Presentation on theme: "Homeostasis This Powerpoint is hosted on"— Presentation transcript:
1Homeostasis This Powerpoint is hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints
2Glossary Maintain – keep up. Constant – the same. Internal – inside the body.Environment – surroundings of the body.Feedback - a cycle in which the output of a system “feeds back” to modify or reinforce the actions of the system in order to maintain homeostasis.
3GlossaryNegative feedback - a change causes system 1 to send a message to system 2 to restore homeostasis. When system 1 detects that system 2 has acted, it stops signaling for action and system 2 stops (turned off).Positive feedback - the original stimulus is promoted rather than stopped. Positive feedback is rarely used to maintain homeostasis. An example of positive feedback is childbirth.
4What is Homeostasis? Body cells work best if they have the correct TemperatureWater levelsGlucose concentrationYour body has mechanisms to keep the cells in a constant environment.
5What is Homeostasis?The maintenance of a constant environment in the body is called Homeostasis
6Controlling body temperature All mammals maintain a constant body temperature.Human beings have a body temperature of about 37ºC.E.g. If your body is in a hot environment your body temperature is 37ºCIf your body is in a cold environment your body temperature is still 37ºC
7Controlling body temperature Animals with a large surface area compared to their volume will lose heat faster than animals with a small surface area.Volume = _______Surface area = ______Volume : Surface area ratio = ___________Volume = _______Surface area = ______Volume : Surface area ratio = ___________
8Controlling body temperature Volume : Surface area ratio = 1:6Volume : Surface area ratio = 1:5For every 1 unit of heat made, heat is lost out of 6 sidesFor every 1 unit of heat made, heat is lost out of 5 sides
9Controlling body temperature Volume : Surface area ratio = 1:6Volume : Surface area ratio = 1:5The bigger the Volume : Surface Area ratio is, the faster heat will be lost.
11What mechanisms are there to cool the body down? SweatingWhen your body is hot, sweat glands are stimulated to release sweat.The liquid sweat turns into a gas (it evaporates)To do this, it needs heat.It gets that heat from your skin.As your skin loses heat, it cools down.
13What mechanisms are there to cool the body down? VasodilationYour blood carries most of the heat energy around your body.There are capillaries underneath your skin that can be filled with blood if you get too hot.This brings the blood closer to the surface of the skin so more heat can be lost.This is why you look red when you are hot!
14This means more heat is lost from the surface of the skin If the temperature rises, the blood vessel dilates (gets bigger).
15What mechanisms are there to warm the body up? VasoconstrictionThis is the opposite of vasodilationThe capillaries underneath your skin get constricted (shut off).This takes the blood away from the surface of the skin so less heat can be lost.
16This means less heat is lost from the surface of the skin If the temperature falls, the blood vessel constricts (gets shut off).
17What mechanisms are there to warm the body up? PiloerectionThis is when the hairs on your skin “stand up” .It is sometimes called “goose bumps” or “chicken skin”!The hairs trap a layer of air next to the skin which is then warmed by the body heatThe air becomes an insulating layer.
19Controlling Glucose levels Your cells also need an exact level of glucose in the blood.Glucose moves into the cells for cellular respirationExcess glucose gets turned into glycogen in the liverThis is regulated by 2 hormones (chemicals) from the pancreas called:InsulinGlucagon
20If there is too much glucose in the blood, Insulin converts some of it to glycogen the rest moves into the cells for use in cellular respiration.GlycogenInsulinGlucose in the blood
21GlycogenIf there is not enough glucose in the blood, Glucagon converts some glycogen into glucose.GlucagonGlucose in the blood
22Diabetes Some people do not produce enough insulin. When they eat food, the glucose levels in their blood cannot be reduced.This condition is known as DIABETES.Diabetics sometimes have to inject insulin into their blood. They have to be careful of their diet.
23Glucose levels rise after a meal. Insulin is produced and glucose levels fall to normal again.GlucoseConcentrationNormalTimeMeal eaten
24Meal eaten Glucose levels rise after a meal. Diabetic ConcentrationDiabeticInsulin is not produced so glucose levels stay highTimeMeal eaten
25Insulin The glucose in the blood increases. GlycogenThe glucose in the blood increases.But there is no insulin to convert it into glycogen.Glucose concentration rises to dangerous levels.InsulinGlucose in the blood
26Blood Glucose Feedback Mechanism Pancreas produces InsulinGlucose into cellsOut of bloodBlood glucose increases Homeostasis Blood glucose decreases( High ) (Low)Glucose out of cellsInto bloodPancreas produces Glucagon
27Controlling water levels The control of water levels is carried out by the KIDNEYS.It is closely linked to the excretion of urea.Urea is a waste product that is made when the LIVER breaks down proteins that are not needed by the body.Urea contains the element Nitrogen.
28The kidneysThe kidneys “clean” the blood of waste products and control how much water is kept in the body. The waste products and water make up urine which is excreted via the ureter.“Dirty” blood enters the kidney through the renal artery. Then, several things happen to clean the blood...
291. FiltrationBlood enters the tubule area in a capillary.The capillary forms a small “knot” near the kidney tubule.The blood is filtered so all the small particles go into the tubule.The capillary then carries on to run next to the tubule.
30The kidney tubule now contains lots of blood components including: Glucose:Ions:Water:Urea:
312. Reabsorb sugarThe body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.
322. Reabsorb sugarThe body needs to have sugar in the blood for cells to use in respiration. So all the sugar is reabsorbed back into the capillary.
333. Reabsorb waterWater and ions are the next to be absorbed. It depends on how much is needed by the body.
343. Reabsorb waterWater and ions are the next to be absorbed. It depends on how much is needed by the body.
35Reabsorbing waterIf you have too little water in your blood, you will produce very concentrated urine.(very little water in it)If you have too much water in your blood, you will produce very dilute urine.(lots of water in it)
365. Excrete the wasteEverything that is left in the kidney tubule is waste:All the ureaExcess waterThis waste is called urine. It is excreted via the ureter and is stored in the bladder.Renal veinThe “clean” blood leaves the kidney in the renal vein.Ureter
37Summary of urine production Urea is a waste product made in the LIVERWater content of the body is controlled in the KIDNEYSUrea, water and other waste makes up URINE.Urine travels down the URETER and is stored in the BLADDERUrine is excreted through the URETHRA.
38Temperature regulation, glucose level control and water level control are all examples of NEGATIVE FEEDBACK MECHANISMS.
39Homeostasis in PlantsControl of water levels in the plant is important to the survival of the plant.This is achieved by a number of methods:Waxy cuticle on leavesStorage of waterOpening and closing of stomates
40Function of StomataGuard CellsWhat process involves using CO2 and H2O releasing O2 as a waste product?PhotosynthesisWhat is the plant using this process to make?Carbohydrates-glucoseIf the plant needs water for photosynthesis, why is water coming out of the stoma?Guard CellsWhat goes out?O2H2OCO2What goes in?Stoma OpenStoma ClosedStoma
41Function of Guard Cells These stomata (leaf openings) naturally allow water to evaporate out.Why would the plant close stomata with guard cells?Prevent excess water loss through transpiration. (conserve water)So what is the point of having stomata?Allow gas exchange for photosynthesisGuard CellsGuard CellsStoma OpenStoma ClosedGuard cells open by inflating with extra water. They do this by pumping K+ ions into the cell, which causes water to rush in via osmosis to diffuse the high ion concentration.
42The opening and closing of the stomata maintains water balance in the plant and thus maintains homeostasis.