Chap. 2 – The Muscular System

- Muscles that attached to bones Skeletal Muscle - Muscles that attached to bones - Most prevalent - VOLUNTARY – you make a conscious decision to flex - Striated

Smooth Muscle Surround the body's internal organs Contracts more slowly than skeletal muscle but can remain contracted for longer periods of time INVOLUNTARY

Cardiac Muscle Only found in the heart INVOLUNTARY – autonomic nervous system is responsible for making the muscle fibers contract Muscle tissue is striated in appearance like skeletal muscle

To summarize...

The Neuromuscular System Term referring to the link between the muscular system and the nervous system Before a muscle contracts, a message needs to be sent from the brain The neuromuscular junction is the point where the message from the brain meets the muscle

The Neuromuscular Junction

The Motor Unit Muscle twitch: a single nervous impulse and the resulting contraction Motor unit = the motor neuron, it's axon (pathway) and the muscle fibres it stimulates

The All-or-None Principle The principle that states that when a motor unit is stimulated to contract, it will do so to its fullest potential Example: if a motor unit consists of 50 muscle fibres and they are stimulated to contract, either all of the fibres will contract or none of them

Some educational videos... How muscles contract: http://videos.howstuffworks.com/hsw/6100-the-cell- muscle-cells-video.htm Beating heart: http://www.youtube.com/watch?v=AZ4RnmNgEN0&fe ature=related

Worksheet