SBI4U1 2024 Unit 4 Homeostasis PDF

SBI4U1 – 2024 UNIT 4 – HOMEOSTASIS – LESSON LIST LESSON TITLE HOMEWORK COMPLETED Maintaining an Internal Balance Textbook: 1...

SBI4U1 – 2024 UNIT 4 – HOMEOSTASIS – LESSON LIST LESSON TITLE HOMEWORK COMPLETED Maintaining an Internal Balance Textbook: 1 Chapter 9.1 (pages 428-431) Page 431 (#1, 2, 3, 5, 7) Homeostasis, Feedback Mechanisms, and Textbook: Thermoregulation Page 431 (#9, 11) 2 Chapter 9.1 (pages 428-431) Chapter 9.2 (pages 432-435) Page 435 (#1, 4, 5, 7) Chapter 9.3 (pages 436-441) Page 441 (#1, 2, 8, 11) Water Balance Textbook: 3 Chapter 9.4 (pages 442-445) Page 445 (#1-6) Worksheet: Nephron Function 4 The Excretory System Urinalysis Case Study Chapter 9.5 (pages 446-454) Textbook: Page 454 (#2, 3, 4, 62) The Endocrine System Textbook: 5 Chapter 10.1 (pages 468-472) Page 472 (#1, 2, 6, 9) Textbook: The Endocrine Glands Page 482 (#1-3, 5, 6, 8) 6 Chapter 10.2 (pages 473-482) Worksheet: Endocrine System Case Study Regulating Blood Sugar Textbook: 7 Chapter 10.3 (pages 483-487) Page 487 (#1, 2, 4, 6, 7) The Reproductive Hormones Textbook: 8 Chapter 10.7 (pages 496-503) Page 503 (#1, 2, 6, 9, 10) Worksheet: The Nervous System The Nervous System 9 Chapter 11.1 (pages 516-521) Textbook: Page 521 (#1, 3, 4, 5) Nerve Signals Worksheet: 10 Chapter 11.2 (pages 522-529) Nerve Signals The Central Nervous System Textbook: 11 Chapter 11.3 (pages 530-536) Page 536 (#1-5, 7, 8) The Peripheral Nervous System 12 Chapter 11.4 (pages 537-542) The Senses Textbook: 13 Chapter 11.5 (pages 542-548) Page 547 (#1, 2) The Body and Stress Textbook: 14 Chapter 11.6 (pages 549- Page 553 (#2, 4, 6, 8) 1 SBI4U1 – 2024 UNIT 4 – HOMEOSTASIS – EVALUATION LIST ASSESSMENT DESCRIPTION DUE DATE SUBMITTED 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Endocrine case study? Hormone research assignment Reflux virtual lab Neuron simulation PhET Mouse party assignment 2 SBI4U1 – 2024 1. MAINTAINING AN INTERNAL BALANCE BRAINSTORM – What things in your body need to be kept within a normal range? INTRODUCTION TO HOMEOSTASIS All organisms have preferred environments, but they can live in a tolerable range of environmental conditions One of the most critical factors for maintaining proper cell function is temperature Metabolic processes performed by cells can only successfully occur within a fairly narrow range of temperatures. o Human Body Cells – Internal temperature of roughly 37 °C (normal body temperature) Small variations from this temperature can have damaging or deadly effects o Below 35 °C or greater than 37.8 °C can cause some bodily processes to malfunction The human body has several mechanisms that regulate its internal temperature o I.e., We sweat when we are hot and when we are cold, we shiver to produce thermal energy External environmental conditions also affect the body’s internal conditions; therefore, the body must adjust to ensure that it functions efficiently HOMEOSTASIS Regulation of internal environment through the constant physiological adjustments of the body in response to external environment changes Physiological state of the body in which the internal physical and chemical conditions are maintained within an acceptable or tolerable range that is suit- able for essential biological processes. Homeostasis is not a “steady state”, it is dynamic and constantly changing in response to the environment o Always approaching dynamic equilibrium 3 SBI4U1 – 2024 HOMEOSTASIS OF EXERCISING What are some physical effects observed in your body when you exercise? Sweat – Increase in body temperature Increased heart rate and breathing rate – Increased oxygen demand Muscle ache – Increased cellular respiration (anaerobic because there isn’t enough oxygen) Body temperature increases – Evaporation of sweat helps to cool off Oxygen levels being used up – Heart and breathing rate increases to increase blood flow Increased cellular metabolism – Pancreas signals breaking down of biomolecules ORGANS INVOLVED IN HOMEOSTASIS Organ System Main Organs Nervous System Brain, spinal cord, peripheral nerves, sensory organs Endocrine System Pituitary, thyroid, adrenal, pancreas, other hormone-secreting glands Muscular System Skeletal, cardiac, smooth muscle Integumentary System Skin, sweat glands, hair, nails Excretory System Kidneys, bladder, ureter, urethra Reproductive System Female: Ovaries, oviducts, uterus, vagina, mammary glands Male: Testes, sperm ducts, accessory glands, penis Nervous System – Coordinates rapid responses to stimuli via electrical signals (known as action potentials) Endocrine System – Coordinates long-term responses using chemical signals (hormones) Hormones – Chemical signals carried by blood and cause specific changes in target cells o Help regulate energy use, metabolism, growth o Maintains homeostasis 4 SBI4U1 – 2024 HOMEOSTATIC MECHANISMS Responsible for maintaining homeostasis by responding to changes in either the internal environment or the external environment Involves three elements: a sensor, an integrator, and an effector Sensor – Detects any environmental stimulus to the body Integrator – Receives and processes the signals delivered from sensors o Compares the signals from optimal functioning conditions (set points) Effector – Cells that respond to a regulatory signal o If conditions are outside of set points, integrator will activate effectors to return body back to homeostasis 5 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 9.1 on page 431 of your textbook: #1, 2, 3, 5, 7. 1. Explain the meaning of homeostasis and give an example of how homeostasis occurs in the body. 2. Why is homeostasis not considered to be a “constant” condition? Be specific in your response. 3. List the body’s responses to being too hot or too cold. What are some of the organ systems that may be involved in these responses? 5. Diabetes, a disease that disrupts the blood glucose homeostasis, can be lethal if not monitored and maintained. Research and describe how humans artificially maintain their blood glucose levels. 7. Explain how cruise control on a vehicle is a good metaphor for homeostasis. 6 SBI4U1 – 2024 2. HOMEOSTASIS, FEEDBACK MECHANISMS, AND THERMOREGULATION Feedback systems used by the body to maintain homeostasis are constantly detecting internal and external conditions If conditions to determine deviate from the norm and are outside of the optimal functioning range, the mechanisms take corrective action to bring the body back into balance NEGATIVE FEEDBACK MECHANISMS Negative Feedback – Response of a system that acts to maintain equilibrium by compensating for any changes made to the system o Primary mechanism of homeostasis Mechanism used to bring the body back to homeostasis “Negative” because its purpose is to produce the opposite effect of the change detected by the sensor Sensor – the element of a feedback system that detects changes in the environment o Consists of tissues or organs that detect any change (or stimulus) such as pH, temperature, or concentrations of molecules (i.e., glucose or hormone molecules) Integrator – The element of a feedback system that compares existing conditions with ideal conditions Set point – The optimal value for a given variable of a system Effector – the element (or elements) of a feedback system that acts to return the system to its optimal state Sensor and integrator are usually part of the nervous or endocrine system, whereas the effector may include parts of any tissues and organs. To bring internal conditions back into balance, negative feedback mechanisms use antagonistic effectors 7 SBI4U1 – 2024 o The “antagonistic” in their name means that they act to produce the opposite effect of the change recorded by the sensor THE THERMOSTAT AS A NEGATIVE FEEDBACK MECHANISM A sensor inside the thermostat measures the temperature A circuit (integrator) in the thermostat compares the measured temperature to the set point programmed by the user o If the temperature increases or decreases by any amount, the integrator circuit activates an electrical effector (either a furnace or an air conditioner), which returns the temperature to the set point. Optimal room temperature: 22˚C o T < 22˚C: thermostat turns on the furnace o T > 22˚C: thermostat turns off the furnace NEGATIVE FEEDBACK MECHANISMS IN ANIMALS Mammals and birds also have a homeostatic mechanism that maintains body temperature within a relatively narrow range around a set point The integrator in this mechanism is located in a brain centre called the hypothalamus In humans, groups of neurons in the preoptic region of the anterior hypothalamus receive information from thermoreceptors in various locations, including the skin, the spinal cord, and the hypothalamus itself o This information is then compared to the set point, which is 35 to 37.8 °C (centred on 37 °C) o If the temperature deviates from the set point, the hypothalamus activates a set of physiological and behavioural responses to re-establish the normal body temperature. 