Senior Science

9.3Medical Technology – Bionics

Section 2

Maintaining

Blood Flow

9.3Section 2 ::: Maintaining Blood Flow

9.2The regular beating of the heart and continuity of the flow of blood through the heart and around the body is needed to maintain good health
9.3.2 a / Explain the relationship between the structure and function of the following parts of the heart
–Valves
–Atria
–Ventricles
– Major arteries and veins
9.3.2 b / Explain that specialised tissues in the heart produce an electrical signal that stimulates rhythmic contractions of the cardiac muscle
9.3.2 c / Discuss the problems that can result from interruptions to the normal rhythm of the heart
9.3.2 d / Identify that a pacemaker will produce a regular electrical impulse
9.3.2 e / Identify the types of materials used to make pacemakers and the properties that make these suitable for implanting in the body
9.3.2 f / Describe the problems that can result from faulty valves in the heart
9.3.2 g / Describe the properties of materials such as Teflon/pyrolytic carbon that make them versatile materials for making artificial body parts, including heart valves
9.3.2 h / Describe and explain the effects of a build up of plaque on the walls of major arteries and veins on blood flow to and from the heart
9.3.2.i / Discuss ways in which plaque could be eliminated or altered to ease blood flow
9.3.2. i / Gather, identify data sources, plan, choose equipment or resources for, perform a first-hand investigation and analyse information about changes in the heart beat rate before and after sustained physical activity
9.3.2 ii / Plan and perform an investigation to identify individual aspects that comprise the heart beat
9.3.2 iii / Identify data sources, gather, process and analyse information to outline the historical development of pacemakers and use available evidence to identify types of technological advances that have made their development possible
9.3.2 iv / Construct a simple model to demonstrate the function of valves in the heart
9.3.2 v / Gather, process and analyse information to outline areas of current research in heart transplants and/or artificial hearts and their impact on society
9.3.2 vi / Gather information from secondary sources on techniques used, including angioplasty, to ease blood flow to and from the heart and in blood vessels, when there has been a build up of plaque
9.3.2 vii / Process information to identify different types and functions of artificial valves
in the heart

Introduction

The Human Circulatory System consists of a heart and three types of blood vessels – arteries, capillaries and veins. An artery is a blood vessel taking blood away from the heart. A vein is a blood vessel carrying blood to the heart. A capillary is a tiny blood vessel that joins arteries and veins. The exchange of materials into and out of the blood takes place across the thin walls of the capillaries.

A description of one circuit of the circulatory system is written below.

Blood returns to the heart from body tissues.

It enters the right atrium (upper right chamber of the heart).

The heart contracts pumping blood into the right ventricle (via the tricuspid valve).

The right ventricle contracts pumping blood towards the lungs (via the pulmonary valve).

The blood travels to the lungs via the pulmonary artery.

It then enters the lung capillaries where it releases carbon dioxide and collects oxygen.

The blood then travels back to the heart via the pulmonary vein.

It enters the left atrium (upper left chamber of the heart).

The left atrium contracts pumping blood into the left ventricle (via the bicuspid valve).

The left ventricle contracts pumping blood into a large artery, the aorta (via the aortic valve).

The aorta branches several times to send blood to all parts of the body.

The blood enters capillaries in various parts of the body.

In the capillaries the blood releases oxygen into the body tissues and collects carbon dioxide.

The blood returns from the body to the heart via the veins (vena cavas).

It enters the right atrium (upper right chamber of the heart).

Role of the Circulatory System

The role of the circulatory system is to function as a transport network throughout the body. As such particular functions of the circulatory system are:

  • It transports oxygen from the lungs to body cells
  • It transports carbon dioxide from body cells to the lungs
  • It transports nutrients (digested food) from the small intestine to body cells
  • It transports wastes from body cells to the excretory organs for elimination.
  • It distributes heat energy produced by body muscles to all areas of the body.
  • It carries white blood cells that are important in fighting disease.

Notes Questions

  1. Name the three blood vessels in the circulatory system.
  1. When blood flows around the body it passes through various parts of the circulatory system. Put the following parts of the circulatory system in the correct order.

Right atriumVeins (vena cavas)Left ventriclePulmonary vein

Left atriumPulmonary arteryAortaLung capillaries

Right atriumRight ventricleBody capillaries

  1. Name the four valves in the heart
  1. Name five things transported by the circulatory system

9.3.2 i / Gather, identify data sources, plan, choose equipment or resources for, perform a first-hand investigation and analyse information about changes in the heart beat rate Before and after sustained physical activity

Activity 2– 1Exercise and Heart Rate

The task is to investigate changes in the heart beat rate during rest and during sustained physical activity. This will require students to:

  • Gather, Identify data sources,
  • Plan,
  • Choose equipment or resources for,
  • Perform a first-hand investigation and
  • Analyse information gathered

