IB BIO - 6.2 The transport system

• 6.2.1 

  • Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

• 6.2.1 

  • Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart.

• 6.2.2 

  • State that the coronary arteries supply heart muscle with oxygen and nutrients.

• The coronary arteries are a pair of blood vessels that supply the heart muscle (myocardium) with oxygen and nutrients, ensuring its proper function. Here's an outline of how the coronary arteries supply the heart muscle:

  • 1. Origin and Structure: The coronary arteries originate from the base of the aorta, just above the aortic valve, which is the main artery that carries oxygenated blood from the heart to the rest of the body. The coronary arteries branch off from the ascending aorta and encircle the heart, forming a network of blood vessels that penetrate the myocardium.

  • 2. Distribution: The coronary arteries branch into smaller arteries and arterioles that penetrate the myocardium and supply oxygenated blood to the heart muscle cells (cardiomyocytes). These blood vessels distribute oxygen, nutrients, and other essential substances to every part of the myocardium, ensuring that all regions of the heart receive adequate blood supply.

  • 3. Oxygen and Nutrient Delivery: Oxygenated blood from the coronary arteries is delivered to the myocardium during diastole, the phase of the cardiac cycle when the heart relaxes and fills with blood. As the heart muscle relaxes, the coronary arteries are compressed less by surrounding tissue, allowing blood to flow more freely through them and deliver oxygen and nutrients to the myocardial cells.

  • 4. Coronary Circulation: The coronary arteries form a complex network of blood vessels within the myocardium, consisting of epicardial arteries on the surface of the heart and intramural arteries that penetrate deep into the myocardium. These arteries give rise to smaller branches, arterioles, and capillaries that supply blood to individual myocardial cells. Oxygen and nutrients diffuse from the capillaries into the surrounding tissue, providing the necessary fuel for cellular metabolism and energy production.

  • 5. Regulation of Blood Flow: Coronary blood flow is regulated by various factors, including metabolic demands, neural inputs, and local vasodilator and vasoconstrictor mechanisms. During periods of increased cardiac activity or oxygen demand, such as during exercise or stress, coronary blood flow is enhanced to meet the metabolic needs of the myocardium. Conversely, during rest or relaxation, coronary blood flow may decrease to conserve energy.

  • 6. Venous Drainage: After delivering oxygen and nutrients to the myocardium, deoxygenated blood is collected by cardiac veins and drained into the coronary sinus, a large vein located on the posterior surface of the heart. The coronary sinus empties into the right atrium of the heart, completing the cycle of coronary circulation.

• In summary, the coronary arteries supply the heart muscle with oxygen and nutrients by forming a network of blood vessels that penetrate the myocardium and deliver blood to every part of the heart. This ensures the continuous nourishment and oxygenation of myocardial cells, enabling the heart to function effectively as a pump.

• 6.2.3 

  • Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.

• The action of the heart involves a series of coordinated events that allow it to collect blood, pump blood, and regulate blood flow through the opening and closing of valves. Here's an explanation of each aspect:

  • 1. Collecting Blood:

    •    - Blood enters the heart through two large veins called the superior vena cava and inferior vena cava, which carry deoxygenated blood from the body back to the heart.

    •    - The right atrium receives the deoxygenated blood from the venae cavae. As the atrium fills with blood, its muscular walls relax, allowing it to expand and accommodate the incoming blood.

    •    - Simultaneously, the left atrium receives oxygenated blood from the lungs through the pulmonary veins. It also expands to accommodate the incoming blood.

  • 2. Pumping Blood:

    •    - Atria Contraction: Both atria contract simultaneously (atrial systole), pushing the blood into the ventricles through open atrioventricular (AV) valves (tricuspid valve on the right side and mitral valve on the left side).

    •    - Ventricular Contraction: The atrioventricular valves close to prevent backflow of blood into the atria. The ventricles contract (ventricular systole), forcing blood out of the heart through the semilunar valves (pulmonary valve on the right side and aortic valve on the left side).

