Ch 7, 8 and 9 (Homeostatic Processes in Body)

Sweating

(above environmental temp. of 28C) -As a person becomes hotter they will begin to sweat. -Sweat is secreted from sweat glands beneath the skin's surface -Sweat is water containing dissolved substances such as sodium chloride, lactic acid, urea and potassium -As the water evaporates from the skin's surface, heat is removed and therefore cooling the body=cooling of blood flowing through skin -effective only is fairly dry, non humid conditions, otherwise sweat stays on skin or drips as can't evaporate

Thermoregulation (nervous response-shivering)

(never use example of hairs standing up for a response) -Cold temperatures=stimulate hypothalamus to send messages to parts of the brain that increase skeletal muscle tone -increased muscle tone=rapid, involuntary, rhythmic muscle tremors=shivering (muscle contraction) -=increase in body heat, within minutes, due to increased heat production -under primary control of hypothalamus, but conscious input from cerebral cortex can suppress urge to shiver

Water concentration (HLLH, LHHL)

-(high)High water concentration (low Osmotic Pressure) =(low)less ADH secreted by posterior pituitary gland =(low)low reabsorption rate into blood =(high)high urine output -(low)Low water conc. (high osmotic pressure) =(high)increase in ADH =(high)increased reabsorption =(low)lower urine output

How is excretion different to elimination?

--Excretion is the removal of waste products of metabolism. These wastes can become harmful if they accumulate in the body. --Elimination is the removal of undigested food, it has not been produced by the body

Antidiuretic Hormone (ADH)

-ADH is produced by the hypothalamus and released from the posterior lobe of the pituitary gland -It controls the amount of reabsorption of water from the kidney tubules into the peritubular capillaries -High levels of ADH in the blood plasma increases the tubules permeability to water, thus more water leaves the tubules and enters the capillaries (concentrated urine). -Low levels of ADH in the blood plasma reduces the tubules permeability to water, thus less water leaves the tubules and the urine is more dilute -The water and dissolved substances that remain in the kidney's tubules make up the urine. -Urine is carried by the collecting ducts to the ureter and then to the bladder where it is stored

Kidneys in Greater Detail

-Around 60% of water lost from the body is excreted by the kidney in the form of urine -The kidneys regulate amount of water excreted from the body, and regulation of composition of body fluids -This controls the amount of dissolved substances within the body fluid. The skin and lungs are not able to do this (skin water loss (sweat) directly linked to temperature regulation, thus can't use to regulate conc. of dissolved substances).

Nephron

-Blood enters the glomerulus at high pressure -Filtration: The high pressure forces the water and small dissolved molecules out of the blood and into the Glomerular (Bowman's) Capsule (known as filtrate) -Reabsorption: Filtrate passes through PCT, loop of Henle, DCT and collecting duct. Water and other useful substances reabsorbed into peritubular capillaries. About 99% of water forced into the glomerulus will be reabsorbed from the kidney's tubules. Na, K, glucose and amino acids are actively reabsorbed back into the blood capillaries in the proximal convoluted tubule where they are transported around the body. Sodium is also actively reabsorbed in the Loop of Henle into tissue fluid (to assist with osmosis). Water is reabsorbed in the collecting duct and is influenced by ADH. The large amount of sodium outside the collecting duct helps the water move via osmosis.

Thermoregulation

-Body temperature is approximately 37 degrees Celsius -achieved heat gained=heat lost from body -Managing the balance between heat production and heat loss is called thermoregulation.

Cortisol

-Cortisol releases stored glucose (glycogen) = increases blood glucose levels providing "needed" energy. It does this by: --Increase the breakdown of proteins in muscles and thus increase the amount of amino acids in the bloodstream. ->these amino acids can be used to produce glucose in gluconeogenesis. --Stimulate glycogenolysis -Prolonged secretion of cortisol (a stressful lifestyle) is not healthy and can lead to many problems. -Weight gain is also associated with high levels of cortisol because extra glucose is produced and may not be used (ie. Stressed but not exercising etc) and must be stored as fat

Decreasing/increasing heat loss/production

-Decrease heat loss:vasoconstriction, reduced sweating, jumper, wind sheltering, reduce SA -Increase in heat production: shivering, increased voluntary activity, increased metabolic rate -increase heat loss: vasodilation, sweating, remove clothing, fan, increase SA -decrease heat production: decrease voluntary activity, decreased metabolic rate

Kidneys in Greater Detail

-Each kidney has around 1.2 million nephrons -The nephron is responsible for excretion and the removal of water (functional unit of kidney)

Preventing Body Temperature from Increasing

-Excess heat from exercising or the external environment must be lost in order for our internal body temperature to be maintained at around 37˚C -Most heat loss is from the skin -Some heat loss is removed from the mouth or whilst defecating or urinating

Lungs

-Excrete carbon dioxide which is a waste produced from cellular respiration. -Carbon dioxide is carried through the blood mainly as bicarbonate ions and then excreted through the lungs.

Fluids in the Body

-Fluid is composed of: --Intracellular fluid/cytosol =Fluid inside the cell =2/3 of total body water --Extracellular fluid =Fluid between cells (interstitial(b/w cells), intercellular or tissue fluid) =Blood plasma

How is water removed from the body?