Planning

Information to consider

/

What to do

Discuss the information and questions below. After the discussion plan your investigation.
Define pulse rate.
Describe how to measure pulse rate.
Caution about risks involved in exercising.
Should subjects warm up before exercising?
Work in pairs – one exercising, one recording
Clearly state when pulse rate is measured?
How long will heart rate be measured?
Is pulse rate measured before, during and after exercise?
How many times after exercise is pulse rate measured?
Describe the physical activity to be used, in such a way that it can be repeated.
Clearly state how long the subjects exercise?
State measurements that need to be repeated.
How many subjects will exercise?
Record results in a table /
  1. Write a heading for the investigation.
  1. Write an aim for the investigation.
  1. List possible risks associated with exercising
  1. Make a list of equipment needed.
  1. Write a method for the investigation.
  1. List the instructions to be followed for each test, in point form.
  1. Tabulate results [A sample is shown]
  1. Graph results
  1. Write a conclusion

Results

A table like the one below can be used for the results.

Before Exercise / After Exercise (minutes)
1 / 2 / 3 / 0 / 1 / 2 / 3 / 4
Beats for 10 secs.
Beats for 1 min.
PULSE RATE

Conclusion

Write an appropriate conclusion for this investigation

Discussion

  1. Evaluate the validity of the data collected.[5 marks]
  2. Evaluate the appropriateness of the method used to solve the problem.[5 marks]

Marking criteria for Plan – Exercise and Heart Rate[12 marks]
Syllabus Outcome – H11.2Plan first – hand investigations
The report should be written so that it is clear from reading the laboratory report that:
  1. The investigation is attempting to find if one Variable changes (dependent) because of the change in another Variable (independent) [2]
  2. Some variables need to be kept constant[2]
  3. It is clear how the pulse rate will be Measured[2]
  4. The instructions for the Activity are:[3]
  5. Easily followed - sequence of steps in a logical order.
  • In point form and numbered (1st, 2nd 3rd etc)
  • There is enough detail so that the investigation can be repeated.
  1. Enough data will be collected so that results are reliable – Number[1]
  2. Safety issues are identified.[2]

Marking criteria for Final report – Exercise and Heart Rate[23 marks]
Syllabus Outcome – H12.4
  1. Evaluate the validity of the data collected (Discussion question).[5]
Syllabus Outcome – H13Present information
  1. Use the laboratory report scaffold.[2]
  2. Data table used for results – column headings, units, ruled, data accurate[4]
  3. Line graph – drawn to scale, axes labelled, units, ruled, data accurate[5]
Syllabus Outcome – H14Draws conclusion
  1. Identifies trends and relationships[2]
  2. Evaluate the appropriateness of the method used to solve the problem (Disc question).[5]

Discussion Questions[26 marks]

Syllabus Outcome – H11 -11.2 a,b,c,d, -11.3 a,b; H12 -12.2 b;

  1. The dependent variable in this investigation is the amount of activity.

Identify the independent variable? [1 mark]

  1. Name TWO variables that need to be kept constant? [2 marks]
  2. Explain why all subjects need to do the same exercise. [2 marks]
  3. Name the TWO groups in the investigation. [2 marks]
  4. Describe how these TWO groups are the same. [3 marks]
  5. Identify what is measured in this investigation. [1 mark]
  6. Explain why the activity should be repeatable. [2 marks]
  7. Discuss the validity of the data collected in this investigation. [5 marks]
  8. Outline how the number of subjects makes this investigation reliable. [2 marks]
  9. Identify TWO risks in this investigation. [2 marks]
  1. Discuss why heart rate changes as the level of physical activity changes.[4 marks]

Discuss (and evaluate) questions are unstructured and require an extended answer
  • In order to answer such a question, you must provide some structure.
STEP 1Identify (& highlight) the important words in the question
STEP 2Recall definitions of these important words (if necessary)
Discuss – identify issues and provide points for and against
Validity –

STEP 3Develop your own answer that reflects the depth required (Verb & marks)

The pulse rate varies greatly in individuals. The average rate for adults who are relaxed mentally and physically is about 65 – 70 in men and 70 – 75 in women. It is much higher in babies. The count slows during sleep. Withy mild exercise the pulse rate will increase gradually. It increases greatly when a person works hard or becomes very excited. The count may reach 200 per minute. Other conditions, such as surgical shock, haemorrhage, and fever also cause a marked increase in the pulse rate.
9.3.2 a / Explain the relationship between the structure and function of the following parts of the heart
–Valves
–Atria
–Ventricles
– Major arteries and veins

Parts of the Heart – Structure and Function

The heart is a large hollow muscle. Tubes called veins bring blood to the heart. Other tubes called arteries carry blood away from the heart. Regulators called valves control the flow of blood through the heart itself.

The heart consists of four chambers. The two chambers in the upper half of the heart are called atria (atrium). The atria are thin walled. They are relatively thin walled because of their functions. They only collect blood flowing into the heart from the body and then squeeze blood a short distance into the ventricles. Then the atria contract and squeeze blood through the tricuspid valve into the right ventricle and through the bicuspid valve into the left ventricle.

