350: Exam 2a (PART 1/5)

skeletal muscles

• Responsible for movement

  • Contractions produce force that cause/limit joint movement 

• Also provide: protection, stability of joints, posture and support, and total body heat 

• Aggregate muscle action

skeletal muscles has over

600 muscles which makes up 40-50% body weight 

• 215 pairs work in cooperation to perform opposite actions at joints

  • Antagonist pairs

muscles work in _______ to achieve desired motion

groups

difference of muscle shape and fiber arrangement affect

muscle’s ability to exert force & effective range of force exertion on bones

greater cross-section diameter means

greater force

in relation to the ability to shorten, longer muscles

have greater range

how many types of fiber arrangement (includes names)

two; parallel and pennate

parallel

fibers arranged parallel to length of muscle & produce greater range of movement

shapes of parallel fiber arrangements are

flat, fusiform, strap, radiate, sphincter, or circular

pennate

• shorter fibers arranged obliquely to tendon & increases cross-sectional area which means greater power/force

pennate are categorized by arrangement between

fibbers and tendon: unipennate, bipennate, and multipennate

muscle architecture

physiological cross-sectional area (PCSA)

longitudinal/parallel

• small PCSA

• small force

• more shortening

bipennate

• big PCSA

• big force

• less shortening

four properties of muscle tissue

• irritability/excitability

• contractility

• extensibility

• elasticity

irritability/excitability

sensitive to chemical, electrical, or mechanical stimuli

contractility

• ability to contract and develop force

extensibility

ability to passively stretch beyond resting length

elasticity

 ability to deform and return to resting length 

intrinsic

•  muscles within or belonging solely to body part upon which they act 

extrinsic

muscles that originate outside of body part upon which they act

action

specific movement of joint during concentric contraction of muscle

innervation

segment of nervous system responsible for stimulating specific muscle fibers 

amplitude

• Muscle - range of fiber length between maximal and minimal lengthening 

• Nervous - size of neural signal 

gaster

belly or body; Central portion of muscle that increases in diameter as muscle contracts 

tendon

 fibrous connective tissue, cordlike appearance, and connects muscle to bone

aponeurosis

• dense fibrous connective tissue, sheet or ribbonlike, resembles a flattened tendon, and bind muscles together or connect muscle to bone 

fascia

•  sheet or band of fibrous connective tissue + envelopes, separates, or binds parts of the body together

fascia includes

• Retinaculum which retain tendons close to the body 

origin

 proximal attachment or part that attaches closest to the midline or center of body

insertion

 distal attachment or part that attaches farthest from the midline or center of body 

muscle terminology include

• intrinsic

• extrinsic

• action

• innervation

• amplitude

• gaster

• tendon

• aponeurosis

• fascia

• origin'

• insertion

muscle actions are

• contractions

• passive movement

• isokinetic

• specific roles

• actual actions depends on several factors

• different methods

contractions

• Development of tension due to a stimulus 

contractions are used to

• cause, control, or prevent joint movement

  • to speed up a body segment

  • to slow down a body segment

  • prevent movement of the body segment

all contractions are

isometric or isotonic

isometric

static, active tension, no change in joint angl

isotonic

• dynamic, change in active tension development results in joint angle shortening, concentric , eccentric

concentric

muscle shortening

eccentric

muscle lengthening

passive movement

• Movement can occur without a muscle contraction 

passive movement must be

caused by an external force (person, object, gravity)

isokinetic

dynamic muscle contraction that has controlled speed

during isokinetic muscle action, velocity of movement is

constant

• Joint angular velocity is constant (deg/s), thus muscle shortening or lengthening is constant 

during isokinetic muscle action, muscle contraction is

sustained throughout movement

isokinetic has specific systems known as

biodex and kincom

specific roles are

• agonist

• antagonist

• stabilizers

• synergists

• neutralizers

• force couple

agonist

prime mover (can act concentrically or eccentrically)

antagonist

works in opposition to prime mover

stabilizers

contract to fixate or stabilize specific area

synergists

assist action of agonist

Two types of synergists are

helping synergists and true synergists

helping synergist

•  help move in desired motion and simultaneously prevent undesired motion

true synergist

• prevent undesired joint action and do not affect agonist action 

neutralizers

counteract action of another muscle

force couple

•  two or more forces pulling in different directions on an object & causes object to rotate about its axis 

actual actions depends on these following factors

• Motor units activated

• Joint position at time of contraction

• Planes of motion allowed in joint 

• Axis of rotation possible in joint 

• Muscle length

• Relative contraction or relaxation of other muscles acting on the joint 

different methods of muscle action include

• Anatomical lines of pull 

• Anatomical dissection 

• Palpation 

• Models

• Electromyography (EMG) of muscle associated with an action 

• Electrical stimulation (STIM)