-From the kidneys as urine -Through the skin as sweat -Through the lungs via exhalation -Through the alimentary canal via elimination (faeces)

Kidneys in Greater Detail

-Humans have two kidneys -They are reddish brown in colour, about 11 cm long, located in the abdomen either side of the vertebral column -The ureter leaves each kidney, drains the urine into the bladder where it is stored ready for excretion through the urethra

Preventing Body Temperature from Falling

-If the temperature outside is cold or you move from a warm area to a cooler area, the cold receptors in the skin send messages to the hypothalamus. -The hypothalamus then sends out impulses aimed at reducing heat loss and increasing heat production (maintaining body temperature)

Adrenaline and Noradrenaline

-In emergency situations (and exercise), adrenaline and noradrenaline are released into the body to override the homeostatic control of glucose -Adrenaline=very fast acting hormone -This is done to promote glycogenolysis for the emergency. This happens very quickly. -Once the emergency is over, and adrenaline levels drop, the homeostatic controls are once again back in place

How do we get fluid into the body?

-In the form of liquid -In the food we eat -Small percentage from respiring cells (metabolic water)

Fluids in the Body

-Intracellular: 2/3 proportion of total body water, components=fluid inside the cell (cytosol) -Extracellular: 1/3 proportion of total body water, components=fluid outside the cell --Blood Plasma: 1/4 of extracellular fluid, components=liquid part of blood --Intercellular fluid=3/4 of extracellular fluid, components=lymph fluid, joint fluid, fluid in the eyes, chest, abdomen etc

Glycogenolysis (=hypoglycaemia)

-Low levels of blood glucose=Hypoglycaemia -Glycogenolysis=stored glycogen is converted back into glucose (broken down), in liver -stimulated by the glucagon, generally in b/w meals. Glucagon is secreted from the alpha cells in the Islets of Langerhans of the pancreas. -Glucagon acts on the liver cells and accelerate the conversion of glycogen into glucose -The glucose formed from glycogenolysis is released into the blood and the blood sugar levels rise. -When the levels of blood glucose increase again, the alpha cells are no longer stimulated to release glucagon (negative feedback)

Alimentary Canal

-Passes out bile pigments (broken down products of haemoglobin from RBC's) that entered the small intestine with the bile. -Water can be removed via the alimentary canal.

Peripheral Thermo-receptors

-Provide the hypothalamus with information about the external environment. -There are two types: 1. Cold receptors -Are stimulated when the external temperatures are lower than normal -When stimulated, hypothalamus initiates heat conservation and production mechanisms 2. Heat receptors -Are stimulated when the external temperatures are higher than normal -When stimulated, hypothalamus initiates mechanisms to reduce heat production and increase heat loss

Feedback Loop (high water) (hormonal)

-STIMULUS:Decreased osmotic pressure (high water in plasma) -RECEPTOR:Osmoreceptors in hypothalamus -MESSAGE:Sensory cells generate a message in the form of a nerve impulse -MODULATOR:Hypothalamus (Posterior lobe of the pituitary gland) -MESSAGE:Less ADH released -EFFECTOR:Nephron of the kidney -RESPONSE:Decrease in permeability of CD, decreased water intake -FEEDBACK:Increased osmotic pressure

Feedback Loop-Thirst Reflex

-STIMULUS:Increased osmotic pressure (low plasma in water) -RECEPTOR:Osmoreceptors in hypothalamus -MESSAGE:Sensory cells generate a message in the form of a nerve impulse -MODULATOR:Hypothalamus -MESSAGE:Nerve impulse -EFFECTOR:Cerebral cortex -RESPONSE:Have a drink -FEEDBACK:Decreased osmotic pressure

Feedback Loop (low water) (hormonal)

-STIMULUS:Increased osmotic pressure (low water in plasma) -RECEPTOR:Osmoreceptors in hypothalamus -MESSAGE:Sensory cells generate a message in the form of a nerve impulse -MODULATOR:Hypothalamus makes ADH (Posterior lobe of the pituitary gland) -MESSAGE:Release of ADH by PPG, travels in blood -EFFECTOR:Nephron of the kidney (holes become bigger so water can go back into blood) -RESPONSE:Increase in permeability of CD, increased water intake -FEEDBACK:Decreased osmotic pressure

Nephron

-Secretion: Hydrogen ions (controls pH) and creatinine are secreted into the distal convoluted tubule to be removed from the body. -Urine: water and dissolved substances that remain make up urine. Urine carried by collecting ducts to ureter and then to bladder. (-reabsorption occurs through walls of kidney tubules along entire length. Reabsorption at PCT and LoH is by osmosis. Reabsorption at DCT and CD is active.)

Skin

-Skin is the biggest organ in the body. -It protects our internal organs, maintains the ideal body temperature and allows the excretion of water (via sweat glands)

Control of Water Loss

-The amount of urine produced is dependant on how much water there is in the body fluids. -Drinking more water means more urine which will be diluted (less concentrated due to a higher volume of water than solute). -Drinking less water means less urine produced which is highly concentrated

Thermoregulation-when temp. outside limits (hypo/hyperthermia)

-The body's temperature must be maintained at a constant temperature because many chemical reactions occurring in cells are heat sensitive. -Core temp. above 42C=dangerous and above 45C can die. High temp. usually due to fever -Excess heat must be removed otherwise the body temperature will rise which may lead to nerve malfunction, change in protein structure or death in some cases (Hyperthermia occurs if the body temperature becomes higher than 40˚C). -Death may also result if the body temperature is too low (Hypothermia occurs if the body temperature becomes lower than 35˚C metabolic rate so low that heat production unable to replace heat loss).

