The document discusses excretion and homeostasis in the body. It covers the roles of the liver and kidneys in excretion. The liver forms urea from excess amino acids and filters toxins from the bloodstream. The kidneys filter waste from the blood to form urine, selectively reabsorbing nutrients. Hormones regulate water reabsorption to maintain osmotic balance.
A2 - Unit 4 - Module 2 - OCR - Excretion - All Notes Final Pırıl Erel
Slides specifically for OCR syallbus during A-Levels, this is for A2 - Unit 4 - Module 2 - 1.2.1 - 1.2.8. I have made these for my students and they have found them very useful.
Includes Summary Questions, Further Application questions and key definitions at the end of the slides
Slides aimed for teachers, but can be used as revision slides for students also.
More than welcome to download, good luck with exams!
1.2.3 - OCR - A2 - Module 2 - Function of the Liver by Piril ErelPırıl Erel
The liver has many important functions including controlling blood glucose and lipid levels, synthesizing proteins and bile, storing vitamins and iron, and detoxifying alcohol and drugs. The liver breaks down excess amino acids through a two-step process of deamination and the ornithine cycle to form urea, which is less toxic than ammonia and is excreted in urine. Chronic alcohol consumption can lead the liver to store fatty acids instead of breaking them down, resulting in fatty liver disease. Genetic variations in cytochrome P450 enzymes mean some people more effectively break down toxic molecules like drugs.
The document discusses homeostasis and osmoregulation in animals. It explains that animals must maintain fairly narrow concentrations of water and solutes. It then describes different mechanisms that aquatic, desert, and marine animals use for osmoregulation. These include adaptations for water uptake, conservation of solutes, and regulation of water and solute balance between internal fluids and the external environment. The document also discusses the roles of the kidneys, nephrons, and associated structures in vertebrate osmoregulation and excretion.
The document summarizes key concepts about osmoregulation and excretion in animals. It discusses how different animals, such as fish, terrestrial vertebrates, and invertebrates, regulate water and salt balance and excrete waste through various organs like kidneys, gills, and nephridia. In humans, the kidneys play an important role in homeostasis by excreting urea and maintaining water-salt balance and acid-base balance. The kidneys work with other systems like the lungs, skin, and hormones to precisely control fluid and electrolyte levels in the blood.
The kidneys play a key role in regulating acid-base balance through excreting either acidic or basic urine. The kidneys precisely control blood hydrogen ion concentration around a normal pH of 7.4 by reabsorbing bicarbonate ions and secreting hydrogen ions into the tubules. When acidosis occurs, the kidneys produce bicarbonate and retain it to raise blood pH back to normal. In alkalosis, the kidneys fail to reabsorb filtered bicarbonate, excreting it in urine to lower blood pH toward normal. Along with buffer systems and respiration, the kidneys help defend the body against changes in hydrogen ion levels.
The document provides instructions for comparing urine samples from two subjects and identifying which sample belongs to each subject. It discusses observing the color, volume, smell, temperature, and texture/taste of solutions A and B. Subject X's urine was collected one hour after drinking water, while subject Y's urine was not collected for 5 hours without drinking water. The document also contains information about the structure and functions of the urinary system.
This document discusses the removal of metabolic waste from the body through excretion. It describes two main substances: carbon dioxide and nitrogen-containing compounds like urea. Carbon dioxide is produced by cells during respiration and is transported to the lungs via the bloodstream to be exhaled. Urea is produced in the liver from excess amino acids and transported to the kidneys to be excreted in urine. The document also provides details on where these wastes are produced and excreted from the body.
The urinary system acts as the body's filtration and fluid balance system. The kidneys filter blood and regulate electrolyte and fluid levels through producing urine. The kidneys contain millions of nephrons, which are the functional units that filter blood in the glomerulus and reabsorb and secrete substances through the renal tubules. Precise control of glomerular filtration rate, tubular reabsorption and secretion allows the kidneys to regulate urine volume and composition to maintain fluid and electrolyte balance.
A2 - Unit 4 - Module 2 - OCR - Excretion - All Notes Final Pırıl Erel
Slides specifically for OCR syallbus during A-Levels, this is for A2 - Unit 4 - Module 2 - 1.2.1 - 1.2.8. I have made these for my students and they have found them very useful.
Includes Summary Questions, Further Application questions and key definitions at the end of the slides
Slides aimed for teachers, but can be used as revision slides for students also.
More than welcome to download, good luck with exams!
1.2.3 - OCR - A2 - Module 2 - Function of the Liver by Piril ErelPırıl Erel
The liver has many important functions including controlling blood glucose and lipid levels, synthesizing proteins and bile, storing vitamins and iron, and detoxifying alcohol and drugs. The liver breaks down excess amino acids through a two-step process of deamination and the ornithine cycle to form urea, which is less toxic than ammonia and is excreted in urine. Chronic alcohol consumption can lead the liver to store fatty acids instead of breaking them down, resulting in fatty liver disease. Genetic variations in cytochrome P450 enzymes mean some people more effectively break down toxic molecules like drugs.
The document discusses homeostasis and osmoregulation in animals. It explains that animals must maintain fairly narrow concentrations of water and solutes. It then describes different mechanisms that aquatic, desert, and marine animals use for osmoregulation. These include adaptations for water uptake, conservation of solutes, and regulation of water and solute balance between internal fluids and the external environment. The document also discusses the roles of the kidneys, nephrons, and associated structures in vertebrate osmoregulation and excretion.
The document summarizes key concepts about osmoregulation and excretion in animals. It discusses how different animals, such as fish, terrestrial vertebrates, and invertebrates, regulate water and salt balance and excrete waste through various organs like kidneys, gills, and nephridia. In humans, the kidneys play an important role in homeostasis by excreting urea and maintaining water-salt balance and acid-base balance. The kidneys work with other systems like the lungs, skin, and hormones to precisely control fluid and electrolyte levels in the blood.
The kidneys play a key role in regulating acid-base balance through excreting either acidic or basic urine. The kidneys precisely control blood hydrogen ion concentration around a normal pH of 7.4 by reabsorbing bicarbonate ions and secreting hydrogen ions into the tubules. When acidosis occurs, the kidneys produce bicarbonate and retain it to raise blood pH back to normal. In alkalosis, the kidneys fail to reabsorb filtered bicarbonate, excreting it in urine to lower blood pH toward normal. Along with buffer systems and respiration, the kidneys help defend the body against changes in hydrogen ion levels.
The document provides instructions for comparing urine samples from two subjects and identifying which sample belongs to each subject. It discusses observing the color, volume, smell, temperature, and texture/taste of solutions A and B. Subject X's urine was collected one hour after drinking water, while subject Y's urine was not collected for 5 hours without drinking water. The document also contains information about the structure and functions of the urinary system.