8 SBI4U1 – 2024 POSITIVE FEEDBACK MECHANISMS Positive Feedback – the response of a system that acts to increase the effect of any changes made to the system o Does not return the body back to a state of homeostasis THERMOREGULATION Regulation of internal body temperature Maintenance of body temperature within an acceptable range E.g., Humans live in climates of varying temperature but are able to maintain constant body temperature 9 SBI4U1 – 2024 THERMOREGULATION MECHANISMS Conduction – Flow of energy through molecules that are in direct contact Convection – Losing heat through the movement of air or water molecules across the skin Radiation – Transfer of energy in the form of electromagnetic radiation Evaporation – Loss of heat through the conversion of water to gas Endotherms – Animals that can regulate body temperatures through internal physiological mechanisms Ectotherm – Behavioural mechanisms that use the environment to regulate body temperature Ectotherm Endotherm Metabolic rate Low High Heat generation Too little to warm body Enough to keep body warm Stable, regardless of external Internal body temperature Determined by environment fluctuations Examples Fish, reptiles, amphibians Mammals, fish TORPOR, HIBERNATION, AND ESTIVATION Torpor – A short-term state of reduced metabolic rate and body temperature that reduces the demand for energy during the night or day o E.g., Hummingbird. During the day, the hummingbird is actively feeding, but it cannot feed at night, and so it becomes inactive and allows its body temperature to drop to conserve energy Hibernation – A state of greatly reduced metabolic rate and activity that enables an animal to survive the winter by reducing the demand for energy when food is unavailable o E.g., Hedgehogs, groundhogs, and squirrels – Experience a 20 °C or greater drop in body temperature during hibernation o E.g., The Arctic ground squirrel – hibernates for 8-10 months of the year (only known mammal whose body temperature falls below freezing) Estivation – A state of torpor that enables an animal to survive the summer by reducing the demand for energy o E.g.. The ground squirrel – Remain inactive in the cooler temperatures of their burrows during extreme summer heat 10 SBI4U1 – 2024 THERMOREGULATION – HUMANS Core temperature – Humans have a normal temperature of around 36.2˚C to 37.2˚C o Above (hyperthermia): lead to possible infection o Below (hypothermia): cell death THERMOREGULATION – HUMANS: HEAT STRESS 1. Monitor Thermoreceptors of the Peripheral Nervous System detects an increase in body temperature Sends message via sensory neurons to brain (Central Nervous System) 2. Coordinate Hypothalamus (CNS) signals via motor nerves to sweat glands 3. Regulate Sweat glands initiate sweating (evaporation of sweat off the skin causes cooling) Blood vessels in the skin dilate to allow for more blood flow (heat from blood is lost to the skin so blood can return to core of your body and cool the internal organs) 11 SBI4U1 – 2024 THERMOREGULATION – HUMANS: COLD STRESS 1. Monitor Thermoreceptors of the Peripheral Nervous System detects a decrease in body temperature Sends message via sensory neurons to brain (Central Nervous System) 2. Coordinate Hypothalamus sends a message via the motor neurons 3. Regulate Arterioles of the skin constrict, therefore limiting blood flow and reducing heat loss from the skin Smooth muscle that surrounds hair follicles in your skin contract, causing the hair to “stand on end” trapping warm air Skeletal muscles contract causing shivering and increasing your metabolism to make heat 12 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 9.1 on page 431 of your textbook: #9, 11. 9. Why does the body sometimes go outside normal homeostasis ranges? 11. Explain the relationship of the terms “regulation” and “feedback” to the concept of homeostasis. Complete the following questions from Chapter 9.2 on page 435 of your textbook: #1, 4, 5, 7. 1. Put the following terms in the correct order as they apply to a negative feedback mechanism: “effector, stimulus, sensor, response, integrator. Give an example of each. 4. Homeostasis in animals is usually maintained through negative feedback systems rather than positive feedback systems. Why do you think this is so? 13 SBI4U1 – 2024 5. Explain, in simple terms, how your body uses positive feedback when it reacts to being frightened. 7. Compare and contrast negative feedback and positive feedback. Give an example of each. Complete the following questions from Chapter 9.3 on page 441 of your textbook: #1, 2, 8, 11. 1. Describe thermoregulation in humans. What occurs when the body temperature is too low? What occurs when it is too high? 2. When an animal wakes in the morning, its core temperature is below the set point. How might an ectotherm and an endotherm respond to this situation differently? 14 SBI4U1 – 2024 8. Suggest two advantages and one disadvantage of endothermy. 11. What is the danger of performing heavy physical activity in extremely cold weather? 15 SBI4U1 – 2024 3. WATER BALANCE OSMOSIS Water molecules moves from a region of high concentration to low concentration across a selectively permeable membrane Osmotic pressure – Pressure that results from a difference in water concentration, or a water concentration gradient, between the two sides of a selectively permeable membrane. o The greater the water concentration gradient, the greater the osmotic pressure difference between the two side Hyperosmotic – the property of the solution on one side of a selectively permeable membrane that has the lower concentration of water Hypoosmotic – the property of the solution on one side of a selectively permeable membrane that has the higher concentration of water Isosmotic – the property of two solutions that have equal water concentrations 16 SBI4U1 – 2024 OSMOREGULATION Osmoregulation – the process of actively regulating the osmotic pressure of bodily fluids and cells Process of actively regulating the osmotic pressure of bodily fluids and cells Management of the body’s water content o Blood pressure Management of solute composition o Body fluid composition, metabolite concentration, blood pH levels Control movements of solutes between internal fluids and external environment o Excretion of metabolic waste EXAMPLES OF OSMOREGULATOR Marine Iguana Have special organ that takes salt out of their system Salt is then spit out the top of their head Pacific salmon **WATCH** Spends part of its life in freshwater and salt water Sneezing Marine Iguana (~0.5 min) Able to manage body water content in different osmotic environments OSMOREGULATION – EXCRETION To maintain homeostasis, cells also regulate their ionic balance and pH balance Therefore, certain ions and toxic compounds, such as the metabolites of nitrogenous compounds (e.g., amino acids and nucleic acids) must be eliminated Animals maintain their ionic and pH balance through the process of excretion o Excretion is the elimination of waste products and foreign matter from the body 17 SBI4U1 – 2024 Controls composition of body fluids (metabolic concentration) Regulates blood pH Regulates blood volume and blood pressure Excretion of metabolic waste o By-products in cellular reactions o Breakdown of proteins and nucleic acids for energy and when they are converted to carbohydrates and fats o Does not include feces (feces is what your body never absorbed) Maintains the ionic and osmotic equilibrium that is necessary for cell functions Excretory (or urinary) system regulates the removal of wastes o Main organs are the kidneys and the bladder NITROGENOUS WASTE Major waste product: nitrogenous waste o Ammonia o Urea o Uric acid (1) Ammonia Released when liver breaks down proteins (amino acids) by deamination (removal of amine groups) Very soluble Very toxic, can only tolerate low concentrations (0.005mg NH 3 is lethal) Must be diluted with water o Excretion requires a large volume of water Common in aquatic species 18 SBI4U1 – 2024 Example: Excretion – Fish Fish can excrete ammonia directly through their gills Why is it safe for fish to excrete ammonia? Animals with an abundant supply of water (such as bony fish and marine invertebrates) are able to secrete ammonia directly from the body in this very dilute form. If other organisms were to change to excrete ammonia, what would be the disadvantage that isn’t applicable to fish? (2) Urea Product of two waste molecules o Ammonia o Carbon dioxide Conversion occurs in the liver Low toxicity o Can be safely stored and transported o Reduces amount of water required for excretion The major component of urine In mammals, some reptiles, and most amphibians, the liver combines ammonia with HCO 3– to create urea, a very soluble substance with 0.001 % the toxicity of ammonia (3) Uric Acid Product of nucleic acid breakdown o Specifically of purine bases (A and G) Released through liver metabolism o Very energetically expensive to make Non-toxic Insoluble in water (low solubility) o Excreted as semisolid paste o Little water loss Birds excrete uric acid directly with feces 19 SBI4U1 – 2024 OSMOREGULATION IN HUMANS *Explained in detail in lesson 4* 20 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 9.4 on page 445 of your textbook: #1 – 6. 