Download Y7 Skeleton and muscles

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Page 131
Summary sheet
B8
The body and respiration
Animals with ‘backbones’ are called vertebrates. The backbone is part of the
skeleton which is made of bones. Bones are:
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hard (to stand up to knocks and pressure)
light (to allow them to be moved easily).
Skull protects the brain. Bones
in the skull form fixed joints
(which cannot move)
Ribs protect the heart and lungs
The elbow is a hinge joint
(a flexible joint which can
move to and fro only)
The backbone supports the
body and protects a large
collection of nerve cells
called the spinal cord
The skeleton:
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The hip is a ball and socket joint
(a flexible joint which can move
in many directions)
protects organs
supports the body
allows the body
to move using
flexible joints.
The human skeleton
Flexible joints are moved by muscles. These are controlled by nerve cells and contract
(get shorter and fatter) to pull a bone. When a muscle stops contracting it is said to
relax. It can go back to its original shape when it is relaxed. Muscles cannot push and
so joints need pairs of muscles (antagonistic pairs) to pull in opposite directions.
An antagonistic pair
Triceps muscle –
pulls the lower
arm down
Biceps muscle –
pulls the lower
arm up
Muscles are
attached to
bones by
tendons
Bones are
attached to
each other by
ligaments
Synovial fluid fills the gap
between the bones to stop
them rubbing each other.
Joints that contain this fluid
are called synovial joints
Cartilage is a slippery substance that covers
the ends of bones to stop them wearing away.
It is also found in the ears and nose
The elbow joint
Energy is released in muscles by respiration, which happens in mitochondria in the
cytoplasm of cells. This is a chemical reaction and can be shown by this word equation:
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carbon dioxide + water (+ energy)
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glucose + oxygen
Reactants
Products
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9541_b8_p121_132_sb4 9/4/01 16:11 Page 132
B8
B
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Summary sheet (continued)
The oxygen for respiration
is taken in by the lungs
(part of the breathing
system).
windpipe (trachea)
These muscles
(called intercostal
muscles) push ribs out.
The intercostal
muscles relax and
the ribs move back in.
Oxygen is carried in red
blood cells in the blood.
These are made in the
bone marrow in the
middle of some bones.
Blood travels through
blood vessels and is
pumped by the heart. The
heart and the blood vessels
form the circulatory
system. There are three
sorts of blood vessel.
The diaphragm
moves downwards
rib
lung
The diaphragm rises
capillary
lungs
contain
air sacs
Veins carry
blood to the
heart
Arteries
are narrower
than veins.
They have
thick walls.
They take
blood away
from the
heart
Capillaries have very thin walls. Substances
enter and leave the blood in capillaries. Part
of the blood (plasma) leaks out forming
tissue fluid. This supplies the cells with oxygen
and food. Waste carbon dioxide comes out of the
cells and goes back into the capillaries. It is carried,
dissolved in the plasma, to the lungs where it is
released (an example of excretion)
When you exercise your breathing rate (number of breaths in one minute) and your
pulse rate (number of times your heart beats in one minute) increase. This is because
your cells need more oxygen and glucose for respiration.
Drugs are chemicals that affect how your body works. Medicines are drugs that help
people with diseases. Some drugs are illegal and harmful. Even legal drugs can do you
harm. Cigarettes contain a drug called nicotine which is addictive (you feel you
cannot do without it). The chemicals in cigarettes cause diseases.
Poison in cigarette smoke
Harm it causes
nicotine
Makes arteries narrower, causes heart disease
tar
Clogs up the lungs and stops the cilia working, causes cancer and bronchitis
carbon monoxide
Stops red blood cells carrying so much oxygen
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© Pearson Education Limited 2001