How the Body Moves

Joints

There are three kinds of joint and their classification is dependant upon how the bones are joined together.

There is no cavity or movement in these joints and fibrous tissue holds the bones together. Examples of this are in the skull and pelvis.

Copyright S-cool

As these joints are linked by cartilage there is some movement but it is very slight.

There is no cavity.

Examples of these joints can be found between the vertebrae and between the ribs and sternum.

Copyright S-cool

These joints allow for greater ranges of movement and the type of movement will depend upon the type of joint between the bones.

Copyright S-cool

A ball and socket joint: found in the shoulder and hip. This joint allows the greatest range of movement.

Copyright S-cool

A hinge joint: found at the elbow and knee. The range of movement is limited to one plane just like a door hinge.

Copyright S-cool

A condyloid joint: found at the wrist and ankle. Movement in two planes but not as great as the ball and socket.

Copyright S-cool

A pivot joint: found in the neck. Part of the bone fits into another ring of bone as in take atlas and axis, allowing rotation of the head.

Copyright S-cool

A saddle joint: found at the base of the thumb. This joint allows the thumb to be moved in two directions.

Copyright S-cool

A gliding joint: found in the wrist and vertebral column. Two bones have a small range of movement limited by connecting ligaments.

Levers

It is due to muscles acting upon a system of levers; the skeleton that movement of some part of the body occurs. There are three types of lever but all levers have three parts:

The Fulcrum: the point of movement or pivot, generally at the centre of a joint.

A Load: the body's weight or some external object.

An Effort: a muscular force to move the load.

There are three classes of lever and each is classified depending upon where in relation to each other the fulcrum, the load and the effort are.

The fulcrum is between the effort and the load.

Both effort and load are in the same direction.

An example of this is the head where the head pivots on the atlas (fulcrum).

The load is the weight of the head going down.

The effort is the muscles at the back of the neck pulling down.

Copyright S-cool

The fulcrum is at one end of the lever.

The load is in the middle of the lever.

The effort is at the opposite end of the lever to the fulcrum withthe direction of effort opposite the load.

An example of this is stepping up onto your toes. The fulcrum is at the toes. The load is that of the body going through the middle of the foot and the effort is in the calf muscles pulling the body upon to the toes.

This is the most effective lever as a relatively small force can move a largeweight.

Copyright S-cool

Like second order levers the fulcrum and load are at opposite ends of the lever but the effort is off-centre of the lever towards the fulcrum. This is not as efficient as second order levers but small muscle movement creates long lever movement.

An example of this is a biceps curl. The load is in the hand, the fulcrum is at the elbow and the biceps make the effort.

Copyright S-cool

The Muscles

Attached to the skeleton are the muscles of the body. Although the skeleton provides the underlying framework, the muscles give the body its unique appearance. The importance of muscles is that they are needed for all body actions, ranging from moving to digestion and breathing.

There are three main types of muscles in the body. Each type has a special purpose that is vital to the normal functioning of the body.

Found in the bowel, the gut and internal organs. There is no direct control of this muscle - it works automatically.

Cardiac or heart muscle is specialised muscle that contracts constantly and automatically. Some factors can affect the speed of the contractions such as exercise and the release of hormones such as adrenaline. Further details of the heart can be found in the 'Circulatory System'.

Skeletal muscles are the ones that can easily be seen as a shape under the skin. Unlike smooth muscle or cardiac muscle, we can control skeletal muscles and because of this it is sometimes known as voluntary muscle.

The diagrams below show front and back views of the major skeletal muscles:

Copyright S-coolCopyright S-cool

Skeletal Muscles

When viewed under a microscope, skeletal muscle has a striped appearance and is therefore sometimes called striated muscle.

This striped appearance is caused by thousands of long, narrow fibres or cells that are able to contract (shorten in length).

These fibres are enclosed in a sheath of connective tissue, known as the epimysium.

Muscle fibres are made up of very small threads called myofibrils and each myofibril consists of rows of protein molecules, actin and myosin. It is the interaction between the actin and myosin molecules that causes the muscle to contract

Remember: muscles can only pull they cannot push.

