Endocrine System and Hormones PDF

▪ The Endocrine System regulates, coordinates and controls: ▪ Growth and development. ▪ Male and female development. ▪ How your body uses energy. ▪ Levels of salts and sugars in your blood. ▪ The amount (volume) of fluid in your body. ▪ Appetite. ▪ Many other body function...

▪ The Endocrine System regulates, coordinates and controls: ▪ Growth and development. ▪ Male and female development. ▪ How your body uses energy. ▪ Levels of salts and sugars in your blood. ▪ The amount (volume) of fluid in your body. ▪ Appetite. ▪ Many other body functions. ▪ The Endocrine Glands are the organs of the Endocrine System. ▪ They produce and secrete (release) Hormones. ▪ They are located all over your body. Gland What it Regulates Pituitary “Master Gland” that regulates all other Endocrine Glands, also releases growth hormone Thyroid Metabolism, body heat, bone growth Parathyroids Use of Calcium and Phosphorous Hypothalamus Links nervous system to endocrine system Adrenal Response in emergency or stressful situations, metabolism, blood pressure, salt balance Pancreas Blood sugar Ovaries Production of eggs; female characteristics Testes Production of sperm; male characteristics Thymus Parts of the immune system  Hormones are chemical messengers that are secreted (released) from glands into the blood and affect cells in another part of the body. ▪ Hormones only work on certain cells, called target cells. ▪ The target cells have special receptors that “recognize” the hormones and allow them to influence that cell. Target Target Cell Cell for for Target Cell for Target Cell for Hormone Hormone A A Hormones A and B Hormone B Hormone A Hormone B These receptors recognize the hormones. They “fit” like a lock and key. External stimuli Internal stimuli by way of nerves from the sensory by way of nerves organs in the nervous and other hormones system from inside the body  Stimulus: ▪ You hear a loud noise ▪ A large dog runs toward you, growling and barking ▪ You eat a large candy bar ▪ You have not eaten in six hours ▪ You have strep throat ▪ A chain of events occur that lead from the stimulus to the response. Hypothalamus & Pituitary Figure 11-3: Autonomic control centers in the brain Hypothalamus ▪ Integrates functions that maintain chemical and temperature homeostasis ▪ Controls the release of hormones from the anterior and posterior pituitary Hypothalamus ▪ Synthesizes releasing hormones in cell bodies of neurons ▪ Hormones are transported down the axon and stored in the nerve endings  Hypothalamic Releasing Hormones Five important releasing hormones are made in the hypothalamus ▪ Thyrotropin-releasing hormone (TRH) ▪ Corticotropin-releasing hormone (CRH) ▪ Gonadotropin-releasing hormone (GnRH) ▪ Growth hormone-releasing hormone (GHRH) ▪ Prolactin-releasing factor (PRF)  Hypothalamus Releasing Hormones Secretion: ▪ Is influenced by emotions ▪ Can be influenced by the metabolic state of the individual ▪ Delivered to the anterior pituitary via the hypothalamic-hypophyseal portal system  Anterior Pituitary Secretes tropic hormones Anterior Pituitary Hormones Each of anterior pituitary hormone is synthesized by a cell population. - ACTH - Prolactin - GH - TSH - FSH, LH  Anterior Pituitary Hormones Growth Hormone (GH): primary hormone responsible for regulating body growth, and is important in metabolism Thyroid-stimulating Hormone (TSH): stimulates secretion of thyroid hormone & growth of thyroid gland Adrenocorticotropic Hormone (ACTH): stimulates cortisol secretion by the adrenal cortex & promotes growth of adrenal cortex  Anterior Pituitary Hormones Follicle-stimulating Hormone (FSH): Females: stimulates growth & development of ovarian follicles, promotes secretion of estrogen by ovaries. Males: required for sperm production Luteinizing Hormone (LH): Females: responsible for ovulation and regulation of ovarian secretion of female sex hormones. Males: stimulates cell in the testes to secrete testosterone Prolactin: Females: stimulates breast development and milk production. Males: involved in testicular function HYPOTHALAMIC EFFECTS ON THE HORMONE ANTERIOR PITUITARY Thyrotropin-releasing hormone Stimulates release of TSH (TRH) (thyrotropin) and Prolactin Corticotropin-releasing hormone Stimulates release of ACTH (CRH) (corticotropin) Gonadrotropin-releasing Stimulates release of FSH and hormone (GnRH) LH (gonadotropins) Growth hormone-releasing Stimulates release of growth hormone (GHRH) hormone(GH) Prolactin-releasing factor (PRF) Stimulates release of prolactin(PRL)  Posterior Pituitary