    •    - Blood is pumped from the right ventricle into the pulmonary artery, which carries it to the lungs for oxygenation. Simultaneously, blood is pumped from the left ventricle into the aorta, which distributes oxygenated blood to the rest of the body.

  • 3. Opening and Closing of Valves:

    •    - Atrioventricular (AV) Valves: These valves, including the tricuspid valve on the right side and the mitral valve on the left side, open to allow blood to flow from the atria into the ventricles during atrial systole. They close during ventricular systole to prevent backflow of blood into the atria.

    •    - Semilunar Valves: These valves, including the pulmonary valve on the right side and the aortic valve on the left side, open to allow blood to flow from the ventricles into the pulmonary artery and aorta, respectively, during ventricular systole. They close to prevent backflow of blood into the ventricles during diastole.

• The opening and closing of the heart valves are controlled by changes in pressure within the chambers of the heart and the contraction and relaxation of the heart muscle. This rhythmic sequence of events ensures the efficient and coordinated pumping of blood through the heart and circulation throughout the body, allowing for the delivery of oxygen and nutrients to tissues and the removal of waste products.

• 6.2.4 

  • Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).

• The control of the heartbeat involves a complex interplay of intrinsic and extrinsic factors that regulate myogenic muscle contraction within the heart. Here's an outline of the key components involved in the control of the heartbeat:

  • 1. Myogenic Muscle Contraction:

    •    - The heartbeat is primarily myogenic, meaning it originates within the heart muscle itself rather than being initiated by external stimuli.

    •    - Specialized cardiac muscle cells called pacemaker cells, located in the sinoatrial (SA) node and atrioventricular (AV) node, generate electrical impulses that trigger contraction of the heart muscle.

  • 2. Role of the Pacemaker:

    •    - The sinoatrial (SA) node, located in the right atrium, serves as the primary pacemaker of the heart. It generates rhythmic electrical impulses at regular intervals, initiating each heartbeat.

    •    - The electrical impulses generated by the SA node spread rapidly across the atria, causing them to contract and pump blood into the ventricles.

  • 3. Nervous Control:

    •    - The autonomic nervous system, composed of the sympathetic and parasympathetic branches, modulates the activity of the heart.

    •    - The sympathetic nervous system, activated during times of stress or increased physical activity, releases neurotransmitters such as norepinephrine (noradrenaline), which increases the heart rate and force of contraction.

    •    - The parasympathetic nervous system, activated during rest or relaxation, releases neurotransmitters such as acetylcholine, which slows the heart rate and decreases the force of contraction.

  • 4. Role of the Medulla of the Brain:

    •    - The medulla oblongata, a region of the brainstem, contains cardiovascular control centers that regulate heart rate and rhythm.

    •    - The medulla receives input from sensory receptors (such as baroreceptors and chemoreceptors) that monitor blood pressure, blood oxygen levels, and other physiological parameters.

    •    - Based on this input, the medulla adjusts the activity of the autonomic nervous system to maintain cardiovascular homeostasis.

  • 5. Epinephrine (Adrenaline):

    •    - The adrenal glands, located atop the kidneys, release epinephrine (adrenaline) into the bloodstream in response to stress or stimulation by the sympathetic nervous system.

    •    - Epinephrine acts on cardiac muscle cells to increase heart rate and contractility, enhancing the ability of the heart to pump blood to vital organs during fight-or-flight responses.

• Overall, the control of the heartbeat involves the intrinsic rhythmicity of pacemaker cells, modulation by the autonomic nervous system, integration by cardiovascular control centers in the brainstem, and hormonal regulation by epinephrine. These mechanisms work together to ensure the coordination and efficiency of cardiac function in response to changing physiological demands.

• 6.2.5 

  • Explain the relationship between the structure and function of arteries, capillaries and veins.

• Arteries, capillaries, and veins are three types of blood vessels in the circulatory system, each with distinct structures and functions that are closely related to their roles in the circulation of blood throughout the body. Here's an explanation of the relationship between the structure and function of arteries, capillaries, and veins:

  • 1. Arteries:

    •    - Structure: Arteries have thick, elastic walls composed of three layers: the tunica intima (innermost layer), tunica media (middle layer), and tunica externa (outermost layer). The tunica media is particularly thick and contains a high proportion of smooth muscle fibers and elastic fibers, allowing arteries to withstand the high pressure generated by the heart's pumping action.

