Chapter 11 Lecture Muscles Flashcards
Learn names and locations of muscles
The muscular system
Consists only of skeletal muscles
Muscle organization dramatically affects power, range, and speed of movement
Muscles are classified based on patterns of fascicle arrangement
Parallel muscles
Convergent muscles
Pennate muscles
Circular muscles
Parallel muscles
Fascicles are parallel to long axis of muscle
Some are flat
Cylindrical muscles have a central body (belly)
Example: biceps brachii
Tension developed during a contraction depends on total number of myofibrils
Convergent muscles
Muscle fibers spread out like a fan and converge on an attachment site
Example: pectoralis muscles
Muscle may pull on
Tendon
Aponeurosis
Raphe (slender band of collagen fibers)
Fibers pull in different directions, depending on activity
Pennate muscles
Unipennate
All fascicles on same side of tendon
Example: extensor digitorum
Bipennate
Fascicles on both sides of a central tendon
Example: rectus femoris
Multipennate
Tendon branches within muscle
Example: deltoid
Circular muscles (sphincters)
Act as valves in digestive and urinary tracts
Surround body openings and hollow organs
Contraction makes diameter of opening smaller
Example: orbicularis oris of the mouth
Almost all skeletal muscles attach to bones
Site of connection to a bone affects force, speed, and range of movemen
Each bone acts as a lever (a rigid, moving structure)
Moves on a fixed point (fulcrum) when muscles provide applied force to overcome the load
Each joint is a fulcrum
Levers can change
Direction of applied force (AF)
Distance and speed produced by AF
Effective strength of AF
Three classes of levers
Based on relative positions of applied force, fulcrum, and load
First-class lever
Second-class lever
Third-class lever
First-class lever
Fulcrum lies between applied force and load
Like a pry bar or crowbar
Example: extension of the neck and lifting the head
Second-class lever
Load lies between applied force and fulcrum
Like a wheelbarrow
Small force moves a large weight
Example: ankle extension (plantar flexion) by calf muscles
Third-class lever
Applied force is between load and fulcrum
Like a pair of tongs
Most common lever in the body
Maximizes speed and distance traveled at expense of effective force
Origins and insertions
Fixed point of attachment of a muscle to bone is the origin
Movable point of attachment is the insertion
Origin is usually proximal to insertion
Muscle interactions
Muscles work in groups to maximize efficiency
Smaller muscles reach maximum tension first, followed by larger, primary muscles
Four terms refer to how muscles work together
Agonist
Antagonist
Synergist
Fixator