1. (a) Describe the similarities and differences between diffusion and osmosis. (b) Why is osmosis particularly important for biological functions? 2. Why do cells need to use osmoregulation? 3. What is the relationship between osmoregulation and excretion? 4. Explain the advantages and disadvantages for terrestrial animals of creating urea rather than other forms of nitrogenous waste. 21 SBI4U1 – 2024 5. Why is it an advantage for birds to create uric acid as their nitrogenous waste compound? (Think in terms of birds’ specialized adaptation of flight.) 6. What animals do you think would produce more urea: carnivores with a high-protein diet or herbivores with a high-carbohydrate diet? Which would require more water? Why? 22 SBI4U1 – 2024 4. THE EXCRETORY SYSTEM In multicellular organisms, individual cells cannot effectively secrete wastes to the external environment Main Functions of the Excretory System (aided by Osmoregulation): 1. Concentrate wastes and expel them from the body 2. Regulate fluids and water within the body Most metabolic wastes and toxins are dissolved in the body’s internal environment, so maintenance of the body fluids is essential for keeping the body free of waste products and enabling it to function properly MAMMALIAN EXCRETORY SYSTEM Kidneys Ureter (duct) Urinary Bladder Urethra (duct) 23 SBI4U1 – 2024 THE KIDNEY Bean-shaped excretory organs in vertebrates Part of the urinary system, the kidneys filter wastes from the blood and excretes them, along with water, as urine Role: removes wastes, balances blood pH, and maintaining the body’s water balance Term “renal” refers to “kidney-related” Mammals have two kidneys – located on each side of the spine o Right kidney sits lower than the left to accommodate the liver o Left kidney sits below the diaphragm and adjacent to the spleen URINE 4x more concentrated than blood Fluid for urine comes from extracellular fluid (plasma and interstitial fluid) Solution of metabolic waste consists of: o Water o Salts o Organic compounds o Urea o Other wastes/toxins URINE EXCRETION When approximately 300-400mL of urine has been collected in the bladder, the walls stretch and signals are sent to the brain At 600mL, urine will involuntarily be released Average person loses 2L of liquid per day o Suggested consumption of water daily is 2L 24 SBI4U1 – 2024 KIDNEY STRUCTURE Renal Cortex – The outer layer of the kidney Medulla – An inner layer found beneath the cortex Renal Pelvis – Inner portion of kidney that connects the kidney to the ureter, through which urine passes to the urinary bladder o Once the bladder is full (with roughly 300 to 400 mL of urine), the urine exits the body through the urethra NEPHRON ANATOMY Nephron – Basic unit of a kidney About a million nephrons make up the kidney Consists of tubules/ducts surrounded by blood vessels BLOOD FLOW IN THE KIDNEYS Blood supply – Renal artery and renal vein Blood enters kidney through renal artery o Renal arteries stem from the aorta Filtered blood exits kidney through renal vein o Inferior vena cava 25 SBI4U1 – 2024 Blood Flow Pathway 1. Renal artery 2. Afferent arteriole 3. Capillaries of glomerulus 4. Efferent arteriole 5. Peritubular capillaries 6. Renal vein FILTRATION PATHWAY 1. Bowman’s capsule 2. Proximal convoluted tubule 3. Loop of Henle 4. Descending segment of loop of Henle 5. Ascending segment of loop of Henle 6. Distal convoluted tubule 7. Renal pelvis 8. Ureter 9. Bladder 10. Urethra THE FORMATION OF URINE Process: 1. Filtration of blood 2. Reabsorption of valuable substances 3. Secretion of toxins and excess ions 4. Excretion of the contents of the tubule **WATCH** The Excretory System (~12.5 min) 26 SBI4U1 – 2024 1. FILTRATION Filtration – Process in which blood and fluid pass through a selectively permeable membrane o Nutrients flow from glomerulus into Bowman’s Capsule due to high blood pressure Retain large molecules o Cells ▪ Proteins Filter is non-selective for small molecules o Water o Small solutes o Nitrogenous waste (urea) 2. REABSORPTION Proximal Convoluted Tubules Fluid that enters the Bowman’s capsule have the same concentration as the blood plasma Once the filtrate enters the proximal convoluted tubules, o Specialized ion pumps and transport proteins transport K+, Na+, Cl–, amino acids, glucose, and other important nutrients back into the blood surrounding the tubules o Urea and other waste molecules are not reabsorbed Inner walls of tubules contain microvilli o Increases surface area Reabsorption of nutrients causes the interstitial fluid to be hyperosmotic and forces water to flow out through aquaporins 27 SBI4U1 – 2024 Loop of Henle (Descending): Nutrients and water reabsorbed enter the peritubular capillaries to be used again by the body Additional reabsorption of water by osmosis (passive transport) through aquaporins Filtrate becomes increasingly concentrated as it moves down into the medulla Loop of Henle (Ascending): First part, filtrate is concentrated enough that Na+ and Cl– can be passively diffused out Second part, Na+ and Cl– need to be actively transported out Filtrate towards the end of the loop of Henle becomes more concentrated with nitrogenous waste and urea 28 SBI4U1 – 2024 Distal Convoluted Tubule: Additional ions are reabsorbed which causes further transport of water out through aquaporins Amount of nitrogenous waste and urea remains the same Collecting Ducts: Collecting ducts run from renal cortex through the renal medulla Collects from several nephrons o Many convoluted tubules connected to each collecting duct More ions and solutes move out of ducts → leads to more water transported out At the bottom of collecting ducts are some urea transport o Allows some nitrogenous waste to move into the interstitial fluid 3. SECRETION & EXCRETION Process of transporting waste material from the internal environment (blood) and the interstitial fluid out of the body o Products of detoxified poison from the liver o Medication such as penicillin o Small amounts of ammonia Secreted at multiple points of the nephron Active secretion of H+ ions is coupled with the passive absorption of HCO3– o Helps to balance the acidity levels 29 SBI4U1 – 2024 TRY THIS – You need to be able to do this for your test! Sort the following into either blood flow or filtrate flow. Descending segment of loop of Henle Renal Artery Urethra Bowman’s capsule Ureter Efferent arteriole Proximal convoluted tubule Renal pelvis Distal convoluted tubule Afferent arteriole Ascending segment of loop of Henle Bladder Peritubular capillaries Capillaries of glomerulus Renal vein Blood Flow Filtrate Flow Renal artery Bowman’s Capsule Afferent arteriole Proximal convoluted tubule Capillaries of glomerulus Descending segment of loop of Henle Efferent arteriole Ascending segment of loop of Henle Peritubular capillaries Distal convoluted tubule Renal vein Renal pelvis Ureter Bladder Urethra 30 SBI4U1 – 2024 KIDNEY STONES Buildup of mineral solutes (oxalates, phosphates, and carbonates) Combine with calcium to produce crystals that form stones when it accumulates Sharp stones that get lodged in the renal pelvis or ureters **WATCH** How do your kidney’s work? (~4 min) **WATCH** The Mammalian Kidney (~6 min) Table 1: Functions and Roles of Different Parts of the Nephron and Collecting Ducts 31 SBI4U1 – 2024 HOMEWORK: NEPHRON FUNCTION 1. Complete the chart using the information from your notes and the video shown in class. Secretion Reabsorption Thicker & ion permeable Collects filtrate Reabsorption of H2O Active transport of ions Diffusion of ions Passive movement of water Thinner & water permeable Region in Nephron What happens to the filtrate in each region of the nephron? Bowman’s capsule and glomerulus (cortex) Proximal tubule (cortex) Loop of Henle Primary Function: (medulla) Differences between ascending and descending loop: Ascending loop (thick): Ascending loop (thin): Descending loop: Distal tubule and collecting duct (spans cortex and medulla) 32 SBI4U1 – 2024 2. Label the section of the nephron. 3. Indicate what & where the following substances are moving into & out of the nephron and whether it is active or passive.. - Nutrients, wastes, water, H2O 33 SBI4U1 – 2024 4. Make a T-chart to identify how the blood plasma and filtrate are alike and different (e.g., contents, location, colour). 5. How does the movement of substances in the ascending limb of the loop of Henle affect the movement of substances in each of these areas: a. The descending limb b. The distal tubule c. The collecting duct 6. What is the difference between reabsorption and secretion? Where does each occur in the nephron? 7. What areas of kidney tissue surrounding the nephron would you expect to find an area of high concentration of mitochondria? Explain. 34 SBI4U1 – 2024 HOMEWORK: URINALYSIS CASE STUDY 35 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 9.5 on page 454 of your textbook: #2, 3, 4, 6. 2. Victims of accidents and diseases are able to live healthy lives with just one kidney. With this in mind, what may be the reasons that the body normally uses two kidneys? 3. Describe the flow of blood into and out of the kidneys. Compare the contents of the blood when entering and exiting the kidneys. 