This document discusses the removal of metabolic waste from the body through excretion. It describes two main substances: carbon dioxide and nitrogen-containing compounds like urea. Carbon dioxide is produced by cells during respiration and is transported to the lungs via the bloodstream to be exhaled. Urea is produced in the liver from excess amino acids and transported to the kidneys to be excreted in urine. The document also provides details on where these wastes are produced and excreted from the body.
The urinary system acts as the body's filtration and fluid balance system. The kidneys filter blood and regulate electrolyte and fluid levels through producing urine. The kidneys contain millions of nephrons, which are the functional units that filter blood in the glomerulus and reabsorb and secrete substances through the renal tubules. Precise control of glomerular filtration rate, tubular reabsorption and secretion allows the kidneys to regulate urine volume and composition to maintain fluid and electrolyte balance.
The document discusses the physiology of the kidneys, describing their role in maintaining homeostasis through functions like regulating water balance and electrolyte concentrations, as well as their internal structure including nephrons and the processes of glomerular filtration, reabsorption of water and salts, and production of urine. Key concepts covered include kidney anatomy, the roles of different kidney structures like the nephron and collecting duct, and physiological mechanisms involved in filtration, reabsorption, and regulation of fluids and electrolytes.
The document provides an overview of the human gastrointestinal system, including its main components and functions. It describes the pathway that food takes through the digestive system, starting with ingestion in the mouth and ending with elimination in the large intestine and anus. Key parts discussed include the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. The roles of saliva, gastric juices, enzymes, hormones and bile in breaking down food are also summarized.
The document summarizes the functions and components of the urinary/excretory system. The key functions of the kidneys are to excrete waste, regulate blood volume and pressure, control solute concentration in the blood, regulate pH levels, regulate red blood cell synthesis, and aid in vitamin D synthesis. The major components are the kidneys, ureters, urinary bladder, and urethra. Each kidney contains over a million nephrons, which are the functional units that form urine through filtration, reabsorption, and secretion processes.
The document summarizes key aspects of excretion and the kidney's role in excretion and maintaining water balance. It describes the three main processes involved - ultrafiltration in the malpighian body, selective reabsorption in the proximal convoluted tubule, and urine formation in the loop of henle and collecting duct. It also outlines the structures of the nephron and kidney, and how different regions work together to filter and regulate blood content.
INTERGRATED RESPONSE TO A MEAL V. INTESTINAL PHASE (ii)SAMOEINESH
The document summarizes the anatomy and physiology of the liver and biliary system. It describes:
1. The liver's dual secretory and excretory functions, and its location in the abdomen.
2. The hepatic lobes, lobules, hepatocytes, and bile canaliculi that make up the liver's structure.
3. How bile is secreted by hepatocytes and stored/concentrated in the gallbladder before release into the small intestine.
The document discusses excretion in animals and plants. It describes the process of excretion and the major waste products excreted, such as carbon dioxide, urea, and bile pigments. It also outlines the key excretory organs in mammals, including the lungs, kidneys, skin, and liver. The kidneys play an important role in homeostasis by removing nitrogenous wastes like urea from the blood and regulating water and salt concentrations. The basic unit of the kidney is the nephron, where blood is filtered to form urine and allow for reabsorption of useful substances and removal of wastes.
The circulatory system consists of the heart and blood vessels. The heart has four chambers and circulates blood through two circuits. The electrical conduction system begins with the sinoatrial node and coordinates heart contractions. Blood is composed of plasma and formed elements like red blood cells, white blood cells, and platelets. The cardiac cycle involves repeated heart contraction and relaxation that pumps blood through the vessels. Blood vessels include arteries, arterioles, capillaries, venules and veins, with arteries carrying oxygenated blood away from the heart and veins carrying deoxygenated blood back to the heart.
The document discusses excretion and the kidney. It begins by defining excretion as the removal of metabolic waste from the body. The two main waste products excreted are carbon dioxide and urea. Urea is produced in the liver from excess amino acids and removed from the blood by the kidneys. The kidneys contain nephrons, which are the functional units. Nephrons contain a glomerulus for blood filtration and a tubule for reabsorption and urine production. Urine is formed through ultrafiltration in the glomerulus and reabsorption along the nephron tubule. Most reabsorption occurs in the proximal tubule, while the loop of Henle helps concentrate urine through countercurrent
The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter waste from the blood to produce urine. Each kidney contains over a million nephrons, the functional units that filter blood. Urine is composed of water and waste products like urea and passes from the kidneys through the ureters to the bladder. Hormones and the nervous system help regulate urine production to maintain fluid balance and blood pressure within tight limits.
Chapter 11 Excretion Lesson 2 - The Mammalian Urinary Systemj3di79
The mammalian urinary system consists of kidneys, ureters, a urinary bladder, and a urethra. The kidneys remove urea and excess water from the blood while the ureters, bladder, and urethra transport and store urine. Urine formation involves ultrafiltration of small molecules through the kidney tubules and selective reabsorption of useful substances like glucose and amino acids back into the bloodstream. The final urine contains excess water, mineral salts, and nitrogenous waste products like urea.
The kidneys and urinary system work to remove waste from the body through urine. The kidneys contain millions of nephrons that filter blood to produce urine. Glomerular filtration removes wastes and excess molecules from the bloodstream. Most of the filtered water and useful molecules are reabsorbed, while wastes like urea remain. Tubular secretion further regulates ions. The resulting urine is transported through the ureters to the bladder and then exits through urination. The kidneys play a vital role in homeostasis by precisely regulating waste removal and maintaining the body's internal balance.
The kidneys are paired organs located retroperitoneally that are responsible for filtering blood and regulating fluid and electrolyte balance. The kidneys contain nephrons, which are the functional filtering units. Blood enters nephrons via the glomerulus and is filtered, and the filtrate undergoes reabsorption and secretion as it passes through the renal tubules. Urine is formed and collects in the renal pelvis before exiting through the ureters. Kidney function can be assessed through urinalysis and measurements of substances such as creatinine, BUN, and inulin clearance.
The document provides an overview of the digestive system, including its main components and functions. It discusses the roles and structures of the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. Key points covered include the breakdown of carbohydrates, proteins and fats by digestive enzymes, and the absorption of nutrients into the bloodstream. The digestive tract protects itself through secretions, peristalsis and layers of tissue.
The document summarizes chapter 20 of Hole's Human Anatomy and Physiology textbook on the urinary system. It describes the key components of the urinary system including the kidneys, ureters, urinary bladder and urethra. It explains the location and structure of the kidneys and nephrons, and how they function to filter blood and produce urine through glomerular filtration, tubular reabsorption and secretion. It also briefly discusses how glomerular filtration rate is regulated to maintain homeostasis.
