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Muscular System
CHAPTER 45.3
Muscular System
 Major Function = Allows body to move & provides
force that pushes substances through out the body.
 Voluntary vs. Involuntary:
conscious vs. unconscious
Muscle Types
Skeletal
-responsible for the moving parts of the body.
-voluntary muscles
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
Muscle Structure
Organizational Structure:
1. muscle
2. bundle of muscle fibers
3. muscle fiber (cell)
4. myofibril
5. sarcomere
6. proteins: actin (thin filament)
myosin (thick filament)
-gives a striated appearance.
Muscle Structure
Muscle Contraction
-Sarcomere’s are the functional units of muscle
contraction. Contain the proteins actin and myosin
that interact with each other.
Muscle Contraction = shorter sarcomere
Muscle Relaxation = longer sarcomere
Driven by ATP!
Muscle Contraction Clip
Muscle Movement of Bones
-Skeletal muscles are attached to bones via tendons.
Origin- point where the muscle attaches to the stationary
bone.
Insertion- 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!
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.