Homeostasis - hormones
Hormones and homeostasis are somewhat abstract concepts. Students have direct experience of a lot of the actions. For example, they know if they drink a lot of water, they will go to the toilet more often to get rid of the excess water. However, the underlying mechanisms of homeostasis are less clear. The challenge comes in helping students to link the internal biology that is taking place with the experiences they have of their own body.
Feedback loops are an important feature and time should be taken to help students to understand the concept. Without a good grounding in this idea, it is difficult to see how various interactions can maintain a regular state.
It is useful to stress why homeostasis is important and explain why we need to keep a constant body temperature, rather than just studying the process in isolation.
Whilst this list provides a source of information and ideas for experimental work, it is important to note that recommendations can date very quickly. Do NOT follow suggestions which conflict with current advice from CLEAPSS, SSERC or recent safety guides. eLibrary users are responsible for ensuring that any activity, including practical work, which they carry out is consistent with current regulations related to Health and Safety and that they carry an appropriate risk assessment. Further information is provided in our Health and Safety guidance.
Links and Resources
This web resource was written specifically for 14-16 students. It covers the main aspects of hormones and their actions. The resource could be used in a range of ways.
It helps to download the zip file and install it onto a stand-alone computer. The direct link to the resource may not work well in all web browsers.
You could devise a series of questions that students are able to research and find the answer in the resource. These could cover basics, such as the names and actions of different hormones. More complex problems could see students describing the body’s hormonal response to certain situations. In doing so, their understanding of control mechanisms and feedback loops can be assessed.
Section 4 has a very good representation of the hormones involved in the menstrual cycle. Students can be challenged to interpret the graph and describe the effects of the hormone involved. This will reinforce their understanding of the menstrual cycle and also practice the analysis of information.
Section 6 contains information on the regulation of blood sugar levels and how it goes wrong in diabetes. It is worthwhile running the animations to show the responses to high and low blood sugar levels. Directed questioning can then be used to assess students' understanding using voting cards containing the phrases: release insulin; release glucagon; do nothing. Describe a range of scenarios and ask the students to give the response of pancreas cells. For example, what would the response be after a sugary meal, during hard exercise, following a period of fasting etc.
This resource contains a lot of relevant material.
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 and how hormones work. Look at the activity to see which examples are relevant to your students. The initial examples look at the control of a steam iron’s temperature. Another typical example is the thermostat of a central heating system.
Whichever example is used, it is worthwhile stressing the point that the detector causes a response that returns the system back to normal. Constant monitoring and changing of response is called a feedback loop.
To relate this to homeostasis in the body, the cards on page 84 can be used. These show the process of osmoregulation. Note that the number order is not the correct order of events. In groups, have students go through the process. If they have not yet covered kidney function, a set of cards that show a sequence of events in the regulation of body temperature could be produced.
As a further extension of the idea, students can be challenged to produce their own cards and do the same for the control of blood sugar levels.
Section 4 in the book (starting on page 70) contains a range of activities relating directly to hormonal control systems. A simple experiment on phototropism (page 74) can be used to show students that hormones are involved in the control of plant growth. It helps to remains students that plants are complex organisms.
These resources can be used to illustrate an example of the work of a successful scientist and to extend students’ understanding of diabetes.
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.
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 not pick this up as it is briefly covered in the second video clip, and so it may need to be pointed out. It is also covered in the notes on page 13.
This observation is useful in developing drugs to help treat type II diabetes.
The data in activity 8 (page 15) can be used. It is a dose-response graph for a drug being tested to see its effectiveness in closing potassium channels.
In addition to the relevance to diabetes, the materials help to show the work of a female scientist and the videos convey her enthusiasm and commitment.
This article, from Catalyst magazine, looks in the broader sense at homeostasis. It discusses examples including the regulation of:
• blood pH
• carbon dioxide and oxygen
• blood sugar levels
• water balance
The good thing about the article is that it describes the effects of imbalances on the cells of the body. This is often an area that is failed to be emphasised. It is assumed that students will know why it is a good idea to maintain a constant body temperature. Reinforcing the link to enzyme optimum temperatures is often omitted.
Students can read the article and then be give time to consider a more open-ended question. “Why is it important to regulate.....” You can choose one of the factors that the students are familiar with and ask them to make the connections with as many body systems (or plant systems) as possible. Students could work individually or in groups. Outputs could include a piece of extended writing, concept map or group discussion.
This catalyst article may be useful to challenge students to think about connections between different areas of biology. It also gives an example of how teams of scientists work together on a problem.
It is a good way of revising understanding of DNA, genes and inheritance.
The article looks at diabetes and contains useful information about the disorder. It’s main thrust however is about research into the genetics of the disorder.
A useful exercise is to inform students 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 focussed on diabetes and how many focussed on the genetics?
When looking at the approach of the team, students can be challenged to list the different people involved in the research. This is a good way of looking at how scientists work and the range of career opportunities available.