Control of Thermoregulation

-The hypothalamus exerts control over maintaining body temperature -The hypothalamus receives impulses from thermo-receptors throughout the body which then results in physiological responses in order to keep the body temperature at an approximate 37˚C -A negative feed back loop is produced where the hypothalamus aims to remove the stimulus that caused a response

Central Thermo-receptors

-The internal core of the human body must be maintained and therefore the peripheral thermo-receptors do not work alone -Central thermo-receptors are found in the spinal cord and abdominal organs -All are connected to the hypothalamus, which receives the information from these thermo-receptors and will send out nerve impulses to either help increase or decrease the body's temperature

Kidneys

-The primary excretory organ. (produces urine) -Responsible for maintaining constant amounts of materials in the body fluids. -Removes excess water and dissolved ions such as creatinine (a waste product that indicates kidney function). -Removes urea which is a by product of breaking down proteins via the liver

Thirst Reflex

-This normally occurs when the osmotic pressure is very high. -Most people are already dehydrated when they feel thirsty. -This is why you should drink water regularly and not only when you are thirsty. -This is a nervous response and NOT a hormonal response.

Feedback Loops

-To maintain homeostasis the body must be able to detect changes in the internal and external environment and must be able to compensate for those changes. -The endocrine system and the nervous system are the main systems that detect change and respond to those changes. -Feedback Loops provide a model to demonstrate the body's response to changes in its environment with the response altering the original stimulus.

Cerebral Cortex

-When blood glucose levels are high, there is a decrease in appetite and a person becomes full -When blood glucose levels are low, there is an increase in appetite and a person seeks out food (sugar cravings)

Water Intoxication/poisoning

-When water is consumed in excess. -Cells take in too much water by osmosis (are diluted). -Occurs when a person loses lots of water and salts but rehydrates with plain water. The water should contain dissolved substances to replace the lost salts as well as the water. -first signs=lightheadedness, then headache, vomiting and collapse.

Regulating Water Intake

-When water is lost from the blood, the plasma becomes more concentrated and therefore has a greater osmotic pressure (lower water concentration) -This results in water moving into the blood plasma from the intercellular fluid by osmosis -Intercellular fluid now more concentrated, so water moves into the extra cellular environment and cells begin to shrivel from dehydration. This sends a message from the osmoreceptors to the posterior pituitary gland (-Increased solute=increased osmotic pressure)

Dehydration

-When water loss exceeds water intake. -Loss can be from sweating, diarrhoea or vomiting. -Symptoms appear when humans lose around 2% of their body water and include: Headache Dizziness Thirst Low blood pressure -untreated person becomes delirious, loses consciousness and dies

Diabetes (diabetes mellitus)

-abnormally high blood glucose=hyperglycaemia -usually balance b/w insulin and glucagon keep blood glucose levels normal -does not produce enough insulin, or cells have abnormal resistance to insulin effects -amount of glucose in blood remains high and they excrete large amounts of urine

Glucocorticoids

-after a stressful situation, the anterior pituitary gland is stimulated to secrete: --Adrenocorticotrophic hormone (ACTH) (the brain is overriding the homeostatic mechanisms in place). ->Adrenocorticotrophic hormone flows in the blood and stimulates the adrenal cortex to secrete glucocorticoids, namely cortisol. -Cortisol is released in the body during times of stress, hence the name the "stress hormone". -Cortisol allows a quick burst of energy, heightened awareness and lowers sensitivity to pain

Regulation of Gas Concentrations

-all cells need continuous supply of O2 for respiration and produce CO2 as waste product in respiration, thus it's crucial that levels of these gases are regulated -respiratory system responsible for taking in O2 and excreting CO2 -lungs are where exchange of CO2 for O2 occurs -changes in breathing thus change the amount of O2 taken in and amount of CO2 excreted -circulatory system carries O2 from lungs to cells where it's used. Takes away CO2 produced and delivers to lungs for excretion from body, this CS involved in regulation of gas concentrations

H+ concentration

-as H+ conc. in blood increases, pH decreases=increase in breathing rate -decrease in pH directly stimulates chemoreceptors in aortic and carotid bodies, which transmit impulses to respiratory centre=increase in breathing rate

Oxygen concentration

-as O2 consumed by cells, its conc. in blood begins to fall. -if conc. of O2 falls below normal while other factors are held constant, breathing rate increases -however, w/in the normal range of blood O2 conc., effect on breathing is only slight. The conc. has to fall to very low levels before it has major stimulatory effect -thus, under normal circumstances, O2 plays little part in regulation of breathing -there are groups of cells w/in walls of aorta and carotid arteries (major arteries) that are sensitive to changes in conc. of O2 in blood plasma. These groups of chemoreceptors are the aortic and carotid bodies (peripheral chemoreceptors) -There are also central chemoreceptors in medulla oblongata=modulator -large decrease in O2 conc. stimulates chemoreceptors, and nerve impulses are transmitted to respiratory centre -these nerve impulses stimulate transmission of messages to diaphragm and IM=breathing rate increases