Copyright S-cool

There are two types of muscle fibre: slow and fast twitch.

They are physiologically different.

The amounts of fast twitch or slow twitch fires in the muscle will determine their suitability to certain sporting activities.

The amount of each fibre type in our muscles is also determined genetically, that is, we are born with it.

Training will have little effect on altering the ratio of fast twitch to slow twitch fibre in the muscle.

This is why there are people who are 'natural' endurance athletes; they have greater amounts of slow twitch fibre which contracts slowly with little force but do not tire easily.

Other people have greater amounts of fast twitch fibres and are 'naturally' good at sprinting and throwing. These fibres produce larger forces but tire quickly.

Skeletal muscle contractions are stimulated by electrical signals transmitted along motor nerve fibres that have been sent from the central nervous system. (See 'Nervous system').

Cross-bridges are formed between the myosin and actin molecules. The cross-bridges originate on the myosin molecule and attach themselves to the actin molecule. They then drag the actin molecule towards the origin of the muscle. It is the actin molecule that is active and moves the myosin molecules are fixed.

Copyright S-cool

Every time a cross-bridge is formed energy is required.

This energy is provided in the form of a chemical known as Adenosine Triphosphate (ATP).

When the nervous stimulus arrives at the muscle cell ATP breaks down into a chemical known as Adenosine Diphosphate (ADP).

During this break down energy is released which is used to form one cross-bridge.

Copyright S-cool

Duration of the nervous stimulus will determine the duration of the muscle contraction.

The strength of the stimulus will determine the force that the muscle contraction exerts.

There is a limited quantity of ATP in the muscle and for muscle contraction to continue over a long period of time.

ATP has to be re-built from ADP + P. The re-building of ATP is known as muscle respiration and described in detail in Muscle Respiration.

Muscles and Movement

Muscles can only contract and pull. Therefore, joints have to have two or more muscles working opposite each other.

As the first muscle contracts, so the second muscle relaxes. As the second muscle contracts, so the first muscle relaxes. This is known as antagonistic muscle action.

For this to occur one end of the muscle must be fixed, this is known as the origin. When the muscle contracts, the other end of the muscle then moves towards the origin.

The end that moves is known as the insertion.

A good example of this is the upper arm where the triceps and biceps areon opposite sides of the humerus.

The origins of both the triceps and the biceps are at the top of the humerus near the shoulder joint.

As the bicep contracts, the lower arm (radius and ulna) moves up towards the shoulder. The triceps relax to allow this movement to happen.

The bicep is the prime mover or agonist, while the tricep is the secondary mover or antagonist.

Copyright S-cool

Muscles are attached to bones at either side of the joints by tendons.

These are very strong flexible cords of connective tissue that extend from the epimysium and transmit large amounts of energy from the muscle to the bone.

The ends of tendons are embedded into the surface of the bone.

There are three types of muscle contraction:

Isometric - During isometric contraction, the muscle remains the same length. While performing a handstand, many of the bodies muscles are contracting.

Isokinetic - Isokinetic contraction occurs when the speed of the contraction remains constant throughout the movement. An example of this can be seen in cycling.The legs are moving at a relatively constant speed, although forces applied by the leg alter during a peddling cycle.

Isotonic - Isotonic contraction can be divided into two types:

  • Concentric: the muscle shortens as it contracts.
  • Eccentric: the muscle lengthens but is still under tension.

Due to the range of movements required in sport, it is useful to be able to describe them technically:

Flexion: bringing two parts of a limb together - bending at the joint.

Extension: moving two parts of a limb away from each other - straightening at the joint.

Abduction: moving limbs away from the centre of the body.

Adduction: Moving limbs towards the centre of the body.

Circumduction: the movement of a limb around a joint.

Exam-style Questions

 

 

  1. a) State four functions of the skeleton.

    (4 marks)

    b) Name the four bones labelled A-D from the diagram above.

    (4 marks)

    c) Name one type of bone and give one example.

