Body systems and energy for physical activity Chapter 1
Chapter 1
Body systems and energy
for physical activity
Introduction
The body consists of complex structures that are made up of many parts,
and each part has its own specific role. Four of the systems have an
important role in sport and physical activity: the skeletal system, muscular
system, the respiratory system and the cardiovascular system. The skeletal
system is for supporting and protecting the body and is our framework for
movement; it also stores minerals and manufactures blood. The muscular
system is for facilitating movement, maintaining posture and producing
heat. In the cardiovascular system, the heart pumps blood around the body
so the blood can transport oxygen, carbon dioxide, nutrients and waste. In
the respiratory system, oxygen is taken from the air and supplied to the
Figure 1.1
blood, and carbon dioxide is removed.
Hydration is essential
Skeletal muscles cause movement when they contract and relax. Athletic
for the human body.
performance depends on the body’s ability to take in oxygen, transport it
to the working muscles, use it at the working muscles, and remove carbon dioxide.
To create movement for physical activity, the body uses chemical energy that is
taken into the body in three forms of food: carbohydrate, fat and protein. Each
form of energy comes from different foods, has different uses in the body, and
fuels different types of activities. Food, or chemical energy, is taken into the
body and is transformed into mechanical and heat energy. Water is
also important for movement and performance because it aids all cell
functions, regulates temperature, and transports nutrients and waste.
The body has three energy systems for breaking down fuel in order to provide
energy for movement: the two anaerobic systems – the ATP–PC system and
the lactic-acid system – and the aerobic system.
Key knowledge
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The structure and function of the skeletal system
The structure and function of the muscular system
The structure and function of the circulatory system
The structure and function of the respiratory system
Energy and physical activity
Interrelationships between the body systems
Hydration and physical activity
Figure 1.2
The muscular system in action.
Area of Study 1 Foundations of physical activity
Structure and function of
the skeletal system
The skeletal system includes the bones of the skeleton and the cartilages,
ligaments and other connective tissue that stabilise or connect the bones. The
bones not only support the body’s weight; they work together with the muscles to
both maintain body position and produce controlled, precise movements. If the
contracting muscle fibres did not have the skeleton to pull against, we would not
be able to sit, stand, walk or run.
The skeletal system is made up of two main sections: the appendicular skeleton
and the axial skeleton. The appendicular skeleton consists of the arms and legs and
is attached to the main body structure. The axial skeleton includes 80 of the body’s
206 bones, all of which are in the upper body. It includes three groups: the skull,
the vertebra and the thorax.
“Bone is a hard substance that consists of living cells
as well as minerals.”
The main purpose of the axial skeleton is to protect, and the three groups protect
the brain, the spinal cord, and the heart and lungs, respectively. As is the case with
all bones, this area is also a stable platform for a variety of movements.
Role of the skeletal system
Some animals have a hard, protective exterior called an exoskeleton. Humans,
along with other mammals, and birds, reptiles and amphibians, have an internal
skeleton. The human skeleton is made up of bones and cartilage, and the body
would look very different if humans did not have a skeleton.
Bone is a hard substance that consists of living cells as well as minerals. The main
mineral is calcium, which is obtained from milk and other products in the diet
and is the source of the bones’ hardness. The bones’ cells keep the bones in good
repair and mend them if they break. The bones of the skeleton are strong but light.
Cartilage is another tissue that is part of the skeletal system. It is not as hard as bone,
but it is more flexible. Cartilage is found at the joints and in the spine, nose and ears.
The bones of the skeleton have five major functions:
1. They are its framework for supporting the body.
2. They are for protection, especially of our vital organs.
3. The skeleton has rigid rods, or levers, that work together with the muscles to
facilitate movement.
4. The skeleton is one of the body’s places for storing minerals, the most notable
of which is calcium.
5. The bones are responsible for producing blood cells, millions of which are renewed
every second so that oxygen, carbon dioxide and digested foodstuffs can keep
travelling around the body, and are also for maintaining our ability to fight infection.
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Body systems and energy for physical activity Chapter 1
Skull
Our skeleton has 206
bones in it.
Mandible
Cervical
Vertebrae
Thoracic
Vertebrae
Lumbar
Vertebrae
Pelvis
Sacrum
Coccyx
Clavicle
Scapula
Sternum
Ribs
Humerus
Radius
Ulna
Visit www.innerbody.
com to check your
anatomical knowledge
of the skeletal system.
Carpals
Metacarpals
Phalanges
Femur
Patella
Tibia
Fibula
Tarsals
Metatarsals
Phalanges
Figure 1.3
The skeletal system.
The skeleton is divided into the following two sections:
The axial skeleton
This section consists of the bones in the middle of the body: the skull, spine, ribs
and sternum. Their major functions are to protect, store and support.
The appendicular skeleton
This section consists of the limbs and the girdles they are attached to. Their major
functions are to be a framework for movement and to store and manufacture
blood cells.
Types of bones
The skeleton is not only divided into two sections; it consists of various types of
bone. Bones are classified according to their shape, as shown in Table 1.1.
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Area of Study 1 Foundations of physical activity
Table 1.1 Bone types and their functions, and examples.
Bone type
Function/s
Examples
Long bone: the bone is
longer than it is wide.
To be a rigid rod for muscle The thigh bone (femur) and the inner shin
attachment and to facilitate bone (tibia)
a wide range of movement
Short bone: the bone is
square shaped.
To facilitate strength
The wrist bones (carpals), the ankle bones
(tarsals) and the kneecap (patella)
Flat bone: the bone is thin Usually to protect the vital
and flat and is often curved. organs
The ribs, the breastbone (sternum), the
collarbone (clavicle), the shoulder blade
(scapula) and the skull
Irregular bone: the bone Varied functions
does not fall into any of the
other three categories.
The hip bones (pelvis) and the vertebral
column (vertebrae)
1. Distinguish between the structure and function of the axial skeleton and the
appendicular skeleton.
2. Identify the main functions of the skeletal system.
3. Outline the various bone types and their functions, and give an example of each bone type.
4. On a diagram of the human skeleton, label the major bones.
Types of joints
A joint is a place at which two or more bones meet.
