MYP 5 Homeostasis and Hormones 2024-2025 PDF

HOMEOSTASIS Homeostasis refers to the processes that keep the internal conditions of the body within rcertain narrow limits What is Homeostasis? Body cells work best if they have the correct Temperature Water levels Glucose concentration Your body has mechanisms to keep the cells...

HOMEOSTASIS Homeostasis refers to the processes that keep the internal conditions of the body within rcertain narrow limits What is Homeostasis? Body cells work best if they have the correct Temperature Water levels Glucose concentration Your body has mechanisms to keep the cells in a constant environment. What is Homeostasis? “LA FIXITÉ DU MILIEU INTÉRIEUR EST LA CONDITION DE LA VIE LIBRE.” (Claude Bernard)1 What is Homeostasis? The constancy of the internal environment is the condition for free and independent life: the mechanism that makes it possible is that which assured the maintenance, within the internal environment, of all the conditions necessary for the life of the elements. Standard Equilibrium values Internal equilibrium is maintained by adjusting physiological processes, including: Body temperature (normally between 36 – 38ºC) Carbon dioxide concentration (normally 35 – 45 mmHg) Standard Equilibrium values Internal equilibrium is maintained by adjusting physiological processes, including: Blood pH (normally between 7.35 – 7.45) Blood glucose levels (normally 75 – 95 mg/dL) Water balance (varies depending on individual body size) Body temperature What are some of the factors that cause the human body to gain heat Group discussion 2 minutes Body temperature Factors causing heat gain: Gain of heat directly from the enviroment through radiation and conduction. Excessive fat deposits make it harder to lose the heat that is generated through activity. Heavy excersise especially with excessive clothing. Controlling body temperature What mechanisms do humans use to ensure they maintain the same body temperature on a hot day?. What mechanisms are there to cool the body down? 1. Sweating When your body is hot, sweat glands are stimulated to release sweat. The liquid sweat turns into a gas (it evaporates) To do this, it needs heat. It gets that heat from your skin. As your skin loses heat, it cools down. Sweating The skin  What mechanisms are there to cool the body down? 2. Vasodilation Your blood carries most of the heat energy around your body. There are capillaries underneath your skin that can be filled with blood if you get too hot.  What mechanisms are there to cool the body down? 2. Vasodilation This brings the blood closer to the surface of the skin so more heat can be lost. This is why you look red when you are hot!  This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger). Body temperature What are some of the factors that cause the human body to lose heat Group discussion 2 minutes Body temperature Factors causing heat loss: Wind chill factor accelerates heat loss through convenction. Heat loss due to temperature difference between the body and the environment. The rate of heat loss is increased by being wet, by inactivity, inadequate clothing. Controlling body temperature Human beings have a body temperature between 36ºC and 38ºC. If your body is in a cold environment of about -2ºC your body temperature would still be maintained at between 36ºC to 38ºC Controlling body temperature What mechanisms do humans use to ensure they maintain the same body temperature on a cold day?. What mechanisms are there to warm the body up? 1. Vasoconstriction This is the opposite of vasodilation The capillaries underneath your skin get constricted (shut off). This takes the blood away from the surface of the skin so less heat can be lost.  This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off). What mechanisms are there to warm the body up? 2. Piloerection This is when the hairs on your skin “stand up”. It is sometimes called “goose bumps” or “chicken skin”! The hairs trap a layer of air next to the skin which is then warmed by the body heat The air becomes an insulating layer. What mechanisms are there to warm the body up? 3 Shivering This is when there is uncontrolled contraction of the body muscles to generate heat. HOMEOSTASIS There are two main systems responsible for the homeostatic control mechanisms of the body: the nervous system the endocrine system HOMEOSTASIS The nervous and endocrine systems of the body are communication systems that coordinate activities of the body by either sending electrical impulses (messages) or chemical messages  THE NERVOUS SYSTEM THE ENDOCRINE SYSTEM It is a system of organs It is a system of organs that coordinates activities that coordinates activities of the body by sending of the body by sending electrical impulses chemicals (hormones) in through nerves the blood THE ENDOCRINE SYSTEM THE ENDOCRINE SYSTEM The endocrine system is a group of endocrine glands that release their secretions directly into the bloodstream THE ENDOCRINE SYSTEM Endocrine glands are