Homeostasis (including non-communicable diseases)
With the topic of homeostasis students often fail to make the link between external changes (effect of drinking a lot of water, resulting in increased urine output) with the internal changes that bring about the external changes.
Students need to be able to explain the importance of maintaining a constant internal environment in response to internal and external change, this includes (but is not limited to!) an explanation of how insulin controls blood sugar levels in the body. The level of detail required is important for the study of the topic at GCSE, in explaining how insulin controls blood sugar students should include how glucagon reacts with insulin. Students should also be able to compare type 1 and type 2 diabetes and explain how they can be treated.
Other homeostatic mechanisms and considerations also need to be explained these include, temperature regulation, effect on cells of osmotic changes in body fluids and functioning of the kidneys in maintaining water balance. In describing the function of the kidneys in maintaining water balance students should include the effect of ADH on permeability of kidney tubules.
Students often have misconceptions in relation to homeostatic mechanisms, one such misconception is the role of the kidneys. Delivery of this topic should clearly explain the role of the kidneys in filtering substances from the blood in response to external and internal stimuli. Animations are useful teaching tools to help support learning in this area. Another misconception students have is that insulin raises blood sugar levels, when delivery this aspect of the topic ensure that key words are clearly defined and highlighted to students. Students could work in pairs to produce poster size flow diagrams which they must then display for other students to critique.
Students often seem to get confused between vasoconstriction and vasodilation, using the terms the wrong way round, it would be worth spending some time going through the temperature regulation processes step by step- perhaps students could produce their own animation or provide a voice over to an animation. Ensure that students do not talk about blood vessels moving towards or way from the skin surface.
Links and Resources
This Catalyst article is about the importance of maintaining a steady state and not so much about the mechanisms which control any changes that take place. As such, it provides a really useful introduction to the topic of homeostasis.
Students could be given this article to read for homework and prepare a 5 minutes summary of the article to be presented to the class as the introduction to the first lesson on the topic of homeostasis.
There are many ways to make effective use of Catalyst articles, a booklet has been produced which provides ideas on how Catalyst articles can be used with students and includes six exemplar activities. This booklet can be accessed at: https://www.stem.org.uk/elibrary/resource/27308>
This is a relatively dated publication, but one which contains a lot of very useful activities for this topic a lot of ideas for teaching activities that could easily be adapted. An activity that begins on page 63 looks at control systems and feedback loops. This is a vitally important concept for students to grasp if they are to fully understand homeostasis.
The card sort for osmoregulation on page 84, for example, would make a useful activity to determine if there are misconceptions that need to be addressed.
Students could then be challenged to produce a similar set of cards for either thermoregulation or the control of blood sugar levels. If they do this in pairs, the pairs can then swap the cards produced to see if they can place them in the correct order. Other ideas, such as making a jigsaw (page sixteen), could be adapted for example to a cross section of the kidney
This resource was developed to highlight the work of successful scientists. In this resource the scientist is Frances Ashcroft who is working on the regulation on insulin secretion, and this therefore provides a really useful resource for this topic area.
The video clips show Frances Ashcroft talking about her work on the regulation of insulin secretion. Her discovery was that glucose causes potassium channels in pancreatic beta cell membranes to shut. This stimulates the secretion of insulin. The mechanism helps to explain how high glucose levels in the blood lead to the secretion of insulin.
Students may need some help to ensure they have picked up on the points in the video.
There are teachers notes and activities to accompany the video; pages 8 to 12 of the activities can be used to explain and reinforce the control of blood sugar levels and the effects of diabetes
This is a Catalyst article about juvenile diabetes, a genetic disease also known as Type 1 diabetes, which affects over 200,000 people in the UK. The article covers a number of different topic areas and may be useful to challenge students to think about connections between different areas of biology.
Whilst the main focus of the article is about research into the genetics of the disorder it does contains useful information about the disorder itself.