The skin and temperature regulation

-changes in skin can speed up/slow down rate at which heat lost from body -diameter of blood vessels to the skin controlled by autonomic nerves, which increase or decrease flow of blood near surface -sweating must occur when large amounts of heat must be lost and skin blood vessels are already at max. dilation -sweating=active secretion of fluid by sweat glands and periodic contraction of cells surrounding ducts to pump sweat -production and transport of sweat stimulated by sympathetic nerves -continual loss of heat via evaporation, even when not sweating

Fluids in the Body-movement b/w cells and capillaries etc

-continuous exchange of materials b/w body fluids -plasma separated from intercellular fluid by thin walls of capillaries, and there is relatively free exchange of materials b/w them -Water moves easily through cell membranes, blood capillary walls and throughout the body. -Fluid moves easily through the capillary walls and into the tissue fluid (intercellular fluid). However large molecules (e.g. proteins of plasma) that are dissolved in the fluid can not pass through the membrane/capillary walls. -Fluid within the body constantly moves from one area to another- it is not contained within any one part of the body. -Moving fluid allows the exchange of some materials such as dissolved gases and nutrients. -water moves easily through plasma membranes, thus any change in osmotic pressure (b/w intracellular and extracellular fluid) are easily restored (ie. differences in solute concentrations dissolved in the water) due to osmosis.

Exercise and Breathing

-during exercise contracting muscles require large amounts of O2 and produce large amounts of CO2 -thus respiratory system increases both rate of breathing and depth to cater for increased gas exchange demand -during heavy exercise, volume of air going into and out lungs each minute increase (possibly x10-20) -conc. of blood plasma, CO2, H+ and to lesser extent, O2, influence this (as they also do at rest)

Voluntary control of breathing -Why is it important?

-e.g during speech, if fall into a swimming pool or there is a gas leak=hold breath -voluntary control comes via connections from cerebral cortex (make the choice here) to descending tracts in spinal cord -voluntary control thus bypasses respiratory centre (involuntary breathing) in medulla=protective device as enables us to prevent irritating gases and water entering lungs -we cannot stop breathing forever as build up of CO2 in plasma stimulates respiratory centre to send impulses to inspiratory muscles, thus we are eventually forced to take a breath

CO2, O2 and H+ combined

-each factor interacts w/ the others (are not independent) -they also are not the only factor to play role in control of breathing -thus, at any instant the rate of breathing is regulated by a number of factors, and the sensitivity of some factors (e.g. O2) is not as great as the sensitivity of others (e.g. CO2)

Role of adrenal glands

-each gland composed of two parts: cortex (outer) and medulla (inner part) -secrete glucocorticoids from adrenal cortex and adrenaline (epinephrine) and noradrenaline (norepinephrine) by adrenal medulla -in stressful and emergency situations, these hormones are released into the body to override the homeostatic control of glucose -AC stimulated by adrenocorticotropic hormone (ACTH) from anterior lobe of PG, and secretes glucocorticoids, one of which is cortisol -these regulate carbs metabolism by making sure enough energy is provided to cells. -also increase rate at which aa's may be converted to glucose by liver if glycogen and fat levels are low -glucocorticoids also promote metabolism of fatty acids from adipose tissue, allowing muscle cells to shift from glucose to fatty acids for much of their metabolic energy -cortex: stimulates conversion of glycogen into glucose, protein b/d in muscles and conversion of aa's into glucose -medulla: synthesises adrenaline and noradrenaline, which have same effects as those of sympathetic nerves of autonomic nervous system (short lived response to stress). Adrenaline elevates blood glucose levels and thus counteracts effects of insulin-> Stimulates production of lactic acid from glycogen in muscle cells, and the lactic acid can then be used by liver to manufacture glucose (medulla stimulates b/d of glycogen in liver and release of glucose into blood)

Heat Exhaustion

-from extreme sweating and vasodilation to lose heat. -Loss of water in sweating reduces volume of blood plasma and vasodilation reduces resistance to blood flow. -Blood pressure reduced and output of blood from heart decreases. -Thus can collapse. -The body temp. is however almost normal, unlike heat stroke

Effect of glucagon on blood glucose

-glucagon from alpha cells increase blood sugar -stimulates glycogenolysis -glucose formed then released into blood=blood sugar rises -glucagon also stimulates liver to produce new sugar molecules from fats and amino acids (gluconeogenesis) -also may have mild stimulating effect on protein b/d -regulation of glucagon secretion determined by level of blood sugar and is based on negative feedback -when blood sugar falls below normal, chemical sensors in alpha cells stimulate those cells to secrete glucagon -as blood sugar increases, cells are no longer stimulated and production is reduced

Glycogen

-glucose stored as glycogen, molecule made of glucose -form in which carbs stored in body, mainly in liver and muscle cells -pancreas and adrenal glands secrete hormones that affect level of glucose in blood. -cannot be used by cells, must be converted back to glucose or other simple sugars -stored in liver available for conversion into glucose to maintain blood sugar levels and supply energy for liver activity -glycogen in muscle cells provides glucose required for muscle activity