special groups of cells that secrete hormones into the blood HORMONES HORMONES Hormones are chemical messengers secreted by cells or glands of the endocrine system that control and regulate the activity of other cells or glands in other parts of the body HORMONES The hormones are transported in the blood to specific target cells HORMONES The target tissue may be found in a single gland or organ or may be scattered throughout the body so that many areas are affected EXAMPLES OF ENDOCRINE GLANDS, THEIR HORMONES, TARGET ORGANS AND FUNCTIONS CONTROL OF BLOOD GLUCOSE CONCENTRATION Understanding Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration CONTROL OF BLOOD GLUCOSE CONCENTRATION The body needs glucose to make ATP via cell respiration However, blood glucose values need to be kept within certain limits of 70 to 130 milligrams per decilitre (mg/dl) CONTROL OF BLOOD GLUCOSE CONCENTRATION This ensures that the blood has a certain osmotic balance as well as ensuring that the cells of the body, especially brain cells, have an ample supply of glucose for cellular respiration CONTROL OF BLOOD GLUCOSE CONCENTRATION The organs responsible for the homeostatic control of blood glucose concentration are the Liver and Pancreas THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION Understanding Insulin and glucagon are secreted by β and α cells of the pancreas respectively to control blood glucose concentration THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION The homeostatic control of blood glucose concentration is carried out by two hormones secreted by endocrine tissue in the pancreas called the islets of Langerhans THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION There are two types of cells in the islets of Langerhans that secrete the two different types of hormones: the alpha cells and the beta cells THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION The α and β cells act as the receptors and the central control for this homeostatic mechanism THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION The alpha cells synthesize and secrete glucagon if the blood glucose levels falls below the set point THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION Glucagon stimulates the conversion of glycogen to glucose in the liver cells and its release into the blood, increasing the concentration THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION The beta cells synthesize and secrete insulin if the blood glucose levels rise above the set point THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION Insulin stimulates the uptake of glucose by the liver skeletal muscles and its conversion into glycogen in those cells THE ROLE OF THE PANCREAS IN THE CONTROL OF BLOOD GLUCOSE CONCENTRATION Insulin reduces blood glucose concentration DIABETES Application Causes and treatment of Type I and Type II diabetes DIABETES Diabetes mellitus is a condition where a person has a consistently too high blood glucose levels even during prolonged fasting, leading to elevated levels of glucose in the urine DIABETES It is caused by the loss of the ability to control blood glucose levels DIABETES If untreated, diabetes can lead to serious long-term complications, such as heart disease, kidney failure and retinal damage SYMPTOMS OF DIABETES SYMPTOMS OF DIABETES Fatigue Increased thirst Blurred vision/ glaucoma Rapid heart rate and breathing rate or deep breathing SYMPTOMS OF DIABETES Behavioural changes Confusion Fainting Unconsciousness or comatose Dizziness SYMPTOMS OF DIABETES Slow (wound) healing Poor circulation Frequent urination SYMPTOMS OF DIABETES Weight loss, Nausea Vomiting Abdominal pain Hunger TYPES OF DIABETES Application Causes and treatment of Type I and Type II diabetes TYPES OF DIABETES There are two types of diabetes: Type I diabetes and Type II diabetes TYPE I DIABETES Application Causes and treatment of Type I and Type II diabetes TYPE I DIABETES Type I diabetes is also known as insulin-dependent diabetes mellitus (IDDM) or early or juvenile-onset diabetes TYPE I DIABETES This is because it mainly affects young people TYPE I DIABETES Type I diabetes is an autoimmune disease in which the immune system attacks the beta cells of the islets of Langerhans in the pancreas and destroy them TYPE I DIABETES The loss of the beta cells means that insulin is no longer produced or sufficient, so blood glucose concentration is not controlled TYPE I DIABETES The risk factor associated with type I diabetes is genetic predisposition TREATMENT OF TYPE I DIABETES Application Causes and treatment of Type I and Type II diabetes TREATMENT OF TYPE I DIABETES Type II diabetes is treated by taking blood samples regularly to test the glucose concentration and injecting insulin when it is too high or likely to become too high TREATMENT OF TYPE I DIABETES The injections are often done before a meal to prevent a peak of blood glucose as the food is digested and absorbed TREATMENT OF TYPE I DIABETES Mini-pumps which deliver the exact