1. The Muscular System
“myo = muscle”

2. Muscular System There are over 600 skeletal muscles
They make up 40-50% of our body weight
Muscles play a crucial role in communication
No other animal has as complex facial muscles as humans
The smallest muscle in the body is the stapedius and controls the stapes (stirrup bone in the ear)
The largest muscle in the body???
Gluteus maximus!

3. Skeletal Muscle Cells Muscle cells=muscle fibers
Layers of connective tissue group muscles fibers together and give them strength
The epimysium, perimysium, and endomysium, are continuous with each other.
Perimysium holds muscle cells together to form a fascicle.
Fascia is tough connective tissue that covers muscle organ including the epimysium

4. Levels of Organization of a Muscle
Muscle Fascicles Muscle Fiber(cell) Myofibril Thick/Thin filaments

5. Shape, Size and Arrangement
Skeletal muscles are considered organs
Their arrangement and shape are suited to their function
Parallel
Convergent
Pennate
Bipennate
Sphincter
They form small fibers, flat sheets or bulky masses
Long muscles have greater range of motion than short ones
Long and short fibers can contract with equal force

6. Origin and Insertion Points
During contraction one bones usually stays stationary
Skeletal muscles can only contract
Origin is point of attachment that doesn’t move
Insertion is point that does move with contraction

7. Muscle Actions Agonist Antagonist Synergist Fixator muscles
Also called the prime mover
Contracts to produce movement
Antagonist
Performs opposing action of agonist
Relaxes during contraction
Synergist
Contract at same time of agonist
Makes prime movers action more efficient
Fixator muscles
Stabilize joints
Help maintain posture during movement

8. Lever Systems First class levers Second class levers
Work like seesaws
Second class levers
Work like wheelbarrow
Third class levers
Flexing of forearm at elbow
Most common type in body

9. Major Muscles of the Body

10. How Muscles are Named Location Action Direction of fibers Shape
Brachialis(arm) & gluteus(buttocks)
Action
Adductor brevis
Direction of fibers
Rectus abdominis
Shape
Deltoid (triangular)
Number of heads/divisions
Biceps, triceps, quadriceps
Origin and Insertion
Sternocleidomastoid (sternum, clavicle, mastoid)
Relative Size of muscle
Gluteus maximus, medius and minimus

11. Quick Review Connective tissue that covers individual muscle fibers?
Endomysium
Connective tissue that surrounds and connects fascicles?
Perimysium
Covers the muscle as a whole?
Fascia
Which term includes all the rest- thin filament, muscle fiber, myofibril, fascicle?
fascicle
This connects muscle to bone?
Tendon
Name three fiber arrangement?
Parallel, convergent, pennate, bipennate, sphincter
Point of attachment that does not move with contraction?
Origin
Does move with attachment?
Insertion
Muscle that directly performs a movement?
Agonist
Muscles the help maintain balance?
Fixator muscles
What is the most common type of lever system found in the body?
3rd class
Name two ways muscles are named and give examples.
Points of insertions-biceps, Shape deltoid, direction of fibers-rectus abdominis, functions-adductor group, location- medialus, lateralis, intermedius