4. Describe the flow of fluid through a nephron and to the external environment. Include a simple labelled sketch with your description. 6. You learned that 50 % of the urea is reabsorbed in the proximal convoluted tubes. Why does this not greatly concentrate the nitrogenous waste in the body? 36 SBI4U1 – 2024 5. THE ENDOCRINE SYSTEM HORMONES Hormones – chemicals produced by cells in one part of the body that regulate the processes of cells in another part of the body Act as chemical messengers – Chemical signals carried by blood and cause specific changes in target cells Produced by the endocrine glands – Ductless secretory organs that secrete hormones directly into the blood for transport Hormones are then circulated throughout the body which is why the body has a large variety of hormones Target cells – respond to a specific hormone because they only have receptor proteins that will recognize and bind to that type of hormone Function: Regulate energy use, metabolism and growth Maintain homeostasis Types of hormones o Protein hormones o Steroid hormones 37 SBI4U1 – 2024 PROTEIN HORMONES Short peptide sequences (chains of amino acids of varying lengths) Water soluble Cannot pass through cell membrane (phospholipid) Released into the blood or extracellular fluid by the cells in the endocrine glands where they are produced Binds to receptor on surface of target cell and triggers a signal transduction pathway Involved in phosphorylating proteins Hydrophilic (high affinity for water and diffuse well through blood and intercellular fluids Includes the growth factors which regulate the division and differentiation of many types of cells in the body Mechanism Signals from hormone is amplified and sent through the cell Tends to greatly amplify effect and have different effect on different target cells 38 SBI4U1 – 2024 STEROID HORMONE Made from cholesterol Insoluble in water (lipophilic) Can enter target cell by diffusion through cell membrane Bind to intracellular receptor in cytoplasm or nucleus When a steroid hormone contacts a cell, it is released from its carrier protein Usually combined with hydrophilic carrier proteins to form water-soluble complexes It passes through the plasma membrane of the target cell and then binds to internal receptors in the nucleus or cytosol Includes aldosterone, cortisol, and the sex hormones o Some steroid hormones have very similar structures but produce very different effects Involved in turning DNA genes on or off Mechanism: 39 SBI4U1 – 2024 HORMONE MECHANISMS Many hormones are secreted in an inactive or less active form called prohormones o Prohormones – Converted by the target cells or by enzymes in the blood or other tissues to the active form Amplification – magnifies the effects of hormones (which are usually secreted in small amounts) o “Chain Reaction” – amplifies the effect of the small amount of hormone initially received ▪ Once a receptor cell activates a few proteins, these proteins activate other proteins, each of which activates other proteins, and so on HORMONES AS PART OF FEEDBACK MECHANISMS Hypothalamus will release a hormone to act on the pituitary gland The pituitary gland will release a second hormone that will act on other endocrine glands to stimulate hormone release E.g., Thyroid-releasing hormone (TRH) and thyroid-stimulating hormone (TSH) Final hormone will target specific tissue AND inhibit the pituitary gland from releasing more hormones Body processes such as oxidative metabolism, digestion, growth, sexual development, and reactions to stress are all controlled by multiple hormones Negative feedback loops adjust the level of secretion of hormones that act in opposing ways This creates a balance in their effects that maintains homeostasis in the body 40 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 10.1 on page 472 of your textbook: #1, 2, 6, 9. 1. What is a hormone? 2. Name and describe the two most common types of hormones, classified according to their molecular structure. 6. Testosterone is a hormone derived from cholesterol. Explain how you would expect testosterone to perform its intended action in a cell. 9. Why does the imbalance of a particular hormone affect the entire body and cause so many different symptoms? 41 SBI4U1 – 2024 6. THE ENDOCRINE GLANDS The endocrine system is a system of glands located in various parts of the body o Glands produce hormones and secrete them into the bloodstream, which carries them throughout the body o Hormones act as a chemical management system for the body HYPOTHALAMUS AND PITUITARY GLAND Hypothalamus – Region of the brain that releases hormones to control the pituitary gland, which, in turn, controls other endocrine glands Neurohormone – A hormone produced by neurons, such as in the hypothalamus, that controls the production of other hormones in the pituitary gland **WATCH** How do your hormones work? (~5 min) 42 SBI4U1 – 2024 NEUROHORMONE PATHWAY Stimulus signals hypothalamus to produce hormones that directly act on target cells without stimulating endocrine glands Hypothalamus: region of the body that releases hormones to control the pituitary glands Hormones released by the hypothalamus are known as neurohormones that travel along the nerve cells and travel through the blood stream until it reaches the pituitary gland PITUITARY GLAND Located at the base of the hypothalamus Two parts – Anterior & posterior Sometimes referred to as the “master gland” – produces hormones that control most of the other endocrine glands 1. THE POSTERIOR PITUITARY GLAND Extension of the brain (hypothalamus) Does not make any hormones itself Stores and secretes hormones that were synthesized in the hypothalamus Two main hormones it releases: Antidiuretic hormone (ADH) – targeted tissue is the kidneys; increases blood volume and pressure by increasing water reabsorption in the kidneys Oxytocin – targeted tissues are uterus and mammary glands; promotes uterine contractions; stimulates milk release from the breasts 43 SBI4U1 – 2024 2. THE ANTERIOR PITUITARY GLAND Separate structure from the hypothalamus Hypothalamus release two types of hormones to anterior pituitary gland Releasing hormone: stimulate gland to secrete hormones Inhibiting hormone: inhibit gland from secreting hormones Makes its own set of hormones that are stimulated or inhibited Hormones produced by the Anterior Pituitary gland Hormone produced Target Tissue Function Prolactin (PRL) Mammary glands Stimulates breast development and milk production Stimulates the growth of bones and soft tissues; helps to Growth Hormone (GH) Bone, soft tissue control the metabolism of glucose and other fuel molecules Stimulates the secretion of thyroid hormones and the Thyroid-stimulating hormone (TSH) Thyroid gland growth of the thyroid gland Stimulates the secretion of glucocorticoids by the Adrenocorticotropic hormone (ACTH) Adrenal cortex adrenal cortex Stimulates the egg growth and development and the Ovaries (females) secretion of sex hormones in females Follicle-stimulating hormone (FSH) Testes (males) Stimulates the sperm production in males Ovaries (females) Regulates ovulation in females Luteinizing hormone (LH) Testes (males) Regulates the secretion of sex hormones in males Melanocyte-stimulating hormone Melanocytes in Promotes darkening of the skin (MSH) skin Pain pathways in Endorphins Inhibit the perception of pain nervous system 44 SBI4U1 – 2024 GROWTH REGULATION GROWTH HORMONE: Function: Binds to target cells: bones and muscles Signals the release of Insulin-like Growth Factor (IGF) o A protein hormone that directly stimulates growth Stimulates growth o Hypertrophy: increase in size/volume of cells o Example: increase in bone thickness Stimulates cell reproduction o Increased rate of mitosis o Example: increase in bone length Stimulates cell metabolism o Increase glycogen and fat breakdown for energy o Increase protein synthesis Secretion: Secreted in bursts (not continuous) Released the most during sleep o Changing sleep patterns affect release Growth Hormone production declines with age 45 SBI4U1 – 2024 GROWTH HORMONE DISORDERS Dwarfism Deficiency in growth hormone secretion during child’s development Adult height: 4’10 ” or shorter Gigantism Over-production of growth hormone during childhood Excessive growth and height Average brain size Tumor formed by pituitary gland Poor blood flow due to large body Increased muscle mass but weaker muscles Excess GH produces salt in muscle tissues Muscles swell with water Acromegaly Increased growth hormone secretion as an adult Bone thickens o Forehead expands o Eyebrow ridge bulges outwards o Cheekbone more prominent o Bottom jaw enlarges and pushes lower teeth outward 46 SBI4U1 – 2024 47 SBI4U1 – 2024 THYROID AND PARATHYROID HORMONES THYROID GLAND Located at the base of neck in humans Main thyroid hormone is known as thyroxine (T4) o Contains 4 iodine atoms o Enters the cell and loses an iodine atom (T3); alters gene expression Regulates metabolism o Increase glucose metabolism o Increase protein synthesis o Increase oxygen consumption (blood pressure, heart rate) o Regulates growth and tissue differentiation Digestion, reproduction, bone growth, muscle tone, nerve cells THYROID REGULATION: Stimulus Decrease in metabolic rate Detected by hypothalamus Effect Hypothalamus releases thyroid-releasing hormone (TRH) Anterior pituitary releases thyroid-stimulating hormone (TSH) Thyroid gland releases thyroxine (T4) Thyroxine acts on cells in the body Result Increase in metabolic rate 48 SBI4U1 – 2024 THYROID DISORDERS Hyperthyroidism Overactive thyroid gland Does NOT necessarily imply that thyroxine levels are elevated IF over-active thyroid gland does increase thyroxine levels, then the effect is high glucose metabolism o Weight loss with increased appetite o Anxiety o Increased heat release Thyroxine part of negative feedback loop to ensure the anterior pituitary gland does not over-secrete TSH Iodine deficiency means not enough thyroxine can be produced o Halts this negative feedback loop o Over-secretion of TSH will over stimulate the thyroid o Thyroid becomes swollen (goiter) Low iodine levels means low levels of T3/T4 Body tries to compensate by working the thyroid gland more to make more T3/T4 Grave’s Disease Antibody targets TSH receptors Stimulate TSH secretion Causes protruding eyes (“bugged-eyes”) Eye irritation and double vision 49 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 10.2 on page 482 of your textbook: #1, 2, 3, 5, 6, 8. 