Almost every bone in the body has formed at least one
joint with another bone. Joints can facilitate not only
movement but stability.
There are three types of joints: fixed (immovable)
joints; cartilaginous, or slightly movable, joints; and
synovial, or freely movable, joints.
Fixed, or immovable, joints
An example is the joints between the bones of the
skull, which are for protecting the brain.
Cartilaginous, or slightly movable, joints
An example is the joints in vertebral column, which
consists of many bones positioned one on top of the
other, with a pad of cartilage, known as a disc, between
them. The vertebral column is S shaped.
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Vertabrae
Vertebral disc
Figure 1.4
The vertebral column.
Exploring PASS
Body systems and energy for physical activity Chapter 1
Movement is possible because the discs can compress slightly so that
one bone can move in relation to the other. The amount of movement
that actually takes place at each joint is minimal, but because of the
combined movement, the spine is able to be considerably flexible.
The body has more
than 230 joints in it.
Synovial, or freely movable, joints
An example is the joints in the limbs. This type of joint varies in shape, and the
variability in turn affects the movements that are possible. Synovial joints do,
however, have a number of common features:
ƒƒMembrane that lines the outside of the joint and encloses the synovial fluid
ƒƒSynovial fluid, which is within the joint capsule and which absorbs shock and
reduces friction
ƒƒLigaments, which are fibrous straps through which bones are attached to bones
at the joints and which have the functions of holding the bones together and
preventing dislocation
ƒƒCartilage, which is a hard, rubbery substance and which has the function of
preventing the bones from rubbing together
The body has six types of synovial joint: ball and socket, hinge, pivot, saddle,
gliding, and condyloid, outlined as follows:
The ball-and-socket joint
This type of joint facilitates the movements of flexion, extension, adduction,
abduction, rotation and circumduction; examples are the joints in the hips and
shoulders.
The hinge joint
This type of joint facilitates the movements of flexion and extension; examples are
the joints in the elbows, knees and fingers.
The condyloid joint
This type of joint facilitates the movements of flexion, extension, adduction, abduction
and circumduction; an example is the joint in the wrist.
The pivot joint
This type of joint facilitates the movement of rotation; examples are the atlas and
axis joints in the neck and the radius and ulna in the forearm.
BALL AND SOCKET
Figure 1.5
A ball-and-socket joint.
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HINGE
Figure 1.6
A hinge joint.
CONDYLOID
Figure 1.7
A condyloid joint.
Figure PIVOT
1.8
A pivot joint.
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Area of Study 1 Foundations of physical activity
The gliding joint
This type of joint facilitates a slight sliding
movement; examples are the bones of the
wrist and the bones between the vertebrae.
The saddle joint
This type of joint facilitates the
movements of flexion, extension,
adduction, abduction and circumduction;
an example in the joint in the thumb.
SADDLE
PLANE
Figure 1.9
A gliding joint.
Figure 1.10
A saddle joint.
Basic contribution to efficient movement
The human skeleton mainly moves via a system of levers and axes. In the skeletal
system, our bones are usually the levers, and the joints are the axes, or pivot points,
on which the levers move.
The main work of the human skeletal system and muscular system is to facilitate
movement. The skeletal system mainly consists of calcified bones and a softer mass
called cartilage, which are connected to the muscles by way of tendons. When the
bone has to move, the muscle attached to it either contracts or releases, thereby
causing the attached bone to move. The muscles, by themselves, cannot cause any
movement; for movement to occur, the muscles require the aid of the skeleton.
Through the combined movements of the joints in the skeletal system, an almost
unlimited number of movement possibilities is facilitated. If you compare the
movement of the gymnast, the tennis player, the athlete, the weightlifter and the sailor,
you begin to appreciate the skeletal system’s contribution to sporting performance.
Structure and function of
the muscular system
The muscular system is the body’s system through which power and movement
are facilitated for various body parts. Muscles are able to contract actively in order
to facilitate the force for movements of body parts. Muscles facilitate not only
the movements that are under our conscious control but the movements that are
responsible for activities such as breathing, digestion of food and the movement of
blood around the body.
The muscular system has several roles in the human body. It is essential for
locomotion, balance and posture; absorption of shock and heat; breathing; and
digestion of food. These are just a few of the important functions the muscular
system performs. If your body did not have muscles, you would not be able to move
or breathe, and your heart would not be able to circulate blood throughout your body.
The body has three types of muscle: cardiac muscles, which are in the heart; smooth
(involuntary) muscles, which are controlled by the autonomic nervous system; and
skeletal muscles, which are attached to bones and facilitate our ability to move.
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Body systems and energy for physical activity Chapter 1
Role of the muscular system
If we did not have muscles, our body would not be able to move or to
perform digestion of food, breathing or many other biological functions.
The muscular system has several functions, including protection of
the body’s internal organs, facilitation of the skeleton’s movement,
maintenance of posture and production of heat.
Muscle movement
Skeletal muscles are arranged in pairs around joints, so that one muscle moves
the joint in one direction and the other moves it back. In order for a muscle to
move a joint, it must span the joint, and that means it must be attached to the
bones on both sides of the joint; for example, a muscle that moves the elbow
must be attached to the lower arm as well as to the upper arm or shoulder.
Muscles are attached to bones by way of tendons.
Movement terms
Flexion
Flexion means bending, or decreasing the angle at a joint. An example
of this type of movement is when you are flexing your elbow during the
upward phase of a bicep curl.
Extension
Extension means straightening, or increasing the angle at a joint.
An example of this type of movement example is when you are
straightening your knee when kicking a ball.
Adduction
Adduction means moving a body part towards the midline, or centre.
An example of this type of movement is when you are bringing your
legs together in the second part of a star jump.
Abduction
Abduction means moving a body part away from the midline.
An example of this type of movement is when you are moving your
legs apart during a star jump.
Figure 1.12
Flexion.
FLEXION
FLEXION
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ABDUCTION
Figure 1.13
EXTENSION
Extension.
ADDUCTION
Figure 1.14
Adduction.
Figure 1.11
The muscular system in action.
The body’s strongest
muscle is the gluteus
maximus, more
commonly known as the
buttocks. The secondstrongest muscle is
inside your mouth – can
you guess what it is?