Comprised of the endings of axons from cell bodies in the hypothalamus Axons pass from the hypothalamus to the posterior pituitary via the vessels Posterior pituitary hormones are synthesized in the cell bodies of neurons  Posterior Pituitary Hormones synthesized in the hypothalamus are transported down the axons to the endings in the posterior pituitary Hormones are stored in vesicles in the posterior pituitary until release into the circulation Principal Hormones: Vasopressin(ADH) & Oxytocin Secretion of Posterior Pituitary Hormones Figure 7-12: Synthesis, storage, and release of posterior pituitary hormones Oxytocin -Acts primarily on the mammary gland and uterus -Secretion is increased during labor Vasopressin (ADH) Is also known as antiduretic hormone (ADH) Participates in body water regulation (Water is lost from lungs, sweat, feces and urine on a daily basis) Negative Feedback Controls: Long & Short Loop Reflexes Figure 7-14: Negative feedback loops in the hypothalamic-anterior pituitary pathway  Pathologies: Over or Under Production ▪ "no bad hormones – just too much or too little" ▪ Hypersecretion: too much ▪ Tumors or cancer ▪ Grave's disease- thyroxin ▪ Hyposecretion: too little ▪ Goiter – thyroxin ▪ Diabetes – insulin Do you know where each hormone comes from, where it acts, and what the action is? Guess first, then click each to find out. Adrenali Progest ne Testoster erone one Thyroxin Insulin e Cortisol Estrogen Done ▪ Where it comes from: Adrenal Gland ▪ Where it acts: heart, blood vessels, eyes ▪ What it does: stimulates heart rate, increases blood pressure, dilates pupils ▪ Causes "Adrenaline Rush” ▪ A 'fight and flight' hormone. ▪ It is released in high stress conditions or in excitement or fear. ▪ Loud noise, high temperature etc. may also trigger its release since these are also high stress situations. Return to hormones slide ▪ Where it comes from: outer part of adrenal gland ▪ Where it acts: multiple tissues ▪ What it does: mental stimulation, breaks down fat and protein to glucose, anti-inflammation ▪ It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety. Return to hormones slide  Where it comes from: ovary (where an egg was released) Where it acts: uterus What it does: controls menstruation in women and plays a role in pregnancy. One of the components of birth control pills Return to hormones slide ▪ Where it comes from: ovary ▪ Where it acts: breast tissue, reproductive structures in female ▪ What it does: stimulates development of female sexual characteristics ▪ Estrogen levels may be related somehow to migraine headaches in women. Return to hormones slide ▪ Where it comes from: thyroid gland ▪ Where it acts: most cells of the body ▪ What it does: controls the rate of metabolic processes (how energy is used) in the body and influences physical development ▪ People may not produce enough of this hormone and get a condition known as hypothyroidism. They can take thyroxine to treat this condition. Return to hormones slide ▪ Where it comes from: testicles ▪ Where it acts: body-hair cells, muscle, reproductive structures ▪ What it does: stimulates development of male sexual characteristics ▪ Testosterone is a steroid and has been administered to athletes in order to improve performance. This is considered to be a form of doping in most sports and is a very dangerous practice. ▪ Females also produce small amounts of testosterone in their ovaries that affect muscle development and other body functions. Return to hormones slide ▪ Where it comes from: Insulin is produced in the pancreas ▪ Where it acts: liver, muscle, and fat tissue ▪ What it does: Insulin causes cells to take up glucose (sugar) from the blood, storing it in the liver and muscle, and stopping use of fat as an energy source. ▪ Problems with insulin production or use in the body can lead to diabetes. Return to hormones slide ▪ What are the functions of the Endocrine System? ▪ Name 5 Endocrine Glands and what they do. ▪ What are hormones? ▪ How do hormones work? ▪ Name some hormones and what they do. ▪ At what times in your life do you think your Endocrine System is most active?  