Glucose Storage

-glucose stored mainly in liver and muscle cells

Aldosterone

-hormone that aids regulation of water output and sodium content (if we retain more water, we should retain more salt) -adrenocorticotropic hormone (ACTH) releasing factor released by hypothalamus, anterior pituitary gland releases ACTH (causes body to retain water, thus also salt) -secreted by adrenal cortex -acts on kidney tubules to increase amount of sodium reabsorbed into bloodstream to increase amount of potassium excreted in urine -as water reabsorbed along with sodium, aldosterone also regulates water content of body -increasing water reabsorption increases blood volume=increased blood pressure, thus increased aldosterone secretion has indirect effect of increasing blood pressure

Blood Sugar

-in blood, sugar in form of glucose - Blood sugar levels refer to how much sugar is in a person's blood stream. -source of energy for all cells, required for cell. resp. -energy released from glucose molecules by cellular respiration, therefore glucose must be in a constant supply and must be able to enter the cells: Glucose+O2->CO2+H2O+energy -Source of glucose=food -carbs in food broken down during digestion (mechanical and chemical) into glucose and absorbed into blood through walls of small intestine (villi) -after meal, blood glucose levels can rise sharply, thus homeostasis mechanism operate to reduce its conc. to normal -excess glucose removed and stored for use in cellular activities b/w meals

Role of Pancreas-IoL, alpha and beta cells, insulin

-in pancreas=clusters of hormone-secreting cells called islets of Langerhans. -there are 2 types of cells in it: alpha cells secrete glucagon, and the beta cells secrete insulin. Both hormones are secreted into the bloodstream and are concerned with the control of blood sugar levels -insulin causes a decrease in blood sugar, in two ways, and binds w/ receptor proteins in the cell membrane, resulting in: --accelerates uptake of glucose from blood into cells, especially those of the skeletal muscles --accelerates conversion of glucose into glycogen. --Also stimulates conversion of glucose into fat in adipose tissue (fat storage tissue)=lipogenesis, and causes an increase in protein synthesis in some cells -slow the process of glucose formation from lactic acid -Increases the uptake of amino acids in some cells and therefore protein synthesis -level of blood sugar regulates secretion of insulin via negative feedback, as the levels of glucose are reduced and beta cells no longer stimulated, thus blood glucose returns to normal -when blood sugar rises above normal, chemical sensors in beta cells of islets stimulate those cells to secrete insulin -as the level of blood sugar lowers, cells are no longer stimulated and production is reduced

Feedback Loop (increase CO2)

-increase CO2 conc. in blood=stimulus (=decrease pH/acidic/high [H+] -receptors=aortic, carotid bodies (in aorta and carotid arteries, which blood flows through)/medulla -modulator=medulla oblongata -respiratory muscles=effectors -increase in breathing rate=response=increase in CO2 expelled from body -decrease in CO2 conc.=negative feedback

Role of liver, where does its blood supply come from?

-liver cells convert glucose into glycogen for storage, or glycogen to glucose for release into blood in b/w meals, regulating glucose levels -most of its blood supply comes from hepatic portal vein, which brings blood directly from stomach, spleen, pancreas and small and large intestines. Thus, liver has 1st chance to absorb nutrients from digested food -after high carb meal, breakdown of products, mainly glucose, are absorbed into blood capillaries of villi of small intestine. Hepatic portal vein carries glucose to liver, where: --glucose may be removed from blood by liver (absorbed) to provide energy for liver functioning --may be removed by liver and/or muscles and converted into glycogen for storage, stored in liver/muscle cells --may continue to circulate in blood, available for body cells to absorb and use as source of energy --glucose in excess of that required to maintain both normal blood sugar level and tissue glycogen level is converted into fat for long-term storage -about 1/5 of glycogen is stored in liver, rest stored in skeletal muscle cells -if level of glucose in blood drops below normal due to its consumption by muscle cells during exercise or body tissues b/w meals, glycogen stored in liver and muscle cells can be broken down into glucose -glycogen stored in liver is short term energy supply. Can provide glucose for body cell use for about 6 hours if no other supply available. If more energy required, body uses stored fat for energy

Heat Production

-metabolic rate=rate at which energy released by breakdown of food -When cells undergo respiration, energy is released when an ATP molecule is broken down. -Some energy is used for muscle contraction, for active transport, synthesis of new molecules etc. -However most energy is released as heat from metabolic processes occurring within the body. -During exercise, muscular activity increases metabolic activity of cells and large quantities of heat is produced (up to 40 times more than usual).

Control of breathing-respiratory muscles, respiratory centre, H+ conc.

-muscles that cause air to movie in and out of lungs=diaphragm (muscle that separates thorax from abdomen), and the intercostal muscles (muscles b/w ribs) =skeletal muscles and require stimulation from nerve impulses to initiate contraction -diaphragm stimulated by impulses from phrenic nerves, while impulses from intercostal nerves stimulate intercostal muscles -these spinal nerves have origin in spinal cord at level of the neck and thorax -if these nerves or their origin are injured, = complete paralysis of the muscles that ventilate the lungs, and death follows unless artificial respiration is rapidly applied -nerve impulses to these skeletal muscles are controlled by respiratory centre in medulla oblongata -2 regions w/in respiratory centre: one controls expiration and other controls inspiration -to coordinate breathing, messages need to pass back and forth b/w the neurons in these 2 regions -O2 and CO2 carried in blood and their concentrations affect breathing rate -the conc. of CO2 in blood plasma affects the conc. of H+ -when CO2 dissolves in water, it forms carbonic acid (H2CO3) which breaks down readily to form H+ and bicarbonate ions (HCO3-): CO2+H2O->H2CO3->H^(+)+HCO3- <- <-