ABDUCTION
ADDU
Figure 1.15
Abduction.
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Area of Study 1 Foundations of physical activity
CIRCUMDUCTION
ROTATION
Figure 1.16
Circumduction.
Figure 1.17
Rotation.
DORSIFLEXION
DORSIFLEXION
Figure 1.18
Dorsiflexion.
Circumduction
Circumduction means moving a joint in a circular
motion, and can occur at joints that flex, extend,
adduct and abduct. Two examples of this type of
movement are the action of your arms when you are
swimming freestyle and when you are bowling during
a cricket game.
Rotation
Rotation means turning or twisting a bone along its
axis. An example of this type of movement is when a
ballet dancer is performing a turn.
PLANTAR
PLANTAR
FLEXION
FLEXION
Figure 1.19
Plantarflexion.
About 35 per cent of
female body weight
and 45 per cent of male
body weight is made up
of skeletal muscle, and
the body contains more
than 600 muscles!
Dorsiflexion
Dorsiflexion means moving the toes towards the shin bone, and can occur at only
one joint. An example of this type of movement is when you are pulling your toes
towards your tibia when performing a hamstring stretch.
Plantarflexion
Plantarflexion means moving the toes away from the shin bone, and like dorsiflexion,
can occur at only one joint. An example of this type of movement
is when you are pointing your toes towards the ground.
Posture
When you are standing, although you do not necessarily
think that your muscles are working, because they are not
moving, they are moving. The postural muscles are constantly
contracting and relaxing in order to keep the body balanced.
Think of what happens to your head when you are nodding off
to sleep while sitting!
The postural muscles are also vitally important in sporting
performance. They might work to keep one part of the body
still while another part is moving; for example, the postural
muscles of the back and stomach keep your body still and
straight during a push-up. They might also contract in order to
stabilise joints and to aid absorption of force, such as when you
are playing football.
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Figure 1.20
Muscles are used
to maintain posture.
Exploring PASS
Body systems and energy for physical activity Chapter 1
1. Identify one of the body’s ball-and-socket joints and the movement it facilitates.
2. Identify one of the body’s hinge joints and the movement it facilitates.
3. Outline the function of:
a) tendons
b) ligaments
c) cartilage.
4. Outline the difference between flexion and extension, and give examples.
Structure of voluntary muscles
The body has three types of muscle: smooth muscle, cardiac muscle and skeletal muscle.
Smooth muscle
This type of muscle is located in the walls of blood vessels and the digestive
system. Because these muscles cannot be controlled, they are known as
involuntary muscles.
Cardiac muscle
The only part of the body that this type of muscle is located in is the heart. The
cardiac muscle contracts and relaxes, causing the heart to beat, and it, too, is an
involuntary muscle.
Skeletal muscle
These muscles are attached to the skeleton, and cause movement when they
contract and relax. They are generally under our conscious control and are
therefore known as voluntary muscles.
Skeletal-muscle cells are long and thin, and contain fibres. Each fibre is about as
thick as a hair but is many times stronger. The fibres slide over each other when
the muscle contracts. The muscle fibres are arranged in groups within the muscle,
and there are two basic types of them: slow-twitch fibres and fast-twitch fibres.
Every person has both types of muscle fibre, but the proportion of each fibre type that
is present in each muscle tends to be inherited. People who are born with a higher
percentage of slow-twitch muscle fibres in their legs might well be better suited to
endurance events, whereas people who are born with a higher percentage of fasttwitch fibres might be better suited to explosive-type events such as sprinting.
Although muscle contraction does not always result in movement, without
muscle contraction, controlled movement would not occur. People’s ability to
harmoniously use their nervous, muscular and skeletal systems leads to their
ability to perform skilful movement.
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Area of Study 1 Foundations of physical activity
Basic contribution to efficient movement
Muscles are arranged in
pairs, so that if one
muscle moves a body part in
one direction, another can
move it back. Looking at the
elbow joint as an example,
Agonist (bicep)
the pair of muscles are the
biceps and triceps. The
biceps muscle is positioned
at the front of the upper
arm, and the triceps muscle
is positioned at the back
Antagonist
of the upper arm. The two
muscles work as a pair, so
Figure 1.21
that when the biceps is
Flexion of the bicep: the agonist and antagonist muscle.
contracting to cause the
elbow to flex, the triceps
is relaxing. In this example, the bicep is known as the agonist, or prime mover,
and the triceps is known as the antagonist.
Agonist: the muscle that is causing the movement.
Antagonist: the muscle that relaxes so that movement can occur.
“Muscles are arranged in pairs, so that if one
muscle moves a body part in one direction,
another can move it back.”
Perform each of the following actions, and state the agonist and antagonist muscles.
You’ll find it helpful to feel and observe the muscle!
ƒƒ From a sitting position, extend one knee.
ƒƒ In a sitting position, raise one arm to the side.
ƒƒ In a standing position, rise on to your toes.
ƒƒ In a standing position, lift your leg backwards.
ƒƒ Perform the upward stage of a sit-up.
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In order for muscles to perform their main job of moving the skeleton,
they must have the following characteristics:
ƒƒExcitability: the muscle will respond to a stimulus.
ƒƒExtensibility: the muscle can change in length.
ƒƒContractibility: the muscle will tighten so a force can be produced.
ƒƒ Elasticity: the muscle will return to its original length.
When an impulse is sent from the brain to the muscle, the muscle will
respond to the stimulus, causing itself to contract. The three types of
contraction are isometric, isotonic and isokinetic, outlined as follows:
Go to www.getbody
smart.com to
investigate the origin,
insertion and action of
the muscles of the arm.
Isometric contraction
In this type of contraction, the muscle develops tension but there is no change in
the length of the muscle; an example is when you are pushing against a closed door.
Isotonic contraction
In this type of contraction, the muscle develops tension and there is a change in
the length of the muscle; an example is when you are performing a biceps curl.
The two types of isotonic contraction are eccentric contractions and concentric
contractions, outlined as follows:
a) Concentric contractions: These occur when the muscle shortens; an example is
the upward phase of a bicep curl.
b) Eccentric contractions: These occur when the muscle lengthens; an example is
the downward phase of a bicep curl.
