MUSCULAR SYSTEM

PROPERTIES OF MUSCLE TISSUE (Contractility, extensibility and elasticity)

1. Contractility: shortening of the muscle. Ability of muscle to contract and generate force when it is stimulated by a nerve.

2. Extensibility: ability of muscle to stretch beyond its normal resting length

3. Elasticity: ability of muscle to return to its original shape and size after being stretched

4. Atrophy: the loss/deterioration of muscle tissue

5. Hypertrophy: gaining of muscle (getting larger/ more muscle cells)

6. Excitability: ability to respond quickly to stimuli

7. Controlled by nerve stimuli

8. Fed by capillaries

Fascia is a connective tissue between and surrounding other tissues such as muscles and bones.

Fascia -> fibrous tissue, adipose tissue and fluid

3 layers of fascia in each individual skeletal muscle:

• Epimysium: outer layer covers muscle

• Perimysium: surrounds fascicles

• Endomysium: surrounds individual muscle fibers

Muscle fibers are formed by smaller structures called myofibrils that give the muscle striated appearance. These are organised in functional units called sarcomeres which contain actin and myosin (proteins) that are important for muscle contraction.

When muscle is trained it gets bigger or experiences hypertrophy due to an increase in myofibrils. When muscle is not used they reduce experiencing atrophy. (vago o malo en la cama)

TENDONS

When layers of fascia continue on beyond the muscle fibers --> form tendons (tough, flexible bands of fibrous connective tissue connecting muscle to bone)

Groups of tendons can be enclosed in tubes of fibrous connective tissue -> tendon sheaths (wrist)

These sheaths contain synovial fluid, which helps to reduce friction as the tendons move back and forth across each other.

Tendons are very strong and transmit the forces generated by muscles to bone, therefore they play an important role in muscle contraction and joint movement.

The fleshy middle section of the muscle is called the muscle belly and this becomes prominent when the muscle contracts.

MUSCLES

Have good nerve and blood supply

Nerves that bring impulses to muscles -> motor neurons (Release neurotransmitters into blood and stimulate muscle to contract and produce force)

Capillaries provide oxygen, nutrients and calcium and remove waste products

ORIGIN AND INSERTION OF MUSCLES

Most muscles cross over one joint and are involved in movement at that joint. Two ends of muscle are attachment points called origin and insertion

Both concepts refer to where they attach to bones.

Origin: the attachment of muscle tendon to a stationary bone (usually more superior)

Insertion: the attachment of a muscle tendon to a movable bone (usually more inferior)

MUSCLES OF THE TRUNK

Large and powerful play important role in stability

MUSCLES OF UPPER EXTREMITIES

Stabilize the pectoral girdle and allow muscles around shoulder generate higher levels of force.

MUSCLES OF LOWER EXTREMITIES

Bear the weight of body and forcefully push off the ground to move the body (walking)