The kidney is made up of approximately 1 million filtering units called nephrons. Each nephron contains a glomerulus for initial blood filtration and a tubule for reabsorption and waste excretion. The kidneys play crucial roles in regulating blood pressure, electrolyte balance, and removing waste from the blood in the form of urine. Common kidney functions include filtering the blood, reabsorbing necessary nutrients, and secreting hormones to support other bodily processes. Damage to the kidneys can impair these functions and potentially lead to serious health issues like kidney failure.
The document discusses the structure and function of the kidneys. It describes the key roles of the kidneys in excretion, homeostasis, osmoregulation, and regulating salts and pH in the body. The gross and microscopic structures of the kidneys are outlined. Key components include the cortex, medulla, nephrons, glomeruli, and tubules. Ultrafiltration and selective reabsorption processes are explained in relation to kidney function. The production and transport of urea from deamination of proteins is also summarized.
The kidneys remove waste from the blood in the form of urea and regulate water and electrolyte balance. Each nephron acts as the functional unit of the kidney, filtering blood in the cortex and reabsorbing useful substances along the tubule in the medulla. Urine is stored in the bladder and released through the urethra. Dialysis can temporarily perform the functions of damaged kidneys by filtering blood through a semipermeable membrane. A kidney transplant is the best long term treatment but requires immunosuppressant drugs to prevent rejection by the recipient's immune system.
1st science 19 urinary system structure and functionsShirley Sison
The document discusses the structure and function of the urinary system. It describes the location and roles of the kidneys, ureters, bladder, and urethra. The kidneys filter waste from the blood to produce urine, and contain nephrons that remove waste and regulate chemical balances before urine passes through the ureters to the bladder for storage and eventual expulsion through the urethra.
hi guys!
This is my latest slide on Excretory system, based on Cambridge GCE 'O' level syllabus.
These slides cover much on the essential points and might not be really comprehensive.
These slides are constructed to be interactive to further boost your understanding by eliminating superfluous words and adding more animations.
Thus, I RECOMMEND you to download the slides to access the many animations to interact with your mind.
Follow my slideshare profile to receive updates on new slides!!
or contact me:
Email: fazzydoo@gmail.com
facebook: faiz abdullah
twitter: @fazzydoo
if you have questions or would like to address mistakes on my slides or simply just to request me to personally make your slides.
All images and materials are copyright protected and have no affiliations to me
The document discusses cellular respiration. It begins by explaining that respiration uses energy stored in molecules like carbohydrates and fats to produce ATP through pathways like glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation in the mitochondria. It then discusses the specific multi-step pathways of aerobic cellular respiration, the role of coenzymes, and the structure and function of mitochondria. It concludes by describing anaerobic respiration pathways like lactic acid fermentation in humans and alcoholic fermentation in yeast that can function without oxygen.
Photosynthesis has two stages - a light-dependent stage that uses light energy to produce ATP and NADPH, and a light-independent stage where CO2 is fixed using the ATP and NADPH to produce glucose. [1] The light-dependent stage occurs in the thylakoid membranes of chloroplasts where light is absorbed by chlorophyll and drives photophosphorylation to produce ATP and the reduction of NADP. [2] The light-independent Calvin cycle then uses the ATP and NADPH to fix CO2 into 3-carbon compounds that are used to ultimately produce glucose and other carbohydrates. [3] Photosynthesis provides the essential organic molecules that sustain all life on Earth.
The document discusses the physiology of the kidneys, describing their role in maintaining homeostasis through functions like regulating water balance and electrolyte concentrations, as well as their internal structure including nephrons and the processes of glomerular filtration, reabsorption of water and salts, and production of urine. Key concepts covered include kidney anatomy, the roles of different kidney structures like the nephron and collecting duct, and physiological mechanisms involved in filtration, reabsorption, and regulation of fluids and electrolytes.
The document provides an overview of the human gastrointestinal system, including its main components and functions. It describes the pathway that food takes through the digestive system, starting with ingestion in the mouth and ending with elimination in the large intestine and anus. Key parts discussed include the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. The roles of saliva, gastric juices, enzymes, hormones and bile in breaking down food are also summarized.
The document summarizes the functions and components of the urinary/excretory system. The key functions of the kidneys are to excrete waste, regulate blood volume and pressure, control solute concentration in the blood, regulate pH levels, regulate red blood cell synthesis, and aid in vitamin D synthesis. The major components are the kidneys, ureters, urinary bladder, and urethra. Each kidney contains over a million nephrons, which are the functional units that form urine through filtration, reabsorption, and secretion processes.
The document summarizes key aspects of excretion and the kidney's role in excretion and maintaining water balance. It describes the three main processes involved - ultrafiltration in the malpighian body, selective reabsorption in the proximal convoluted tubule, and urine formation in the loop of henle and collecting duct. It also outlines the structures of the nephron and kidney, and how different regions work together to filter and regulate blood content.
INTERGRATED RESPONSE TO A MEAL V. INTESTINAL PHASE (ii)SAMOEINESH
The document summarizes the anatomy and physiology of the liver and biliary system. It describes:
1. The liver's dual secretory and excretory functions, and its location in the abdomen.
2. The hepatic lobes, lobules, hepatocytes, and bile canaliculi that make up the liver's structure.
3. How bile is secreted by hepatocytes and stored/concentrated in the gallbladder before release into the small intestine.
The document discusses excretion in animals and plants. It describes the process of excretion and the major waste products excreted, such as carbon dioxide, urea, and bile pigments. It also outlines the key excretory organs in mammals, including the lungs, kidneys, skin, and liver. The kidneys play an important role in homeostasis by removing nitrogenous wastes like urea from the blood and regulating water and salt concentrations. The basic unit of the kidney is the nephron, where blood is filtered to form urine and allow for reabsorption of useful substances and removal of wastes.
The circulatory system consists of the heart and blood vessels. The heart has four chambers and circulates blood through two circuits. The electrical conduction system begins with the sinoatrial node and coordinates heart contractions. Blood is composed of plasma and formed elements like red blood cells, white blood cells, and platelets. The cardiac cycle involves repeated heart contraction and relaxation that pumps blood through the vessels. Blood vessels include arteries, arterioles, capillaries, venules and veins, with arteries carrying oxygenated blood away from the heart and veins carrying deoxygenated blood back to the heart.
The document discusses excretion and the kidney. It begins by defining excretion as the removal of metabolic waste from the body. The two main waste products excreted are carbon dioxide and urea. Urea is produced in the liver from excess amino acids and removed from the blood by the kidneys. The kidneys contain nephrons, which are the functional units. Nephrons contain a glomerulus for blood filtration and a tubule for reabsorption and urine production. Urine is formed through ultrafiltration in the glomerulus and reabsorption along the nephron tubule. Most reabsorption occurs in the proximal tubule, while the loop of Henle helps concentrate urine through countercurrent
The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter waste from the blood to produce urine. Each kidney contains over a million nephrons, the functional units that filter blood. Urine is composed of water and waste products like urea and passes from the kidneys through the ureters to the bladder. Hormones and the nervous system help regulate urine production to maintain fluid balance and blood pressure within tight limits.
