Body in Action

Credit Objectives

Sub-topic (a) MovementDescribe 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.

CartilageCushions and protects ends of bones, absorbs

shock to allows free movement of joint.Synovial membraneSecretes synovial fluid which lubricates inner

joint surfaces, allowing friction-free movement.Synovial cavityActs as a cushion, preventing friction between

cartilage-covered ends of bones.

CapsuleCompletely encases and protects the joint.LigamentsHold 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.

CartilageThe 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) CoordinationDescribe 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.

Sensory nerveRelay 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 co-ordinates all the systems of the human body.

Identify the parts of the brain and state their functions.

CerebrumThe largest part of the brain. Controls

memory,reasoning, conscious thought etc. Also contains the motor and sensory strips.

CerebellumControls balance and muscular co-ordination.MedullaControls the rate of breathing and heartbeat.

Cerebrum

Cerebellum

Medulla

Sub-topic (d) Changing levels of performanceExplain 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.