PRELIMINARY HSC PDHPE

CQ1 – How do the musculoskeletal and cardiorespiratory systems of the body influence and respond to movement?

How do the musculoskeletal and cardiorespiratory systems of the body influence and respond to movement?

Students learn about: skeletal system − major bones involved in movement

structure and function of synovial joints joint actions, eg extension and flexion

Students learn to: • identify the location and type of major bones involved in

movement, eg long bones articulate at hinge joints for flexion and extension

muscular system − major muscles involved in movement − muscle relationship (agonist, antagonist) − types of muscle contraction (concentric, eccentric,

isometric)

• identify the location of the major muscles involved in movement and related joint actions

• perform and analyse movements, eg overarm throw, by examining:

− bones involved and the joint action − muscles involved and the type of contraction

respiratory system − structure and function − lung function (inspiration, expiration) − exchange of gases (internal, external)

• analyse the various aspects of lung function through participation in a range of physical activities

circulatory system − components of blood − structure and function of the heart,

arteries, veins, capillaries − pulmonary and systemic circulation − blood pressure.

• analyse the movement of blood through the body and the influence of the circulatory and respiratory systems on movement efficiency and performance.

CIRCULATORY SYSTEM - watch video 1

The circulatory system, which includes the cardiovascular system, is made up of three main parts: the heart, blood vessels and blood. Its role is to transport materials such as nutrients, blood, hormones and waste products to muscles and organs around the body via the blood stream, and convert lactic acid into pyruvic acid.

components of blood

Blood is a specialised type of connective tissue—it is a thick liquid that is heavier and more viscous (thicker) than water. Blood accounts for about 8% of our total body weight. Healthy adult males have around 5–6 litres of blood and females about 4–5 litres. Its colour depends on the amount of oxygen it is carrying, varying from dark red (oxygen poor) to scarlet red (oxygen rich).

Blood performs a number of important specialised functions related to transportation, protection and regulation. Blood: transports nutrients, oxygen, carbon dioxide, waste products and

hormones to cells and organs around the body protects us from bleeding to death (via clotting) and protects us from

disease (by destroying invasive microorganisms) and toxic substances acts as a regulator of temperature and the water content in cells.

components of blood - watch video 2

Erythrocytes (red blood cells)

Erythrocytes (red blood cells) make up more than 99 % of the formed elements in blood. They contain an oxygen-carrying pigment called haemoglobin, which gives blood its red colour. Oxygen is carried by haemoglobin to all cells in the body. Some carbon dioxide is also carried. Erythrocytes live for around 120 days, and are replaced at the astonishing rate of 2 million per second. They are formed in the adult red bone marrow of some bones. A healthy female has around 4.8 million/mm3 of blood, and a healthy male has around 5.4 million/mm3.

Leukocytes (white blood cells)

Leukocytes (white blood cells) are responsible for fighting infections. They attack and destroy germs and infections as they enter the body. When the body has an infection, the number of white blood cells increases in order to fight it. They do this by ingesting foreign microbes (microscopic organisms) in a process called phagocytosis. Leucocytes only live from a few hours to a few days. Blood normally contains 5000–10 000/mm3 of leucocytes.

Thrombocytes (platelets)

Thrombocytes (platelets) are the blood-clotting agencies that help stop bleeding. When we cut ourselves or break a blood vessel, platelets stick to the damaged blood vessel to block the blood flow. They have a lifespan of five to nine days. Blood contains 250 000–400 000/mm3 of platelets.

Plasma

Blood plasma is the liquid part of blood that transports materials such as blood cells, nutrients, hormones and gases around the body. It is predominately water and contains mainly oxygen.

structure and function of the heart, arteries, veins, capillaries - watch video 3

The cardiovascular system provides the pump for circulating blood to the blood vessels in all cells in the body. As blood flows through the tissues of the body, oxygen and nutrients are dropped off and carbon dioxide and wastes are picked up. The pump is the heart, and it beats daily for our whole lives without a rest.

The heart

The heart is an involuntary muscle with striated muscle fibres. An adult’s heart weighs around 300 grams. It is a cone-shaped muscular organ that is about 12 centimetres long, 9 centimetres wide at its widest point and 6 centimetres thick.

Structure of the heart

The superior chambers of the heart are called the left atrium and the right atrium, which are separated by a thin wall. The inferior chambers are called the left ventricle and the right ventricle. They are separated by a thick wall called the septum. The atria act as receiving chambers for blood that is returning to the heart. The atria are relatively small and thin walled. This is because they only have to pump blood into the chambers next door, the ventricles. The ventricles are quite large, because they are responsible for propelling blood from the heart into circulation around the body.

Structure of the heart

Dense connective tissue structures called valves prevent the back flow of blood into chambers by opening and shutting when the heart contracts and relaxes. There are four valves in the heart. Two lie between each atrium and ventricle: the atrioventricular valves, with the tricuspid on the right and the bicuspid on the left. Both arteries coming from the heart have a semilunar valve on them to prevent blood from flowing back into the heart. They are the pulmonary semilunar valve and the aortic semilunar valve.

Structure of the heart

Arteries - watch video 4

Arteries carry blood away from the heart to tissues. They have thick, elastic walls because blood is pumped through them at high pressure in surges. We call these surges the heartbeats. Our pulse is actually the surge of the heart felt through arteries near the skin’s surface. The arteries become smaller at their ends, further away from the heart. The pressure decreases as blood is passed through small vessels known as arterioles.

Veins

Veins carry blood from tissues back to the heart. The small vessels at the ends of veins are called venules. The walls of veins are thinner and less elastic than artery walls, because the pressure decreases as the blood gets closer to the heart. The contraction and relaxation of muscles assists the blood to stream back steadily to the heart.