Isokinetic contraction
In this type of contraction, the muscle develops tension and there is a change in
the length of the muscle. The tension remains constant through the full range of
movement. For this type of contraction, you require special equipment in order to
constantly maintain the tension through the full range of movement.
1. Identify the difference between fast-twitch and slow-twitch muscle fibres. Give examples
of sports or activities that are suited to people who have a high percentage of fast-twitch
muscle fibres and people who have a high percentage of slow-twitch muscle fibres.
2. Identify a range of sports or activities in which isometric strength is important.
3. Describe the difference between agonist and antagonist muscles.
4. Identify three bodily movements and the agonist and antagonist muscle that facilitates
the movement.
5. Outline the four characteristics of muscles that occur when the skeleton is moving.
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Area of Study 1 Foundations of physical activity
Structure and function of
the circulatory system
The structure of the circulatory system consists of the heart, the arteries, veins and
capillaries. The heart consists of two muscular pumps known as the left and right
ventricles which pump blood throughout the body, the blood vessels are intricate
networks of hollow tubes that transport blood throughout the entire body. The
function of human circulatory system is to transport blood around the body. At
rest, the average heart pumps approximately 5 litres of blood throughout the body
every minute. The circulatory system is responsible for:
ƒƒ Respiration - delivers oxygen to the cells and removing carbon dioxide from them.
ƒƒNutrition - carries digested food substances to the cells of the body.
ƒƒWaste removal - disposes of waste products and poisons that would harm the
body if they accumulated.
ƒƒImmunity - helps protect the body from disease.
ƒƒCellular communication - the circulatory system provides a mode of transport
for hormones.
ƒƒThermoregulation - the circulatory system transports heat (can both warm
and cool body).
Role of the circulatory system
The circulatory system works in conjunction with the respiratory system in order to:
ƒƒsupply oxygen and nutrients to every cell in the body
ƒƒremove carbon dioxide and waste products
ƒƒmaintain body temperature.
“The blood carries oxygen and dissolved nutrients on
its way to the cell, and on the return journey, it carries
carbon dioxide and waste products.”
The heart is about the size of a fist, and lies beneath the sternum, slightly to the
left. The heart pumps blood through vessels that travel to every cell in the body.
The blood carries oxygen and dissolved nutrients on its way to the cell, and on the
return journey, it carries carbon dioxide and waste products.
In the cardiovascular system, the amount of blood flowing to the various parts of
the body can vary, depending on the need. For example, if the body is getting very
hot, the blood will be directed to the skin, where it can cool down. This is why
your face often gets red when you are playing sport. If a person gets extremely
cold, the blood will move away from the skin, to the centre of the body, in order to
try to maintain warmth for the internal organs.
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Body systems and energy for physical activity Chapter 1
Major components of the circulatory system
The circulatory system is also called the cardiovascular system,
whereby ‘cardio’ means ‘heart’ and ‘vascular’ means the blood vessels.
The cardiovascular system therefore consists of the structures and
substances shown in Figure 1.22.
Complete the quiz at
www.betterhealth.
vic.gov.au to test
your knowledge of the
circulatory system.
Heart
Cardiovascular System
Blood Vessels
Arteries
Veins
Capillaries
Your heart beats
about 100,000 times
every day!
Blood
Red Blood Cells
White Blood Cells
Plasma
Figure 1.22
A flowchart of the circulatory system.
The heart is a hollow sack of cardiac muscle that fills
with blood and that also contracts, forcing the
blood out to the body between 60 and 80 times
per minute when the body is at rest. As a result
of the action of the heart, the blood starts
circulating around the body. The heart pumps
blood through vessels that travel to every cell
in the body. On its way to the cells, the blood
carries oxygen and dissolved nutrients, and
during the return journey, it carries carbon
dioxide and waste products.
When blood is forced out of the heart during
a contraction, the blood moves as a wave along the
arteries. At various places in the body at which the
artery is located close to the surface, the wave can
be felt. The easiest waves of blood to locate and feel
are the radial pulse, at the wrist, and the carotid
pulse, at the neck.
Exploring PASS
Figure 1.23
The circulatory system
throughout the body.
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Area of Study 1 Foundations of physical activity
Basic contribution to efficient movement
When you exercise your muscles, you produce more carbon dioxide and need more
oxygen, so you need more blood flow to your muscles. Your body responds to this
demand in a number of ways: your heart beats faster and more strongly, and the
blood is directed from other organs, such as the stomach, towards the muscles.
The increase in the amount of blood that the heart pumps can be explained by
way of the following equation:
Heart rate (HR) × Stroke volume (SV) = Cardiac output (CO)
‘Heart rate’ is the number of beats per minute, ‘Stroke volume’ is the amount
of blood pumped per beat, and ‘Cardiac output’ is the amount of blood pumped
per minute.
Cardiac output is the product of the stroke volume and heart rate. When you
regularly undertake aerobic exercise, you strengthen your heart muscle and enable
it to increase its stroke volume. Compared with a sedentary person, a wellconditioned person usually has a lower heart rate for the same cardiac output.
A typical value for a sedentary male whose body is at complete rest is only 75
millilitres (mL) per beat, whereas a typical value for a trained male endurance
athlete whose body is at rest is 105 mL per beat. The average cardiac output for
a person whose body is at rest is between 5 and 6 litres (L) per minute. Because
endurance athletes have a high stroke volume, they are able to have a cardiac
output of more than 30 L per minute during exercise.
1. Explain why the blood flowing to the surface of the skin will aid the body in cooling down.
2. Identify the four chambers of the heart.
3. Identify the vessels in which blood is supplied to the heart.
4. Identify the vessels in which blood is removed from the heart.
5. Identify and describe the factors that affect a person’s pulse rate.
6. Explain the physiological changes that occur in the body as the pulse rate increases.
7. Calculate your maximum heart rate using the following formula:
220 – Your age = [Your maximum rate]
8. Write down your resting heart rate, run continuously for two minutes, write down your heart
rate, and draw the results on a line graph.
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Body systems and energy for physical activity Chapter 1
Structure and function of
the respiratory system
In order to stay alive, the cells of the human
body require a constant stream of oxygen. In
the respiratory system, oxygen is provided
to the body’s cells, and carbon dioxide, a
waste product that can be lethal if allowed
to accumulate, is removed. The three major
parts of the respiratory system are the airway,
the lungs, and the muscles of respiration.
