Chapter 11: The Muscular System Flashcards
Muscular System
(Relationship: bones and skeletal muscles)
Voluntary controlled muscles of your body.
Skeletal muscles produce movements by exertion on tendons which in turns pulls bones and other structures (skin).
Muscle cross at least one joint that is attached to articulating bones that form joints.
Origin
Attachment of a muscles tendon to a stationary bone.
Insertion
Attachment of the muscles other tendons to the movable bone.
Belly
Fleshy portion of the muscle between tendons
Actions
Main movement in muscles that occur when muscles contract.
Reverse Muscle Action (RMA)
Certain muscles have this capability.
During specific movements of the body the actions of muscles are reversed. The position of the origin and insertion of the specific muscle are switched.
Lever Systems and Leverage for Movement
Bones act as levers and joints function as fulcrums of these levers.
Lever
A rigid structure that can move around a fixed point.
Falcrum
Symbolized by F inside a triangle.
Fixed point a lever moves around.
Lever System Action
A lever is acted on at 2 different points by 2 different forces:
The effort (E): causes movement
The load (L inside blue square): or resistance, opposes movement
The effort is the force exerted by muscle contraction.
The load is typically the weight of the body part that is moved, or some resistance that the moving body part is trying to overcome.
Mechanical Advantage
A small effort is required to move large loads over a small distance due to the load being closer to the fulcrum and the effort farther from the fulcrum.
Mechanical Disadvantage
A large effort is required to move a small load but at greater speed is due to the load is farther from the fulcrum and the effort is applied closer to the fulcrum.
Lever Categories
Categorized into 3 types according to the positions of the fulcrum, the effort and the load.
1. First Class Levers
2. Second Class Levers
3. Third Class Levers
First Class Lever
(think seesaw)
fulcrum is between the effort and the load. Can produce both mechanical advantages/disadvantages depending on wether the effort or load is closer to the fulcrum.
Second Class Levers
(think wheelbarrow)
The load is between the fulcrum and the effort. Always produce mechanical advantage as the load is always closer to fulcrum than the effort.
This type of arrangement gives up speed and range of motion to produce force. This type creates the most force. This lever is uncommon in the body.
Third Class Levers
(Think a pair of forceps)
Effort is between the fulcrum and the load.
Always produce mechanical disadvantages as the effort is always close to the fulcrum than the load.
This arrangement favors speed and range of motion over force. Most common levers in the body.
Fascicles
Bundles of skeletal muscle fibers within a muscle cells.
Patterns of Facicles
Can form 5 patterns with respect to the tendons
1. Parallel
2. Fusiform (spindle shaped)
3. Circular
4. Triangular
5. Pennate
Parallel Fascicles
Are parallel to longitudinal axis of muslce
Terminate at either end in flat tendons
Have fewer fascicles but have long fibers that extend the length of the muscle giving them a greater range of motion but less power.
(Ie) sternohyoid muscle
Fusiform Facicles
Nearly parallel to longitudinal axis of muscle
Terminates in flat tendons
Muscle tapers towards tendons where diameter is less than at belly.
(ie) digastric muscle