volumes of insulin that is needed can also be used TREATMENT OF TYPE I DIABETES A carefully controlled diet also helps to maintain a near-constant concentration of glucose in the blood TREATMENT OF TYPE I DIABETES A permanent cure may be achieved by stimulating stem cells to develop into fully functional beta cells which can then be implanted in the pancreas TYPE II DIABETES Application Causes and treatment of Type I and Type II diabetes TYPE II DIABETES Type II diabetes is also known as non insulin-dependent diabetes mellitus (NIDDM), or adult- onset diabetes TYPE II DIABETES This is because it often begins later in life TYPE II DIABETES Type II results from an inability to process or respond to insulin because of a deficiency of insulin receptors or glucose transporters on target cells TYPE II DIABETES The main risk factors associated with type II diabetes include sugary, fatty diets, prolonged obesity due to habitual overeating and lack of exercise together with genetic factors that affect metabolism TREATMENT OF TYPE II DIABETES Application Causes and treatment of Type I and Type II diabetes TREATMENT OF TYPE II DIABETES Type II diabetes is treated by regulating the diet to include frequent small meals, rather than large infrequent meals TREATMENT OF TYPE II DIABETES Foods with high sugar content should be avoided Starchy food should only be eaten if it has a low glycemic index, indicating that it is digested slowly TREATMENT OF TYPE II DIABETES High fibre foods should be included to slow the digestion of other foods TREATMENT OF TYPE II DIABETES Weight loss and strenuous exercise are beneficial as they improve insulin uptake and action MELATONIN Humans are adapted to living in a 24 hour cycle and have rhythms in behaviour that fit this cycle known as the circadian rhythm MELATONIN Circadian rhythms are driven by an internal (endogenous) circadian clock, although they can be modulated by external factors MELATONIN The circadian rhythm is controlled the by the secretion of a hormone called melatonin by the pineal gland of the brain MELATONIN The pineal gland is a small endocrine gland found near to the centre of the brain between the two hemispheres It is reddish-grey and shaped like a pine cone about 0.8 cm long MELATONIN The cicardian rhythms in humans depends on two groups of cells in the hypothalamus called the suprachiasmatic nuclei (SCN) MELATONIN The SCN set a daily rhythm about the time of day In the brain, they control the secretion of melatonin by the pineal gland MELATONIN Light exposure to the retina is relayed via the SCN in the hypothalamus which then passes the information to the pineal gland MELATONIN The pineal gland then adjusts the melatonin concentrations in the blood to coincide with a normal 24- hour cycle MELATONIN Melatonin secretion is suppressed by bright light (principally blue wavelengths) MELATONIN Thus, melatonin secretion increases in the evening and drops to a low level at dawn in response to light MELATONIN The body reacts to melatonin in several ways: the body core temperature drops receptors in the kidney cause decreased urine production all of which increases sleepiness MELATONIN Over a prolonged period, melatonin secretion becomes entrained to anticipate the onset of darkness and the approach of day MELATONIN AND JET LAG Application Causes of jet lag and use of melatonin to alleviate it MELATONIN AND JET LAG Jet lag is a physiological condition resulting from a change to the body’s normal circadian rhythm when a person crosses three or more time zones during air travel MELATONIN AND JET LAG The symptoms of jet lag include: difficulty in remaining awake in daylight hours difficulty in sleeping through the night fatigue headaches irritability indigestion CAUSES OF JET LAG Jet lag is caused by the body’s inability to rapidly adjust to a new time zone following extended air travel ('jet' lag) from one time zone to another CAUSES OF JET LAG The pineal gland continues to secrete melatonin according to the old time zone so that the sleep schedule is not synchronised to the new time zone CAUSES OF JET LAG This is because the level of light one is exposed to is no longer matched up with the levels of melatonin in the body CAUSES OF JET LAG Jet lag only lasts for a few days, during which impulses are sent by ganglion cells in the retina to the SCN when they detect light and helps the body to adjust to the new regime TREATMENT OF JET LAG WITH MELATONIN Application Causes of jet lag and use of melatonin to alleviate it TREATMENT OF JET LAG WITH MELATONIN Melatonin is sometimes used to prevent or reduce jet lag It is orally taken at the time when sleep should ideally be commencing TREATMENT OF JET LAG WITH MELATONIN Most trials of melatonin have shown that it is effective at promoting sleep and helping to reduce jet lag especially if travelling eastwards and crossing five or more time zones ADRENAL GLANDS ADRENAL GLANDS These glands are attached to the back of the abdominal cavity, one above each kidney