    (2 marks)

    Install Flash

    (Marks available: 10)

    Answer

     

    Answer outline and marking scheme for question: 1

    a) Award yourself 1 mark for each of the following 4 correct functions of the skeleton:

    1. Support
    2. Protection
    3. Movement
    4. Blood production

     

    (4 marks)

    b) Give yourself 1 mark for each correctly named bone, which were:

    Install Flash

    c) There are four types of bone so award yourself up to 2 marks for correctly stating one of the following types and a correct example:

    1. Long bones, for example, humerus, radius, ulna, femur, tibia, fibula, clavicle, ribs, metatarsals, metacarpals and phalanges.
    2. Short bones, for example, carpals and tarsals.
    3. Flat bones, for example, scapula, pelvis and cranium.
    4. Irregular bones, for example, patella and the vertebrae.

    (2 marks)

    (Marks available: 10)

  2. a) Name the group of muscles, which originate from the upper shaft of the femur on the front of the thighs.

    (1 mark)

    b) Name the group of muscles, which originate from the back of the base of the femur and insert via the Achilles tendon into the heel.

    (1 mark)

    c) Name the three different types of muscle and give one example for each.

    (6 marks)

    d) What are ligaments and what do they do?

    (2 marks)

    (Marks available: 10)

    Answer

     

    Answer outline and marking scheme for question: 2

    a) Give yourself 1 mark for correctly naming the Quadriceps.

    (1 mark)

    b) Award yourself 1 mark for correctly naming the Gastrocnemius/Calf muscle.

    (1 mark)

    c) Award yourself up to 6 marks for naming all 3 different types of muscle and giving an appropriate example for each:

    1. Cardiac muscle, for example, the heart
    2. Smooth or Involuntary muscle, for example, gut, bladder, uterus
    3. Striped, Skeletal, Striated or Voluntary muscle, for example, biceps, triceps, quadriceps...

     

    (6 marks)

    d) Give yourself 1 mark for explaining that ligaments are strong cords and straps, and another mark if you stated that they lash bones together or hold a joint in place.

    (2 marks)

    (Marks available: 10)

  3. a) Name the two movements which take place at a hinge joint.

    (2 mark)

    b) Explain what happens to a muscle when it contracts and when it relaxes.

    (2 marks)

    c) If an athlete is made up of predominantly fast twitch muscle fibres what activities would they be more suited to?

    (1 mark)

    d) Excluding the hinge joint, name two other types of synovial joint and give one example of each.

    (4 marks)

    e) Name the type of muscular contraction where the muscles contract but stay the same length.

    (1 mark)

    (Marks available: 10)

    Answer

     

    Answer outline and marking scheme for question: 3

    a) To get your 2 marks you have to state that only flexion and extension take place at a hinge joint.

    (2 marks)

    b) You receive 1 mark for stating that when a muscle contracts the muscle shortens and 1 mark for saying that when a muscle relaxes it lengthens.

    (2 marks)

    c) Remember, fast twitch fibres contract with a lot of force and tire quickly. So, to get your 1 mark you need to say that the athlete would be more suited to activities that need bursts of strength and power, for example, sprinting, weightlifting.

    (1 mark)

    d) Give yourself 1 mark for naming each type of joint and another for an appropriate example to go with it, up to 4 marks in total.

    1. Ball and socket joint, for example, hip and shoulder
    2. Pivot joint, for example, joint between atlas and axis, joint between radius and ulna
    3. Saddle joint, for example, base of thumb
    4. Condyloid joint, for example, wrist, joint between the base of skull and atlas
    5. Gliding joint, for example, joints between carpals and tarsals, joints between vertebrae

     

    (4 marks)

    e) If you have stated that they are contracting isometrically you get 1 mark.

    (1 mark)

    (Marks available: 10)

The Skeleton

The Skeleton is a framework of bones that is held together by ligaments and joints, and has the following four functions:

Movement

The joints of the skeleton, where two or more bones come together, allows some movement depending upon the type of joint and the types of bone. These variations will determine the kind of movement there can be.