Chapter 11 Excretion Lesson 2 - The Mammalian Urinary Systemj3di79
The mammalian urinary system consists of kidneys, ureters, a urinary bladder, and a urethra. The kidneys remove urea and excess water from the blood while the ureters, bladder, and urethra transport and store urine. Urine formation involves ultrafiltration of small molecules through the kidney tubules and selective reabsorption of useful substances like glucose and amino acids back into the bloodstream. The final urine contains excess water, mineral salts, and nitrogenous waste products like urea.
The kidneys and urinary system work to remove waste from the body through urine. The kidneys contain millions of nephrons that filter blood to produce urine. Glomerular filtration removes wastes and excess molecules from the bloodstream. Most of the filtered water and useful molecules are reabsorbed, while wastes like urea remain. Tubular secretion further regulates ions. The resulting urine is transported through the ureters to the bladder and then exits through urination. The kidneys play a vital role in homeostasis by precisely regulating waste removal and maintaining the body's internal balance.
The kidneys are paired organs located retroperitoneally that are responsible for filtering blood and regulating fluid and electrolyte balance. The kidneys contain nephrons, which are the functional filtering units. Blood enters nephrons via the glomerulus and is filtered, and the filtrate undergoes reabsorption and secretion as it passes through the renal tubules. Urine is formed and collects in the renal pelvis before exiting through the ureters. Kidney function can be assessed through urinalysis and measurements of substances such as creatinine, BUN, and inulin clearance.
The document provides an overview of the digestive system, including its main components and functions. It discusses the roles and structures of the mouth, esophagus, stomach, small intestine, large intestine, liver, gallbladder and pancreas. Key points covered include the breakdown of carbohydrates, proteins and fats by digestive enzymes, and the absorption of nutrients into the bloodstream. The digestive tract protects itself through secretions, peristalsis and layers of tissue.
The document summarizes chapter 20 of Hole's Human Anatomy and Physiology textbook on the urinary system. It describes the key components of the urinary system including the kidneys, ureters, urinary bladder and urethra. It explains the location and structure of the kidneys and nephrons, and how they function to filter blood and produce urine through glomerular filtration, tubular reabsorption and secretion. It also briefly discusses how glomerular filtration rate is regulated to maintain homeostasis.
The kidney is made up of approximately 1 million filtering units called nephrons. Each nephron contains a glomerulus for initial blood filtration and a tubule for reabsorption and waste excretion. The kidneys play crucial roles in regulating blood pressure, electrolyte balance, and removing waste from the blood in the form of urine. Common kidney functions include filtering the blood, reabsorbing necessary nutrients, and secreting hormones to support other bodily processes. Damage to the kidneys can impair these functions and potentially lead to serious health issues like kidney failure.
The document discusses the structure and function of the kidneys. It describes the key roles of the kidneys in excretion, homeostasis, osmoregulation, and regulating salts and pH in the body. The gross and microscopic structures of the kidneys are outlined. Key components include the cortex, medulla, nephrons, glomeruli, and tubules. Ultrafiltration and selective reabsorption processes are explained in relation to kidney function. The production and transport of urea from deamination of proteins is also summarized.
The kidneys remove waste from the blood in the form of urea and regulate water and electrolyte balance. Each nephron acts as the functional unit of the kidney, filtering blood in the cortex and reabsorbing useful substances along the tubule in the medulla. Urine is stored in the bladder and released through the urethra. Dialysis can temporarily perform the functions of damaged kidneys by filtering blood through a semipermeable membrane. A kidney transplant is the best long term treatment but requires immunosuppressant drugs to prevent rejection by the recipient's immune system.
1st science 19 urinary system structure and functionsShirley Sison
The document discusses the structure and function of the urinary system. It describes the location and roles of the kidneys, ureters, bladder, and urethra. The kidneys filter waste from the blood to produce urine, and contain nephrons that remove waste and regulate chemical balances before urine passes through the ureters to the bladder for storage and eventual expulsion through the urethra.
hi guys!
This is my latest slide on Excretory system, based on Cambridge GCE 'O' level syllabus.
These slides cover much on the essential points and might not be really comprehensive.
These slides are constructed to be interactive to further boost your understanding by eliminating superfluous words and adding more animations.
Thus, I RECOMMEND you to download the slides to access the many animations to interact with your mind.
Follow my slideshare profile to receive updates on new slides!!
or contact me:
Email: fazzydoo@gmail.com
facebook: faiz abdullah
twitter: @fazzydoo
if you have questions or would like to address mistakes on my slides or simply just to request me to personally make your slides.
All images and materials are copyright protected and have no affiliations to me
The document discusses cellular respiration. It begins by explaining that respiration uses energy stored in molecules like carbohydrates and fats to produce ATP through pathways like glycolysis, the link reaction, the Krebs cycle, and oxidative phosphorylation in the mitochondria. It then discusses the specific multi-step pathways of aerobic cellular respiration, the role of coenzymes, and the structure and function of mitochondria. It concludes by describing anaerobic respiration pathways like lactic acid fermentation in humans and alcoholic fermentation in yeast that can function without oxygen.
Photosynthesis has two stages - a light-dependent stage that uses light energy to produce ATP and NADPH, and a light-independent stage where CO2 is fixed using the ATP and NADPH to produce glucose. [1] The light-dependent stage occurs in the thylakoid membranes of chloroplasts where light is absorbed by chlorophyll and drives photophosphorylation to produce ATP and the reduction of NADP. [2] The light-independent Calvin cycle then uses the ATP and NADPH to fix CO2 into 3-carbon compounds that are used to ultimately produce glucose and other carbohydrates. [3] Photosynthesis provides the essential organic molecules that sustain all life on Earth.
This document discusses biology concepts related to communication and homeostasis. It covers 3 main topics: 1) the need for cellular communication to maintain internal conditions, 2) examples of neuronal and hormonal communication systems that allow organisms to respond to environmental changes, and 3) the process of homeostasis, including negative feedback loops that help regulate internal conditions. Key points are stimulus-response relationships, mechanisms of signal transmission between cells, and the role of communication systems in coordinating responses to keep internal environments within safe ranges despite external fluctuations.
This document discusses ecosystems and sustainability. It defines key ecosystem concepts like producers, consumers, decomposers, trophic levels, food chains and food webs. It explains how energy and nutrients cycle through ecosystems and how human activities like using pesticides, fertilizers and different forestry practices can influence these cycles and food chains. Succession and factors affecting population sizes are also covered. The document advocates for sustainable forest management techniques like rotational coppicing to balance resource use and conservation of biodiversity.
