Blood system
Activity 1 - The discovery of the circulatory system by Harvey
Galen studied anatomy in Italy with Fabricus who had wondered why veins had valves, there was no explanation for them. At the time it was thought that the blood only flowed away from the heart. An idea suggested by Galen, the Greek philosopher 1300 years before.
These Introductory slides show how Harvey's evidence changed thinking about the flow of blood in the body.
harvey_ideas_blood.pdfHaving read the slides above about Harvey's discovery of blood circulation answer the following Nature of Science IB style question.
Nature of science question
The work of Harvey on blood circulation illustrates an important principal of the Nature of Science, a theory is never 100% certain as there is always a possibility that new evidence will falsify the theory.
Outline two pieces of evidence which Harvey used to support his ideas about circulation and falsify the old ideas of Galen.
(2 marks)
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Click the eye icon below to reveal a model answer.
Model answer:
Experiments showed that blood flowed back to the heart.
These included the following:
Fish hearts having their veins tied. The hearts emptied of blood, then refilled when the tie was removed.
Blood was shown flowing towards the heart in veins of a human arm.
Calculations of blood volume and pulse rates showed that huge volumes of blood were leaving the heart
Answer the questions on the Artery and vein worksheet below.
Blood_vessels_student_sheet.pdfActivity 3 Composition of the Blood
Using prepared slides of blood try to identify the number of different types of cells in the blood. If you haven't god real slides available take a look at this great Exploratorium blood cell feature - including a nice video.
Complete the questions on the Blood composition student sheet
blood_composition_ss.pdfTeachers notes
There is a great short video animation of Arteries from Blausen here
Model answers for the activity 2 worksheet on blood vessels can be found here: Blood vessels - model answers
Model answers for activity 3 can be found here: Composition of blood - model answers
These links contain resources about the work of William Harvey on the circulation of blood
Excellent historical records from Glasgow University Library
very good detail about Harvey's experiments and Galen's view of the heart at the time too.
Listen to an extract from the in our Time podcast from the BBC. about Blood and the ideas at the time of Harvey. They make his discoveries even more impressive. Biography on the BBC
There are some interesting resources on blood histology and the functions of different blood cells:
Activity 1 - Worksheet activity.
Read the bullet points on the worksheet which summarise the key details of the control of heart beat. Highlighting a few key words in each bullet point to help you remember it later.
Use these phrases as labels to annotate the diagram on the back of the sheet. Control of heart rate worksheet
Memorize the annotations as whole points.
sl_control_of_heartbeat_activity.pdfActivity 2 - Think / Pair / Share
Think for a minute or two about what you would say if someone asked you to explain the diagram on the worksheet. Run through the explanation in your head. Ask for any clarifications you need and make a note of answers.
Pair up with someone in the class for just five minutes and take turns to say your explanation out loud.
Offer suggestions of improvements to your partner.
Share your explanation with the whole class - at the whiteboard if you are confident enough.
Activity 3 - IB Style questions
Answer these IB style heart rate questions. Remember to use the new details which you have learnt.
sl_control_of_heartbeat_ibstyle_qns.pdfsl_control_of_heartbeat_ibstyle_ans.pdfTeachers notes
This page can be projected on the whiteboard during the lesson.
The central part of the activity is a printable worksheet, there is a starter activity, an IB style question and a video animation which could be used as an extension.
Aims:
The myogenic nature of heartbeat
The control of heartbeat by the medulla using nerves
The hormonal control of heartbear by the adrenal glands
A possible lesson plan
Starter (10 minutes)
Students get out notes and consider how the body might control the rate of heart beat.
Plenary 'discussion' of the myogenic nature of the heart beat and a recap of the structure of the heart.
Main (30 minutes)
Students read through the points on the worksheet, identify any points they don't understand and look for clarification of any confusion.
Students label the diagram on the reverse side of the worksheet.
Encourage the students to remember the labels as much as possible.
Think Pair Share activity will help build student confidence in their understanding of the control of heartbeat
One or two students can share their explanations with the whole class.
End (20 minutes)
Students attempt the IB style questions
Students could mark these using the model answer sheet.
Extension work
Show the video to the whole class, or individual students can watch the final animation while others complete the questions.
Activity 1 Heart Diagram Activities
Using the screen cast below complete a diagram of the structures of the heart including labels
Activity 2: NEW Heart Dissection Experiment (with emphasis on form and function)
Carry out the experiment on the New Heart dissection worksheet below. Of course this could be a demonstration.
heart_dissection_inthkng_new.pdfActivity 3 Learn annotations for the heart diagram
Check your understanding, study the flashcards below. As you read them through click the star for difficult terms. As you become more confident select one of the other study modes bottom right.
Teachers notes
This lesson could easily take more than 1 hour. It would be wise to plan for this, or set activity one or three as a homework task as follow up or in preparation for the dissection.
The heart dissection has been recently reviewed and completely re-written to emphasise qualitative observations and to ask students to record information about structure and function of the heart, using diagrams and photos. It also improves the way the students see the functioning of the semilunar and atrioventricular valves as well as valves in the coronary veins.
Of course this could be a demonstration or students could work in groups to reduce the use of hearts or if students prefer not to dissect. There is no requirement in IB to carry out dissections.
The older heart dissection was designed as a quantitative IB lab and students are asked to measure and estimate the uncertainty for these measured values. Carry out the experiment on the Heart dissection worksheet below.
heart_dissection_inthkng.pdfShould students learn how to draw heart diagrams by heart ?
(sorry about the pun!)
The guide doesn't explicitly say that students have to be able to draw the heart structure. However, the teacher support material which lists the changes in the new guide doesn't say that this has been removed from the topic 6.2.
I have also checked through the specimen exam papers for the new guide, and there is a question to label a photo of the heart from a dissection in the SL paper 2, but no question to draw it.
Personally I think that the activity of drawing a heart will help students to remember the names of the parts and also to understand the structure of a heart while they do a dissection.
But yes, drawing a diagram of a heart is less likely to be a question in future exams.
It is hard to know exactly what future exams will contain with the new guide. The description of student understanding and skills allows a wider range of questioning for examiners.
I could imagine a question asking students to explain some of the details listed in the guide, e.g. flow of blood through the heart and the function of valves, using diagrams if they wish to.