Excess and deficiency of thyroid hormone

-over or under secretion of thyroid hormones: thyroxine and tri-iodothyroxine -imbalance of thyroxine can sometimes be due to imbalance of TSH

Hyperventilation

-rapid, deep breathing, provides more O2 than required and removes more CO2 than necessary -can occur voluntarily or stimulated by physical stress e.g. severe pain or emotional stress e.g. extreme anxiety -usually corrects itself because the reduction in CO2 conc. means chemoreceptors are not stimulated and there is no urge to breathe until CO2 levels return to normal -hyperventilation before swimming under water=very dangerous, although does allow person to stay under water longer, due to loss of CO2 -the breath holding ability could be increased to such an extent that the person loses consciousness from lack of O2 to brain before feeling urge to breathe

Homeostasis of Water

-regulates body fluid: 1. Release of ADH (Hormone control) 2. Thirst Reflex (Nervous control)

CO2 concentration

-relatively small increase in conc. of CO2=enough to cause marked increase in rate of breathing -as conc. of CO2 in plasma is associated w/ conc. of H+, any increase in CO2=associated increase in H+=decrease pH -increase in conc. of both these chemicals in blood stimulates central and peripheral chemoreceptors (aortic, carotid=typically they pick up pH change quicker), which transmit nerve impulses to respiratory centre (in MO)=increase in breathing rate -chemoreceptors most sensitive to changes in conc. of CO2=those located in medulla -neurons making up these central chemoreceptors are separated from, but communicate with, neurons of respiratory centre -these chemoreceptors are responsible for 70-80% of increase in breathing rate resulting from increase in CO2 conc. on blood -however, this response takes several minutes -immediate response in breathing rate that occurs after increase in CO2 conc. is produced by stimulation of aortic and carotid bodies, stimulated by associated increase in H+ conc. --CO2 CHANGE IN CONC.=MORE IMPORTANT THAN O2 CHANGE

Hypothyroidism

-too little thyroxine -due to either problems w/ thyroid or pituitary or hypothalamus -symptoms=slow heart rate, unexplained weight gain, fatigue, lack of energy, cold intolerance, swelling of face and goitre -one problem=due to lack of iodine. -Iodine in diet needed as it makes up chemical structure of T3 and t4. -Deficiency of iodine in diet can prevent thyroid gland from making enough hormones and thyroid gland may become enlarged in effort to increase hormone production=goitre on side of neck (to try and compensate) -to ensure people get enough iodine=compulsory placement of iodine in most breads -during pregnancy, iodine=important, otherwise retards physical development of baby and bad for brain development. In serious cases, may be born w/ severely retarded mental and physical growth and impaired movement or hearing=cretinism -most common cause=attack on thyroid gland by immune system(=Hashimoto's disease). Also caused if surgery for cancer of thyroid involves removal of all or large part of the gland -if cause is lack of iodine, treatment=more iodine in diet -treatment of other causes=tablets containing thyroid hormone (T3 & T4), must be taken for rest of life, no cure (must carefully monitor dosage, otherwise leads to hyper/hypothyroidism)

Hyperthyroidism

-too much thyroxine -most common type=Grave's disease=enlargement of thyroid caused by immune system reaction --not inherited, however may be a genetic susceptibility -as cells are overstimulated, symptoms=rapid heartbeat, weight loss, increased appetite, fatigue, sweating, anxiety and for Grave's disease=protruding eyeballs -treated w/ --drugs that block thyroid gland's use of iodine (used to produce thyroxine 3 and thyroxine 4) --or by surgery to remove some or all of gland, --or patient given drink containing radioactive iodine, Radioactive iodine molecules taken up by thyroid cells, which are then killed by radioactivity. Cells elsewhere do not absorb it and are unaffected, and the radioactive iodine eventually excreted in urine

Type 1 Diabetes (insulin dependent diabetes)

-usually begins in childhood (juvenile diabetes/early onset) -fault in person's immune system causes destruction of beta cells in islets of Langerhans, they CAN NOT produce insulin (autoimmune attack on beta cells) -CAN respond normally to insulin=can be given regular injections of insulin or use programmable pump that provides continuous supply of insulin under skin=only treatment -must have regular injections to stay alive, and can still have long term effects of kidney failure, heart attack, stroke, amputations, blindness, nerve damage -no cure

Type 2 Diabetes (non-insulin dependent/adult-onset diabetes)

-usually people over 45 years -CAN produce insulin but cells do not respond (can not take up glucose from blood) -lifestyle disease --lack of physical activity; diet high in fat, sugar, salt and low in fibre; high blood pressure; high blood cholesterol; smoking -develops gradually, often no symptoms or they're not noticed -no cure, but earlier diagnosis=greater chances for successful management -if undiagnosed or untreated=heart disease, stroke, kidney disease, eye problems, nerve damage, skin and foot problems -treatment=management program that keeps blood glucose levels in normal range=careful diet, regular exercise, healthy weight, monitoring blood glucose and sometimes medication if blood glucose cannot be controlled by other ways -preventable by adopting healthy lifestyle

