MUSCULAR+SYSTEM

=//MUSCULAR SYSTEM// = **



Muscles can account for about 40% your body weight.

Muscles can only pull, they cannot, as some people assume, push.

The longest muscle has muscle cells that can be over a foot long.

The smallest muscles are in the middle of the ear;examples are the tensor tympani, and stapedius.

The strongest, pound for pound, are the masseters, the chewing muscles. There are 640 individual names for muscles. Muscles need OXYGEN and FOOD to function properly. The hardest working muscles in the body are the muscles in the eye. It takes 17 muscles in the body to smile. There are muscles in the root of our hair that gives us goose bumps! **

The muscles estructure

**A large strong muscle, such as thoses forming your Quadriceps would have a large number of fibres within each bundle. A smaller muscle used for precision movement, such as those in the hand would contain far fewer fibres per Fasciculi.**

= = ====** Cardiac muscle is only in the heart and makes up the atria and ventricles (heart walls). Like skeletal muscle, cardiac muscle contains striated fibers. Cardiac muscle is called involuntary muscle because conscious thought does not control its contractions. Specialized cardiac muscle cells maintain a consistent heart rate. **==== **
 * Cardiac muscle **

Smooth muscle ** **

Smooth muscle is throughout the body, including in visceral (internal) organs, blood vessels, and glands. Like cardiac muscle, smooth muscle is involuntary. Unlike skeletal and cardiac muscle, smooth muscle is nonstriated (not banded). Smooth muscle, which is extensively within the walls of digestive tract organs, causes peristalsis (wave-like contractions) that aids in food digestion and transport. **

====** Except the heart, any action that the body performs without conscious thought is done by smooth muscle contractions. This includes diverse activities such as constricting (closing) the bronchioles (air passages) of the lungs or pupils of the eye or causing goosebumps in cold conditions. **==== **

Skeletal muscle ** 


 * A skeletal muscle has regular, ordered groups of fascicles, muscle fibers, myofibrils, and myofilaments. Epimysium (thick connective tissue) binds groups of fascicles together. A fascicle has muscle fibers; perimysium (connective tissue) envelops the fascicle. Endomysium (connective tissue) surrounds the muscle fibers.**

==== **A muscle fiber divides into even smaller parts. Within each fiber are strands of myofibrils. These long cylindrical structures appear striped due to strands of tiny myofilaments. Myofilaments have two types of protein: actin (thin myofilaments) and myosin (thick myofilaments).** ==== **

Muscle fibers and exercise ** **

Skeletal muscles have two types of muscle fibers: fast-twitch and slow-twitch. Anaerobic exercise uses fast-twitch fibers. Such exercise includes activities that are fleeting and require brief high-energy expenditure. Weightlifting, sprinting, and push-ups are examples of anaerobic exercise. Because all cells require oxygen to produce energy, anaerobic exercise depletes oxygen reserves in the muscle cells quickly. The result is an oxygen debt. To repay the debt, humans breathe deeply and rapidly, which restores the oxygen level. Anaerobic exercise creates excess lactic acid (a waste product). By increasing oxygen intake, the liver cells can convert the excess lactic acid into glucose, the primary food molecule used in cellular metabolism. **

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