released from the sensory neuron. 4. The released neurotransmitters float across the synaptic cleft between neurons, reaching neighbouring neurons; allowing the nerve impulse to continuous throughout all neighbouring neurons (step 2. – 4.). 5. In the spinal cord, the ‘extreme heat’ nerve impulse reaches the relay neurons, that relay/pass the nerve impulse from the sensory neurons to the motor neurons. 6. The motor neurons synapse with each other, extending the spinal cord and down along the arm and the hand. 7. The motor neurons synapse with muscle cells in one’s arm and hand, passing the nerve impulse, which causes both to contract, and one pulls one’s arm and hand away from the hot pot. 32. Chemical released by nerve cells at the synaptic cleft. 33. A hormone is a product of living cells, which circulates in fluids like blood or sap, and produces a specific, usually stimulatory effect on the activity of cells, remote from its point of origin. Therefore, hormones are chemical messengers that aid the communication between different parts of the body by sending chemical signals from one to the other 34. IB DP question, your answer should include as much as possible: Similarities a. both used for communication between cells/tissues/organs/parts of the body / WTTE b. both cause a response/change in specific/target cells OR both use chemicals that bind to receptors / hormones and neurotransmitters are both chemicals c. both can stimulate or inhibit (processes in target cells) / WTTE d. both can work over long distances/between widely separated parts of the body / WTTE e. both under (overall) control of the brain/CNS / brain (has role in) sending hormones and nerve impulses f. both use feedback mechanisms/negative feedback / both used in homeostasis Differences Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 40  m. example of use of hormonal and use of nervous communication 35. The innate immune system is the body's first line of defence against germs entering the body. It responds in the same way to all germs and foreign substances, which is why it is sometimes referred to as the "nonspecific" immune system. The adaptive immune system takes over if the innate immune system is not able to destroy the germs. It specifically targets the type of germ that is causing the infection. But to do that it first needs to identify the germ. This means that it is slower to respond than the innate immune system, but when it does it is more accurate. 36. IB DP question, your answer should include as much as possible: a. cells of skin provide a physical barrier/produce fatty acids/lactic acid/lysozyme which stops entry of microbes OR mucous membranes produce mucus to trap pathogens b. platelets start the clotting process preventing access of pathogens; c. (two types of) white blood cells fight infections in the body; d. phagocytes ingest pathogens (by endocytosis/phagocytosis); e. gives non-specific immunity to diseases / ingest any type of pathogen; f. production of antibodies by lymphocytes/B cells; g. in response to particular pathogens/antigens; h. gives specific immunity; i. lymphocyte/B cell makes only one type of antibody; j. plasma cells produce large quantity of (one type of) antibody; k. some lymphocytes act/remain as memory cells; l. can quickly reproduce to form a clone of plasma cells if a pathogen carrying a specific antigen is re- encountered; m. results in faster defence against second exposure to specific antigen/pathogen/disease Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 41  37. IB DP question, your answer should include as much as possible: a. produce antibodies b. memory cells confer immunity c. specific immunity results from production of antibodies specific to a particular antigen d. recognize pathogens e. destroy foreign cells/cancer cells Booklet created by Mrs. Margarida Coimbra Edited for academic year 2023-2024 at Oeiras International School (OIS) | Page: 42