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The
Body
In
Action
A
Movement
The skeleton
The skeleton provides a framework for support and muscle
attachment. It also protects important organs such as the brain,
lungs, heart and spinal cord.
Bones
Bones are mad of living cells that form flexible fibres. These cells
are supplied with food and oxygen by blood vessels. This is why
when you break a bone it will bleed. The fibres are surrounded by
hard minerals, mainly calcium phosphate. Bones provide a strong,
hard framework for your muscles and body organs.
Freshly roasted chicken bones lose their flexibility because the
living, flexible part has been destroyed. Acid soaked chicken bones
become very pliable and lose their firmness because the acid has
dissolved all the minerals from the bone.
Joints
Where bones of the skeleton meet, joints are formed. Joints allow
the skeleton to bend and move in different ways.
A typical
Hinge joint
A typical ball
and socket joint
Type of joint
Examples
Ball and socket
Hip, shoulder
Hinge joint
Knee, elbow
Type of
movement
Allows movement in
different planes
Allows moment in
one plane only
The structure of a joint
At a joint, the bones are held together by ligaments. The joint
allows smooth movement.
Part of the joint
Function
Ligament
Hold bones together
Synovial membrane
Makes and releases synovial
fluid
Synovial fluid
Lubricates the ends of the
bones , ensuring frictionless
movement
Cartilage
Cushions the ends of the
bones; acts as a shock absorber
The human arm
Muscles are attached to bones by tendons. When a muscle
contracts (gets shorter), the tendon pulls on the bones and the
arm moves. Tendons are inelastic ie they do not stretch very much
so that the movement of the muscle will be passed on to the bone.
Muscles can only contract and relax. Therefore most muscles work
against each other in pairs. If one muscle straightens the arm, the
other muscle bends it.
Straight arm
Bent arm
Biceps muscle relaxed
Biceps muscle contracted
Triceps muscle contracted
Triceps muscle relaxed
B
The need for Energy
Energy needs
The amount of energy needed by a person will vary according to
their age, gender and lifestyle. If you take in more energy than
you use in activity, your body will store fat.
If you take in less energy in food than you require for activity, your
body will lose fat.
Breathing
You need oxygen to release the energy from your food. In order to
do this, a waste gas, carbon dioxide, is produced. You obtain
oxygen and get rid of carbon dioxide by breathing. Your lungs are
the organs that allow you to do this.
Lung Structure
The lungs are spongy organs that have a very large surface area.
They feel spongy and will float in water because they have air in
them. They are pinky red in colour because they have a good
blood supply. Cartilage rings are found around the trachea and
bronchi to prevent them from collapsing.
The lining of air passages
Air contains dust and germs that damage your lungs. The air you
breathe is cleaned by cells lining the air tubes. These cells have
tiny hairs or cilia that move in waves up to the mouth. A slippery
liquid called mucus is made by the cells and this traps dirt. The
mucus acts like a conveyor belt that is moved by the beating cilia.
In this way dirt and germs are moved up to the mouth where they
are swallowed.
Gas exchange in the air sacs
The bronchi divide into smaller and smaller tubes called
bronchioles. Each bronchiole ends in an air sac that is lined in
moisture. Oxygen dissolves in this moisture and diffuses from the
lungs into the blood because there is a higher concentration in the
sir sac than in the blood. Carbon dioxide diffuses in the opposite
direction because there is a higher concentration in the blood than
in the air sac.
Why lungs are efficient gas exchange structures
1.
They air sac are thin walled to let gases through easily.
2.
The air sacs have many blood capillaries in close contact
with them.
3.
Because there are so many air sacs, they make a very large
surface area.
4.
The air sacs are lined with mucus that is moist so that the
gases can dissolve.
Breathing movements
Movements of the chest help us to inhale (take in air) and exhale
(give out air).
The diaphragm and the intercostal muscles between the ribs are
used to help us to breathe.
Exhalation
Inhalation
Diaphragm relaxes and move
up
Diaphragm contracts and
flattens
Intercostal muscles relax
Intercostal muscles contract
Ribcage moves down and in
Ribcage moves up and out
Chest volume decreases
Chest volume increases
The heart
Oxygen and food are carried to all the body’s cells by blood
vessels. The heart pumps blood round the body.
Facts about the heart
1.
2.
3.
4.
5.
6.
The heart is made of muscle.
There are four chambers in the heart
Right atrium
Left atrium
Left ventricle
Left ventricle
The coronary arteries supply food and oxygen to the heart
muscle. When these blood vessels get blocked, you suffer a
heart attack.
Heart valves stop blood flowing in the wrong direction and
allow blood to flow in one direction only. Valves are found
between the atria and ventricles and, also, as the blood
leaves the heart, in the aorta and the pulmonary artery.
The ventricles have thicker walls than the atria. The left
ventricle has a thicker wall than the right ventricle because
the left ventricle has to pump blood right round the body
whereas the right ventricle only has to pump blood to the
heart.
A pulse indicates that blood is flowing through an artery.
Blood flow through the heart
Deoxygenated blood is blood low in oxygen returns to the heart
via the vena cave. After travelling to all parts of the body, it enters
the heart at the right atrium.
The right ventricle then pumps blood out through the pulmonary
artery to the lungs.
In the lungs, the blood picks up oxygen and loses carbon dioxide.
The oxygenated blood then returns to the heart via the pulmonary
vein, entering the left atrium. The left ventricle pumps blood out
through the aorta to the body.
Arteries, veins and capillaries
Blood is carries away from the heart in arteries.