The airway, which includes the nose, mouth,
pharynx, larynx, trachea, bronchi and
bronchioles, carries air between the lungs and
the body’s exterior.
The functions of the human respiratory system
are to transport air into the lungs, to facilitate
diffusion of oxygen into the bloodstream, to
receive the waste product carbon dioxide from
the blood, and to exhale the carbon dioxide.
Pharynx
Larynx
Alveoli
Bronchi
Figure 1.24
The respiratory system.
Role of the respiratory system
The respiratory system works in conjunction with the cardiovascular
system to transport oxygen to every cell and to remove carbon
dioxide. For these functions to be performed, the body must take
air in from the environment.
Air enters the respiratory system through the nose and mouth and then
passes down the windpipe, or trachea, into the lungs. On the way to
the lungs, the air is warmed, filtered and moistened. The trachea splits
into two bronchi, which carry the air into the lungs. In the lungs, gases
are exchanged, whereby oxygen can enter the bloodstream and waste
products can leave the bloodstream.
Major components of the respiratory system
The major components of the respiratory system are labelled on the
diagram in Figure 1.24. The respiratory system relies on both the skeletal
system and the muscular system in order to perform the function of
breathing. The lungs are attached to the ribs by way of suction. The
sequence of events is set out in the flowchart in Figure 1.25.
The diaphragm also has a vital role in the function of breathing. The
diaphragm is a round sheet of muscle that encloses the bottom of the rib
cage. When the diaphragm receives an impulse, it contracts and flattens,
and the size of the lungs increases. Both events are contributory factors
in the function of breathing in, which is known as inspiration.
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Lung
Bronchioles
Impulse is sent
from the brain
Impulse received by muscles
of the ribs and chest
Muscles of the ribs
and chest contract
Ribs are pulled
upwards and outwards
Air rushes
into the lungs
Figure 1.25
How the respiratory
system works.
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Area of Study 1 Foundations of physical activity
The function of breathing out, or expiration, is a result of the relaxation of the
diaphragm and the muscles of the ribs. The relaxation causes the ribs to lower
and the diaphragm to return to its dome shape. The air inside the lungs is
squeezed out through the nose and mouth, in the same way that air is squeezed
out of a deflating balloon.
The breathing rate changes when you are exercising. When your body is at rest, you
breathe about 12 times per minute and take in about half a litre of air. In the following
equation, you can see how much air is ventilated (breathed in and out) in one minute:
12 breaths per minute × 0.5 litre = 6 litres ventilated per minute
During exercise, both the rate and the depth of breathing increase significantly.
1. Explain the terms ‘inspiration’ and ‘expiration’.
2. Draw a flow diagram of the sequence of events that occurs during expiration.
3. Draw and label the major components of the respiratory system.
4. Explain the effect that the size of the lungs has on the movement of air into and out of the lungs.
5. Calculate your resting breathing rate and your breathing rate after one minute of
strenuous exercise.
When air enters the lungs, it travels down the bronchus, which divides, like a tree,
into tiny branches, or bronchioles, which get smaller and smaller. At the end of each
bronchiole is a structure called an alveolus, which is like a little balloon or air sac.
Alveoli are full of oxygen-rich air that has been drawn
into the lungs during inspiration. The oxygen has to
get into the blood so that the cardiovascular system
If you were to spread
can perform its function of transporting the oxygen to
out an adult’s alveoli,
the working cells. This movement of the oxygen occurs
they would cover a
in the alveoli, where a capillary can always be found
tennis court!
close by, and the oxygen can move from one place to
the other, that is, from the lungs into the blood.
The capillary that is close to the alveoli is carrying blood that has been pumped
from the body via the heart. It is carrying a lot of carbon dioxide. The carbon
dioxide moves from the blood into the alveoli at the same time that the oxygen is
moving in the other direction, in a process known as gaseous exchange.
The movement of oxygen from the alveoli to the blood can be less efficient if people
are suffering from a respiratory disease and have mucus built up in their lungs.
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Body systems and energy for physical activity Chapter 1
Basic contribution to efficient movement
The cardiovascular and respiratory systems are dependent on each other in their
roles of delivering oxygen and nutrients to the body’s cells and removing carbon
dioxide and waste. They are consequently sometimes jointly referred to as the
cardiorespiratory system.
The muscles cannot work for very long without oxygen, and even if you are
participating in an activity such as long jump or a throwing event, your muscles
will require oxygen in order to recover.
“The more oxygen that athletes can take in and use,
the better their performance in endurance activities. ”
Maximal oxygen uptake
Endurance athletes such as long-distance runners, cross-country skiers
and cyclists have a high level of aerobic fitness. Their performance
depends on their body’s ability to:
ƒƒtake in oxygen
ƒƒtransport oxygen to the working muscles
ƒƒuse oxygen at the working muscles
ƒƒremove carbon dioxide.
The more oxygen that athletes can
take in and use, the better their
performance in endurance activities.
The amount of oxygen that can be
taken in and used is known as maximal
oxygen uptake, or VO2 max.
Measurement of VO2 max can be undertaken
by way of gas-analysis techniques, for which
specialist equipment is required. However,
a number of tests have been devised for
estimating people’s VO2 max from their
performance. The tests include the multistage fitness test, or beep test; the
‘12-minute run’ test; the cycle test;
and the step test.
Visit http://biology.
about.com and make
a working model of
the lungs.
Figure 1.26
Cyclists have high levels of aerobic fitness.
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Area of Study 1 Foundations of physical activity
The practical experiment detailed as follows is designed for investigating the changes that
are observed in the cardiovascular and respiratory systems during rest and during varying
intensities of exercise. Working in pairs, one person is the subject and the other person records
the results. Read through the instructions before you start the investigation.
Design a table to record the results.
Practise taking your partner’s pulse before you start the investigation.
1. Record your partner’s pulse rate over one minute when he or she is sitting.
2. Count the number of normal breaths your partner takes per minute.
3. Time your partner while he or she is briskly walking for five minutes.
4. Record your partner’s pulse rate for the first 15 seconds after the activity ceases. Multiply
the figure by four to work out the number of beats per minute.