The effect of behaviour

-what we do can affect homeostasis of blood sugar and gas concentrations -e.g. mental stress before starting a long distance race causes your blood glucose to rise and in anticipation of the increased muscular activity, heart rate and blood pressure increases -when race begins, breathing rate and depth increases, CO rises and blood glucose stays at high level Also increase in blood supply to working muscles and corresponding decrease in supply to internal organs e.g. stomach and intestines -during prolonged, steady exercise, many factors e.g. heart rate and breathing rates are homeostatically controlled at higher level than when at rest -when exercise ceases, homeostasis returns all these factors to normal level

Thermoregulation-inputs

1. Heat from metabolism 2. Heat from the environment/surrounding heat (via conduction and radiation)

Feedback Loop Components

1. STIMULUS A change in the environment 2. RECEPTOR The stimulus is detected by sensory cells 3. MESSAGE Sensory cells generate a message in the form of a nerve impulse or hormone 4. MODULATOR A control centre processes the messages received from the receptor 5. MESSAGE A new message is sent from the modulator 6. EFFECTOR Muscles or glands receive the message from the modulator 7. RESPONSE The effector brings about a reaction 8. FEEDBACK The response changes the original stimulus

ADH

1. Water concentration in blood plasma decreases, increased osmotic pressure (It's a hot day, more water loss through sweat) 2. Osmoreceptors in the hypothalamus are stimulated. 3. posterior lobe of pituitary gland stimulated to release ADH 4. ADH carried all over body by blood but affects target organs:nephron tubules. Increase in permeability of DCT and CD to water (Body needs to retain water) 5. More water is absorbed into blood plasma in the capillaries from tubules and ducts 6. Increased water concentration (back to normal conc., is not a high conc.) in blood plasma, decreased osmotic pressure 7. Original stimulus eliminated/reduced=negative feedback

Thermoregulation (endocrine process-decrease)

1. decrease in body temp.=stimulus (IMPORTANT-w/out stimulus, nothing happens) 2. detected by core thermoreceptors in the hypothalamus (also have peripheral receptors in skin) 3. hypothalamus produces and releases Thyroid Stimulating Hormone releasing factor (TSHrf)-TSHrf travels through blood capillaries to the Anterior Pituitary Gland 4. APG produces and releases TSH 5. TSH travels through the bloodstream to the thyroid gland 6. Thyroid gland increases production of thyroxine 7. thyroxine targets all body cells 8. increases cell metabolism 9. more heat is produced in body 10. increase in body temp. 11. negative feedback (takes longer to have an impact but is longer lasting)

Preventing Body temp. from increasing-behavioural (conscious decision)

1. decreased activity=reduces heat gain through metabolic processes/muscle contractions 2. increased water intake/eating foods high in water content=assists with process of heat loss via sweating 3. staying cool/being in a shaded area=reduces heat gain through radiation from sun 4. fanning/method of moving cool air across the body/increase SA exposed=increases heat loss by convection/improves evaporation 5. cool shower/swim/contact with cool surface=increases heat loss by conduction 6. removing clothing=improves heat loss by radiation/convection/evaporation

Thermoregulation (endocrine process-increase)

1. increase in body temp. 3. hypothalamus produces and releases Thyroid Stimulating Hormone inhibiting factor (TSHif) 4 .APG produces and releases less TSH 6. Thyroid gland decreases production of thyroxine 8. decreases cell metabolism (everything else same/opposite to decrease)

Thirst Reflex- a Nervous Response

1.As water is lost from the body, the volume of blood plasma is reduced. This increases the osmotic pressure (high solute, high osmotic pressure). 2.Receptors in the thirst centre of hypothalamus (osmoreceptors) detect this rise in osmotic pressure. 3.Mouth becomes dry, person feels thirsty (cerebral cortex is now the effector) and the person stimulated to drink. 4.This water consumed enters the blood via the small intestine (alimentary canal). 5.As blood circulates through body (b/w intra and extracellular fluid), enables intercellular fluid and intracellular fluid to return to proper osmotic conc. There is a lowering of the osmotic pressure (greater water concentration). Any excess fluid in extracellular fluid collected by lymph system and returned to blood by lymph vessels that join veins in upper chest 6.The receptors of the hypothalamus are no longer stimulated, therefore the need to drink is reduced. Negative Feedback

Feedback Loop (decrease in temp.-general/all processes)

1.STIMULUS Decreased body temp 2.RECEPTOR Thermoreceptors in skin and hypothalamus 3.MESSAGE Receptor cells send a message to the hypothalamus 4.MODULATOR Hypothalamus 5.MESSAGE A new message is sent from the hypothalamus to the effector 6.EFFECTOR Blood vessels, cerebral cortex, anterior pituitary gland, muscles 7.RESPONSE Vasoconstriction, put on clothes, increased thyroxine, shivering 8.FEEDBACK Increased body temperature

Feedback Loop (increase)

1.STIMULUS Rising body temp 2.RECEPTOR Thermoreceptors in skin and hypothalamus 3.MESSAGE Receptor cells send a message to the hypothalamus 4.MODULATOR Hypothalamus 5.MESSAGE A new message is sent from the hypothalamus to the effector 6.EFFECTOR Blood vessels, sweat glands, cerebral cortex, anterior pituitary gland 7.RESPONSE Vasodilation, sweating, take off clothes, decreased thyroxine 8.FEEDBACK Negative: Decreased body temperature