ADRENAL GLANDS One part of the adrenal gland is a zone called the adrenal medulla ADRENAL GLANDS The medulla receives nerves from the brain and produces the hormone adrenaline ADRENALINE ADRENALINE It is the hormone secreted in ‘fight or flight’ situations ADRENALINE Adrenaline bridges the gap between nervous and hormonal control because of its fast and short lived action IN-CLASS ACTIVITY What are fight or flight situations? What might be some examples of fight or flight situations? EFFECT OF ADRENALINE ON THE BODY EFFECT OF ADRENALINE ON THE BODY It causes breathing to become faster and deeper EFFECT OF ADRENALINE ON THE BODY It causes the heart beats faster, resulting in an increase in pulse rate EFFECT OF ADRENALINE ON THE BODY It causes the pupils of the eyes to dilate, making them look much blacker ROLE OF ADRENALINE IN THE CHEMICAL CONTROL OF METABOLIC ACTIVITY ROLE OF ADRENALINE IN THE CHEMICAL CONTROL OF METABOLIC ACTIVITY It causes the liver to convert glycogen to glucose, increasing the release of glucose in the blood for muscle contraction ROLE OF ADRENALINE IN THE CHEMICAL CONTROL OF METABOLIC ACTIVITY It causes the heart rate to increase so that glucose and oxygen are delivered to the muscles for energy release TRIAL QUESTION EXAMPLES OF SITUATIONS IN WHICH ADRENALINE SECRETION INCREASES EXAMPLES OF SITUATIONS IN WHICH ADRENALINE SECRETION INCREASES Seeing a snake crawl past you When a masked man walks up to you Going on a roller coaster IMPORTANCE OF ADRENALINE PRODUCTION IMPORTANCE OF ADRENALINE PRODUCTION It allows for escape or avoidance or preparation for activity or to survive ADVANTAGE OF RELEASING ADRENALINE TO COORDINATE THE BODY RATHER THAN USING NERVE IMPULSES ADVANTAGE OF RELEASING ADRENALINE TO COORDINATE THE BODY RATHER THAN USING NERVE IMPULSES Adrenaline travels around the whole body and there is no need to transmit impulses to specific places ADVANTAGE OF RELEASING ADRENALINE TO COORDINATE THE BODY RATHER THAN USING NERVE IMPULSES It allows the stimulation of many or simultaneous responses ADVANTAGE OF RELEASING ADRENALINE TO COORDINATE THE BODY RATHER THAN USING NERVE IMPULSES Less energy needed Its effect(s) last longer TRIAL QUESTION FEATURE NERVOUS ENDOCRINE SYSTEM SYSTEM Structures Nerves Glands Form of information Electrical impulses Hormones (chemicals) Pathways Along neurones Blood Speed of transfer Fast Slow Duration of effect Short-lived Long-lasting  Kidneys Skill: Drawing and labelling a diagram of the human kidney The kidney functions as the blood’s filtration and water balancing system – it removes metabolic wastes for excretion Blood enters the kidneys via the renal artery and exits the kidneys via the renal vein Blood is filtered by specialised structures called nephrons which produce urine The urine is transported from the kidneys via the ureter, where it is stored by the bladder prior to excretion Understanding: The composition of blood in the renal artery is different from that in the renal vein The kidney contains specialised structures called nephrons which function to filter the blood and eliminate wastes Consequently, the composition of blood entering the kidney (via renal artery) differs to that exiting the kidney (via renal vein) Blood in the renal vein (i.e. after the kidney) will have: Less urea (large amounts of urea is removed via the nephrons to form urine) Less water and solutes / ions (amount removed will depend on the hydration status of the individual) Less glucose and oxygen (not eliminated, but used by the kidney to generate energy and fuel metabolic reactions) More carbon dioxide (produced by the kidneys as a by-product of metabolic reactions) Nephrons Skill: Annotation of diagrams of the nephron The nephron is the functional unit of the kidney, with each nephron being comprised of the following components: Bowman’s capsule – first part of the nephron where blood is initially filtered (to form filtrate) Proximal convoluted tubule – folded structure connected to the Bowman’s capsule where selective reabsorption occurs Loop of Henle – a selectively permeable loop that descends into the medulla and establishes a salt gradient Distal convoluted tubule – a folded structure connected to the loop of Henle where further selective reabsorption occurs Nephrons The blood to be filtered enters the Bowman’s capsule via an afferent arteriole and leaves the capsule via an efferent arteriole Within the Bowman’s capsule, the blood is filtered at a capillary tuft called the glomerulus The efferent arteriole forms a blood network called the vasa recta that reabsorbs components of the filtrate from the nephron Each nephron connects to a collecting duct (via the distal convoluted tubule), which feed into the renal pelvis The collecting ducts are shared by nephrons and hence are not technically considered to be part of a single nephron Nephron Function Nephrons filter blood and then reabsorb useful materials from the filtrate before eliminating the remainder as urine This process occurs over