The document provides an overview of biology concepts related to cellular control, biotechnology, environments, and responding to the environment. It covers topics such as how DNA codes for proteins through gene expression and protein synthesis, cellular control mechanisms like the lac operon, genetic inheritance and mutations, developmental biology processes like apoptosis and meiosis, and more. The document is organized into 8 sections that describe these concepts through explanatory text, diagrams, and lists.
1. The document is Issue 13 of Big Picture magazine, published in January 2011. The issue focuses on cells and cell biology.
2. It contains articles on the structure and function of cells, how cells divide and develop, how cells interact with their environment, the lifespan of cells and what happens when they die, stem cells and their roles in development and medical research.
3. The issue also includes "real voices" interviews with three people discussing how cells impact their lives.
1. The document contains 25 multiple choice questions about the heart's conduction system and cardiac cycle. It tests knowledge about the sinoatrial node as the normal pacemaker, conduction pathways like the atrioventricular node and Purkinje fibers, the functions of different structures, and the sequence and timing of heart events.
2. Key aspects addressed include the heart's ability to spontaneously depolarize without nervous input, the roles of different conduction tissues, what happens if the sinoatrial node is blocked, the effects of heart block, and explanations for features of ventricular depolarization and the cardiac cycle.
3. The questions cover both details of the heart's electrical conduction system and the broader physiology of how imp
The document summarizes key evidence and experiments that helped establish the nature of genes as made of DNA:
1. In the 1940s-50s, experiments showed that genes were made of DNA, not proteins, including Avery's finding that a bacterial agent causing genetic change was inactivated by DNAase.
2. Analysis of DNA content found it was constant in all body cells of an organism and diploid in somatic cells versus haploid in germ cells.
3. Hershey and Chase's experiment in 1952 demonstrated that the genetic material injected by bacteriophages into bacteria was DNA, not proteins.
4. All these findings helped Watson and Crick propose their 1953 double helix
A Fact sheet specifically tailored for OCR AS Biology, however can be suitably applied to Edexcel and AQA specifications.
This fact sheet focuses on malaria. More fact sheets can be found on my channel.
The document summarizes several key parts of the central nervous system (CNS). It describes the meninges as protective membranes that surround the CNS and cerebrospinal fluid (CSF), which is contained within the inner meninges. It then discusses the cerebrum, made up of left and right cerebral hemispheres connected by the corpus callosum. Each hemisphere is divided into four lobes and performs sensory, association, and motor functions. The thalamus channels sensory signals to the appropriate brain region, while the hypothalamus is involved in homeostasis. The cerebellum coordinates movement and posture, and the medulla regulates autonomic functions.
Palms are tropical and subtropical plants that require carbon dioxide and water, along with sunlight, to perform photosynthesis. During this process, plants use carbon dioxide and water to produce oxygen and energy-rich sugars through their chloroplasts, located mainly in their leaves. The green pigment chlorophyll allows plants to absorb sunlight to drive photosynthesis.
A Fact sheet specifically tailored for OCR AS Biology, however can be suitably applied to Edexcel and AQA specifications.
This fact sheet focuses on HIV / AIDS. More fact sheets can be found on my channel.
1. There are two types of cell division: mitosis and meiosis. Mitosis occurs in somatic cells during growth and repair and results in identical daughter cells. Meiosis occurs in germ cells and results in gametes with half the number of chromosomes, allowing for genetic variation in offspring.
2. Meiosis has two divisions and involves homologous chromosomes pairing up and crossing over, then separating randomly into four haploid daughter cells. This contributes to genetic diversity.
3. The key differences are that mitosis produces identical somatic cells while meiosis produces egg and sperm cells with half the normal chromosome number to allow for fertilization and genetic recombination.
This document provides guidance on writing the Biology BIOL5 exam essay. It emphasizes selecting the easier essay title and answering the question by bringing in relevant principles and concepts from multiple modules. Key points, common mistakes from past essays, and tips for scoring marks in scientific content, breadth, relevance and quality of written communication are outlined. Example essay titles from past exams cover topics like ATP use, cell structure and function, and inorganic ion use in organisms.
Here are the key points about homeostasis:
- Homeostasis refers to maintaining stable internal conditions in the body despite external changes.
- Conditions like temperature, water level, blood sugar, pH, and carbon dioxide levels are maintained within narrow ranges.
- Hormones help regulate these conditions and bring them back to normal levels when needed. Hormones are released from glands and travel through the bloodstream to target organs.
- For example, insulin and glucagon work together to maintain normal blood sugar levels. When blood sugar is too high, the pancreas releases insulin to lower it. When blood sugar is too low, the pancreas releases glucagon to raise it.
- The body also maintains a
The liver plays a key role in metabolism and homeostasis. It receives a dual blood supply and filters waste from the blood to produce urea, which is excreted. Excess alcohol is broken down but can overload the liver, causing fatty deposits. The kidneys filter blood to produce urine via nephrons and selective reabsorption maintains electrolyte balance. Kidney failure requires dialysis or transplant. Pregnancy and drug tests analyze samples for target hormones or compounds.
The excretory system removes waste from the body through various organs. The kidneys are the primary organs of excretion, removing nitrogenous wastes such as urea and excess water and salts. The kidneys contain nephrons, which filter the blood to produce urine. Urine passes from the nephrons to the bladder through the ureters for storage and later excretion through the urethra. Homeostasis is maintained as the kidneys regulate water balance and the concentration of substances in the blood and tissues.
The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The kidneys filter waste from the blood to produce urine. Urine travels from the kidneys down the ureters into the urinary bladder, where it is stored until urination. The urethra then carries urine from the bladder out of the body. The kidneys contain nephrons, which filter the blood, reabsorb useful substances, and secrete waste products to form urine and maintain homeostasis.
The document provides information about urine analysis and the urinary system. It discusses the anatomy and functions of the kidneys and other structures of the urinary system such as the ureters, bladder, and urethra. It also describes the formation of urine through glomerular filtration, tubular reabsorption, tubular secretion, and concentration. Common abnormalities of urine like proteinuria and oliguria are also summarized. The document is an in-depth review of the urinary system and urine analysis.
The document summarizes key processes related to excretion and kidney function. The kidneys remove metabolic waste from the blood in the form of urine. The liver breaks down excess amino acids into ammonia, which is converted to urea to be less toxic and transported to the kidneys. In the nephrons of the kidneys, ultrafiltration removes plasma from blood to form urine. Most of the filtrate is then reabsorbed, except for waste. The loop of Henle creates an ion gradient used to reabsorb remaining water in the collecting duct. The kidneys excrete waste and regulate water and ions to purge the body of toxins.
Cape biology unit 2-_the_kidney_and_osmoregulationHilton Ritch
The kidneys remove waste from the blood to form urine. They have an extensive blood supply so waste does not build up. Each kidney contains thousands of nephrons that filter blood to form urine in 5 steps: ultrafiltration, reabsorption, concentration in the loop of Henle, secretion in the distal tubule, and further concentration in the collecting duct. Hormones like ADH regulate water concentration to form either dilute or concentrated urine for excretion.
