Role of the Muscles, Ligaments and Tendon

8/2/2019 Role of the Muscles, Ligaments and Tendon

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Role of the muscles,

ligaments and tendon in

movement



Antagonistic Muscles

For every muscle or group of muscles that bringsabout movement of a certain part of the body, thereis another muscle or group of muscles which bring

about an opposite movement. Such muscles,bringing about opposite movements, arecalled antagonistic muscles. They make thesmooth co-ordination of movement possible. As theone muscle contracts, the other (which is able to

bring about an opposite movement) will relax, andvice versa.



All skeletal muscles exits in pairs and they

act as antagonistic pairs. Antagonistic - One muscles contract, the

other must relax.

Examples of antagonistic muscles:

*Biceps

*Triceps



Joint structure and antagonistic muscle

pairs A. Humerus (upper arm) bone.

B. Synovial membrane that enclosesthe joint capsule and producessynovial fluid.

C. Synovial fluid (reduces friction andabsorbs pressure).

D. Ulna (radius) the levers in theflexion and extension of the arm.

E. Cartilage (red) living tissue that

reduces the friction at joints. F. Ligaments that connect bone to

bone and produce stability at the joint.



Antagonistic Pairs

To produce movement at a joint muscles work in pairs.

Muscles can only activelycontract and shorten. Theycannot actively lengthen.

One muscles bends the limb atthe joint (flexor) which in theelbow is the biceps.

One muscles straightens thelimb at the joint (extensor)

which in the elbow is thetriceps.



Elbow joint structure.

1. Humerus forms the shoulder joint also the origin for each of thetwo biceps tendons

2. Biceps (flexor) muscle providesforce for an arm flexion (bending).As the main muscle it is known as

the agonist. 3. Biceps insertion on the radius of

the forearm

4. Elbow joint which is the fulcrumor pivot for arm movement

5. Ulna one of two levers of theforearm

Technically in a flexion like this theBiceps performs a concentric

contraction.



6. Triceps muscle is the extensorwhose contraction straightens thearm.

7. Elbow joint which is also the pivot

(fulcrum)for this movement. It should be noted that the description

of movement is fairly complex. A trueTriceps extension takes place againstgravity.

Exercise: Bend your arm in a flexion.

Point your elbow upwards vertically.Raise your hand vertically above yourhead. This is a true concentriccontraction of the Triceps

Pick up a heavy object in concentricBiceps flexion. Now lower andstraighten your arm. You should feelyour Biceps contracted but Tricepsrelaxed. That an eccentric contractionof the Biceps This just shows howcomplex movement can be!



Muscles Ligaments Tendon

● Made up of bundles of

muscles fibers. ● Made up of tough and strong

connective tissue ● Made up of non-

stretchable fibers

● Elastic ● Flexible, strong, elastic ● Strong, tough, inelastic.

● Attached to the bone ● Bone to bone ● Muscle to bone

● Contract, relax to produce

movement

● Allow two bones to hold together.

● Ensures the bones do notdislocated.

● Transmit the force

produce by skeletal musclesto the bone



Bending the forearm

When the biceps muscle contract the tricepsmuscle relax.

Contraction of the biceps muscles produced

force.

The force is transmitting to radius by tendonand the radius is pull up.

Thus, bending the arm at the elbow joint



Straightening the forearm

When the triceps muscle contracts, thebiceps muscle relax.

Contraction of the triceps muscles produced

force.

The force is transmitting to ulna by tendonand the ulna is pull down.

Thus, straightened the arm at the elbow joint



Why does muscles need to work in

pairs? Since a muscle cannot push, but

only pulls, it has to be extending

back to its original lengths by theopening action of another muscle.

Therefore, muscle must work inpairs.

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Role of the Muscles, Ligaments and Tendon