    •    - Function: Arteries carry oxygenated blood away from the heart to various tissues and organs throughout the body. The elastic nature of arterial walls enables them to expand and recoil in response to the pulsatile flow of blood from the heart, helping to maintain steady blood pressure and ensuring continuous blood flow to tissues during diastole (relaxation phase of the cardiac cycle). The muscular walls of arteries also allow for vasoconstriction and vasodilation, regulating blood flow and distribution to different tissues based on metabolic demands.

  • 2. Capillaries:

    •    - Structure: Capillaries are the smallest and thinnest blood vessels in the body, consisting of a single layer of endothelial cells surrounded by a basement membrane. Capillaries lack smooth muscle and elastic fibers found in arteries and veins, making them highly permeable to gases, nutrients, and metabolic waste products.

    •    - Function: Capillaries facilitate the exchange of gases (oxygen and carbon dioxide), nutrients (such as glucose and amino acids), metabolic waste products (such as carbon dioxide and urea), and hormones between the blood and surrounding tissues. Their thin walls allow for rapid diffusion of substances across the endothelial barrier, ensuring efficient exchange of substances required for cellular metabolism and waste removal.

  • 3. Veins:

    •    - Structure: Veins have thinner walls compared to arteries and contain less smooth muscle and elastic tissue. They have larger lumens and are more compliant (able to stretch) than arteries. Veins also contain one-way valves, which prevent backflow of blood and facilitate venous return to the heart.

    •    - Function: Veins carry deoxygenated blood from the tissues back to the heart. Their thin walls and larger lumens allow veins to accommodate a larger volume of blood at lower pressure. One-way valves in veins prevent blood from flowing backward (against gravity) and ensure efficient return of blood to the heart, particularly from the lower extremities. Veins also serve as reservoirs for blood, helping to regulate blood volume and maintain venous pressure.

• In summary, the structure and function of arteries, capillaries, and veins are intricately related to their roles in the circulation of blood throughout the body. Arteries are designed to carry oxygenated blood away from the heart under high pressure, capillaries facilitate the exchange of substances between blood and tissues, and veins return deoxygenated blood back to the heart while serving as blood reservoirs. Each type of blood vessel is adapted to perform its specific function efficiently, contributing to the overall function of the circulatory system in maintaining homeostasis and supporting cellular metabolism.

• 6.2.6 

  • State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.

• Blood is a complex fluid that consists of several components, each with distinct roles in maintaining homeostasis and supporting bodily functions. Here's an outline of the composition of blood:

  • 1. Plasma:

    •    - Plasma is the liquid component of blood, making up approximately 55% of its volume.

    •    - It is a straw-colored fluid composed mostly of water (about 90%) along with various solutes, including proteins, electrolytes, nutrients, hormones, gases, and waste products.

    •    - Plasma serves as the medium for transporting nutrients, gases, hormones, and waste products throughout the body. It also plays a critical role in maintaining osmotic balance, pH balance, and temperature regulation.

  • 2. Erythrocytes (Red Blood Cells):

    •    - Erythrocytes are the most abundant cells in the blood, comprising approximately 40-45% of its volume.

    •    - They are specialized cells that contain hemoglobin, a protein that binds oxygen and carbon dioxide.

    •    - Erythrocytes are responsible for transporting oxygen from the lungs to tissues and organs throughout the body and transporting carbon dioxide from tissues back to the lungs for exhalation.

  • 3. Leukocytes (White Blood Cells):

    •    - Leukocytes are a diverse group of cells involved in the body's immune response and defense against pathogens.

    •    - There are two main types of leukocytes:

    •      - Phagocytes: Phagocytes, including neutrophils, monocytes, and macrophages, are cells capable of engulfing and digesting foreign particles, such as bacteria, viruses, and cellular debris.