UNIT 4 HOMEOSTASIS I. INTRODUCTION A. Definition – a process of maintaining a constant internal environment despite changes in the external environnment B. Feedback Loop 1. a feedback loop is any system in which part of an output of the system is connected back into one of its inputs 2. eg. Ecosystems in an ecosystem in which weasels eat mice we have a feedback loop if the weasels eat more mice then there are fewer mice to eat which will result in fewer weasels over time if there are fewer weasels, there will be more mice 🡪 more food for weasels and more weasels  3. eg. thermostat Sensor Co-ordinator regulator Bimetallic Thermostat Furnace strip switches on result Cool room Warm room result Furnac Thermostat Bimetallic e off switches strip regulator Co-ordinator Sensor 4. Parts of a feedback loop a. sensor - part that detects the difference b. co-ordinator - part that manages the response c. regulator - part that affects a change d. result - the effect of the regulator change 5. negative feedback – a system that is activated to restore the original condition eg keep room at 20oC 6. positive feedback loop – a system which is designed to amplify a small effect eg. contractions at childbirth  Thermoregulation in humans – maintaining the body at 37oC regardless of outside conditions Co-ordinator Skin blood vessels dilate so more blood flow to Hypothalamus reacts result skin to lose heat to high temperature in blood and switches regulators Body on cooling temperature decreases Sweat glands initiate sweating Sensor Sweat evaporates and cools Carotid artery sensors skin detect blood temp. too high Body temperature  Body temperature too low Carotid artery sensors detect blood temp. Skin blood vessels contract and so sensors less heat is lost Hypothalamus reacts to Body temperature low temperature in result increases regulators blood and switches on heating Skeletal muscles contract,. shivering generates heat Co-ordinator Body hair becomes erect, raised hair traps warm air -the blood passes through the carotid arteries in the neck on the way to the hypothalamus in the brain -if this blood is cooled, you feel cool and if this blood is warm, you feel warm eg. a scarf keeps the neck warm & so you feel warm eg. when you are hot, a wet cloth around the neck makes you feel cool II) HORMONES & THE ENDOCRINE SYSTEM A. Hormones 🡪 chemicals released by cells in one part of the body that affect cells in other parts of the body. 1. source - endocrine glands -these secrete hormones directly into the blood 2. transport - blood -hormones go to every cell 3. target cells -these are cells with receptors for the hormones -a hormone may have one specific target cell or a hormone may target every cell Types of hormones a. Steroid hormones b. Peptide hormones B. Steroid hormones 3. hormone circulates 1. Hormone made in in blood endocrine cell 4. hormone enters target cell 5. hormone binds to 2. hormone hormone receptor diffuses into blood 6. hormone-receptor complex DNA. diffuses into nucleus 7. this binding activates a gene nucleus 8. mRNA is transcribed & a new protein is made target cell 9. the new protein leaves the cell C. Protein hormones 4. Hormone binds to receptor on cell 1. Hormone made in 3. hormone surface endocrine cell circulates in blood 5. cAMP ATP hormone-receptor complex causes 2. hormone diffuses ATP🡪 cAMP into blood 6. cAMP activates existing enzyme / protein 7. activated protein target leaves cell cell D. The Master Gland – the Pituitary Gland - the pituitary gland is located under the hypothalamus, the area of the brain associated with homeostasis - there are two lobes of the pituitary, - the posterior lobe stores & releases hormones - the anterior lobe produces many hormones  BLOOD GLUCOSE CONTROL  Blood glucose control 1. The goal is to maintain the level of glucose within a narrow range. If there is too little blood glucose, the body cells will not be able to get enough in and so will be low in energy If there is too much blood glucose, the body cells will not be able to get enough in and so will be low in energy 2. Hormones The hormones insulin and glucagon are the major controllers The hormones epinephrine and nor-epinephrine plus glucocorticoids are also involved in control at a minor level  INSULIN in feedback loops II) HORMONES & THE ENDOCRINE SYSTEM  Liver converts glucose to glycogen regulators Body cell uptakes more glucose coordinator result Pancreas(Beta cells in Islets of Langerhans) release INSULIN Blood sugar drops sensor Hypothalamus detects high blood glucose high Blood glucose  Blood glucose low sensor Hypothalamus detects low blood sugar Blood sugar rises Pancreas(Alpha cells in the Islets of Langerhans) secrete results GLUCAGON coordinator regulator Liver converts glycogen to glucose Insulin increases fat storage Glucagon increases fat release  Insulin action 1. Stimulates glucose uptake into cells thus reducing blood glucose insulin glucose insulin active recepto r A TP cAMP glucose uptake Now, skip ahead to “Insulin Actions” 2. Stimulates protein synthesis by increasing amino acid transport 3. Inhibits lipid breakdown 4. Inhibits glycogen breakdown and stimulates glycogen synthesis DIABETES DEFINITION: ? “A metabolic disease in which the body’s inability to produce any or enough insulin causes elevated levels of glucose in the blood.”  