The excretory system eliminates wastes from the body through various organs. The lungs, skin, large intestine, liver, and urinary system all play roles in excretion. The kidneys are the primary excretory organs, filtering wastes from the blood and regulating fluid and electrolyte balance. Nephrons are the functional units of the kidney that filter blood to form urine, reabsorbing necessary substances while excreting waste.
This document provides information about excretion and the organs involved. It discusses that excretion removes metabolic wastes through organs like the skin, lungs, liver and kidneys. The kidneys are particularly important as they regulate water, remove wastes and produce hormones. The nephron is the functional unit of the kidney that filters blood to form urine, removing wastes and reabsorbing necessary materials like water.
The urinary system consists of the kidneys, ureters, bladder and urethra. The kidneys filter waste from the blood to produce urine. The nephrons in the kidneys remove wastes and regulate water and electrolyte balance. Urine travels from the kidneys down the ureters to the bladder. When full, the bladder contracts to expel urine through the urethra. The system helps maintain homeostasis by regulating water balance and removing toxins from the body.
The document discusses animal excretion and osmoregulation. It describes how animals eliminate nitrogenous waste through excretion systems and regulate water and ion concentrations through osmoregulation. The key points are:
1) Excretion involves removing nitrogenous wastes from the body through systems like the kidneys, which filter blood to produce urine for waste elimination.
2) Osmoregulation maintains water and ion balances in body fluids through mechanisms like selective reabsorption and secretion.
3) Aquatic animals like fish use specialized gills and kidney functions to regulate salt and water levels to match their environments.
The urinary system consists of the kidneys, ureters, bladder, and urethra. The kidneys filter the blood to remove wastes and produce urine. Each kidney contains over a million nephrons, the functional units of filtration. Within each nephron, blood is filtered by the glomerulus and waste products are removed through tubular reabsorption and secretion. The resulting urine is collected and stored in the bladder before exiting the body. The kidneys also regulate fluid balance and blood pressure through hormones like renin and erythropoietin.
The document discusses excretion in various organisms. In humans, the kidneys filter blood and produce urine containing waste like urea. The urine travels through the ureters to the bladder and is then excreted through the urethra. Kidneys play an important role in osmoregulation by regulating water and salt levels in the blood. Kidney failure can occur if the kidneys stop functioning, requiring dialysis or transplant treatment.
The excretory system removes waste from the body through excretion. The kidneys are the main organs of excretion, filtering waste such as urea and excess water and salts from the blood and excreting it as urine. The nephrons are the functional units of the kidneys that filter the blood in a two-step process of filtration and reabsorption, where most of the filtered water and nutrients are reabsorbed but waste remains and becomes urine. Urine is transported from the kidneys to the bladder for storage until excretion.
Marine bony fish maintain osmotic balance by drinking seawater and excreting salts to counteract water loss, while freshwater fish excrete large volumes of dilute urine and absorb salts through their gills. The kidneys play a key role in osmoregulation and excretion for humans and other animals by filtering waste from the blood into urine via nephrons, and reabsorbing useful solutes while regulating water and electrolyte levels through hormones like ADH and aldosterone.
The document discusses the structure and function of the urinary system. It describes how the kidneys, ureters, urinary bladder, and urethra work together to produce, store, and eliminate urine from the body. The kidneys filter waste from the blood to produce urine and also play an important role in maintaining water, salt, and pH balances in order to regulate blood pressure and volume. Urine is formed in microscopic tubules called nephrons through processes of filtration, reabsorption, and secretion.
This document provides information on excretion in humans and other organisms. It discusses the key organs and processes involved in excretion in the human body, including the lungs, skin, and kidneys. In the kidneys, glomerular filtration occurs, along with reabsorption of useful substances and production of urine. The liver is described as having many functions including detoxification and producing urea from excess proteins. Excretion in plants, fish, and amoebas is also summarized, noting their various adaptations for osmoregulation.
The document summarizes key concepts about osmoregulation and excretion. It discusses how marine and freshwater animals regulate water and solute levels, the nitrogenous wastes produced by different organisms, and excretory organs in invertebrates and humans. It focuses in depth on osmoregulation and waste removal in fish, the structures and functions of the human urinary system including the kidney and nephron, and how the kidney aids homeostasis through filtration, reabsorption, secretion and hormone regulation.
The document summarizes the major excretory systems of the human body. It focuses on the urinary system including the kidneys, ureters, and bladder which filter waste from the blood and produce urine for excretion. The kidneys remove metabolic waste products and regulate water, electrolyte, and acid-base balance. Urine travels from the kidneys through the ureters to the bladder for storage until release. The skin is also involved in excretion through sweat glands that help regulate body temperature and remove salts and water.
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1. Biology – Communication, Homeostasis and Energy
Module 2 – Excretion
1) EXCRETION
Excretion is the removal of metabolic waste from the body, i.e. the removal of by-
products or unwanted substances from normal cell processes.
Almost any cell product formed in excess by the metabolic processes occurring must
be excreted. The main excretory products are carbon dioxide, a waste product of
respiration, and nitrogen-containing compounds, such as urea, which is
produced in the liver from excess amino acids.
How?
Carbon dioxide diffuses out of respiring cells into the surrounding tissue fluid and
eventually into the bloodstream. It travels in the blood (mostly in the form of
hydrogencarbonate ions) to the lungs, where it diffuses through the alveoli walls and
is expired.
Urea is formed when amino acids are deaminated in the liver. Deamination is the
removal of an amine group from an amino acid to produce ammonia. The urea
travels in the bloodstream to the kidneys (dissolved in the plasma), where it is
removed from the blood to form part of urine. It is then stored as urine in the bladder,
until it passes out of the body via the urethra.
Why?
Carbon dioxide in excess is toxic. A high level of carbon dioxide in the body has
three main negative effects:
1) A high proportion of carbon dioxide is carried in the blood as
hydrogencarbonate ions, which can form hydrogen ions. These hydrogen ions
compete with oxygen for haemoglobin, so too much carbon dioxide in the
blood leads to insufficient oxygen transport to respiring cells.
2) When carbon dioxide binds directly to haemoglobin (forming
carbaminohaemoglobin), it creates a molecule that has a lower affinity for
oxygen than haemoglobin itself.
3) Carbon dioxide in the blood plasma can combine with water to produce
carbonic acid, which then dissociates to produce hydrogen ions. Hydrogen
ions lower the pH of the blood, making it more acidic. If the blood pH falls
below 7.35, the results are slowed or difficult breathing, headache,
2. drowsiness, restlessness, tremor and confusion. This is known as respiratory
acidosis.