three key stages: Ultrafiltration – Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate Selective reabsorption – Usable materials are reabsorbed in convoluted tubules (both proximal and distal) Osmoregulation – The loop of Henle establishes a salt gradient, which draws water out of the collecting duct Ultrafiltration Ultrafiltration is the first of three processes by which metabolic wastes are separated from the blood and urine is formed It is the non-specific filtration of the blood under high pressure and occurs in the Bowman’s capsule of the nephron The basement membrane is size-selective and restricts the passage of blood cells and large proteins Hence when the blood is filtered, the filtrate formed does not contain any blood cells, platelets or plasma proteins Selective Reabsorption Selective reabsorption is the second of the three processes by which blood is filtered and urine is formed It involves the reuptake of useful substances from the filtrate and occurs in the convoluted tubules (proximal and distal) The majority of selective reabsorption occurs in the proximal convoluted tubule, which extends from the Bowman’s capsule The proximal convoluted tubule has a microvilli cell lining to increase the surface area for material absorption from the filtrate The tubule is a single cell thick and connected by tight junctions, which function to create a thin tubular surface with no gaps Osmoregulation Understanding: The loop of Henle maintains hypertonic conditions in the medulla Osmoregulation is the third of three processes by which blood is filtered and urine is formed Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism Osmoregulation occurs in the medulla of the kidney and involves two key events: The loop of Henle establishes a salt gradient (hypertonicity) in the medulla Anti-diuretic hormone (AD) regulates the level of water reabsorption in the collecting duct Understanding: ADH controls reabsorption of water in the collecting duct Water Reabsorption As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis The amount of water released from the collecting ducts to be retained by the body is controlled by anti-diuretic hormone (ADH) ADH is released from the posterior pituitary in response to dehydration (detected by osmoreceptors in the hypothalamus) ADH increases the permeability of the collecting duct to water, by upregulating production of aquaporins (water channels) This means less water remains in the filtrate, urine becomes concentrated and the individual urinates less (i.e. anti-diuresis) When an individual is suitably hydrated, ADH levels decrease and less water is reabsorbed (resulting in more dilute urine) Remember: ADH is produced when you Are DeHydrated Kidney Disease Application: Blood cells, glucose, proteins and drugs are detected in urinary tests Kidney diseases are conditions which incapacitate the kidney’s ability to filter waste products from the blood Individuals with kidney diseases will demonstrate a reduced glomerular filtration rate (GFR) If untreated, kidney diseases can lead to kidney failure – which is life threatening Urinary Analysis Kidneys prevent the excretion of blood cells and proteins (during ultrafiltration), as well as glucose (selective reabsorption) Hence the presence of these materials in urine can be used as an indicator of disease Glucose: The presence of glucose in urine is a common indicator of diabetes (high blood glucose = incomplete reabsorption) Proteins: High quantities of protein in urine may indicate disease (e.g. PKU) or hormonal conditions (e.g. hCG = pregnancy) Blood cells: The presence of blood in urine can indicate a variety of diseases, including certain infections and cancer Drugs / toxins: Many drugs pass through the body into urine and can be detected (e.g. performance enhancing drugs) Application: Treatment of kidney failure by hemodialysis or kidney transplant Hemodialysis Kidney dialysis involves the external filtering of blood in order to remove metabolic wastes in patients with kidney failure Blood is removed and pumped through a dialyzer, which has two key functions that are common to biological membranes: It contains a porous membrane that is semi-permeable (restricts passage of certain materials) It introduces fresh dialysis fluid and removes wastes to maintain an appropriate concentration gradient Kidney dialysis treatments typically last about 4 hours and occur 3 times a week – these treatments can be effective for years Kidney Transplant Hemodialysis ensures continued blood filtering, but does not address the underlying issue affecting kidney function The best long-term treatment for kidney failure is a kidney transplant: The transplanted kidney is grafted into the abdomen, with arteries, veins and ureter connected to the recipient’s vessels Donors must typically be a close genetic match in order to minimise the potential for graft rejection Donors can survive with one kidney and so may commonly donate the second to relative suffering kidney failure