TYPES OF DIABETES: ? Type 1 ? Type 2 ? Gestational diabetes ? Prediabetes  TYPE 1 DIABETES: ⚫ Also known as juvenile diabetes ⚫ Usually diagnosed in children and young adults ⚫ When body’s own immune system destroys the insulin producing cells of the pancreas – beta cells – which produce insulin ⚫ Only 5% of people have this disease ⚫ Body does not produce insulin ⚫ Is not preventable ? No primary intervention ⚫ Causes? ? Predisposition to diabetes – genetics - and something (i.e. weather, virus... etc ) in environment triggers the disease SYMPTOMS OF DIABETES:  TYPE 2 DIABETES: ⚫ Most common form of diabetes – about 90% of cases ⚫ Used to be called adult onset, non insulin dependent diabetes ⚫ Body produces insulin, but does not use it properly ? glucose doesn’t move into cells, they pile up in the bloodstream ⚫ sx’s when they do occur are often ignored because they may not seem serious  RISK FACTORS: ? Genetics ? Family pmHx ? Polycystic ovary syndrome ⚫ Irregular menses ? Race ⚫ African Americans, Hispanics and Asians > whites ? Age ⚫ After age 45, but increases in younger adults and children ? Environmental factors ⚫ Inactivity ⚫ Weight gain G ESTATIONAL DIABETES MELLITUS (GDM): Having diabetes during pregnancy ? Family Hx of diabetes, overweight prior to pregnancy? Having gestational diabetes puts you at risk for diabetes type 2 Giving birth to a baby >9 lbs also puts you at risk for type 2 18 out of every 100 pregnant females will develop GDM HOW TO MONITOR YOUR DIABETES: ? Type 1: PREVENTIONS: ⚫ Not preventable, as of right now. ? Studies on ways to possible prevent further destruction of the beta cells ⚫ Maintain and control sugar levels, insulin injection ⚫ Healthy life style – exercise and diet ⚫ Islet transplantation?  PREVENTIONS: ? Type 2: ⚫ Primary: maintain a healthy lifestyle ⚫ Secondary: check HgA1c, adjust diet ? HgA1c – blood sugar avg over span of 3 months ? Measures what % of your Hg is coated with sugar ? Nl = 4 % - 5.6%, pre diabetes = 5.7% -6.4% and diabetes = 6.5% + ⚫ Tertiary: exercise and eat well ⚫ Foot exam? CONSEQUENCES OF A LACK OF INSULIN Hyperglycemia( High level of blood glucose) 1 – glucose can’t get into cells and the osmotic effect of glucose leads to damage to eyes & kidneys 2- Muscle protein is broken down to release amino acids which are used to make glucose, leads to muscle wasting 3-Fats are broken down to convert lipids to glucose [lipolysis] 4-Diabetic ketoacidosis – breakdown in fat cells leads to production of free fatty acids and ketone bodies. Can lead to coma and death  Treatment Type I Diabetes a. person fails to make sufficient insulin b. Insulin must be added to the body test kit Type II Diabetes a. The pancreas produces insulin but body cells do not react to it b. The body then produces more insulin c. Because of over action eventually the beta cells wear out and no more insulin is made d. To prevent this, a person must change their diet Diabetic diet control 1. Avoid foods high in sugar 2. Eat complex carbohydrates 3. Eat food high in fibre 4. Keep diet low in fat 5. Eat more, smaller meals 6. Bedtime snacks high in protein 7. Exercise daily 8. Keep caffeine intake low 9. Keep alcohol intake low The glycemic index (GI) a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers the higher the number, the greater the blood sugar response.  food type G I roasted peanuts 14 milk chocolate 49 skim milk 31 white rice 98 french fries 75 baked potato 85 potato chips 54 dates 103 fresh pineapple 61 SHORT TERM BLOOG GLUCOSE REGULATION  Short term changes in blood sugar a. Blood glucose is regulated over time by insulin & glucagon but sometimes the body needs a sudden burst of glucose b. These responses are called stress responses and they elevate blood glucose only, there is no hormone to lower blood glucose in these responses c. Because this is not a feedback loop, stress can continue and problems will result  Stress sensed by brain Short-term Hypothalamus responds Long term Spinal chord Pituitary gland releases nerves stimulate ACTH to stimulate Adrenal gland Adrenal gland medulla cortex Epinephrine & Glucocorticoids norepinephrine released released Amino acids 🡪 glucose Glycogen 🡪 glucose Fats 🡪 fatty acids Fatty acids 🡪 glucose Blood glucose increased Blood glucose increased The Excretory System (Kidneys) KEY CONCEPT The excretory system removes wastes and helps maintain homeostasis.  