The Body In MotionHow do the musculoskeletal and

cardiorespiratory systems of the body influence and respond to movement?

Major Bones Involved in Movement

Muscular System

In producing a particular movement, a muscle performs one of three roles: agonist, antagonist or stabiliser.

Agonist: is also known as a prime mover and it causes the major action. There are agonists for all moveable joints and usually more than one is involved in a particular movement.

Antagonist: is a muscle that must relax and lengthen to allow the agonist to contract, thus helping to control an action. The agonist works as a pair with the antagonist muscle.

Muscle Relationship

Stabiliser: is also known as a fixator and acts to stabilise a joint, giving the muscles a fixed base. This permits the action to be carried out correctly and allows other joints to work more effectively.

Muscle Relationship cont.

Muscle Relationship cont.

Isometric A muscle develops tension, but there is no change in the length of the

muscle e.g. pushing against a door frame.

Isotonic A muscle develops tension and there is a change in the length of the

muscle causing movement e.g. bicep curl. Isotonic contractions can be both concentric and eccentric in nature.

ConcentricIs the most common type of muscular contraction. The muscle shortens

under tension causing movement at the joint.

EccentricThis type of contraction occurs when the muscle lengthens while under

tension. The action often happens under the assistance of gravity.

Types of Muscle Contraction

Respiratory System:Structure and Function

The passage of air from the nose to the lungs:1. Air containing oxygen enters the body through the nose

and mouth. As it passes through the nasal cavities it is warmed, moistened and filtered of any foreign materials.

2. Air then passes through the pharynx and into the trachea, through the voice box.

3. The trachea is a hollow tube strengthened and kept open by rings of cartilage. From here the air then enters the thorax which divides into a right and left bronchus which lead to the right and left lungs.

4. The inner lining of the air passages at this stage produces mucus that catches and holds dirt and germs and is lined by hairs called cilia.

Structure and Function cont.

Breathing is the process by which air is moved in and out of the lungs located in the chest (thorax). It is controlled automatically by the brain and involves two phases: inspiration and expiration.

During inspiration, the diaphragm contracts and flattens as the external intercostal muscles (between the ribs) lift the ribs outwards and upwards. This movement increases the volume of the chest cavity (thoracic cavity) and pulls the walls of the lungs outwards, which in turn decreases the air pressure within the lungs. In response to this, air from outside the body rushes into the lungs through the air passages.

Lung Function

During expiration the diaphragm relaxes and moves upwards as the internal intercostal muscles allow the ribs and other structures to return to their resting position. The volume of the chest cavity (thoracic cavity) is therefore decreased, which increases the air pressure inside the lungs. Air is consequently forced out to make the pressures inside and outside the lungs about equal.

Lung Function cont.

Lung Function cont.

During inspiration, the alveoli are supplied with fresh air that is high in oxygen content and low in carbon dioxide. On the other hand, blood in the capillaries arriving at the alveoli is low in oxygen and high in carbon dioxide content. The different concentrations of oxygen and carbon dioxide between the blood and the air result in a pressure difference.

Exchange of Gases

Gases such as oxygen and carbon dioxide move from areas of high concentration or pressure to areas of low concentration or pressure. Oxygen therefore moves from the air in the alveoli across the alveolar-capillary wall into the blood, where it attaches itself to haemoglobin in the red blood cells. At the same time carbon dioxide is unloaded from the blood into the alveoli across the alveolar-capillary wall to be breathed out. This two way diffusion is known as the exchange of gases.

Exchange of Gases cont.

Exchange of gases, using the same principle, occurs between blood in the capillaries of the arterial system and the cells of the body; for example, the muscle cells. Here, oxygen is unloaded to the cells while carbon dioxide resulting from cell metabolism is given up to the blood. Blood that is high in carbon dioxide content (deoxygenated blood) is carried back to the lungs where it unloads carbon dioxide.

Exchange of Gases cont.

Exchange of Gases cont.