Preventing Body Temperature from Falling-Adrenal Medulla

2. Adrenal Medulla Stimulation -Adrenal medulla: inner portion of the adrenal gland on the kidney -The hypothalamus stimulates the adrenal medulla (by sympathetic nerves) to secrete the hormones adrenaline and noradrenaline into the blood -These hormones bring about an increase in cellular metabolism that leads to an increase in heat production -Greater heat production maintains the body's temperature -occurs when there is rapid heat loss

Thermoregulation-outputs

=Radiation, Conduction, Convection, Evaporation from skin and lungs, warm air breathed out, warm urine and faeces

Preventing Body Temperature from Increasing-behavioural

Behavioural Humans can respond to an increase in body temperature by: -Turning on air conditioning -Staying out of the sun -Remove external clothing -Reduce physical activity

Convection and Evaporation

Convection -As cool air comes into contact with your body, it is warmed becoming less dense and then rises -Heat is transferred away from your body Evaporation -The conversion of a liquid to a gas (vapour) such as water -To allow this change to occur, heat energy is required -Heat energy is absorbed from the area where this change is taking place, cooling this area -This is why we sweat when we get hot

Glucose-glycogen conversion

Glucose->Blood sugar level high(e.g. after meal)-> glycogen->blood sugar level low (e.g. during exercise)-> glucose

Preventing Body Temperature from Falling-behavioural (conscious decision)

Humans can make conscious decisions to prevent themselves from losing body heat. -Putting on a jumper -Sheltering from the wind -Turning on a heater -Reducing body surface area (curling up into a ball)

Blood sugar homeostasis

Integration of liver, pancreas and adrenal glands

Heat Production cont.

Other ways in which metabolic reactions are increased include: -Stress -Rising body temperature (eg. during a fever)=biochemical reactions increase -This will also result in an increase in heat production.

Temperature Receptors

Peripheral Thermo-receptors are temperature receptors that are located in the skin and some mucous membranes. Central thermo-receptors are thermo-receptors located in the hypothalamus of the brain. (hypothalamus monitors temp. of blood and receives impulses from peripheral thermoreceptors)

Vasodilation

Physiological 1. Vasodilation -The blood vessels in the skin increase in their diameter, increasing the blood flow through them and skin -The increase in blood flow raises the surface temperature and more heat is lost through convection and radiation -Skin becomes reddish in colour

Radiation and Conduction

Radiation -The transfer of heat from our bodies to cooler objects (such as the ceiling of a room) without any physical contact -However if these objects are at a higher temperature then your body will absorb the heat via radiation Conduction -The transfer of heat through physical contact -The hotter object will lose heat to the cooler object

The kidneys and associated organs

Renal Vein: takes blood away from kidney Renal Artery: takes blood to kidneys Urethra: tube from bladder that opens to outside Ureter: tube that drains urine away from kidney Bladder: muscular bag that holds urine until it is passed out of body

How Does the Body Keep its temperature Constant?

Temperature Receptors -peripheral and central

Fluid Balance

The amount of fluid in the body is kept in equilibrium ie the more fluid taken into the body, the more fluid must be removed from the body. (in=out, about 2.5L)

Negative Feedback Loops

The response causes the stimulus to change in the opposite direction to the original change.

Positive Feedback Loops

The response causes the stimulus to reinforce and intensify the original change.

Glucagon Feedback Loop

blood glucose low->alpha cells in pancreatic islets detect low BG->alpha cells release glucagon->liver and skeletal muscle where glycogenesis/gluconeogenesis occurs->increase in glucose conc. (negative FB)

Insulin Feedback Loop

blood glucose too high->beta cells in pancreatic islets detect ->beta cells release insulin->glucose converted into glycogen through glycogenesis. Insulin increases the cells' uptake of glucose. Insulin increases the rate of protein synthesis-> decrease blood glucose conc.=NFB

Too much or too little of a hormone

can have big impact on homeostasis negatively

Glycogenesis

chemical formation of glycogen from other carbs, especially long chains of glucose, stimulated by insulin, occurs in liver

Gluconeogenesis

conversion of fats (lactic acid) or proteins (amino acids) into glucose (non-carb sources), in liver, stimulated by glucagon

Translocation

glucose moves from the blood into cells

Alcohol impact on ADH

inhibits its secretion, but may not have low osmotic pressure, have high urine output=dehydrated (has an impact on the hormone w/out stimulus)

Lipolysis

lipids broken down to form glucose

Thermoregulation (when cold) (nervous response-vasoconstriction)

vasoconstriction of skin arterioles (blood vessels close to surface of skin) (controlled by vasomotor centre in medulla) -impulses from hypothalamus stimulate sympathetic nerves that cause blood vessels in skin to constrict (decreased diameter) -decreased flow of warm blood to skin from internal organs. The skin becomes cooler because there is less blood flowing through it. -cooler skin=less heat lost from skin surface via radiation (decreased transfer of heat from internal organs to skin)=body temp. maintained

Heat Stroke

when temp. and relative humidity high, difficult for body to lose heat by radiation/evaporation=body temp. rises and regulatory mechanisms cease. Treat by immersing in cold water