These arteries carry blood to the body’s organs and tissues. In the
organs the arteries split up into a network of tiny tubes called
capillaries. Substances are exchanged between the capillaries and
tissues. Blood leaves the tissues in vessels called veins that carry
the blood back to the heart.
More about capillaries
The capillary network allows efficient exchange of gases, food and
waste because
1.
They are narrow and thin walled which gives a greater
surface area to allow fast diffusion of gases etc.
2.
They are very long which also increases surface area.
3.
No cell is ever far away from a capillary thus ensuring easy
exchange of substances.
Red blood cells and plasma
Blood is made up of cells floating in liquid called plasma.
The plasma also carries dissolved substances such as carbon
dioxide, digested food and waste products.
Red blood cells carry oxygen.
Haemoglobin
A red blood pigment called haemoglobin is found in red blood
cells. Its function is to combine with oxygen to form
oxyhaemoglobin. At the lungs haemoglobin haemoglobin combines
with oxygen to form ox haemoglobin.
At the tissues, oxyhaemoglobin releases oxygen and becomes
haemoglobin again.
At lungs
Haemoglobin + oxygen --------------- oxyhaemoglobin
-------------At tissues
Gas exchange at the tissues
Oxygen diffuses from the high concentration in the blood across
into the body cells. Carbon dioxide diffuses from the high
concentration in the tissues into the blood.
C
Coordination
The eye
The eye is the sense organ that you use to detect light.
Part of the eye
Function
Cornea
Tough but transparent layer
Lens
Focuses light on to retina
Iris
Coloured muscle that controls
how much light gets into eye
Retina
Light detecting layer at back of
eye; converts light to nerve
impulses
Optic nerve
Carries nerve impulses to brain
Judging distance with binocular vision
As well as detecting pictures, your eye also allows you to judge
distances. Your eyes are set in the front of your head. This gives
you binocular vision which allows you to see things in three
dimensions.
Each eye sees the object slightly differently and two messages are
sent to the brain which puts these two pictures together so that
the object does not look flat.
The Ear
The ear is the sense organ you used to detect sound.
cochlea
Part of the ear
Function
Eardrum
Thin membrane which vibrates
when sound reaches it
Middle ear bones
Transmit vibrations across to
cochlea
Cochlea
Converts vibrations to nerve
impulses
Auditory nerve
Carries nerve impulses form
cochlea to brain
Semi circular canals
Sends messages to brain re
head movements; these
impulses help to control
balance
The direction of sound
Your ears, as well as detecting sound, can also help you judge the
direction from which the sound is coming.
Two ears are better than one at detecting the direction of sound.
The sound of a ringing bell arrives at the left ear slightly faster
then the right ear, thus giving an indication from where the sound
is coming.
Balance
Your semi circular canals help you to balance. The semi circular
canals are three fluid-filled tubes arranged at right angles to one
another. This so that, when the head moves, fluid in one or more
of the tubes will move. Information is sent from here to your brain
to control your balance.
The nervous system
The nervous system is composed of the brain, the spinal cord and
nerves.
The brain sorts out information.
The spinal cord sends information to the brain.
The brain and spinal cord together make up the central nervous
system (CNS).
Sensory nerves carry information from the senses to the CNS.
The CNC sorts this information out and then sends messages via
motor nerves to the appropriate muscles which then contract.
The brain
The brain is the control centre of the nervous system.
The brain is made up of three main parts: the cerebrum, the
cerebellum and the medulla.
Part of the brain
Function
Cerebrum
Site of conscious thought,
memory and intelligence
Cerebellum
Controls balance and muscular
coordination
Medulla
Controls the rate of breathing
and the heart rate
Reflex Actions
A reflex action is a rapid, automatic response to a stimulus. It is an
involuntary action which does not always involve the brain.
Reflex actions happen so quickly that there is often no time for the
nerve impulses to reach the brain. Often the impulse only goes to
the spinal cord and the brain becomes aware of the action only
after it has happened.
Relay neurone
The reflex arc is an arrangement of nerve cells that makes sure
you react quickly to hazardous stimuli.
Some examples of reflex actions are pupils contracting in bright
light, knee jerk and blinking.
Sensory nerves cells send a message to the spinal cord. A relay
nerve connects the sensory nerve to the motor nerve in the spinal
cord. A message is sent down the motor nerve to make a muscle
contract.
D
Changing levels of performance
Aching muscles
If you exercise for very hard or for a long time, eventually your
muscles will ache.
This is because they are not getting enough oxygen and because a
waste product called lactic acid has built up in the muscles. This is
called muscle fatigue.
Anaerobic respiration in muscles
If not enough oxygen is available for your muscles to carry out
aerobic respiration, they are able to switch to anaerobic respiration
to allow you carry on using the muscles for a while longer. Instead
of producing CO2 and water as in aerobic respiration, your muscles
produce lactic acid. This build up of lactic acid makes your muscles
ache.
With enough O2
glucose + O2---- CO2 + water
With no O2
glucose ---- lactic acid
How exercise affects pulse rate and breathing rate
After exercise the breathing rate will increase. This is so that more
oxygen is absorbed at the lungs.
After exercise the pulse rate will increase. This is so that more
food and oxygen van be carried to the muscles.
The time taken for your heart rate, breathing rate and lactic acid
levels to return to normal after exercise is called the recovery time.
The time taken to recover is an indication of how fit you are. In
general the longer it takes for your body to recover, the less fit you
may be.
The effect of training on fitness
A trained athlete’s heart rate and breathing rate are usually lower
than and untrained or unfit person. Another result of training is
that and athlete’s heart and breathing rate do not increase as
much as an untrained person during exercise.
Therefore it is fair to say that training improves the efficiency of
the heart and lungs.
Also training lessens the recovery time.