MUSCULAR

SYSTEMReporters:Romel Leo B. AlojadoFerdinand Leandrei D. Jomilla

Muscles produce movement of, and inside, the body. Muscle tissue is made up of cells called

fibers that have the ability to contract, or shorten, in order to produce a pulling force.

Muscles are also extensible, and are elastic so that they can be stretched and then recoil and resume their normal resting length.

Muscles are also electrically excitable, so that they can be stimulated to contract by a nerve impulse.

VOLUNTARY MUSCLE Muscle that is under the control of the will and is generally

attached to the skeleton. An individual muscle consists of bundles of long muscle fibres, each bounded by a sarcolemma and containing sarcoplasm,sarcoplasmic reticulum. and many nuclei. It is called voluntary muscle because we can control the movement of the muscle.

Sarcolemma - the cell membrane that encloses a muscle cell (muscle fibre).

Sarcoplasm - The cytoplasm of a muscle fibre. Sarcoplasm contains chemicals that are required for muscle contraction, including glycogen, ATP, and phosphocreatine.

Sarcoplasmic reticulum - The specialized endoplasmic reticulum found in the fibres of voluntary and cardiac muscle, which forms a network of membrane-lined cavities surrounding the contractile myofibrils that run through the fibres.

INVOLUNTARY MUSCLE Muscles that are not controllable consciously, and instead

contract due to unconscious impulses sent by the autonomic nervous system or certain specialized cells or hormones. It is called involuntary muscle because we can not control the movement of the muscle and can contract by itself.

Superficial Muscles: Anterior

Superficial Muscles: Posterior

Characteristics of Muscles

Muscle cells are elongated (muscle cell = muscle fiber)Contraction of muscles is due to the movement of microfilamentsAll muscles share some terminology

Prefix myo refers to musclePrefix mys refers to musclePrefix sarco refers to flesh

There are three types of muscles, namely:

Skeletal muscles Smooth muscles Cardiac muscles

SKELETAL MUSCLES

Most are attached by tendons to bones Cells are multinucleate Striated – have visible banding Voluntary – subject to conscious

control Cells are surrounded and bounded by

connective tissue = great force, but tires easily

Skeletal Muscle Characteristics

Skeletal muscles are attached to the bones of the skeleton. There are more than 640 muscles that makes up more than 40 percent of body weight and give the body its shape. Those just below the skin are called superficial while those below the superficial muscles are called deep.

Each muscle attaches to two or more bones by tough cords of connective tissue called tendons. When skeletal muscles contract across joints, they pull bones, producing a range of movements from running to chewing. Instructions for contraction come from the brain and spinal cord.

Skeletal muscle is also known as voluntary muscle because a person can make a conscious decision to move their body, although under normal circumstances general body movements occur without conscious involvement.

Skeletal muscles also maintain body posture, stabilize and strengthen certain joints and generate heat during contraction hot is used to help maintain body temperature at 37 degrees C.

Endomysium – around single muscle fiber

Perimysium – around a fascicle (bundle) of fibers

Connective Tissue Wrappings ofSkeletal Muscle

Connective Tissue Wrappings ofSkeletal Muscle Epimysium –

covers the entire skeletal muscle

Fascia – on the outside of the epimysium

Epimysium blends into a connective tissue attachment

Tendon – cord-like structure Aponeuroses – sheet-like structure Sites of muscle attachment Bones Cartilages Connective tissue coverings

Skeletal Muscle Attachments

THE SKELETAL MUSCLE:

SMOOTH MUSCLES

Smooth muscles are part of the wall of many internal organs, including the stomach, and the small and large intestines, where they aid in moving food through the digestive tract. They also make up the wall of blood vessels, controlling the flow of blood within the circulatory system.

Smooth muscles are also found lining the interior of the uterus, which help expel the baby through the vagina during childbirth. The cells make up the smooth muscle tissue are spindle-shaped, contain only one nucleus, and do not show striations. The contraction of smooth muscles cannot usually be controlled; smooth muscles are therefore, involuntary muscles.

However, they cannot perform their role without nerve impulses directed by the nervous system. The nervous stimulation travels along neighboring smooth muscle cells via the gap junctions between cells.

THE SMOOTH MUSCLE:

CARDIAC MUSCLES

Cardiac muscles, as the name implies, are found only in the heart. When cardiac muscles contract, the blood contained in the heart chambers is squeezed out. The pumping motion pushes blood throughout the circulatory system.

The cells of the cardiac muscle tissue, like the skeletal muscle, are striated but only smaller. Similar to smooth muscle cells, they contain one nucleus, or two in some. The cardiac muscles contract and relax involuntarily, as directed by the nervous system. The contractions continue tirelessly and rhythmically.

THE CARDIAC MUSCLE:

The End