A useful activity would be to ask students to read the article provided that it is about diabetes and ask them to write a short summary of the article (no more than half a side). Have students share their reviews in small groups and see how they are similar and how they are different. How many reviews focused on diabetes and how many focused on the genetics?
This activity pack gives an interesting context in which to discuss the topic of homeostasis. The resources provided are focused on thermoregulation in the context of an expedition to the South Pole. Polly Hatchard was one of an all-women team who trekked to the South Pole. A range of audio clips describe the preparations and some of the problems she faced during her expedition to the pole.
There is then an activity worksheet for students to complete. It is not necessary to listen to all the audio clips and pages one and three of the activity sheet are the most relevant. The audio clips could just simply be used as stimulus material and students could be asked to produce a detailed flow diagram of the thermoregulation feedback mechanism
This is a three page summary sheet on homeostasis. The resource provides details of the key mechanisms involved in homeostatic responses. As this is a summary the information provided is not extensive, it could however be used as a quick recap, or students could be asked to translate the information provided in particular sections into another non-text format such as a flow diagram , presentation, poster etc.
This animation and video show students the structure and function of the kidneys. It also describes dialysis and kidney transplants. Students can use the animation as a self-study activity once the topic of the kidneys and their broad function has been introduced.
Alternatively, it makes a good revision activity once the topic has been completed.
Depending on the detail required by your course specifications, students can be given a framework of headings so that they can focus onto the relevant sections of the animation. They could make their own notes on the topic, which will help them develop skills in interpreting and summarising information.
There is a good section on dialysis. Ask students to consider the dialysis solution and explain its composition
This is a Catalyst article which describes the structure and function of the kidneys. Students can read the whole article. There is a good diagram which shows the structure of a kidney tubule and relates it to the processes of filtration and reabsorption. This is quite a tricky concept as students are told that kidneys ‘filter’ the blood. Intuitively, this is a one-way process. Reabsorption suggests something else.
Students can be challenged to write three stories that tell the routes through the kidney and beyond of:
• a water molecule destined to be excreted from the body;
• a molecule of urea (from excess protein);
• a sugar molecule.
These stories can then be used to check if the students have understood the process of filtration, followed by reabsorption.
One section of the article describes the control of urine production via ADH. Students could produce flow diagrams to illustrate the control pathways that happen when the body has too much, or too little water.
The activities in this resource take a closer look at renal dialysis, peritoneal dialysis and kidney transplants. The first activities can be used to revise kidney structure and function.
There is a good information sheet on dialysis and transplants. This can be used as the basis of a comprehension activity. Have students produce suitable questions and swap them amongst the class. These can then be peer marked. The answers can be discussed and misconceptions addressed.
A final activity looks at how transplant patients are chosen. This is a good activity to get students thinking about the broader implications of the procedure. How would they decide?
These materials contain a wide range of activities but the ones relating to the kidneys can be found in section 5, starting on page 60.
There are two good activities that will help students to understand how the kidneys work and how dialysis works. The first activity sees students modelling the filtration of the blood. Using a mesh or net, students see how large molecules and blood cells cannot be filtered whilst smaller solute molecules can be. It is worth stressing where this process is happening in the kidney and also that the useful molecules are subsequently reabsorbed.
A second activity uses Visking tubing and a sample of made up ‘blood’ to model dialysis. This will help students to get a grasp of a process that they would otherwise be unable to view. It will help to make it less abstract.
A subsequent activity focuses onto what happens in a renal dialysis machine. Students’ understanding of dialysis can be tested at this point. In the experiment, glucose and salt enter the dialysis fluid. This would then be discarded. How does this compare to a real dialysis machine? What is the composition of the dialysis fluid? How is it adjusted to make sure that useful substances like glucose and salt are not taken out of the blood? After all, the body needs to keep these. It is just the urea that the dialysis machine is designed to remove. This leads to a good discussion about diffusion and concentration gradients.