The two chambers in the lower half of the heart are called ventricles. The walls of the ventricles are made of thick, strong muscles. The right ventricle pumps blood a short distance to the lungs. The left ventricle has walls three times as thick as those of the right ventricle because it has to pump the blood so much further. The left ventricle pumps blood around the entire body.

Valves are made of flaps of thin, strong fibrous tissue. This allows them to rapidly open and close. Valves control the flow of blood through the heart. These flaps permit the flow of blood in one direction, but they prevent it from flowing back. They are like doors that open only in one direction. They respond to the pressure exerted by the blood.

The walls of the arteries are made up of three layers. The structure of each layer is related to its function. The outer layer consists of elastic tissue. Each time the heart beats, this layer stretches to make room for the blood that is being pumped through the artery. The middle layer is muscle (and elastic tissue). After the artery stretches, this muscular tissue contracts and squeezes the blood further through the artery. This means the arteries do a lot of the work of pushing blood around the body. The inner layer, or lining, of the arteries is made of thin, smooth cells (these same cells line the heart, veins and capillaries). This reduces friction and allows blood to flow more easily.

Blood flow through the veins is smooth and continuous rather than in the bursts or pulses of the arteries. The pressure of venous blood is very low. Veins, like arteries, have walls made of three layers. The walls of the veins are thinner, less elastic, and less muscular than artery walls. To make it easier for blood to flow, veins are bigger than arteries and have a bigger bore. The flow of blood in veins is helped by the action of the muscles during movement. As well, in the bigger veins, the lining of the vein has folds that act like valves. Several things can cause the blood to slow down or stop – the weight of the blood, pressure on the vein, or low blood pressure. Then the valves open out, to stop the blood from flowing backward. The valves are usually just above the place where two veins join. Veins that are swollen, stretched, or coiled on themselves, are varicose veins.

Notes Questions

1.What do valves do?

  1. Name the two functions of the atria?
  2. Which chambers of the heart have the thickest walls (largest muscles)?
  3. Which chambers of the heart pump blood the greatest distance?
  4. Suggest a reason why valves are made from thin tissue.
  5. What is the function of valves?
  6. Why is the middle layer of an artery elastic?
  7. Why is the inner layer of an artery smooth?
  8. Which blood vessel has a pulse?
  9. Why do the bigger veins have valves?
  1. Match the three columns in the table below.

Name / Structure / Function
Arteries have / Flaps of thin, strong fibrous tissue / Because it needs to pump blood around the whole body
Valves have / Thick, strong muscles / Because they reduce friction and allows blood to flow more easily
The wall of the left ventricle has / An inner layer made of thin, smooth cells / So they can rapidly open and close
Arteries have / An elastic layer / Because it squeezes blood around the body
Veins have / A thick muscular wall / that stretches to make room for the blood that is being pumped
9.3.2 b / Explain that specialised tissues in the heart produce an electrical signal that stimulates rhythmic contractions of the cardiac muscle

Cardiac Rhythm

Muscles in the body contract in response to signals. These signals are small electric currents delivered by nerves attached to the muscle. The heart is composed of a special type of muscle, called cardiac muscle. It also responds to electrical impulses. The heart has a regular beat because specialised tissues in the heart produce an electrical signal that stimulates the rhythmic contractions of the heart muscle. These specialised tissues are called the Sinoatrial (S-A) node or pacemaker cells. They are located in the right atrium. This group of special conduction cells are capable of sending signals at a rate up to 300 times per minute.

The impulse from the S-A node spreads via special conducting tissue through the atria. The signals reach a second node, the atrioventricular (A-V node) at the bottom of the atrium. These signals then spread between the ventricles via the septum and then up to the outside muscles of the ventricles. This pattern of signals therefore co-ordinates contractions of the heart, so that the upper chambers contract first and then the lower chambers.

Notes Questions

12.What type of tissue carries small electrical currents to the muscles?

  1. Name the cells that stimulate the rhythmic contractions of the heart muscle.
  2. Does the whole heart contract at the same time? Provide some detail in your answer.

9.3.2 c / Discuss the problems that can result from interruptions to the normal rhythm of the heart
Interruptions to the heart rhythm

What to do

Read the information below on interruptions to the heart rhythm.

Use this information to write a discussion on the problems that can result from interruptions to the normal rhythm of the heart.

Blood supply is essential for the cells of the body to survive. The blood transports oxygen and nutrients to the cells and transports carbon dioxide and other wastes from the cells. For this to occur the supply of fresh blood needs to be regular. Under normal circumstances the rhythmic beating of the heart maintains a regular supply of blood to the tissues of the body.

The rate at which the heart beats will vary according to the need for increased circulation of blood around the body. Normal adult heart rates at rest are between 50 and 75 beats per minute. Females’ heart rates are usually higher than males. Also heart rates are fastest at birth and then slow with age.