Waste material disposal in our body is with Solids Digestive system Liquids Excretory system Excretory organs: skin , liver , large intestine , lungs , and kidneys  Nonsolid wastes are eliminated through lungs, skin, and kidneys. Lungs exhale carbon ski n dioxide and water vapor. lun gs Sweat glands in skin release excess water and salts. kidneys Kidneys filter and clean ureters the blood to produce urethra urinary bladder urine.  Kidneys have three basic functions in maintaining homeostasis. – remove waste from blood – help to maintain electrolyte, pH, and fluid balances – release key hormones  The kidneys help to maintain homeostasis by filtering the blood. cortex Kidneys are a pair of medulla bean-shaped organs. – two layers: medulla and renal artery cortex – filtering units called nephrons renal vein – renal artery and renal vein ureter (to bladder) Nephrons clean the blood and produce urine. Nephrons are the filtering units in the kidneys. They clean and rebalance the blood to produce urine. from body to body to body from loop of Henle other nephrons  Nephrons clean the blood in a three-step process. The first step is filtration of the blood. 1 FILTRATION Glomerulus Water,electrolytes,aminoacids,g lucose,urea, and other small molecules diffuse out of the blood,creating the filtrate. Bowman’s capsule  The first step is filtration of the blood. The second step is reabsorption of materials. The third step is excretion of materials. from 2 REABSORPTION body As the filtrate enters the rest of the tubule ,most of the materials are reabsorbed into the blood.Materials not reabsorbed make up the urine,which flows into the loop of Henle. collecting duct 3 EXCRETION to body In the loop of Henle,water can be reabsorbed one final time to from reduce the volume of urine.The other remaining urine flows into a loop of Henle nephrons collecting duct that leads to the ureter. Proteins in our diet a. formula involves C, H, O and N b. breakdown into amino acids & then amino group is removed before converted to pyruvate or oxaloacetate which breakdown into CO2 and H2O c. the -NH2 or amino group is a problem 🡪 it is toxic d. amine wastes are combined with carbon dioxide as follows to form urea O // -NH2 + -NH2 + CO2 🡪 H2N – C – NH2 amine + amine + CO2 >>>>> urea  Nitrogen Compounds The nitrogen compounds through which excess nitrogen is eliminated from organisms are called nitrogenous wastes or nitrogen wastes. They are ammonia, urea, uric acid, and creatinine. All of these substances are produced from protein metabolism. Urinary System Organs 103  Kidney Functions-1 1) Filter 200 liters of blood daily, allowing toxins, metabolic wastes, and excess ions to leave the body in urine, 2) Regulation of water and electrolyte balance: Maintain the proper balance between water and salts, and acids and bases, 3) Excretion of bioactive substances (hormones and many foreign substances, especially drugs) that affects body function, 104  Kidney Functions-2 4) Regulation of arterial blood pressure: by production of renin (vasoactive substances) and regulate volume and chemical makeup of the blood, 5) Regulation of red blood cells production: erythropoietin hormone to stimulate RBC production by bone marrow, 105  Kidney Functions-3 6) Regulation of vitamin D production : 25, cholecalciferol will be activated in the kidneys to 1,25 dihydrocholecalciferol D3, 7) Gluconeogenesis: during prolonged fasting glucose can be synthesized in the liver and kidneys. 106  Internal Anatomy A frontal section shows three distinct regions – Cortex: – the light colored, granular superficial region – Medulla: – exhibits cone-shaped medullary (renal) pyramids 107 108  The Nephron Nephrons are the structural and functional units that form urine, consisting of: – Glomerulus – a tuft of capillaries associated with a renal tubule – Glomerular (Bowman’s) capsule – blind, cup-shaped end of a renal tubule that completely surrounds the glomerulus 109  Renal Tubule Proximal convoluted tubule (PCT) –Reabsorbs water and solutes from filtrate and secretes substances into it. Loop of Henle – a hairpin-shaped loop of the renal tubule Distal convoluted tubule (DCT) –function more in secretion than reabsorption. 