The body cannot store excess amino acids, however, it does not allow them to go
to waste. In the liver, amino acids are deaminated to form a keto acid and a highly
toxic compound, ammonia. The keto acid can be directly respired by cells under
aerobic conditions, or stored as a carbohydrate or fat after conversion. The
ammonia, on the other hand, being toxic, must be converted to a less toxic
substance, urea, which can be transported to the kidneys for excretion.
2) THE LIVER
Liver cells, or hepatocytes, carry out several hundred metabolic processes and the
organ itself plays an important role in maintaining homeostasis. It must have a very
rich supply of blood because of this, so the structure of the liver is arranged to allow
this.
The liver is supplied with blood from two sources:
- Oxygenated blood from the heart travels via the aorta to the hepatic artery,
then into the liver. This supplies the liver cells with much oxygen necessary
for aerobic respiration. Liver cells are very active, so require a lot of ATP
formed from aerobic respiration.
- Deoxygenated blood from the digestive system enters the liver via the
hepatic portal vein, which carries blood rich in digestive products. Since the
concentration of these products is uncontrolled thus far, the blood may
contain toxic compounds that have been absorbed by the intestine. All blood
leaves the liver via the hepatic vein, which joins the vena cava eventually.
The fourth vessel is not a blood vessel, but a bile duct, which carries bile (a
secretion from the liver) to the gall bladder, where it is stored until required to aid the
digestion of fats in the small intestine.
How are the cells arranged?
The liver is divided into lobes, which are further divided into cylindrical lobules. The
cells, blood vessels and chambers in the liver are all arranged to ensure the best
exchange of substances from and into the blood possible.
The hepatic artery and hepatic portal vein split into smaller and smaller vessels as
the run between, and parallel to, the lobules. They are known as inter-lobular
vessels. At intervals, branches from the hepatic artery and hepatic portal vein enter
the lobules, converging to form a sinusoid, which is lined by liver cells. The liver
cells are therefore able to remove molecules from the blood and pass molecules into
3. the blood. The sinusoids then empty into a branch of the hepatic vein, the intra-
lobular vessel. The branches of the hepatic vein from different lobules converge to
form the hepatic vein.
Bile is formed by the liver cells, and this is secreted into the bile canaliculus. These
converge to form the bile duct, which transports the bile to the gall bladder.
Kupffer cells are specialised macrophages that move around the sinusoids. They
are involved in the breakdown of aged red blood cells. One of the products of
haemoglobin breakdown is billirubin, which is excreted as part of the bile and in
faeces.
3) FUNCTIONS OF THE LIVER
The liver is involved in many metabolic functions, including:
- Control of: blood glucose levels, amino acid levels, lipid levels
- Synthesis of: red blood cells in fetus, bile, plasma proteins, cholesterol
- Storage of: vitamins A, D and B12, iron, glycogen
- Detoxification of: alcohol and drugs
- Breakdown of hormones
- Destruction of red blood cells
Forming Urea
We usually eat more than our required amount of protein, so, as it cannot be stored,
it must be excreted, as the amine groups are toxic. Proteins are deaminated which
produces ammonia, a highly toxic compound. It also produces a keto acid, which can
be directly respired or stored.
The ornithine cycle – ammonia must be converted to a less toxic form as quickly as
possible, so it is combined with carbon dioxide to produce urea. Urea is less toxic
than ammonia, and is passed back in the blood to travel to the kidneys.
Ammonia + Carbon Dioxide Urea + Water
4. Detoxification
The liver is able to detoxify many compounds, some produced in the body (such as
hydrogen peroxide) and some consumed (such as alcohol). Toxins can be rendered
harmless by reduction, oxidation, methylation or combination with another molecule.
Since the liver is involved in detoxification, its cells contain many enzymes involved
in the detoxification of substances. Catalase is one such enzyme, which breaks
hydrogen peroxide down to harmless oxygen and carbon dioxide.
Detoxification of Alcohol
Alcohol, or ethanol, is an intoxicating drug that suppresses nervous activity.
However, it also contains chemical potential energy, which can be used in
respiration. It is broken down in the hepatocytes by the action of the enzyme ethanol
dehydrogenase. The resultant is ethanal, which is further dehydrogenated by the
enzyme ethanal dehydrogenase. The final compound is ethanoate (acetate), which
is combined with CoA to form acetyl CoA, which enters the Krebs cycle. In addition,
the hydrogen atoms released by the dehydrogenation reactions are used to reduce
NAD and FAD used in oxidative phosphorylation.
NAD is also required to oxidise and break down fatty acids, so if too much is being
used in the detoxification of alcohol, then the fatty acids are converted back to lipids
and stored in the liver cells, causing an enlarged liver. This can lead to alcohol-
related hepatitis or to cirrhosis.
4) THE KIDNEY
Most people have two kidneys, positioned both sides of the spine and just under the
lowest rib. Each kidney is supplied with blood from the renal artery and is drained by
a renal vein. The kidney removes waste products from the blood and produces
urine, which passes out of the kidney down the ureter to the bladder.
The kidney can be described as consisting of three regions, enclosed within a tough
capsule:
- The outer region, known as the cortex
- The inner region, known as the medulla
- The pelvis of the kidney, leading to the ureter.
Each kidney actually consists of tiny tubules, known as nephrons, which are
abundant and are associated with tiny capillaries. Each nephron begins in the cortex,
where they form a knot known as the glomerulus. This is surrounded by a cup-
shaped structure known as the Bowman’s capsule. The afferent arteriole carries
blood to the glomerular capillary, where it is pushed into the Bowman’s capsule
5. through the process of ultrafiltration. The capsule leads into the nephron, which is
divided into four parts:
- Proximal convoluted tube
- Loop of Henle
- Distal convoluted tube
- Collecting duct
As the fluid moves along the nephron, its composition is altered; achieved by
selective reabsorbtion of salts, water, etc. These substances are absorbed back
into the tissue fluid and blood capillaries surrounding the nephron tubule. The final
product in the collecting duct is urine.
How does the composition of the fluid change?
- In the proximal convolution, the fluid is altered by the reabsorbtion of all
sugars, most salts and some water. In total, around 85% of the fluid is
reabsorbed here.
- In the descending limb of the loop of Henle, the fluid’s water potential is
decreased by the addition of salts and the removal of water.
- In the ascending limb of the loop of Henle, the water potential is increased as
salts are removed by active transport.
- In the collecting duct, the water potential is decreased again by the removal of
water. This ensures that urine has a low water potential, so it has a higher
concentration of solutes than the blood or tissue fluid.
