1. CHAPTER 45.3 Muscular System

2. Function = Allows body to move & provides force that pushes substances through out the body Voluntary vs. Involuntary: contractions can be consciously controlled vs. not consciously controlled.

3. Muscle Types Skeletal -responsible for the moving parts of the body. -voluntary muscles (you control). Smooth Muscle -forms muscle layers found in the walls of the stomach, intestines, blood vessels, and other internal organs. -involuntary muscle Cardiac Muscle -makes up the walls of the heart. -involuntary

4. Muscle Structure Muscle fibers are made up of myofibrils. Myofibrils are made up of thick protein filaments called myosin and thin proetin filaments called actin. Myosin and actin give muscle its striated appearance. They form an overlapping pattern.

5. Muscle Contraction -Sarcomere’s are the functional units of muscle contraction. Contain actin and myosin that interact with each other. Muscle Contraction = shorter sarcomere Muscle Relaxation = longer sarcomere Driven by ATP!

7. Muscle Movement of Bones -Skeletal muscles are attached to bones via tendons. Origin vs. Insertion – Point where the muscle attaches to the stationary bone; point where the muscle attaches to the moving bone. Flexors- a muscle that bends a joint. Extensor- a muscle that straightens a joint. Flexors and Extensors work together, one contracts, one relaxes!

8. Muscle Fatigue Muscle fatigue is a result of depletion of ATP A state of continuous contraction occurs (i.e.. Muscle cramps) Lack of oxygen availability is called oxygen debt Oxygen debt leads to an accumulation of lactic acid.. Which produces the soreness you may experience after prolonged exercise.