Circulation and transport in humans
Students are often very interested in learning about human physiology. It is an area that they can relate to and health-related stories are regularly in the media.
However, consideration should be made when talking about disorders or mortality associated with heart disease. Students may have direct experience through the ill-health of a close relative or friend of the family.
The list looks at the biology of the human circulatory system as well as suggesting several practical activities.
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.
ABPI Heart and circulation web site
This web site has been written specifically for key stage 4 students. It covers the following:
• The need for a transport system
• The circulatory system
• The heart
• The blood vessels
• The blood and blood clotting
• Blood pressure
• Cardiovascular disease
• Prevention and treatment of cardiovascular disease
Each section contains brief self-test questions.
The web site can be used to allow students to learn independently and could be part of a ‘flipped classroom’ approach. This is where students learn content away from the classroom and then use teacher contact time to check understanding, go over misconceptions or tackle questions on the topic.
When using the web site, it is a good idea to give students specific tasks to address. These could include:
• What materials does blood transport throughout the body. Why do these materials need to be carried?
• Describe the role of each of the components in the blood.
• Compare and contrast the structures and functions of arteries, veins and capillaries.
• Explain why humans have a double circulatory system.
• Describe the structure of the heart.
• Describe the sequence of events in a cardiac cycle (heartbeat).
• How does the pressure change in each of the chambers during one heartbeat?
• Describe blood clotting and how this helps to prevent disease.
• Suggest ways that a person could help reduce their risk of having a heart attack.
Let's Dissect - the Heart
This video is a detailed and fairly graphic account of the dissection of a pig’s heart. The dissection, and accompanying commentary, shows all of the main features of the heart. It should be shown after students have been made aware of the heart structure.
Dissection is a sensitive issue. It is worth telling students about the video and any dissection the lesson before it is due to take place. In that way, students with real concerns can talk to you and alternative self-study away from the laboratory can be organised if necessary.
Reassure students that the heart is from a pig and that the animal was not killed for the purpose of the dissection but would have been killed for food production.
The first few minutes of the video clip show the heart connected to a set of lungs. This is good to see but looks quite bloody. You may want to preview this section to see that it is suitable for your students. If in doubt, advance the video to 54seconds where the heart is cleaned up and the anatomy is being described.
The video can be the prelude for an actual dissection of a hearts obtained from the butchers. Take care to be sensitive to cultural objections to using materials from pigs or cows. Discussing this with students prior to the lesson is recommended. In certain circumstances you may want to inform parents in advance of the class. It is worth, have an alternative activity prepared for students who do not wish to take part or watch a dissection.
Remember to consider the sensible precautions for using scissors or scalpels and it is advisable to use cutting boards. Supplying students with disposable gloves can encourage them to use fingers, or glass rods, to explore heart chambers and blood vessels.
Challenge students to find the different chambers and major blood vessels (often the atria are missing as they have been chopped off during butchery of the carcass).
It is worth showing students the coronary arteries that supply the cardiac muscle. Show how small they are and note that these are the vessels that, if blocked, cause a heart attack. Remind students of the link between excess fat in the diet and blocked arteries causing a heart attack.
Cardiac cycle misconceptions
This animation may be used to see if students can spot why it is not truly representative of the cardiac cycle in real life. In doing so, they can gain a better understanding of the cardiac cycle.
The animation suggests that blood passively flows down into chambers that are empty voids. What would be filling these voids? Is it supposed to be air?
In reality, the chambers squeeze blood out and so are at a reduced volume at the end of a contraction. As blood enters, they fill up and expand. There are no air spaces.
A homework could be to challenge students to find a better animation. You can then choose the most realistic to show the class in comparison. There may be several, each with different good points. This illustrates to students that a range of sources should be consulted, rather than just relying on the first they find.
Preventing Heart Disease
These materials are quite old but contain some useful activities.
The first to consider is Task 2, found on sheets 6 and 7. Students are given information about factors that cause heart disease. Questions then ask them to highlight different sections of relevant information. This activity reinforces work on the heart and also allows students to practice skills in identifying key facts. It is worth stressing that this is important when tackling examination questions where they may need to interpret information they are provided with.
Other activities in the materials look at surveying people’s lifestyles and then designing a health education campaign. It can be used to develop skills in collaboration and the collection and interpretation of data.
You may want to consider whether or not to undertake such an activity. This type of information is sensitive and questions can become too intrusive. Information should not be able to be linked to a particular individual. Perhaps, without doing the survey, students can think about the ethics of such a study and how an investigation would be planned to give meaningful results. This will then give them a better insight into findings of similar research that are regularly reported in the media.
Blood Pressure *suitable for home teaching*
Students are likely to have heard of blood pressure and may know someone who is on medication for high blood pressure or hypertension.
This Catalyst article helps to explain what is meant by blood pressure and describes what happens if blood pressure falls suddenly.
It is not easy and relatively inexpensive to get automatic blood pressure monitors. They are available from local pharmacists and even supermarkets sell them. They are easy to use and reasonably accurate.
Students could read the article during the lesson, to find out what is meant by blood pressure, what is normal, what is high blood pressure and what are some causes.
At the same time, students can measure each other’s blood pressure. Several monitors will make this process quicker and easier.
It is worth taking a little time to make sure students can position the cuff correctly around the arm and to tell them not to try more than two attempts if the pressure does not read successfully. The cuff inflates to briefly block off the blood supply to the arm and repeating this too many times is not recommended.
Systolic and diastolic pressures can be recorded anonymously in a table on the whiteboard or interactive board. This data can be used for a range of purposes, for example:
• Calculate the average systolic and diastolic pressures.
• Note the spread of results and how this illustrates natural variation.
• Practicing graph-plotting (spread of pressures in a population).
Entering the data directly into a spread sheet can aid manipulation and graph plotting if appropriate.
Observing the effects of exercise on the human body
This is a classic school biology experiment. Measuring the effect of exercise on heart rate and recovery. Full experimental details are included.
This type of activity is useful but can also be quite personal. Some students may feel uncomfortable taking exercise in front of their peers, especially if they are perceived to be unfit. Similarly, some students may suffer from conditions such as asthma and be sensitive about exercise. A risk assessment relevant to the class (not just a generic one) is clearly warranted.
The materials include a useful students briefing and consent form. It is wise to issue this the lesson before and have students show it to their parents / guardians and get it signed before the lesson. This is also an example of how scientists work. Permission is necessary from participants before any such investigation.
The experiment can be enhanced by the use of ICT. If possible, use a data logger with a heart rate monitor and a pulse oximeter. Blood pressure measurements can be taken with inexpensive monitors available from pharmacists or even some supermarkets.
It is useful to take reliable measurements of resting levels before the exercise begins.
It is worth taking measurements for 10 to 15 minutes after exercise has stopped. Sometimes it is possible to see a temporary dip below resting levels as the body ‘overshoots’ due to negative feedback.