5. Ask your partner to count his or her breaths for the minute immediately following the activity.
6. Repeat steps 4 and 5 after two minutes.
7. Supervise your partner jogging for five minutes.
8. Record your partner’s pulse rate for the first 15 seconds after the activity ceases. Multiply
the figure by four to work out the number of beats per minute.
9. Ask your partner to count his or her breaths for the minute immediately following the activity.
10.Repeat steps 8 and 9 after two minutes.
11.Swap roles, and repeat steps 1 to 10.
1. Identify the structures that oxygen passes on its route from the atmosphere to the alveoli.
Present your answer as a flow diagram.
2. Describe what VO2 max is, and why it is a good indicator of aerobic fitness.
3. Explain the respiratory system’s response to exercise.
4. Explain the respiratory system’s adaptation to exercise.
5. Explain the function of the:
a)pharynx
b)larynx
c)trachea
d)alveoli
e)bronchi
f)bronchioles
g)nose
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Exploring PASS
Body systems and energy for physical activity Chapter 1
Energy and physical activity
Various forms of energy exist in the environment. Energy cannot be
created or destroyed, but it can change from one form to another.
When you’re exercising, your body is constantly working to supply
your muscles with enough energy to keep them going, but the way
energy is made available to your muscles changes depending on the
specific intensity and duration of your exercise.
The three energy systems require an energy source for muscle
contraction to occur, and the energy is provided from the food you eat.
In a complex chemical process within your cells, the energy stored in
the foods you eat is converted into a form that is optimised for use at
your muscles’ cellular level. Once food energy has been converted, it
exists at cellular level in the form of stored energy.
Role of food as fuel sources
Chemical energy is taken into the body in three forms of food:
carbohydrate, fat and protein.
Carbohydrate
This is the body’s most important source of energy, and includes starch,
dietary fibre and sugar.
Simple carbohydrates
These carbohydrates are refined sugars and are the source of additional
nutrients such as fibre and vitamins.
Sun
provides heat energy
Plants
absorb the heat
energy and convert
this to chemical energy
by the process of
photosynthesis
Animals
eat the chemical
energy, store it
and/or convert it
to movement energy
Figure 1.27
How energy changes from one
form to another.
Complex carbohydrates
These carbohydrates are in bread, grain, cereal and vegetables, and include starch and
fibre, which you feel full from eating. Fibre is essential for eliminating body waste and
is the body’s main fuel. Food is broken down into glucose molecules during digestion.
Fat
We need only a small amount of fat in our diet. Fats and oils belong to the chemical
family known as lipids, and are an important source of energy. They are a source of
essential fatty acids, protect vital organs, and insulate us against extreme temperatures.
Saturated fats
These fats are in animal products such as cheese, and are linked to an increase in
cholesterol and a higher risk of heart disease.
Monounsaturated fats
Examples of these fats are the fat in avocado, nuts, olives, oils and chicken.
Polyunsaturated fats
Examples of these fats are the fat in fish, nuts, soy beans and polyunsaturated
margarine. According to scientific evidence, these fats are an aid to lowering the
body’s level of cholesterol.
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Area of Study 1 Foundations of physical activity
Protein
Protein is necessary for growth, healing, and fighting disease and infection. It is an aid
to development of antibodies and provision of energy. Examples of animal-derived
sources of protein are meat, fish, chicken, cheese and eggs, and examples of plantderived sources are nuts, kidney beans, lentils, tofu and textured vegetable protein.
Each form of energy comes from different foods, has different uses in the body,
and fuels different types of activity, as outlined in Table 1.2.
Table 1.2 Food as an energy source
Food type
Example
Use in the body
Type of activity
Carbohydrate
Bread, pasta, potato,
banana
Primary energy source
High- and low-intensity
activities
Fat
Animal products
Secondary energy source
Low-intensity activities such
as jogging
Protein
Meat, dairy products
and nuts
Third energy source
Low-intensity activities of
very long duration
Energy that is taken into the body in the form of food is measured in kilojoules.
The amount of energy that is required, or the number of kilojoules that are required,
depends on the person’s size, body composition, metabolic rate and exercise level.
Anaerobic and aerobic energy production
Humans can convert the chemical energy from food into movement energy.
Carbohydrates, fats and proteins, eaten as food, require a specialised molecule for
converting them into movement.
The molecule is called ATP, which stands for ‘adenosine tri-phosphate’, and
consists of one molecule of adenosine and three phosphate molecules. The body’s
muscles contain very small stores of ATP.
When energy is needed in order to cause muscle contraction, ATP breaks
down into ADP, which stands for ‘adenosine di-phosphate’ and consists of one
molecule of adenosine and two phosphate molecules. In this way, energy is
produced for muscular contraction. The body re-builds the ATP molecule to
enable itself to keep moving.
The aerobic energy system
The slow production of energy is provided by way of the aerobic-energy system, in
which oxygen, along with stored carbohydrates and fats, is used to re-build ATP.
The carbohydrates and fats are broken down completely into carbon dioxide and
water, which are removed by way of our sweating and expiration. This system of
energy production can go on for many hours, as long as the activity level is low.
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Body systems and energy for physical activity Chapter 1
The two anaerobic energy systems
Energy is also provided by way of the following two anaerobic energy systems:
The ATP/PC system
In this system, another chemical that is stored in the muscles, phosphocreatine,
or PC, is used to re-build ATP. Because phosphocreatine exists in the muscle, it
is immediately available to re-build ATP, and can do so very rapidly. This system
can be the source of maximum energy, but for only about 10 seconds, because the
phosphocreatine stores are rapidly depleted.
The lactic acid system
In this system, carbohydrate is broken down to provide the energy for re-building
of ATP. The breaking down can be done reasonably quickly, but the breakdown is
incomplete, whereby lactic acid is built up in the working muscles. The lactic-acid
system is the source of energy for re-building of ATP during activities of medium
intensity, and has a duration of between two and three minutes.
Following is a summary of the energy systems:
Fuel
ƒƒThe ATP/PC system: creatine phosphate is used.