5) FORMATION OF URINE
The barrier between the blood in the capillary and the lumen of the Bowman’s
capsule consists of only three layers of cells:
- The capillary endothelium
- A basement membrane
- The Bowman’s capsule epithelial cells
The endothelium of the capillaries has narrow gaps between its cells to allow
ultrafiltration. They allow the blood plasma (and whatever is in solution in it) to pass
through. The basement membrane is a fine mesh of collagen fibres and
glycoproteins. These act as a filter, only allowing molecules with a relative molecular
mass of less than 69,000 to pass through. Thus, blood cells and proteins are held in
the capillaries. Finally, the epithelial cells of the Bowman’s capsule (known as
podocytes) have finger-like projections called major processes. These ensure that
there are gaps between cells, so that fluid from the blood in the glomerulus can pass
into the lumen of the Bowman’s capsule.
6. What is filtered?
- Water
- Amino acids
- Glucose
- Urea
- Inorganic ions (such as potassium, sodium and calcium).
This means that only blood cells and proteins are left in the capillary, and this causes
a very negative water potential. This low water potential enables the blood to
reabsorb water at a later stage.
The cells lining the proximal convolution are adapted to allow 85% of the filtrate to be
reabsorbed:
- Microvilli, formed by folding the cell surface membrane, increase the surface
area for reabsorbtion.
- The cell surface membrane also contains co-transporter proteins, which
transport glucose, amino acids and sodium ions out of the filtrate by facilitated
diffusion.
- The opposite membrane of the cell contains sodium-potassium ion pumps
that pump sodium ions out and potassium ions in. It is also folded to increase
its surface area.
- As much ATP is required, the cells lining the proximal convolution have many
mitochondria.
How?
- The sodium-potassium ion pumps remove sodium from the cells and thus
reduce the concentration of sodium ions in the cell cytoplasm.
- Glucose and amino acids are transported into the cello by facilitated diffusion,
which means that the concentrations of these substances rise inside the cell.
- The cell’s cytoplasm, because it now contains many solutes, has a lower
water potential than the filtrate in the tubule, so water diffuses into the cells by
osmosis.
- The water potential and concentrations of salts, glucose and amino acids are
lower in the tissue fluid surrounding the cells of the proximal convolution, so
the salts, glucose and amino acids diffuse into the tissue fluid by facilitated
diffusion, and water diffuses into the tissue fluid by osmosis.
- Larger molecules may be reabsorbed by endocytosis.
7. 6) WATER REABSORBTION
When the filtrate reaches the loop of Henle, there is about remaining. The
role of the loop of Henle is to create a low water potential in the tissue of the
medulla. This ensures that even more water can be reabsorbed from the filtrate in
the collecting duct.
The loop of Henle consists of a descending limb that descends into the medulla
and an ascending limb that ascends back out to the cortex. This arrangement
allows salts to be transferred from the ascending limb into the descending limb. The
overall effect is to increase the concentration of salts in the tubule fluid and
consequently they diffuse out into the surrounding medulla tissue fluid, giving it a
very low water potential.
As the tubule descends deeper into the medulla, its water potential begins to fall, due
to the loss of water by osmosis to the surrounding tissue fluid, and also the diffusion
of sodium and chloride ions into the tubule from the surrounding tissue fluid.
As the tubule ascends up the cortex, its water potential begins to rise, because:
- At the base of the tubule, sodium and chloride ions diffuse out of the tubule
into the tissue fluid.
- Higher up the tubule, sodium and chloride ions are actively transported out
into the tissue fluid.
- The wall of the ascending limb is impermeable to water, so water cannot
leave the tubule.
8. - The fluid loses salts, therefore, and no water as it moves up the ascending
limb.
The movement of salts from the ascending limb into the medulla creates a high salt
concentration in the tissue fluid of the medulla, so there is a very negative water
potential. This allows water to be reabsorbed in the distal convolution and the
collecting duct. The amount of water reabsorbed depends on the needs of the
body.
7) OSMOREGULATION
Osmoregulation is the control of water and salt levels in the body. To maintain an
osmotic balance for efficient cellular processes, the correct water potential must be
maintained between cells and surrounding tissue fluids.
Water is gained from food, drink and respiration.
Water is lost through urinating, sweating, exhaling water vapour, and in faeces.
Controlling the loss of water in the urine involves making the walls of the collecting
duct more or less permeable, depending on the body’s need. When less water needs
to be conserved, the walls of the collecting duct are less permeable, and vice versa.
The permeability of the collecting duct walls is influenced by the level of antidiuretic
hormone (ADH) in the blood stream. The cell surface membranes of the cells in the
wall contain receptors specific to ADH.
When ADH binds to these receptors, it activates a second messenger inside the cell,
which causes a chain of enzyme-catalysed reactions. The effect of these reactions is
to insert aquaporins (water-permeable protein channels) into the plasma
membrane. This makes the walls of the collecting duct more permeable to water,
thus allowing more to be reabsorbed and less to be passed out in urine.
Controlling the concentrations of ADH in the blood
Like many of the homeostatic functions, the hypothalamus controls the secretion of
ADH:
- Osmoreceptors in the hypothalamus respond to the effects of osmosis. When
the water potential is low, the osmoreceptors lose water by osmosis, causing
them to shrink.
- The shrinking of the receptors causes stimulation of neurosecretory cells,
which produce and secrete ADH. The ADH is manufactured in the cell body of
these cells, which lies in the hypothalamus. The ADH flows down to the
terminal bulb in the posterior pituitary gland, where it is stored until needed.
9. - When the neurosecretory cells are stimulated, they send action potentials
down their axons, which causes the secretion of ADH.
In order to ensure that ADH does not have a constant effect, it has a half-life of 20
minutes, so it is gradually broken down in the blood, slowing its effect on the
collecting duct’s walls.
8) KIDNEY FAILURE
Kidney failure occurs mostly due to diabetes mellitus, hypertension and infection.
Treatment
Dialysis is the most common treatment for kidney failure, and essentially bypasses
the kidney by removing wastes, excess fluid and salt from the blood by passing it
over a dialysis membrane. It is a partially permeable membrane that allows the
exchange of substances between the blood and the dialysis fluid. The fluid contains
the correct concentrations of salt, urea, water and other substances in the blood
plasma, so any substances in excess will diffuse across the membrane into the
dialysis fluid.
In haemodialysis, blood from a vein is passed through a dialysis machine that
contains a dialysis membrane. It is usually performed at a clinic three times a week
for several hours, however, it can be carried out at home.
In peritoneal dialysis, the filter is the body’s own abdominal membrane. A surgeon
must implant a tube in the abdomen into which dialysis solution is poured. After
several hours, the solution is drained from the abdomen. PD is performed several
times a day at home or work.
A kidney transplant is a less common treatment for kidney failure. A donor, usually
a family member, can donate one of their healthy kidneys to a patient in need of a
kidney transplant. A surgeon implants the new organ into the lower abdomen and
attaches it to the blood supplies and ureter. However, a patient’s body can see the
kidney as a foreign body and initiate an immune response against it. Because of this,
for the life of the organ, the patient must take immunosuppressant drugs.