MUSCLES AND MOVEMENT

Ch. 11 pg 290

Muscles and Movement

The movement in humans involves bones, ligaments, muscles, tendons and nerves.

Bones Provide anchorage for

muscles Act as levers,

changing size and direction of forces

Provide support for the body and protection to internal organs

Blood cell formation Metabolism of

calcium and other minerals.

Ligaments

Tough cords or sheets of tissue

Connect bones together Cover joints and

connections between bones.

Flexible to allow certain movement

Almost inelastic to prevent movement outside normal range of a joint and prevent dislocation

Muscles

Attach to bones and provide forces to change position of bones and the body.

Work in antagonistic pairs

Tendons

Tough cords or straps of tissue Connect muscles to bones Help to anchor muscles to bone and to

transmit forces generated by contraction of muscles.

Joints

These are the points where bones meet. There are many types of joints according to their movement, ex: fixed, ball and socket, pivot and hinge joints.

Joint’s structure:

Cartilage: though, smooth tissue that covers regions of the bone. Prevents contact between bones and absorbs shocks.

Synovial lubricates the joint and helps to prevent friction

Capsule: though ligamentous covering to the joint. Seals the joint, holds the synovial fluid and prevents dislocation.

Biceps and triceps: muscles connected to the humerus.

The striated muscle Muscle used for

movement – skeletal muscle.

Other types of muscle are smooth and cardiac.

Striated muscle is composed of bundles and muscle fibres

A sarcolema surrounds each muscle fibre

The striated muscle

Within each muscle fibre, there are many parallel elongated structures called myofibrils.

Between each myofibril are large numbers of mitochondria

Each muscle fibre contains many nuclei and a specialized E. R. called sarcoplasmic reticulum.

The striated muscle

Myofibrils consist of an alternating series of light and dark bands. In the center of each light band is a disk-shaped structure called the Z line. A part between one Z line and the other is called a sarcomere, the functional unit of a myofibril

The striated muscle

Two filaments compose myofibrils: thin actin and thick myosin filaments.

Actin filaments are attached to the Z line.

Myosin filaments are between actin filaments in the center of the sarcomere.

One myosin filament is surrounded by six actin filaments.

Together they form cross bridges during contraction shortening the length of the muscle fibre.

Muscle contraction

During relaxation, a regulatory protein blocks the binding sites on actin.

When a motor neuron sends a signal to a muscle fibre, the sarcoplasmic reticulum releases Ca+2 that cause the regulatory protein to move.

Myosin cross bridges attach to the actin myofilament.

Muscle contraction

Energy stored in the myosin head causes it to move inwards towards the center of the sarcomere, moving the actin filament a small distance.

Muscle contraction

ATP causes the breaking of the cross-bridges by attaching to the myosin heads

Muscle contraction

Hydrolysis of ATP provides energy for the myosin heads to move away from the center of the sarcomere (cocking of the m. head)

The process continues until the motor neuron stops sending signals to the muscle fibre.

Questions

What is the role of ligaments in the elbow joint?

A. Attach biceps to radius

B. Reduce friction between humerus, ulna and radius

C. Hold humerus, ulna and radius in proper alignment

D. Secrete synovial fluid

The diagram below shows part of a muscle fibre. What parts are labelled I and II?

 I II

The unit between one Z-line and the next is termed:

A. Sarcomere B. MyofibrilC. Sarcoplasmic reticulumD. Sarcolemma

Distinguish between each of the following word pairs:

Hinge joint and pivot joint Radius and humerus Hip and knee joint Actin and myosin ADP and ATP Ligament and tendon Extension and flexion

THE END…