    •      - Lymphocytes: Lymphocytes, including T cells, B cells, and natural killer (NK) cells, are cells involved in adaptive immunity. They produce antibodies, recognize and destroy infected or abnormal cells, and regulate immune responses.

  • 4. Platelets:

    •    - Platelets, also known as thrombocytes, are small, cell-like fragments derived from larger cells called megakaryocytes.

    •    - They play a crucial role in hemostasis, the process of blood clotting, by forming clots to seal off damaged blood vessels and prevent excessive bleeding.

    •    - Platelets release various substances, such as clotting factors and growth factors, that initiate and regulate the clotting process and promote tissue repair.

• In summary, blood is composed of plasma, erythrocytes (red blood cells), leukocytes (white blood cells), and platelets. Each component has specific functions that contribute to the overall health and function of the circulatory and immune systems, ensuring proper oxygen transport, immune defense, and hemostasis.

• 6.2.7 

  • State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.

• The blood serves as a vital transport medium in the body, facilitating the circulation of various substances to and from tissues and organs. Here's an outline of how the following substances are transported by the blood:

  • 1. Nutrients:

    •    - Nutrients, such as glucose, amino acids, fatty acids, vitamins, and minerals, are absorbed from the digestive tract and transported in the bloodstream to tissues and organs throughout the body.

    •    - Glucose is transported by facilitated diffusion or active transport across cell membranes, while amino acids and fatty acids are transported bound to carrier proteins in the plasma.

    •    - Once delivered to tissues, nutrients are taken up by cells and used as energy sources or building blocks for cellular metabolism and growth.

  • 2. Oxygen:

    •    - Oxygen is transported from the lungs to tissues and organs throughout the body via the bloodstream.

    •    - Oxygen molecules bind reversibly to hemoglobin, a protein found in erythrocytes (red blood cells), forming oxyhemoglobin.

    •    - Oxyhemoglobin is carried in the blood to tissues where oxygen is released from hemoglobin and diffuses into cells for cellular respiration.

  • 3. Carbon Dioxide:

    •    - Carbon dioxide is produced as a waste product of cellular metabolism in tissues.

    •    - Carbon dioxide molecules diffuse into the bloodstream and are transported in the plasma, mainly as bicarbonate ions (HCO3-) and dissolved gas.

    •    - In red blood cells, carbon dioxide reacts with water to form carbonic acid (H2CO3), which dissociates into bicarbonate ions and hydrogen ions. This reaction is catalyzed by the enzyme carbonic anhydrase.

    •    - Bicarbonate ions are transported back to the lungs in the plasma, where they are converted back into carbon dioxide for exhalation.

  • 4. Hormones:

    •    - Hormones are chemical messengers produced by endocrine glands and other tissues that regulate various physiological processes in the body.

    •    - Hormones are released into the bloodstream and transported to target tissues or organs, where they exert their specific effects by binding to receptors on target cells.

    •   - Hormones can be transported either freely dissolved in the plasma or bound to carrier proteins, depending on their chemical properties.

  • 5. Antibodies:

    •    - Antibodies, also known as immunoglobulins, are proteins produced by plasma cells (a type of white blood cell) in response to the presence of foreign antigens.

    •    - Antibodies circulate in the bloodstream and lymphatic system, where they bind to specific antigens (such as pathogens or toxins), marking them for destruction by other immune cells.

  • 6. Urea:

    •    - Urea is a waste product of protein metabolism that is produced in the liver and excreted by the kidneys.

    •    - Urea is transported in the bloodstream from the liver to the kidneys, where it is filtered out of the blood and excreted in urine.

  • 7. Heat:

    •    - Heat generated by metabolic processes in tissues is transported in the bloodstream to maintain body temperature homeostasis.

    •    - Blood flow redistributes heat from internal organs to the body's periphery, facilitating heat exchange with the environment through convection and radiation.

• In summary, the blood transports nutrients, oxygen, carbon dioxide, hormones, antibodies, urea, and heat throughout the body, ensuring the proper functioning of cells and organs and maintaining overall homeostasis.