111 1. Most of the water will be removed at the proximal tubule [85%] 2. More water will be removed at the descending arm [5 %] 3. The counter current system is designed to recover additional water from the collecting duct [10 %] Retaining glucose and amino acids a. The cells in the proximal tubule actively transport glucose & amino acids out of urine b. Water follows these molecules out of urine due to the concentration gradient. c. The NaCl concentration of the urine is still 300 μmol/L. [because NaCl is also pumped out of the nephron here] Retaining water a. About 85% of the water leaves the urine in the proximal tubule due to glucose & amino acid gradients. b. 5 % of the water leaves the urine in the descending arm due to the sodium gradient. c. 0 – 10 % water leaves the urine in the collecting duct due to the sodium gradient. d. Remember water can never be pumped It moves due to a concentration gradient Removing urea and wastes from the body a. The urea is dissolved in the plasma and therefore enters through the Bowman’s capsule. b. Some additional wastes are added at the distal tubule by exocytosis. B] Goals of the kidney 1. filter as much blood as possible – 1.2 L per minute 2. conserve the glucose and amino acids in the blood 3. retain sodium in the body 4. retain as much water as possible 5. eliminate the urea and other wastes from the blood 6. be able to adjust system to account for changes in dietary water, proteins, minerals Male and female urinary system kidney ureter bladder urethra Kidney Diseases NEUROANATOMY The Diencephalon ▣ The Diencephalon is the “Inner Brain”, composed of the Thalamus, Hypothalamus, Epithalamus, Pineal Gland ▣ The Thalamus “Edits” what information is processed to the conscious brain in the cerebrum, but research show this information is still sent to the cortex Diencephalon (Continued) ▣ The Hypothalamus is responsible for the instinctual drives of the body (Four F’s of Life) as well as hormonal and regulatory roles  The Brainstem ▣ The Brainstem is responsible for processing of higher level signals, and the running the systems of the body such as ▣ Heart rate ▣ Breathing rate ▣ Wakefulness cycle ▣ Sleep  Cerebellum ▣ The Cerebellum is responsible for motor memory and programming of your muscles for various actions.  The Spinal Cord The Spinal Cord sends signals from the brain, receives signals from the body and also completes simple reflex arcs itself.  Spinal Cord (Cont.d) ▣ The Spinal cord will control the body (extremities) response to stimuli ▣ Simple Reflex Arcs are completed by the spinal cord, without the Brain ▣ The Spinal Cord receives Sensory (Afferent) Neurons and then sends signals to Efferent (Motor) Neurons. ▣ Afferent neurons are sensory neurons that carry nerve impulses from sensory stimuli towards the central nervous system and brain ▣ while efferent neurons are motor neurons that carry neural impulses away from the central nervous system and towards muscles to cause movement. THE NERVOUS SYTEM  1. Dendrite 8. Terminal Bouton 7. Axon Terminal 5. Nodes of 2. Cell body Ranvier 4. Schwann cells 9. Axon Hillock 3. Nucleus 6. Axon 1 dendrites receptors of stimuli 2 body of cell source of ions 3 nucleus source of proteins eg. pumps 4 Schwann cells fats that insulate the neuron 5 Nodes of Ranvier gaps in the insulation 6 axon path of electrical signal  K+ K+ Na+ Na+ Na/K Na+ pump K+ gate Na+ gate K + K + Na+ Na+ inside of neuron K+ K+ Na+ Na+ + Na+ Na+ K outside of neuron Na+ K+ 1. The Na/K pump - pumps 2 K+ in and 3 Na+ out of the neuron 2. The K+ gate - allows K+ to freely move out of neuron 3. The Na+ gate - usually these are partly closed, and so only allows some of Na+ to move back into neuron 4. The result - there are more Na+ ions outside of neuron which gives it a positive charge outside - because there are Cl- ions equally inside and out, the inside of the neuron now has a negative charge after some of the Na+ ions have moved outside - the net result is a -70 mV negative charge inside the neuron compared to outside A. Resting potential B. Stimulus: A stimulus is a change in the environment (either external or internal) that is detected by a receptor. Na + Na + C. Propagating signal: The movement of signals between neurons Na Na + + Na Na+ + D. Further propagation of signal Na+ Na+ Na+ Na+  Action potential The rapid change in electric potential that parts of a nerve cell undergo when a nerve impulse is generated. The action potential involves the movement of sodium and potassium ions across the cell membrane.  