ƒƒThe lactic-acid system: carbohydrate is broken down into muscle glycogen and is
the only fuel source.
ƒƒThe aerobic system: carbohydrates are the main fuel source. Fats and, to a
limited extent, protein can also be used.
The amount of energy supplied
ƒƒThe ATP/PC system: a very limited amount is supplied.
ƒƒThe lactic-acid system: a limited amount is supplied.
ƒƒThe aerobic system: an unlimited amount is supplied at low intensity.
Duration
ƒƒThe ATP/PC system: at between 95 per cent and 100 per cent of maximum
effort, the system will last for between only 10 and 12 seconds.
ƒƒThe lactic-acid system: depending on the level of intensity, the system will last
for between 30 seconds and two to three minutes. At between 90 per cent and
95 per cent of maximum effort, the system will last for about 30 seconds.
ƒƒThe aerobic system: at low intensity, the system will last for a virtually unlimited
amount of time.
Causes of fatigue
ƒƒThe ATP/PC system: creatine phosphate is exhausted after about 10 to 12
seconds.
ƒƒThe lactic-acid system: lactic acid, which is a waste product, builds up in the
muscles, leading to fatigue and exhaustion.
ƒƒThe aerobic system: this system will continue until the body has used muscle
glycogen or stored energy in the form of carbohydrate, fats and protein.
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Area of Study 1 Foundations of physical activity
Waste products
ƒƒThe ATP/PC system: no waste products are
produced.
ƒƒThe lactic-acid system: lactic acid is produced.
ƒƒThe aerobic system: carbon dioxide and water are
produced.
Visit www.exrx.net
and compare the
energy systems that
are mainly used in a
range of sports.
Recovery time
ƒƒThe ATP/PC system: recovery time is between
30 seconds and two minutes.
ƒƒThe lactic-acid system: recovery time is between 20
minutes and two hours, depending on the exercise’s intensity and duration.
ƒƒThe aerobic system: sufficient time – up to 24 hours – is required so that
diminished fuel supplies can be replaced.
Sports in which the energy system is mainly used
ƒƒThe ATP/PC system: 100-metre sprint, javelin, long jump and weightlifting
ƒƒThe lactic-acid system: 100-metre swimming, 400-metre running and the
‘cycling 1 kilometre’ time trial
ƒƒThe aerobic system: triathlon, marathon running, 1500-metre swimming and
the cycling road race
The three energy systems rarely work alone; and considerable overlap occurs
between them. Generally, all the systems are contributory factors in production of
energy in all activities, to varying extents.
1. Explain how ATP is re-synthesised.
2. Outline the implications of an increased lactic-acid level for athletic performance.
3. Explain how lactic acid is removed from the body.
4. Identify how quickly lactic acid is removed from the body.
5. Describe the types of activity in which the aerobic system is mainly used.
7. Identify two track events in which the
lactic-acid system is mainly used.
8. Label the three energy systems
on the following graph:
C
100
Energy Contribution %
6. Identify three sporting performances in which
the ATP, or PC, system is mainly used.
B
90
80
A
70
60
50
40
30
20
10
0
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10 20 30
60
90
120
150
180
210
Exercise Time (Sec)
240
270
300
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Body systems and energy for physical activity Chapter 1
Energy input versus energy output
Food, or chemical energy, is taken into the body and is transformed into
mechanical and heat energy.
If the amount of energy entering the body equals the amount being converted to
movement and heat, the person’s weight will remain stable.
If the amount of energy entering the body exceeds the amount being used, the
excess will be stored as fat and the person will gain weight.
If the amount of energy entering the body is less than the amount being used, the
person will lose weight.
Therefore, in order to lose weight, a person needs to:
ƒƒdecrease energy intake, that is, consume fewer kilojoules
ƒƒincrease energy output, that is, increase exercise
ƒƒdecrease energy input and increase energy output.
Interrelationships between
the body systems
The body’s systems do not work in isolation; each system relies on the
other systems so the body can function efficiently.
The skeletal system
In the skeletal system, the lungs, which are the main organ of the
respiratory system, are protected. Blood cells are manufactured for the
cardiovascular system, the heart is protected, and the skeletal system is
the framework for rigid attachment of the muscular system.
To cause muscular
action, the brain can
send messages at the
rate of 380 kilometres
per hour!
The muscular system
In the muscular system, the ribs are moved so that breathing can occur in the
respiratory system. Cardiovascular efficiency is increased, the heart becomes a
bigger and stronger, and the person is less likely to develop bone disease later in
life. The muscular system causes movement by pulling on the skeleton, whereby
the bones’ health and density are in turn maintained.
The cardiovascular system
In the cardiovascular system, oxygen and nutrients are delivered to the
working muscles, bones and cartilage, and the waste products carbon dioxide
and water are removed.
The respiratory system
In the respiratory system, the air from the atmosphere is used to provide oxygen
for the cardiovascular and muscular systems and for energy production.
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The reliance of body systems on each
other for effective functioning
When you are exercising, the body systems rely on each other to work together so
they can function effectively.
The muscles have to be used in any form of exercise. As they begin to work,
demands are placed on the rest of the body. The heart beats faster so it can supply
more blood to the muscles, and both the depth and the rate of breathing increase
so more oxygen can be supplied to the working muscles.
The body needs to eliminate waste products such as carbon dioxide and lactic acid,
as well as heat, usually in the form of sweat (perspiration).
In order to meet the body’s needs during exercise, the skeletal, muscular,
circulatory and respiratory systems rely on each other to function effectively.
1. For each of the following activities, determine which energy system would mainly be used:
a 100-metre sprint; a 5000-metre running race; a hockey game; batting during a cricket
game; a marathon, an 800-metre running race; javelin; a dance routine; lifting weights; a
1000-metre cycling time trial.
2. Select one of the following movements:
ƒƒ 10 push-ups
ƒƒ 10 sit-ups
ƒƒ 10 bench presses
ƒƒ 10 leg presses
a) List the bones that are moving at each stage.
b) List the muscles that are causing the movements.
c) State how oxygen is transported from the lungs to the working muscle.
d) Describe how oxygen is used during the muscle contraction as well as the waste products
that are produced.
3. Describe how the cardiovascular and respiratory systems combine so that waste products
can be eliminated from the body.