Valves within veins prevent the blood from flowing back the wrong way against the force of gravity. Sometimes after standing for a long time you may notice that your legs feel heavy and swollen. This is a result of blood pooling in the lower legs because of gravity and lack of movement. Once the legs move again, the muscles squeeze the blood up through the veins towards the heart. In general, arteries and veins follow the same path, but the blood in each is flowing in a different direction.

Capillaries

Capillaries are very small networks of vessels through which nutrients are exchanged between blood and the cells of the body. They lie between arterioles and venules, connecting both systems.

Label the pictures below as either: veins, capillaries or arteries.

arteries veins capillaries

The cycle

1. Oxygen-poor (deoxygenated) blood from the body collects in the right atrium, which contracts, filling up the right ventricle.

2. The right ventricle contracts and pushes blood to the lungs. 3. In the lungs, blood loses carbon dioxide and picks up oxygen. 4. Oxygen-rich (oxygenated) blood returns to the left atrium,

which contracts, filling up the left ventricle. 5. A powerful contraction of the left ventricle expels oxygen rich

blood into the aorta, from which artery branches distribute blood throughout the body.

6. In the muscles and body organs, blood releases oxygen and nutrients, and absorbs food and water from the intestines. The liver processes nutrients and, together with the kidneys, purifies the blood.

7. Oxygen-poor blood returns to the heart through the veins.

pulmonary and systemic circulation

Two types of blood circuits are created: Pulmonary circulation (circuit) circulates blood from

the right side of the heart to the lungs, then back to the heart.

Systemic circulation (circuit) pumps blood from the left side of the heart out to all body tissues, then back to the right side of the heart. The colour blue represents deoxygenated blood and the colour red represents oxygenated blood.

pulmonary and systemic circulation

Revision/Homework task Answer/complete the following statements/questions:

Describe the functions of blood. Distinguish between plasma and formed elements in the blood. Explain the route of blood flow in the heart via both pulmonary

circulation and systemic circulation. Identify the site at which freshly oxygenated blood is first received.

Which of the following is it? A. right ventricle B. left ventricle C. left atrium D. right atrium

Research how erythrocytes, leucocytes, and platelets are formed.

Heart rate

The thick muscular walls of the two lower chambers of the heart (ventricles), contract to squeeze blood into the arteries. The upper chambers of the heart (atrium) are the holding spots for blood. A heartbeat has two main phases: diastole—as the heart relaxes and refills with blood; and systole—the contraction that forces blood around the body.

During exercise, stress or excitement, the heart rate increases because a higher volume of blood is needed throughout the body. The heart rate is controlled by the medulla in the brain. It sends electrical impulses along nerves to set an average resting heart rate. The hypothalamus or hormones such as adrenaline can speed up a person’s average heart rate and override the normal heart rhythm.

Heart rate

A person’s resting heart rate (RHR) is usually determined first thing in the morning. At rest, the adult heart usually beats between 60–80 beats per minute. The higher the level of a person’s fitness, the lower their resting heart rate will be. This is because the heart of a fit person is able to effectively pump out more blood using fewer contractions. Taking a person’s pulse will give an indication of how hard their heart is working. The carotid artery (in the neck) and the radial artery (in the wrist) are two common sites used to take a person’s pulse.

Activity/task – In pairs, take each other’s pulse at both the carotid artery and radial artery record for 15 seconds and then multiply that number by 4 to give the bpm).

Explain how a person’s heart rate changes during exercise.

blood pressure - watch video 5

The amount of blood forced out during a contraction from the left ventricle is known as stroke volume. The fitter the person, the greater the volume of blood forced out in one contraction. A heart becomes more efficient when it is able to push out the same volume of blood in fewer contractions. The volume of blood pumped out in one contraction over a minute is known as cardiac output. The volume of blood pumped around the body increases as we exercise.

Blood flows through blood vessels along a pressure gradient from areas of higher pressure to areas of lower pressure. Blood pressure (BP) is the force that blood exerts on the walls of blood vessels. It is expressed in terms of millimetres of mercury (mmHg). Unless otherwise stated, BP is the pressure exerted in systemic arteries by the contraction and relaxation of the ventricles. In a resting young adult, BP rises to around 120 mmHg during systole (contraction) and to 80 mmHg during diastole (relaxation). This is considered a normal range plus or minus 10.

blood pressure

During exercise of increasing intensity, BP changes with the increases in cardiac output: Systolic blood pressure (the top number)

increases in direct proportion to increases in intensity, thereby facilitating the delivery of blood. Exercise should be stopped if systolic BP goes above 250 mmHg, or when it fails to rise, or rises and then falls quite markedly.

Diastolic blood pressure (the bottom number) changes very little during exercise. If it increases 15 mmHg or more above resting levels, exercise should be stopped. Blood pressure is usually measured using a stethoscope (a device to direct body sounds to the ears) and a sphygmomanometer (an inflatable cuff with a pressure meter).

Activity/task Measuring heart rate and blood pressure

Practise taking the heart rate and blood pressure of a partner using a stethoscope and sphygmomanometer, or similar BP-measuring device, when your partner:

systolic diastolic

Lying down

Standing

After moderate exercise

After intense exercise

Activity/task Measuring heart rate and blood pressure

Discuss the changes in blood pressure readings in the four different situations.

Describe this in terms of pressure, blood flow and actions of the heart.

Explain how exercise affects blood pressure. Discuss the impact high and low blood pressure has on the

body. - Watch video 6 & 7