Protection

The skeleton forms protection around some of the more delicate organs ofthe body. An example of this is the skull that protects the brain.

Support

The skeleton provides the body with a rigid structure that gives it its shape. Muscles are attached to the skeletons outside while the vital organs are attached to the inside.

Blood Production

Red and white blood cells are produced in the bone marrow, a substance found inside the larger bones of the body.

There are two parts to the skeleton; the axial skeleton and the appendicular skeleton:

The axial skeleton

This consists of the skull, the rib cage and the vertebral column. The skull is made of eight flat bones that fuse together over time.

The vertebral column or spine is built of 24 movable vertebrae and two groups of fused vertebrae. The vertebrae are grouped together to form different parts of the vertebral column and have particular purposes. (See diagram).

The rib cage consists of 12 pairs of ribs that help protect vital organs and, along with their associated muscle group, is part of the breathing mechanism.

Copyright S-cool

The appendicular skeleton

This is made up from the pelvic girdle and the shoulder girdle. Both these girdles are quite rigid but they are attached to legs and arms that are free to move.

Copyright S-cool

There are four types of bone and each type is given a name dependant of its shape or size.

Type of Bone Example
Long bones The Humerus
Short bones The Phalanges
Flat bones The Scapula
Irregular bones The Vertebrae

Copyright S-cool

Major bones of the skeleton

Copyright S-cool
Copyright S-cool

S-Cool Revision Summary

Functions of the Skeleton:

The Skeleton is a framework of bones that is held together by ligaments and joints, and has the following four functions:
movement, protection, support and blood production.

Parts of the Skeleton:

There are two parts to the skeleton; the axial skeleton and the appendicular skeleton.

The axial skeleton consists of the skull, the rib cage and the vertebral column.

The appendicular skeleton is made up from the pelvic girdle and the shoulder girdle. Both these girdles are quite rigid but they are attached to legs and arms that are free to move.

Bones:

There are four types of bone and each type is given a name dependant of its shape or size:

  1. Long bones, for example, the Humerus.

  2. Short bones, for example, the Phalanges.

  3. Flat bones, for example, the Scapula.

  4. Irregular bones, for example, vertebrae.

Classification of Joints:

There are three kinds of joint and their classification is dependant upon how the bones are joined together.

  1. Fibrous joints, where fibrous tissue holds the bones together.

  2. Cartilaginous joints, these joints are linked by cartilage there is some movement, but it is very slight.

  3. Synovial joints allow for greater ranges of movement and the type of movement will depend upon the type of joint between the bones.

A ball and socket joint: found in the shoulder and hip allows the greatest range of movement.

A hinge joint: found at the elbow and knee where movement is limited to one plane just like a door hinge.

A condyloid joint: found at the wrist and ankle. Movement is in two planes but not as great as the ball and socket.

A pivot joint: found in the neck where part of the bone fits into another ring of bone as in the atlas and axis, allowing rotation of the head.

A saddle joint: found at the base of the thumb allows the thumb to be moved in two directions.

A gliding joint: found in the wrist and vertebral column.

Parts of the Lever

It is due to muscles acting upon a system of levers; the skeleton that movement of some part of the body occurs. There are three types of lever, but all levers have three parts:

  1. The Fulcrum. Is the point of movement or pivot, generally at the centre of a joint.

  2. A Load. The load is the body's weight or some external object.

  3. An Effort. An effort is a muscular force to move the load.

Classification of Levers

There are three classes of lever and each is classified depending upon where in relation to each other the fulcrum, the load and the effort are.

First Order Levers:

The fulcrum is between the effort and the load.

Both effort and load are in the same direction.

An example of this is the head where the head pivots on the atlas (fulcrum).

The load is the weight of the head going down.

The effort is the muscles at the back of the neck pulling down.

Second Order Levers:

The fulcrum is at one end of the lever.

The load is in the middle of the lever.

The effort is at the opposite end of the lever to the fulcrum with the direction of effort opposite the load.

