Presentation is loading. Please wait.

Presentation is loading. Please wait.

Boardworks High School Science Homeostasis

Similar presentations


Presentation on theme: "Boardworks High School Science Homeostasis"— Presentation transcript:

1 Boardworks High School Science Homeostasis

2 Boardworks High School Science Homeostasis
Saving energy? Boardworks High School Science Homeostasis Sayid has decided to save energy by staying in bed all day. How much of his energy do you think this will save? Surprisingly, the answer is only about 30%. The other 70% keeps his body temperature at 37 °C (98.6 °F), and the solutions around his cells at just the right concentration.

3 Boardworks High School Science Homeostasis
What is homeostasis? Boardworks High School Science Homeostasis The body uses so much energy, even during sleep, because it must maintain a constant internal environment. This process of keeping things the same is called homeostasis. A series of automatic control systems ensures that the body maintains a constant temperature and steady levels of water, ions and blood sugar. Photo credit: © 2009 Jupiterimages Corporation Homeostasis allows the body’s cells to work at their optimum.

4 Boardworks High School Science Homeostasis
Keeping comfortable Boardworks High School Science Homeostasis Teacher notes This three-stage animation can be used to introduce the concept of homeostasis in terms of responding to change in external conditions.

5 The organs of homeostasis
Boardworks High School Science Homeostasis Teacher notes This activity could be used as a starter exercise to work on homeostasis.

6 Boardworks High School Science Homeostasis
Why is water important? Boardworks High School Science Homeostasis The human body is about 60-70% water. Water molecules and ions constantly move in and out of cells, and are essential for all life processes. Dehydration (loss of too much water from the body) damages cells. How is water gained and lost? Water is produced by the body during respiration, and absorbed from food and drink. Water is lost from the body in exhaled air, sweat, urine and feces.

7 Boardworks High School Science Homeostasis

8 Boardworks High School Science Homeostasis
What is osmosis? Boardworks High School Science Homeostasis Osmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, across a partially-permeable membrane. A partially-permeable membrane has holes in it that permit water molecules through but are too small to allow larger molecules through. Osmosis can be demonstrated using dialysis tubing filled with a solution and placed in a beaker of pure water. partially- permeable membrane (dialysis tubing) water glucose

9 Dilute vs. concentrated
Boardworks High School Science Homeostasis During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions. Dilute solutions have a high concentration of water molecules. Concentrated solutions have a low concentration of water molecules. pure water dilute solution concentrated solution

10 Boardworks High School Science Homeostasis
Predicting osmosis Boardworks High School Science Homeostasis Teacher notes This drag and drop activity provides the opportunity for informal assessment of students’ understanding of osmosis.

11 Boardworks High School Science Homeostasis
Osmosis in action Boardworks High School Science Homeostasis Teacher notes This activity could be used as a starter exercise to work on osmosis. You may need to allow the simulation to run for a minute or so before the water molecules on either side of the membrane are roughly equal.

12 Remember what the cell membrane looks like:
Boardworks High School Science Homeostasis

13 Boardworks High School Science Homeostasis
Osmosis and cells Boardworks High School Science Homeostasis Plant and animal cells are surrounded by a partially-permeable plasma membrane. This allows water and other small molecules to diffuse across. Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection. plasma membrane cell wall red blood cell plant cell

14 Osmosis and plant cells
Boardworks High School Science Homeostasis Teacher notes This activity could be used to check students’ understanding of the effects of osmosis on plant cells.

15 Osmosis and animal cells
Boardworks High School Science Homeostasis Animal cells do not have a cell wall. This means they respond differently to plant cells to the gain and loss of water. In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and burst. This is called lysis. In concentrated solutions, water loss causes the cells to shrink. When this happens to red blood cells, it is called crenation.

16 Osmosis and animal cells
Boardworks High School Science Homeostasis Teacher notes This activity could be used to check students’ understanding of the effects of osmosis on red blood cells.

17 Factors that affect Passive Transport:
Boardworks High School Science Homeostasis Whether a molecule can move through the membrane depends on: the size of the molecule the type of molecule (polar or nonpolar, ions, etc.) Molecules move by one of the following methods: diffusion, facilitated diffusion, or osmosis.