1. Which hormones are primarily responsible for regulating the metabolism of the body? 2. Which hormones help the body respond to stress? 3. How does the function of the posterior pituitary gland differ from the function of the anterior pituitary gland? 5. Suppose that the thyroid gland had to be removed due to cancer. How would the body be affected, and what treatments do you think would be necessary? 6. What hormones from the anterior pituitary gland are important for reproduction, and what are their functions? 8. Why is epinephrine therapeutic for anaphylaxis? Under what conditions might taking epinephrine be dangerous? 50 SBI4U1 – 2024 HOMEWORK: ENDOCRINE SYSTEM CASE STUDY Dr. _______________________’s Diagnosis of Endocrine Disorders As an endocrinologist, you have the important job of correctly identifying your patients’ endocrine disorders. After listening to patients who have called into your hotline, use your knowledge of the endocrine system to diagnose which disease the patients might have. Take notes in the patient charts below. Patient Symptoms Diagnosis Endocrine Gland Involved A 22-yr old college student-athlete A 41-yr old female computer data employee A 55-yr old married male 51 SBI4U1 – 2024 Patient 1 Hello doctors, I’m a 22-yr old college student during my last year at Western. I’m on the basketball team there and I used to have a lot of energy but lately I’m so tired, I don’t even want to go to class or basketball practice. I’m jumpy and everything seems to bother me. I’m usually relaxed and have no trouble dealing with stress being a student and an athlete, and I was always an honour student. Lately, I’ve been so cranky and so tired. I think I had a flu a couple weeks ago cause my neck was swollen – still hurts a little bit. I can’t seem to shake it! Whenever I’m in practice or climbing to my 3rd floor dorm room, my muscles just feel so weak. My heart just feels like its racing and I’m sweating all the time. I mean as an athlete, I’m used to getting all sweaty but even in my dorm room where everyone says it’s chilly, I’m still sweating. Just this week, my friends noticed my eyes have gotten bigger! During a game, fans from the opposing school started calling me “bug-eyes”! I also noticed my hands would shake a lot when I would be attempting a free throw. Patient 2 I need some help from you doctors. I just had my 41st birthday. It seems like everything is falling apart. I’ve always thought of myself as healthy even though I’ve always been overweight for years. I don’t do a lot of exercise, but I always seems to be hungry and thirsty all the time like I’ve just ran a marathon or something. When I did exercise, I got myself a blister on my foot. It’s been weeks and it still hasn’t healed! I’m also tired, you would think that all this eating and inactivity would make me put on the pounds. The funny thing is, I’m actually losing weight, but I don’t really want to complain about that. Of course, my husband just thinks I’m working too hard at my computer job cause I’m cranky and my vision seems to get blurry at times. My husband says it’s cause I’m staring at that computer all day long. My hand also seems to fall asleep for no reason. So, my husband thought it was cause of all the typing I have to do at work, called it carpal tunnel syndrome. About a month ago, I went to see my primary care physician and she thought it was all due to my extra weight! I also find myself having to go to the bathroom several times at night. Patient 3 Hi doctor, I just turned 55-yrs old last month and I want to retire soon so I decided I need more life insurance. My company sent me to their doctor for a checkup. We’ve never met, and he started to ask me all these questions about the way I looked. I started to worry and began to sweat, even more than usual. I’ve to go through tons of deodorant and now my skin seems to oily all the time. Now that I’m older, I’m quite hairy so I’m a lot warmer that the people around me. My family likes to call me a big-ol-teddy-bear. The doctor asked me if I could still fit into my shirts and gloves, he wondered if my wedding ring was fitting more tightly. I told him I was thinking of starting to go on a diet even though I haven’t gained any weight cause my chest was much larger than when I was young, and I’ve been buying larger clothing to feel more comfortable. I’m getting older and my joints in my hands are starting to hurt and get swollen. I never paid much attention because I’ve always thought it was just arthritis. I’ve also had some headaches lately, a little double vision too. My wife also commented that my chin and nose seem to be bigger and that I snore all night long. 52 SBI4U1 – 2024 7. REGULATING BLOOD SUGAR RECALL: The endocrine system allows the body to regulate its own internal processes and maintain homeostasis Since the body’s cells use glucose as fuel, the regulation of the blood glucose level is crucial to maintaining homeostasis Errors in the endocrine system can lead to homeostasis not being maintained o Some of the bodily processes may become imbalanced or not properly regulated BLOOD GLUCOSE REGULATION Glucose is an important fuel for cells Pancreas maintains blood glucose levels by secreting hormones o Insulin o Glucagon Small region of specialized endocrine cells located on pancreas known as the islet of Langerhans o Alpha (α) cells & Beta (β) cells o Alpha cells secrete glucagon o Beta cells secrete insulin Insulin and glucagon are antagonistic hormones Islet of Langerhans – Endocrine cell clusters inside the pancreas that produce insulin and glucagon 53 SBI4U1 – 2024 INSULIN Stimulant Hyperglycemia: blood glucose levels rise above a set point Occurs naturally after eating a meal Effect Release of insulin from pancreas beta cells Uptake of glucose by body cells Liver converts glucose to glycogen for storage Results Lowering blood glucose levels Decrease stimulus for insulin release 54 SBI4U1 – 2024 GLUCAGON Stimulant Hypoglycemia: lowered blood glucose levels Glucose cleared from the blood stream Effect Glucagon released from pancreas alpha cells Liver to increase breakdown of glycogen Results Higher blood glucose levels Decrease stimulus for glucagon release **WATCH** DIABETES MELLITUS What did dogs teach us about diabetes (~4 min) Common symptoms: frequent urination Types of diabetes: Type I and Type II Type I Immune system attacks insulin producing cells Decreased insulin levels Type II Decreased responsiveness of cells to insulin Inability of insulin to regulate blood glucose levels 55 SBI4U1 – 2024 Glucose is not available to body cells **WATCH** o Hyperglycemia What does the pancreas do? (~3.5 min) o Excessive hunger o Fat used for cellular respiration o Increased blood viscosity and decreased blood flow ▪ Leads to blurry vision (poor blood flow in capillaries of retina) ▪ Foot infections (gravity cause blood to pool in feet) Kidneys start to excrete glucose o Glucose in urine (“sweet” urine) o Frequent urination o Persistent thirst TYPE I DIABETES: INSULIN DEFICIENCY TYPE II DIABETES: INSULIN RESISTANCE 56 SBI4U1 – 2024 57 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 10.3 on page 487 of your textbook: #1, 2, 4, 6, 7. 1. What two hormones, produced by the pancreas, regulate the blood glucose level? 2. What are the three classic symptoms of diabetes mellitus? 4. Describe the differences between type 1 diabetes and type 2 diabetes. 6. Canadian law requires that packaged foods display a Nutrition Facts label. (a) Use the Internet to research what information is listed on a Nutrition Facts label. (b) How can a Nutrition Facts label help a diabetic person choose foods? 7. Why might an insulin pump, which delivers constant and very small doses of insulin to the body, be preferable to insulin injections? 