When an action potential happens, the sodium (Na+) ion channels on the axon open and the Na+ rushes in. Since the Na+ is positively charged, it makes the inside of the axon a little more positively charged. The sodium keeps rushing in until the inside is positive relative to the outside. Sodium-based action potentials usually last for under one millisecond 4. ACTION POTENTIAL 4. ACTION POTENTIAL A. RESTING POTENTIAL - the Na/K pumps are ON - Na+ gates are CLOSED B. DEPOLARIZING - the Na/K pumps are OFF - the Na+ gates are OPEN C. REPOLARIZING - the Na/K pumps are ON - the Na+ gates are CLOSED D. HYPERPOLARIZATION - the Na/K pumps are ON - the Na+ gates are CLOSED - extra positive ions are pumped out, making a larger electrical difference E. REFRACTORY PERIOD - the time during which the neuron can NOT respond to a new signal  C. REPOLARIZING +40 mV 0 mV MILLISECONDS B. DEPOLARIZING -70 mV A A. RESTING POTENTIAL D. HYPERPOLARIZATION E. REFRACTORY PERIOD F. THRESHHOLD VALUES -If a stimulus does not reach the threshold level, the neuron is not activated - A stronger stimulus results in the sending of MORE signals or more neuron sending the same signals 5. SALTATORY CONDUCTION - in mylenated cells Saltatory conduction is the propagation of action potentials along myelinated axons from one node of Ranvier to the next node, increasing the conduction velocity of action potentials. A. RESTING POTENTIAL B. STIMULUS Na+ Na+ C. PROPAGATING THE SIGNAL Na Na + + Na+ Na+ D. FURTHER PROPAGATION OF SIGNAL Na+ Na+ Na Na+ + myelinated neurons send the signal faster as the signal jumps under the Schwann cells thicker neurons have more pumps and more ions and so they can depolarize and repolarize faster Synapses between neurons Synapse: In the nervous system, a synapse is a structure that permits a neuron (or nerve cell) to pass an electrical or chemical signal to another cell 6. PROPAGATING A SIGNAL ACROSS A SYNAPSE 2+ synaptic cleft Ca axon dendrite Ca2+  Ca2+ 1. INCOMING 2 ELECTRICAL axon SIGNAL-arrives at the axon end of the synapse 1 3 2. CALCIUM CHANNELS -are triggered to open and let Ca2+ ions enter the axon 2 Ca2+ 3. PRE-SYNAPTIC VESICLES -the Ca2+ causes pre-synaptic vesicles to move to the end of the axon 4. NEUROTRANSMITTER -the pre-synaptic vesicles release neurotransmitter [acetylcholine] into the synaptic cleft [space] synaptic cleft 5. RECEPTORS -the neurotransmitter binds to receptors in the dendrite 7 dendrite 6. OUTGOING ELECTRICAL SIGNAL -the neurotransmitter / receptor complex [N/R complex]initiates an electrical signal 4 in the dendrite 6 5 7. ENZYME - an enzyme [acetylcholinesterase] is released from the dendrite to get rid of acetylcholine and stop the N / R complex from initiating another electrical signal THE HEALTHY IMMUNE SYSTEM A. Non-specific Mechanical Defenses 1- a. In order to cause a disease, microorganisms must first enter the body in some way. b. The skin protects us from surface pathogens. 2- a. Tears, saliva and mucus help wash away pathogens b. and contain mild bactericidal (bacteria-killing) chemicals. c. If pathogens enter through the air way they are trapped in a layer of mucus. d. They may be removed through the continuous, wave- like motion of cilia, moving dirty mucus up to where it can be swallowed, coughed or sneezed. B. Non-specific - Innate Immune Responses 1- a. several types of leukocytes (white blood cells) that attack and eliminate anything they recognize as foreign. b. macrophages will engulf or eat the invading cells  c. neutrophils will surround invading cells & release lysozymes that destroy the invader & themselves  2. inflammation causes more fluid in an area which allows the entry of other immune cells and chemicals into the infected area and helps limitation of the infection 3. fever raises body temperature over 40oC which is less favorable to viral replication 4. interferon (a chemical released by a virus-infected cell), signals neighboring cells to produce antiviral substances 5. complement (a cascade of 20 anti-infective proteins) released when the first protein in the cascade contacts the cell wall of certain bacteria and fungi a. the complement may surround and kill an invader b. the complement may puncture the cell membrane of the invader c. the complement may tag the invader and attract a macrophage C. Specific Immune Responses 1. Cell-mediated immunity by T-Cells a. They are called ‘T cells’ because they mature in the thymus, high in the chest behind the breastbone. b. The process starts when a macrophage engulfs the invader and processes an antigen [a specific surface component of the pathogen, usually a protein]. antigen pathogen  c. The macrophage displays the antigen fragments combined with a Major Histocompatibility Complex [MHC] protein on the macrophage cell surface. MHC protein processed antigen antigen d. A receptor on a circulating, resting helper T cell recognizes the antigen-protein complex & binds to it. T-cell receptor Helper-T-cell e. The binding process causes the helper T cell to activate the cytotoxic T cell [or Killer T cell] so that it can attack and destroy the diseased cell. The killer T cell does NOT attack the pathogen. f. The helper T cell also releases lymphokines which attract other T cells and B cells g. The body also releases suppressor T cells that will calm the body and shut off the immune response.  