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Body in Action
 Credit Objectives
 Sub-topic (a) Movement
 Describe the structure of a synovial joint.
 Ball and socket and hinge joints are called
synovial joints because each possess a
synovial membrane.
 The structure also includes:
 Cartilage: smooth,slippery and hardwearing.
 Synovial membrane: moist slippery
membrane.
 Synovial cavity: enclosed space full of
synovial fluid.
 Capsule: tough sleeve like extension of
membrane on outside of bone.
 Ligaments: strong cords of fibrous tissue.
 State the functions of the parts of the synovial
joint.
 Cartilage
 Cushions and protects ends of bones,
absorbs shock to allows free movement of
joint.
 Synovial membrane
 Secretes synovial fluid which lubricates inner
joint surfaces, allowing friction-free
movement.
 Synovial cavity
 Acts as a cushion, preventing friction between
cartilage-covered ends of bones.
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Capsule
Completely encases and protects the joint.
Ligaments
Hold bones firmly together while being able to
withstand sudden stress during movement of
joint. Have a small degree of elasticity.
 State that bone is made by and consists of
living cells.
 Explain why tendons need to be inelastic.
 Tendons attach muscle to bone. When the
muscle contracts the muscle will pull the bone
and move the arm. If the tendon was elastic it
would simply stretch when the muscle
contracts and no movement would occur.
 Explain the need for opposing muscles.
 A muscle is able to contract but is unable to
lengthen of its own accord.
 Following contraction a muscle depends on
the action of its antagonistic partner to restore
it to its original length.
 For example the action of the bicep and the
tricep in the upper arm.
 The biceps (flexor) is needed to contract the
tricep (extensor) back to its elongated shape.
 Sub-topic (b) The need for energy
 Describe the mechanism for breathing in
humans.
 Breathing in (inspiration):
 Contraction of the intercostal muscles pulls
the rib cage out and up.
 At the same time, contraction of the
diaphragm lowers the floor of the chest cavity.
 The volume of the chest cavity is increased
(pressure deceased) causing air to be
inhaled.
 Breathing out (expiration):
 On the relaxation of the intercostal muscles,
the rib cage moves down and in.
 Relaxation of the diaphragm (dome shape)
causes a reduction in volume (increase in
pressure) of the chest cavity.
 Air is therefore exhaled.
 Explain the function of cilia, cartilage and
mucus in the trachea and bronchi.
 The trachea and bronchi are lined with tiny
hair-like cilia and cells which secrete mucus.
Rhythmic beating of the cilia sweeps mucus
containing trapped dust and germs up to the
mouth. Germs are normally killed by stomach
acid.
 Cartilage
 The trachea and bronchi are held
permanently open by incomplete rings of
cartilage. Otherwise they would collapse and
close, leading to suffocation.
 Describe the exchange of gases between air
sacs and capillaries.
 Air breathed into the lungs is said to be
deoxygenated.
 Air breathed into an alveolus contains a
higher concentration of oxygen so diffusion
occurs into the capillaries.
 Deoxygenated blood contains a higher
concentration of carbon dioxide than in the
alveolus. Diffusion will occur into the alveolus
 Describe the features that make lungs
efficient at gas exchange.
 The alveoli and associated blood vessels
make the lungs efficient gas exchange
structures.
 Alveoli present a large surface area to absorb
oxygen.
 Alveolar surface is moist to allow oxygen to
dissolve.
 Alveolar lining is thin to allow oxygen to
diffuse through into the blood easily.
 A network of tiny blood vessels surrounds
alveoli to pick up and transport oxygen.
Air sac
Blood capillaries
 Explain the function of haemoglobin.
 The pigment in red blood cells is called
haemoglobin.
 In the presence of a high concentration of
oxygen, haemoglobin readily combines with
the oxygen to form oxy-haemoglobin.
 When the surrounding oxygen concentration
is low, oxy-haemoglobin readily releases
oxygen again.
 When blood passes through lung capillaries,
oxy-haemoglobin is formed.
 When the blood reaches the capillaries
beside respiring body cells oxy-haemoglobin
releases the oxygen.
 Describe the features that make capillary
networks efficient at gas exchange.
 Capillaries are very narrow tubes which
branch repeatedly, forming such a dense
network that that every living body cell is
close to a capillary.
 The combined surface area of the capillary
network is enormous and the capillary walls
are only one cell thick.
 These properties of the capillary network will
allow efficient gas exchange to occur
between the bloodstream and the body cells.
 Sub-topic (c) Coordination
 Describe how the structure of semi-circular
canals is related to their function.
 The three liquid filled canals are situated at
right angles to one another.
 Each contains an ampulla containing a
receptor which is stimulated by movements of
the liquid in the canal.
 These are caused by the canal being rotated
in its respective plane by movements of the
head.
 Messages are carried by a branch of the
auditory nerve to a region of the brain that
controls muscular activity for balance.
 Describe how a reflex action works.
 A reflex action is a rapid, automatic,
involuntary response to a stimulus.
 If the hand came in contact with intense heat
the stimulus would be picked up by pain
receptors in the skin.
 An impulse would be sent up the fibre of the
sensory neurone. The impulse would then
pass through the relay neurone of the spinal
cord.
 The nerve impulse is then picked up by the
motor neurone which have endings that are in
close contact with the flexor muscle of the
arm causing it to contract and move away
from the heat.
Relay nerve
Sensory nerve
Motor nerve
 State the function of the central nervous
system.
 The central nervous system is the brain and
spinal cord. It is connected to all parts of the
body by nerves. The brain is in overall
control. The system controls and coordinates all the systems of the human body.
 Identify the parts of the brain and state their
functions.
 Cerebrum
 The largest part of the brain. Controls
memory,reasoning, conscious thought etc.
Also contains the motor and sensory strips.
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Cerebellum
Controls balance and muscular co-ordination.
Medulla
Controls the rate of breathing and heartbeat.
Cerebrum
Cerebellum
Medulla
 Sub-topic (d) Changing levels of
performance
 Explain muscle fatigue in terms of anaerobic
respiration.
 Under normal circumstances the energy
needed for contraction of muscles comes
from aerobic respiration (glucose and
oxygen).
 During vigorous exercise the supply of
oxygen cannot meet the demand.
 Muscles will continue to use glucose
anaerobically producing lactic acid and a little
energy.
 Oxygen debt is required to remove the lactic
acid so that muscles can work properly.
 State the effects of training on the lungs and
circulation.
 Training involves vigorous exercise over a
period of several weeks.
 The lungs of an athlete are more efficient able
to take in larger volumes of oxygen in each
breath.
 During training the heart muscle tissue
gradually increases in strength and efficiency.
 As a result the same volume of blood can be
supplied to the muscles using fewer
heartbeats.
 Therefore the athlete’s circulation is more
efficient.
 Explain the relationship between the effects
of training and recovery time.
 Recovery time is the time it takes for the heart
rate, breathing rate and the lactic acid levels
to return to normal resting values.
 A person who is in training will notice that the
factors above will return to normal resting
values quicker than a person who is not in
training.
 It can therefore be used as an indicator of
fitness.