58 SBI4U1 – 2024 8. THE REPRODUCTIVE HORMONES In humans, there are separate male and female reproductive systems. The sex glands (or gonads) differ in males and females; however, they are the primary source of the sex hormones. Males – testes Females – ovaries Steroid hormones including androgens, estrogens, and progestins, have similar functions in regulating the development of female and male reproductive systems, characteristics and mating behaviours. Males and females contain all three hormones, but in different proportions. Males – predominantly androgen production Females – predominantly progestin production THE FEMALE REPRODUCTIVE SYSTEM THE OVARIES Pair of ovaries (singular: ovary) are suspended in the abdominal cavity Produce female gametes (ova, or eggs) Produce estrogens and progestins Main Principal Estrogen – ESTRADOIL – Function: Stimulates the maturation of the sex organs at puberty Develops secondary sexual characteristics such as: o breast development o growth of body hair o widening of the pelvis o development of the sex drive 59 SBI4U1 – 2024 Main Principal Progestin – PROGESTERONE – Function: Steroid hormone Prepares and maintains the uterus for the implantation of a fertilized egg and the subsequent growth and development of an embryo Synthesis and secretion of progesterone by cells in the ovaries are controlled by the release of follicle-stimulating hormone (FSH) from the anterior pituitary o The release of FSH and luteinizing hormone (LH) is controlled by gonadotropin- releasing hormone (GnRH) from the hypothalamus o gonadotropin-releasing hormone (GnRH) – hormone released by the hypothalamus that controls the release of LH and FSH from the anterior pituitary, which, in turn, control the synthesis and release of the male or female sex hormones in the gonads STRUCTURE An oviduct leads from each ovary to the uterus. The uterus is a hollow structure with walls that contain smooth muscle. It is lined by the endometrium, which is formed by layers of connective tissue with embedded glands and a rich supply of blood vessels. If an egg is fertilized and begins to develop, it must implant in the endometrium to continue developing. The lower end of the uterus, called the cervix, opens into a muscular canal, called the vagina, which leads to the exterior. Sperm enter the female reproductive tract through the vagina. At birth, the baby passes from the uterus through the vagina to the outside. THE FEMALE REPRODUCTIVE CYCLES OOGENESIS The production of eggs, or ova, from oocytes in the ovaries by two meiotic divisions Controlled by hormones produced by the pituitary gland MENOPAUSE The end of a female’s reproductive capability, after which menstruation ceases and female hormone levels drop 60 SBI4U1 – 2024 OVULATION The monthly release of one or a few developing oocytes into the nearby oviduct Once ovulated, an ovum is pulled through the oviduct by a current produced by the beating of the cilia that line the oviduct o The cilia propel the egg along the oviduct, where fertilization may occur OVARIAN CYCLE AND MENSTRUAL CYCLE Ovarian Cycle – occurs from puberty to menopause and involves the events in the ovaries that lead to the release of a mature egg approximately every 28 days o Coordinated with the menstrual cycle Menstrual Cycle – The monthly cycle of events in a sexually mature female that prepares the uterus for the implantation of a fertilized egg FERTILIZATION AND PREGNANCY – HUMANS An egg can be fertilized only during its passage through the third of the oviduct that is nearest the ovary If the egg is not fertilized during the 12 to 24 h it is in this location, it disintegrates and dies To fertilize the egg, sperm cells must first penetrate the layer of follicle cells surrounding the egg 61 SBI4U1 – 2024 As soon as the first sperm cell reaches the egg: The sperm and egg plasma membranes fuse The tail of the sperm is detached The head of the sperm cell is engulfed by the cytosol of the egg During and after implantation: Human Chorionic Gonadotropin (hCG) is secreted by cells associated with the embryo hCG – a hormone that keeps the corpus luteum in the ovary from breaking down ▪ It suppresses the mother’s immune system to prevent it from rejecting the embryo. Excess hCG is excreted in the urine o Its presence in the urine or blood provides the basis of pregnancy tests After implantation, the embryo begins to grow more rapidly, and a placenta forms o Placenta – an organ formed from the uterine lining with membranes from the uterus. It supports the growth of the embryo THE MALE REPRODUCTIVE SYSTEM THE TESTES Testes (singular: testis) Secrete androgens (steroid hormone) Main Principal Androgens – TESTOSTERONE – Function: Male sex hormone Young males – jump in testosterone levels results in: o Onset of puberty and development of secondary sexual characteristics: ▪ Growth of facial and body hair ▪ Muscle development ▪ Changes in vocal cords ▪ Development of sex drive 62 SBI4U1 – 2024 Synthesis and secretion of testosterone by cells in the testes are controlled by the release of LH from the anterior pituitary gland o Release of LH is controlled by GnRH from the hypothalamus, the same hormone that regulates the sex hormones in females THE MALE REPRODUCTIVE CYCLE SPERMATOGENESIS The production and development of sperm cells in the testes Controlled by the male androgen hormone testosterone Human males have a pair of testes suspended in a bag-like scrotum o Serves to regulate their temperature In human males, each testicle is packed with about 125 m of seminiferous tubules, in which sperm proceed through all the stages of spermatogenesis. Males produce sperm constantly, at a rate of about 130 million per day 63 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 10.7 on page 503 of your textbook: #1, 2, 6, 9, 10. 1. What are the main male and female sex hormones? Describe their functions. 2. What is the relationship between the ovarian cycle and the menstrual cycle? Explain how reproduction is determined by these two cycles. 6. Name three hormones common to both males and females that regulate both the menstrual cycle and the male reproductive functions. 9. How are the effects of testosterone on males and estrogen on females similar? 10. What is the importance of human chorionic gonadotropic hormone (hCG)? 64 SBI4U1 – 2024 9. THE NERVOUS SYSTEM The human brain is the control centre of the body o If something goes wrong with the brain, other parts of the body will likely be affected. The nervous system is the body’s interface with the external environment and the control system that manages the internal environment WARM-UP: Read the following sequence silently, pausing at each dash: 1) MT-VVC-RC-IAU-SAB-MW Look away from the computer and write down any letters from this sequence that you can remember Now, read the following sequence silently, again pausing at each dash: 2) MTV-VCR-CIA-USA-BMW Look away from the computer and write down any letters from this sequence that you can remember ROLE OF THE NERVOUS SYSTEM To transmit information rapidly The brain receives information about the environment and responds accordingly 65 SBI4U1 – 2024 NEURONS Neuron – a nerve cell that is capable of conducting nerve impulses Neural signalling – the reception, transmission, and integration of nerve impulses by neurons, and the response to these impulses Afferent neuron – a neuron that carries impulses from sensory receptors to the central nervous system; also called a sensory neuron Interneuron – a local circuit neuron of the central nervous system that relays impulses between afferent (sensory) and efferent (motor) neurons efferent neuron – a neuron that carries impulses from the central nervous system to skeletal muscles; also known as a motor neuron HOW THE NERVOUS SYSTEM WORKS 1) Detection of stimulus 2) Processing in the brain 3) Response in rest of body INFORMATION-PROCESSING STEPS IN THE NERVOUS SYSTEM 1) stimulus reception by sensory receptors on afferent neurons 2) message transmission by afferent neurons to interneurons 3) integration of neural messages in interneurons 4) response by the transmission of neural messages by efferent neurons to effectors, where appropriate action occurs. NERVOUS SYSTEM MECHANISM Function Description Components Sensory receptor Sensory input Detection of stimulus Afferent/sensory neurons Central nervous system Integration Processing in the brain (brain & spinal cord interneurons) Effector cells (muscle cells Motor Output Response in other body part or glands) Efferent / motor neurons NERVE CELLS 66 SBI4U1 – 2024 Contains an enlarged cell body o Where nucleus and organelles are located Specialized projections that conduct electrical signals o Dendrites – Receives signals and sends them to the cell body o Axon – Conducts signals away from cell body to another neuron Connections between the axon of a neuron to the dendrite of another neuron is your basic pathway of electrical signals of your nervous system 67 SBI4U1 – 2024 ORGANIZATION OF NERVOUS SYSTEM Central nervous system (CNS) Includes our brain and spinal cord Made up of interneurons Peripheral nervous system (PNS) Afferent system – receives input from body receptors and transmits signals to CNS Efferent system – carries signal from CNS to the target part of the body ORGANIZATION OF THE PERIPHERAL NERVOUS SYSTEM Efferent system can be broken down into 2 systems: Somatic system Responds to external and internal stimuli by sending signals to skeletal muscles (voluntary) Autonomic system Responds to stimuli by sending signals to smooth muscle, cardiac muscle, and organs of the body (involuntary) AUTONOMIC SYSTEM Further divided into two groups: Sympathetic nervous system Prepares the body for stress Affected by epinephrine Increased heart rate, vasoconstriction, dilate pupils, etc. Parasympathetic nervous system Restores the body back to normal Increased maintenance activities such as digestion 68 SBI4U1 – 2024 REFLEX ARC Simplest type of neural circuit Type of nerve circuit that regulates the reflex Reflex – rapid, involuntary responses to stimuli Integration occurs in the spinal cord rather than in the brain Examples: Withdrawal reflex Knee-jerk reflex Gag reflex Blink reflex **WATCH** Reflex Arcs (~2 min) 69 SBI4U1 – 2024 70 SBI4U1 – 2024 HOMEWORK: THE NERVOUS SYSTEM The central nervous system (CNS) consists of the brain and spinal cord. It communicates with the peripheral nervous system (PNS), which is made up of the afferent and efferent systems. 