4. Exercise continuously for 10 minutes. Note all the changes that occurred in your body
during the time.
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Body systems and energy for physical activity Chapter 1
Hydration and physical activity
Water is an aid to all cell functions, temperature regulation, and transportation of
nutrients and waste. Water is lost as sweat, during its evaporation from the lungs,
and by way of excretion. In the body, the result can be lack of water, which is
known as dehydration and can be life threatening, because so many of the body’s
vital processes occur in water. During summer, a person should drink three to four
litres of water a day in order to maintain a healthy level of hydration.
Figure 1.28
Adequate water intake is essential.
Role and importance of water intake during
physical activity
Drinking plenty of fluids is an important aspect of hydration maintenance.
Lack of fluid intake can lead to dehydration, which in turn can lead to poor
performance and sometimes health problems associated with heat exhaustion
and heat stroke.
During physical activity, more fluid is lost as sweat, and additional fluid must
therefore be consumed so that what is lost is replaced. The respiratory rate also
rises with vigorous exercise, whereby the amount of fluid lost through evaporation
increases and must also be replaced. The amount of fluid lost, and therefore the
amount to be replaced, will depend on the following factors:
The length of the activity
The longer the activity, the more fluid lost and the more the athlete has to replace it.
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Area of Study 1 Foundations of physical activity
The intensity of the activity
Activities that are more intense result in a greater rise in body temperature, which
causes more sweating, so the athlete has to replace more fluid.
The temperature
When the surrounding temperature is high, the athlete will sweat more because the
sweat does not cool the skin as quickly, so he or she will have to consume more water.
Conversely, breathing rate increases in low temperatures. Therefore, in cold weather,
more fluid is lost through evaporation from the lungs. Just think of the mist-like
water vapour that is visible when you’re breathing out on a cold morning!
“You should drink water before you start exercising,
consume small amounts regularly during the exercise,
and continue drinking water after the exercise so you
aid your recovery.”
The humidity level
When the level of humidity is higher, sweat does not evaporate from the skin as
quickly, so again, the athlete will have to replace more fluid.
Body size
A larger body has a greater surface area for fluid loss,
so the athlete will require more fluid in order to replace
the lost fluid. People who have more body fat might
lose more fluid through sweating, because fat acts as an
insulator and keeps the body temperature raised.
Managing fluid loss and replacement
The only time that many people drink is when
they are thirsty; however, thirst is an indicator of
dehydration. It is important to consume fluids
regularly. You should drink water before you start
exercising, consume small amounts regularly during
the exercise, and continue drinking water after the
exercise so you aid your recovery.
Rather than hydrate the body, alcoholic drinks work as
diuretics, which means they promote fluid loss. People
who are drinking alcohol should ensure they drink a
glass of water for every unit of alcohol they consume.
Athletes should not drink alcohol for at least 24 hours
before training or competition.
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Figure 1.29
Sports drinks are a common
source of hydration for athletes.
Exploring PASS
Body systems and energy for physical activity Chapter 1
Sources of hydration
Water is the best source of hydration and is the best thirst quencher. Sports
drinks are also good, because they contain glucose, which fuels exercise, and
sodium, which aids fluid retention. Sports drinks are especially good for
distance events. Fizzy drinks are not recommended, because they tend to cause
the stomach to be gassy and uncomfortable.
Each of the three main types of sports drink on the market has a specific purpose:
Isotonic drinks
These types of drink are the most common sports drinks. They can be helpful for
athletes who are exercising at a high intensity for 60 minutes or longer. It is not
necessary to replace losses of sodium, potassium and other electrolytes during
exercise, because you are unlikely to deplete your body’s stores of those minerals
during normal training. If, however, you find yourself exercising in extreme
conditions over three or five hours – in a marathon, an Ironman event or an ultramarathon – you might choose to add a sports drink that contains electrolytes.
Hypertonic drinks
These types of drink generally contain a quantity of carbohydrates and are mainly
intended to supply energy; the thirst-quenching effect is secondary. Compared
with water, hypertonic sports drinks are taken up by the body more slowly, and
they are suited to endurance athletes.
Hypotonic drinks
These types of drink generally contain fewer than 4 grams of sugar (carbohydrates)
per 100 millilitres and are intended to be a thirst quencher. For the athlete,
hypotonic drinks are the source of little energy, in the form of sugars. Compared
with water, hypotonic sports drinks are taken up by the body more quickly, and they
are suitable for recreational sports and for exertion that is shorter or less strenuous.
1. Describe the hydration considerations for an endurance athlete pre-event, during the event
and post-event.
2. Explain why two athletes might require different amounts of fluid replacement, despite the
fact that they are participating in the same activity.
3. Suggest times during training sessions, games and competitions when athletes should be
encouraged to take fluids.
4. Explain the consequences of drinking too much water, or over-hydration.
5. Investigate one sports drink that is currently being promoted.
6. Identify and describe the advantages and disadvantages of sports drinks.
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Revision questions
1. Outline the structure and function of the following body systems:
a) The skeletal system
b) The muscular system
c) The respiratory system
d) The cardiovascular system.
2. C
ompare and contrast the structure and function of the appendicular skeleton
and the axial skeleton.
3. Describe and provide an example for each of the following bones types:
a) Long bones
b) Short bones
c) Flat bones
d) Irregular bones
4. Identify the body’s three types of joint, and explain the function of each.
5. Describe how the body produces heat.
6. D
istinguish between agonist and antagonist muscles, and provide two examples
of each type of muscle.
7. Distinguish between isometric, isotonic and isokinetic muscular contractions.
8. E
xplain the following terms:
a) Concentric contraction
b) Eccentric contraction
9. Compare and contrast smooth muscle, skeletal muscle and cardiac muscle.
10.Identify the three forms of chemical energy that the body uses to create movement.
11.Outline the role, fuel and duration of the three energy systems.
12.Outline three strategies to maintain appropriate hydration during an
endurance event.
13.Explain the process that can lead to an accumulation of lactic acid and how this
impacts the performance of an athlete.
14.Which of the following are components of the circulatory system?
a) Heart and kidney
b) Arteries and lungs
c) Brain and hormones
d) Veins and arteries
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