An example of this is stepping up onto your toes. The fulcrum is at the toes. The load is that of the body going through the middle of the foot and the effort is in the calf muscles pulling the body up onto the toes.

This is the most effective lever as a relatively small force can move a large weight.

Third Order Levers:

Like second order levers, the fulcrum and load are at opposite ends of the lever but the effort is off-centre of the lever towards the fulcrum. This is not as efficient as second order levers but small muscle movement creates long lever movement.

An example of this is a biceps curl. The load is in the hand, the fulcrum is at the elbow and the biceps make the effort.

Types of Muscle:

There are three main types of muscles in the body. Each type has a special purpose that is vital to the normal functioning of the body:

  1. Smooth or Involuntary Muscle. Found in the bowel, the gut and internal organs. There is no direct control of this muscle, that is, it works automatically.

  2. Cardiac or heart muscle is specialised muscle that contracts constantly and automatically. Some factors can affect the speed of the contractions such as exercise and the release of hormones such as adrenaline. Further details of the heart can be found in the Circulatory System.

  3. Skeletal muscles are the ones that can easily be seen as a shape under the skin. Unlike smooth muscle or cardiac muscle, we can control skeletal muscles and because of this it is sometimes known as voluntary muscle.

Muscle Fibre Types:

There are two types of muscle fibre, slow and fast twitch.

They are physiologically different and the percentage of each in a muscle is determined genetically.

The amounts of fast twitch or slow twitch fires in the muscle will determine their suitability to certain sporting activities.

This is why there are people who are 'natural' endurance athletes; they have greater amounts of slow twitch fibre which contracts slowly with little force but do not tire easily.

Other people have greater amounts of fast twitch fibres and are 'naturally' good at sprinting and throwing. These fibres produce larger forces but tire quickly.

Contraction of Skeletal Muscles

Skeletal muscle contractions are stimulated by electrical signals transmitted along motor nerve fibres that have been sent from the central nervous system (see Nervous System).

Cross-bridges are formed between the myosin and actin molecules. The cross-bridges originate on the myosin molecule and attach themselves to the actin molecule. They then drag the actin molecule towards the origin of the muscle. It is the actin molecule that is active and moves the myosin molecules are fixed.

Muscle Contraction and Energy

Duration of the nervous stimulus will determine the duration of the muscle contraction.

The strength of the stimulus will determine the force that the muscle contraction exerts.

There is a limited quantity of ATP in the muscle and for muscle contraction to continue over a long period of time.

ATP has to be re-built from ADP + P. The re-building of ATP is known as muscle respiration.

Antagonistic Muscle Action

Muscles can only contract and pull. Therefore, joints have to have two or more muscles working opposite each other. This is known as antagonistic muscle action.

For this to occur, one end of the muscle must be fixed. This is known as the origin. When the muscle contracts, the other end of the muscle then moves towards the origin.

The end that moves is known as the insertion.

A good example of this is the upper arm where the triceps and biceps are on opposite sides of the humerus.

The origins of both the triceps and the biceps are at the top of the humerus near the shoulder joint.

As the bicep contracts the lower arm (radius and ulna) moves up towards the shoulder. The triceps relax to allow this movement to happen.

The bicep is the prime mover or agonist, while the tricep is the secondary mover or antagonist.

Muscles are attached to bones at either side of the joints by tendons.

Muscle Contraction for Movement:

There are three types of muscle contraction.

  1. Isometric: muscle remains the same length.

  2. Isokinetic: the speed of the contraction remains constant throughout the movement.

  3. Isotonic contraction can be divided into two types:

    Concentric: the muscle shortens as it contracts.

    Eccentric: the muscle lengthens but is still under tension.

Types of Body Movement:

Due to the range of movements required in sport, it is useful to be able to describe them technically.

Flexion: bringing two parts of a limb together - bending at the joint.

Extension: moving two parts of a limb away from each other - straightening at the joint.

Abduction: moving limbs away from the centre of the body.

Adduction: Moving limbs towards the centre of the body.

Circumduction: the movement of a limb around a joint.

Syndicate content