1. Which part of the nervous system is used to process information related to each area below? a) Senses: b) Voluntary actions: c) Involuntary actions that speed up respiratory metabolism: d) Involuntary actions that slow down respiratory metabolism: 2. Label the main parts of the nervous system in the figure below. A) B) C) D) E) F) G) H) I) J) K) 71 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 11.1 on page 521 of your textbook: #1, 3, 4, 5. 1. (a) Explain the functions of afferent neurons, efferent neurons, interneurons, and effectors. (b) Describe how they work together. 3. Which nervous system cells provide a supporting role, rather than transmitting nerve impulses? What is their role? 4. Why do you think reflexes have evolved to occur without the need for the brain to process the information? 5. What is a reflex arc? Describe a simple example of a reflex arc. 72 SBI4U1 – 2024 10. NERVE SIGNALS TYPES OF NEURONS There are different type of neurons but they all have similar features Enlarged cell body Dendrites Axon GLIAL CELLS Cells part of the nervous system that are not neurons are called glial cells There are many different types of specialized glial cells o They help to provide and support nerve cells GLIAL CELLS – SCHWANN CELLS Cells that wrap themselves around the axon of a neuron to provide insulation for electrical impulses through an axon Cell form a layer called the myelin sheath o High lipid content so they are poor electrical conductors o This helps to provide electrical insulation Gaps between wrapped Schwann cells are called Node of Ranvier The myelin sheaths and the gaps help to speed up the rate at which electrical impulses travel along the axon 73 SBI4U1 – 2024 MEMBRANE POTENTIAL V(membrane potential) = V(inside of cell) – V(outside of cell) At rest (or Resting Potential): membrane potential of a neuron is -70mV All cells have a membrane potential o Only a few cells can generate a large enough change in membrane potential such as neurons and muscle cells CONDUCTION OF ELECTRICAL SIGNALS BY NEURONS Na+/K+ PUMP Uses ATP to drive active transport Pumps 3 Na+ out of cell, 2 K+ into the cell Maintain ionic gradients (i.e., Resting potential -70mV) ELECTROCHEMICAL GRADIENT Chemical gradient Concentration gradient Chemical force Movement from high to low ion concentration Electrical gradient Ion gradient (relative electrical charge) Electrical force Movement of positive ion to area of negative ion concentration and vice versa 74 SBI4U1 – 2024 ACTION POTENTIAL Action Potential – the voltage difference across a nerve cell membrane when the nerve is excited When a neuron conducts an electrical impulse that causes a change in membrane potential Starts with a positive change to the membrane potential (depolarization), followed by a decrease in membrane potential (repolarization) o Begins as a stimulus that causes positive charges from outside the neuron to flow inward, making the interior side of the membrane less negative 1) PHASE 1: Resting State Before the neuron receives a stimulus, it is in its resting state (-70mV) Na+ channels: closed o Na+ ions not able to enter neuron K+ channels: closed o K+ ions not able to exit neuron 2) PHASE 2: Threshold Depolarization stimulus opens some Na+ channels Results in a graded potential that reaches threshold (-50mV) 75 SBI4U1 – 2024 3) PHASE 3: Depolarization Depolarization opens Na+ channels resulting in more depolarization Stimulates other Na+ channels to open until all are open An example of positive feedback o Depolarization to threshold potential triggers a larger depolarization until peak of action potential 4) PHASE 4: Repolarizing Phase Once peak action potential (+30mV) has been reached, K+ channels begin to open up and allowing K+ ions to exit the cell Na+ channels also begin to close Outward flow of K+ begins repolarization of cell 5) PHASE 5: Undershoot K+ begin closing but very slowly, enough for “more than enough” K+ ions to move out of the cell resulting in hyperpolarization (-80mV) Help re-establish resting potential 76 SBI4U1 – 2024 PERMEABILITY OF IONS DURING AN ACTION POTENTIAL “ALL OR NOTHING” PRINCIPLE Any stimuli cause some degree of depolarization of a neuron, but an action potential is produced only if the stimulus is strong enough to cause the depolarization to reach the threshold Once triggered, the changes in membrane potential take place independently of the strength of the stimulus. Magnitude of action potential is independent of stimulus strength once threshold is reached Amplitude of all action potentials is constant PROPOGATION Action potential “travels” be repeated regeneration along axon Depolarization of influx of Na+ ions depolarizes neighboring region above threshold Unidirectional REFRACTORY PERIOD Refractory Period – Period of time during which the threshold required for the generation of an action potential is much higher than normal Why can’t the action potential be propagated backwards? (bidirectional) Period when neuron is desensitized to depolarization o Caused by a closed Na inactivation gate o Occurs at the beginning of the peak of an action potential o Can only respond to another stimulus when Na inactivation gates are reopened Threshold is slightly higher than normal Purpose: 1. Prevents action potential from moving backwards 2. Limits maximum frequency with action potential can be generated 77 SBI4U1 – 2024 FACTORS AFFECTING SPEED OF CONDUCTION Myelination Exposed areas between myelin sheaths: Nodes of Ranvier Conductions hop from node to the next to speed up travel speed SYNAPSE Synapse – A functional connection between neurons or between neurons and effectors A cell junction that controls communication between a neuron and another cell (neuron or muscle cell) 78 SBI4U1 – 2024 SYNAPSE LOCATIONS Pathway Pre-synaptic Cell Post-synaptic Cell Sensory input (afferent) Sensory receptor Sensory neuron Integration Sensory neuron interneuron Interneuron motor neuron Motor Output (efferent) Motor neuron Muscle cell glands ELECTRICAL SYNAPSE Electrical Synapse – A synapse in which the presynaptic cell makes direct contact with the postsynaptic cell, allowing current to flow via gap junctions between the cells Current from presynaptic cell flows directly to the postsynaptic cell through gap junctions Gap Junctions – Channels between adjacent cells, through which ions and other small molecules can pass Direct communication through physical connection Allows rapid transmission Difficult to regulate CHEMICAL SYNAPSE Chemical Synapse – A synapse in which a neurotransmitter moves from a presynaptic cell to a postsynaptic cell through the synaptic cleft Presynaptic Cell – Nerve cell that will release neurotransmitters Postsynaptic Cell – Nerve cell that will receive neurotransmitters Synaptic Cleft – gap separating pre- and postsynaptic cell Synaptic Vesicles – sacs at the synaptic terminal that contains neurotransmitters Neurotransmitter – a substance released by presynaptic cell as an intercellular messenger into synaptic cleft 79 SBI4U1 – 2024 1. Presynaptic membrane is depolarized by incoming action potential 2. Ca2+ channels open 3. Ca2+ ions enter cell 4. Stimulates exocytosis of synaptic vesicles NEUROTRANSMITTERS Depending on the neurotransmitter, able to cause an excitation or an inhibiting effect Acetylcholine: Most common type in humans Triggers muscle contractions, hormone secretion, wakefulness, memory, and many more Endorphins: Released during pleasurable experiences or physical stress 80 SBI4U1 – 2024 HOMEWORK: NERVE SIGNALS Read the article below and answer the questions that follow. 