18 Egg in hypertonic solution
Boardworks High School Science Homeostasis Water moved out of the egg to try to dilute the solutes outside of the egg and make the external environment have a higher water concentration to match the inside. Chicken egg in syrup

19 Egg in hypotonic solution
Boardworks High School Science Homeostasis Water moved into the egg to reduce the water concentration compared to solutes outside of the egg and make the external environment have a lower water concentration to match the inside. Chicken egg in tap water (or vinegar)

20 Osmosis and animal cells
Boardworks High School Science Homeostasis In order to remain healthy, animal cells need to maintain an isotonic water balance. This means that the water concentration both inside and outside the cell are equal. hypothalamus The concentration of water and salt in the blood are controlled by the kidneys. The kidneys are controlled by the portion of the brain called the hypothalamus.

21 Boardworks High School Science Homeostasis

22 Boardworks High School Science Homeostasis
Waste removal Boardworks High School Science Homeostasis Several organs are important in removing waste from the body. The lungs remove carbon dioxide. The liver converts excess protein into urea. The skin provides a surface for small amounts of water and salt to move out of the body. The kidneys remove unwanted substances such as urea, excess water and salt.

23 Boardworks High School Science Homeostasis
What is urea? Boardworks High School Science Homeostasis Excess amino acids in the body are broken down by the liver, producing a waste substance called urea. This process is important because it converts toxic ammonia to urea, which is done using carbon dioxide. Once formed, urea is transported by the circulatory system to the kidneys. Teacher notes The kidneys typically filter about 1,500 liters of blood every day. The kidneys filter the blood, removing urea and excess water and salt, which forms urine. Urine is stored in the bladder before being excreted from the body.

24 What are the different parts of a kidney?
Boardworks High School Science Homeostasis

25 Boardworks High School Science Homeostasis
Labeling the kidney Boardworks High School Science Homeostasis

26 How does the kidney work?
Boardworks High School Science Homeostasis Teacher notes Stage 1: Filtration occurs as an increased blood pressure forces smaller substances through the capillary wall into the Bowman’s capsule. The glomerulus is a ball of blood vessels. Stage 2: In the first coiled tubule (proximal convoluted tubule) most reabsorption is by active transport. The cells of the first coiled tubule are packed with mitochondria, and have large brush borders to increase the surface area for reabsorption. Stage 3 & 4: Substances move out of the loop of Henle by passive diffusion. The cells of the loop of Henle are thin, with no brush border and relatively few mitochondria. Stage 5: The collecting duct carries water to the ureter.

27 Boardworks High School Science Homeostasis
Stages in the nephron Boardworks High School Science Homeostasis

28 Controlling water content
Boardworks High School Science Homeostasis

29 Regulating water content
Boardworks High School Science Homeostasis

30 Boardworks High School Science Homeostasis
Analysing urine Boardworks High School Science Homeostasis Changes in the colour, clarity, pH and the presence of certain substances in urine can help doctors diagnose medical conditions: Protein or red blood cells in urine can indicate kidney damage or disease, as these substances would not normally filter through the glomerulus. Photo credit: © Shutterstock 2009, Charles Cloutier Teacher notes In order to make a definite diagnosis of medical condition, doctors normally also need to carry out a blood test. The presence of protein in urine can also be an indication of pregnancy. Glucose in urine is often an indication of diabetes. A person with diabetes will have a high level of glucose in the blood.

31 Boardworks High School Science Homeostasis
Which sample? Boardworks High School Science Homeostasis

32 Controlling blood glucose
Boardworks High School Science Homeostasis Between meals, blood glucose levels are topped up from stored deposits in the liver and muscles. After a meal, blood glucose rises but quickly returns to normal. Where does the excess go? Why not leave it in the blood? Excess glucose makes the blood plasma and tissue fluid around cells too concentrated. This can severely damage cells, for example, causing crenation in red blood cells. However, low blood sugar levels can be equally as dangerous, as it can make cells swell up and burst. This is called lysis.


Download ppt "Boardworks High School Science Homeostasis"

Similar presentations


Ads by Google