MHC protein MHC protein__ Killer-T-cell Activated helper-T-cell Infected cell Activated killer-T-cell Cell dies  MHC protein MHC protein__ helper-T-cell Activated helper-T-cell Infected cell Activated killer-T-cell Cell dies 2. Humoral response – B cells a. B-cells are lymphocytes that grow to maturity in the bone marrow b. B-cells produce antibodies that circulate in the blood and lymph streams and attach to foreign antigens to mark them for destruction by other immune cells. c. Antibodies are proteins with the same basic Y shape but with a special region that is highly specific to target a given antigen.  d. The variety of antibodies is very large. Different antibodies are destined for different purposes. i] Some coat the foreign invaders to make them attractive to the circulating scavenger cells, phagocytes, that will engulf an unwelcome microbe. ii] Some antibodies combine with antigens and activate a cascade of nine proteins, known as complement, that have been circulating in inactive form in the blood. Complement helps destroy foreign invaders and remove them from the body. iii] Still other types of antibodies block viruses from entering cells. e. The final group of B cells are the B memory cells that retain the information about the geometry of an antigen so that on a subsequent exposure, the body will ‘recognize’ the invader f. Activation of B cells to make antibody The B cell uses one of its receptors to bind to its matching antigen, which the B cell engulfs. antigen B-cell MHC protein The B cell then displays a piece of the antigen, bound to a MHC protein, on its cell surface. MHC protein This whole complex then binds to an activated helper T cell. activated helper-T-cell This binding process stimulates the transformation of the B cell into an antibody-secreting plasmacell. plasma cell Remember some key points A. Non-specific defenses 1. Mechanical barriers: skin, tears, mucous 2. Innate macrophages, neutrophils, fever, inflammation, interferon, complement B. Specific responses 1. T -cells macrophages, antigens, helper-T-cells, killer-T-cells, suppressor-T-cells 2. B-cells macrophages, antigens, helper-T-cells, B-cells, B memory-cells D. PROBLEMS IN THE IMMUNE SYSTEM 1. ALLERGIES a. a foreign protein is recognized as an invader and the body responds to its presence b. basophil cells [WBC] release histamine c. histamine makes capillaries more permeable to allow WBC to leave & find invaders d. as an indirect result tissues swell – this may be annoying or even life threatening 2. AUTOIMMUNE DISEASES a. the self / non-self system breaks down & self antigens are treated as non-self b. this is usually the result of an injury to specific cells and does not affect all self proteins c. or it is possible that a few killer T cells attack your cells and suppressor T cells fail to control them d. either way, when the suppressor T cells do not control self attacks 🡪 autoimmune disease e. eg. type I diabetes – your own killer T cells attack your beta cells in the Islets of Langerhans Multiple sclerosis(MS) – you attack your own myelin sheath cells 3. Leptin effect on immune system a. Fat cells secrete leptin b. Leptin suppresses the B-cell response c. People with more body fat secrete more leptin d. Therefore, people with more body fat have a suppressed immune system e. These people will heal more slowly after surgery F. PASSIVE & ACTIVE IMMUNITY 1. Passive immunity a. direct passage of antibodies into a person b. placenta passes antibodies into baby from the mother c. colostrum (the first secretion from the mammary glands after giving birth, rich in antibodies)passes transfer factor – protein that helps T cells & B cells recognize pathogens d. a tetanus shot is a shot of antibodies 2. Active Immunity a. this is when something is injected into the body to trigger a T cell and B cell response b. what is injected? -dead pathogens - coat of a pathogen - similar pathogens eg. cowpox for smallpox - antigens of the pathogen c. problem – what if the pathogen changes its antigen?