81 SBI4U1 – 2024 82 SBI4U1 – 2024 11. THE CENTRAL NERVOUS SYSTEM Humans have the most complex nervous system of all animals. The Nervous System is composed of two parts: 1. Central Nervous System (CNS) – brain and spinal cord 2. Peripheral Nervous System (PNS) – nerves that connect the brain and spinal cord to the rest of the body The organization of the brain is exceedingly complex THE CENTRAL NERVOUS SYSTEM Consists of the brain and spinal cord Both are wrapped in three protective membranes called meninges o Meninges – Three layers of connective tissue that surround and protect the brain and spinal cord Spaces between meninges are filled with cerebrospinal fluid o Cerebrospinal Fluid – Circulating fluid that surrounds the membranes of the brain and spinal cord; provides neural connection to the endocrine system Three specific functions: 1. Receives sensory input 2. Performs integration (coordinates) 3. Generates motor (efferent) output **WATCH** **WATCH** The Sensory System (~10.5 min) The Sensory System (~12 min) 83 SBI4U1 – 2024 SPINAL CORD Centre of coordinate of reflexes Allows communication between spinal nerves and the brain Contains interneurons Grey Matter – the tissue of the brain and spinal cord where the cell bodies and dendrites of neurons are located White Matter – the tissue of the brain and spinal cord, composed primarily of axons of neurons; in the spinal cord, it surrounds the grey matter BRAIN Consists of three main regions: 1. Forebrain, 2. Midbrain, and 3. Hindbrain **WATCH** The Brain (~14 min) Medulla Oblongata – T he hindbrain region that connects the spinal cord to the cerebellum; important in autonomic nerve control Cerebrum – The brain region that is involved in motor activities and sensory information; the largest and most developed region of the brain Pons – The brain region that transfers nerve signals between the cerebellum and the medulla CEREBRUM Largest portion in humans Communicates with and coordinates the activities of other parts of the brain A longitudinal fissure divides the cerebrum into left and right hemispheres each having major lobe areas and connected by the corpus collosum 84 SBI4U1 – 2024 85 SBI4U1 – 2024 CEREBELLUM Separated from the brain stem by the fourth ventricle Largest portion of the brainstem Receives sensory input from the eyes, ears, joints, and muscles BRAIN STEM Contains the midbrain, pons, and the medulla oblongata Midbrain – acts as a relay station for tracts passing between the cerebrum and the spinal cord or cerebellum Pons – contains axons that form a bridge between the cerebellum and the rest of the central nervous system Medulla Oblongata – contains reflex centres for vomiting, coughing, sneezing, hiccupping, and swallowing 86 SBI4U1 – 2024 LEFT BRAIN, RIGHT BRAIN The labels “left-brained” and “right- brained” are sometimes used when referring to someone’s abilities These labels can only be used loosely, however, to describe tendencies While there is some measurable dominance of different functions on different sides of the brain, most productive functioning is integrated in both sides There is no clear-cut division of functions, except that the right side of the body is controlled by the left side of the brain, and vice versa 87 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 11.3 on page 536 of your textbook: #1, 2, 3, 4, 5, 7, 8. 1. What are the three main regions of the brain that are shared by all primates? What makes the human brain different? 2. What are the main functions of the spinal cord? 3. In a collision with an opposing player, a hockey player suffers damage to the cerebellum. How might this affect the player’s body movements? 4. Which side of the brain controls which side of the body? What connects the two hemispheres? 88 SBI4U1 – 2024 5. What does it mean to be “left-brained” or “right- brained”? 7. Bigger animals have bigger brains. Does this mean that bigger animals are smarter than smaller animals? Explain your answer. 8. A man suffers a stroke. He is unable to speak, but he can read and understand text. Explain how his brain has most likely been affected. 89 SBI4U1 – 2024 12. THE PERIPHERAL NERVOUS SYSTEM WHAT DOES THE PERIPHERAL NERVOUS SYSTEM DO? Connects the central nervous system to the organs, limbs, and skin Allows the brain and spinal cord to receive and send information to other areas of the body Carries sensory and motor information to and from the central nervous system Regulates involuntary body function like heartbeat and breathing 90 SBI4U1 – 2024 SYMPATHETIC AND PARASYMPATHETIC DIVISIONS Autonomic nervous system is organized into sympathetic and parasympathetic divisions These divisions are always active and have opposing effects on the organs they affect, thus enabling precise control THE SYMPATHETIC AND PARASYMPATHETIC DIVISIONS IN THE BODY SYSTEMS Circulatory System Sympathetic neurons stimulate the heartbeat, increasing its force and rate Parasympathetic neurons inhibit the heartbeat Digestive System Sympathetic neurons inhibit the smooth muscle contractions that move materials through the small intestine Parasympathetic neurons stimulate the same activities. CRANIAL NERVES Cranial Nerves – The 12 pairs of nerves within the parasympathetic division of the autonomic system, which emerge directly from the brain and serve the head, neck, and body trunk 91 SBI4U1 – 2024 13. THE SENSES SENSE ORGANS Sensory neurons can be individual neurons or a combination of neurons forming a sensory organ Some sensory organs and senses include: Sight, hearing, taste, smell, touch **NOTE: the major association areas for these senses are located in the forebrain** INFORMATION INPUT Recall: The afferent system of the PNS has receptors who sense stimuli outside or on the surface of the body and send information to the CNS There are five types of sensory receptors that receive stimuli and send information to the CNS. 1. Mechanoreceptors – Detect mechanical energy, such as changes in pressure, body position, or acceleration Auditory receptors in the ears are mechanoreceptors. 2. Photoreceptors – Detect the energy of light In vertebrates, photoreceptors are mainly located in the retina of the eye 3. Chemoreceptors – Detect specific molecules or chemical conditions, such as acidity Taste buds on the tongue are examples of chemoreceptors 4. Thermoreceptors – Detect the flow of thermal energy Located in the skin, where they detect changes in the temperature of the body surface 5. Nociceptors, or pain receptors – Detect tissue damage or noxious chemicals Their activity registers as pain Located in the skin and in some internal organs 92 SBI4U1 – 2024 THE TRADITIONAL SENSES – VISION The most complex of the five traditional senses in humans. Photoreceptors in the retina, located at the inside rear of the eye, detect light at particular wavelengths Convert the light stimuli to nerve impulses, which move the information via the optic nerve to visual centres in the brain The human eye has a lens that forms images and then focuses the images on the field of photoreceptors, which convert the signals from electromagnetic energy to nerve impulses Signals that originate at the photoreceptors are integrated in the brain into a point-by-point representation of the viewed object The retina holds layers of neurons that perform an initial integration of visual information before it is sent to the brain There are two types of photoreceptors in the retina: rods and cones o Rods – Detection of light at low intensities o Cones – Detection of different wavelengths (colours) o The retina of a human eye contains about 120 million rods and 6 million cones, organized into a densely packed single layer ISSUES WITH YOUR VISION 1) Normal Eye Vision 93 SBI4U1 – 2024 2) Hyperopia Far sighted Image occurs behind retina Refracting power too week Eyeball too short SOLUTION: Conex lens (converging lens) Without Correction With Correction 3) Myopia Near sighted Image in front of retina Refracting power of eye too strong Eyeball too long SOLUTION: Concave lens (diverging lens) Without Correction With Correction 94 SBI4U1 – 2024 4) Astigmatism Occurs when the cornea or lens is cured more steeply in one direction than another Corneal Astigmatism – cornea has mismatched curves Lenticular Astigmatism – lens has mismatched curves 5) Presbyopia Lens becomes rigid Cannot “adjust” for distance then near SOLUTION: reading glasses or bifocals 6) Cataract Lens clouds SOLUTIONS: remove and replace with lens implant 95 SBI4U1 – 2024 HOMEWORK: TEXTBOOK Complete the following questions from Chapter 11.5 on page 548 of your textbook: #1, 2. 1. What is the importance of sensory systems for an organism? 2. Name five sensory receptors and the type of stimulus that each detects. 96 SBI4U1 – 2024 14. THE BODY AND STRESS WHAT IS STRESS? When your body is in a state of homeostasis, you are relaxed and exhibit no signs of stress Stress is the body’s response to a stimulus, or stressor, that triggers a move away from homeostasis. Stress does not always mean something negative; it can also be neutral or positive o Negative stress is also not necessarily harmful BAD STRESS Chronic and repeated stress can harm the body Symptoms of stress include: an increase in respiration rate and heart rate muscle tension frequent urination irritability tiredness trouble sleeping. During stress, the body reduces blood flow to some organs (for example, those of the gastrointestinal