Muscular+System

Structure/Function
The **muscular system**is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture, and circulates blood throughout the body. The muscular system in vertebrates is controlled through the nervous system, although some muscles (such as the cardiac muscle) can be completely autonomous. The muscles are connected to bones via tendons. 

There are three distinct types of muscles
 * skeletal muscles
 * cardiac heart muscles
 * smooth (non-striated) muscles.

=
Perform a coordinated contraction by shortening each sarcomere. The best proposed model for understanding contraction is the sliding filament model of muscle contraction. There are approximately 639 skeletal muscles in the human body===== The gluteus maximus or buttock muscle is the biggest of the 639 named muscles in the human body and the Erector Pili Muscle is the smallest. Confused by others simply because legs weigh more there are in fact mmor muscles in the arms.

Cardiac muscle
Heart muscles are distinct from skeletal muscles because the muscle fibers are laterally connected to each other. Furthermore, just as with smooth muscles, they are not controlling themselves. Heart muscles are controlled by the sinus node influenced by the autonomic nervous system.

Smooth muscle
Main article: Smooth muscle Smooth muscles are controlled directly by the autonomic nervous system and are involuntary, meaning that they are incapable of being moved by conscious thought. Functions such as heart beat and lungs (which are capable of being willingly controlled, be it to a limited extent) are involuntary muscles but are not smooth muscles

= Enzymes/ Hormones =
 * Acetylcholine**, (a neurotransmitter) is released from the axon terminal of the nerve cell when an action potential reaches the microscopic junction, called a synapse. A group of chemical messengers cross the synapse and stimulate the formation of electrical changes, which are produced in the muscle cell when the acetylcholine binds to receptors on its surface.

If there is a problem at the neuromuscular junction, a very prolonged contraction may occur, **tetanus**. Also, a loss of function at the junction can produce **paralysis**.

Regulation
If your body gets too cold, a series of actions are taken to warm your body. Sensors throughout your body can recognize when the temperature drops and might trigger your muscular system to start shivering. The constant contractions of your muscles allow heat to be generated.

Communication
Sensors throughout your nervous system can recognize when the temperature drops and might trigger your muscular system to start shivering. Your nervous and endocrine systems may also contract the blood vessels of your circulatory system to keep blood in the core of your body and not the extremities

Review
How many muscles in the human body ? What connects the muscles to the bone? What is the largest muscle? What is the smallest muscle? Which has more muscles? the arms or legs?