Muscle Structure & Function

Question 1

epimysium

Answer 1

connective tissue that surrounds the muscle

Question 2

perimysium

Answer 2

connective tissue that surrounds the fasicles

Question 3

muscle fiber

Answer 3

long, muscle cells. Myofibers

Question 4

fasicle

Answer 4

groups of muscle fibers

Question 5

sarcolemma

Answer 5

membrane covering muscle fibers

Question 6

endomysium

Answer 6

delicate CT between muscle fibers

Question 7

myofibril

Answer 7

very fine contractile fibers made up of thick (myosin) and thin (actin) filaments

Question 8

myofilaments

Answer 8

threadlike structures occurring in bundles in the myofibrils of striated muscle fibers

Question 9

parallel elastic component

Answer 9

• passive (non-contractive, inert) structures
• lengthen or shorten as muscle lengthens or shortens (acts in parallel with muscle fibers)
• undergoes lengthening during stretching
• slacked position when muscles are at rest
• buckle/crimp when muscle shortens beyond resting position

Question 10

Series elastic component

Answer 10

contractile component & tendon is under tension when the muscle contracts

Question 11

active tension

Answer 11

• tension developed by contractile elements

- movement of actin & myosin

Question 12

active tension depends on

Answer 12

• frequency of firing muscle units
• # of MU
• # of fibers
• # of cross bridges
• fiber size
• muscle cross section area

Question 13

_____ cross sections generate more force than ____ cross sections

Answer 13

BIGGER; SMALLER

Question 14

Muscle is strongest at the positions where there are the _____ cross sections

Answer 14

most

Question 15

Passive tension

Answer 15

• tension is developed in the inert components (CT)

- may or may not add to active tension

Question 16

Total tension =

Answer 16

active (contractile) + passive (inert)

Question 17

greatest tension occurs at _______ (length)

Answer 17

1.2 …..resting length

Question 18

active insufficiency

Answer 18

• decreases the ability of a muscle to produce active tension
• excessively lengthens or shortens
• —- allows to muscle test for 2 joint muscles

(when longer or shorter than optimal position the muscle cannot receive enough force)

Question 19

isometric

Answer 19

constant length

Question 20

concentric

Answer 20

shortening length

Question 21

eccentric

Answer 21

lengthening length

Question 22

potential force production (muscle lengths)

Answer 22

eccentric > isometric > concentric

Question 23

Muscles create better force _____ b/c we are able to control the motion

Answer 23

eccentrically

Question 24

muscle torque = external torque

Answer 24

isometric

Question 25

muscular torque > external torque

Answer 25

concentric

Question 26

muscular torque < external torque

Answer 26

eccentric

Question 27

types of muscle action

Answer 27

- isotonic | - isokinetic

Question 28

isotonic

Answer 28

constant tension | non-physiologic

Question 29

isokinetic

Answer 29

constant velocity | accommodating resistance

Question 30

effect of velocity on force production: concentric

Answer 30

as the speed of shortening increases, the tension decreases

Question 31

effect of velocity on force production: eccentric

Answer 31

as the speed of lengthening increases, the tension increases (as you lengthen muscle quickly the more force can be generated)

Question 32

effect of velocity on force production: isometric

Answer 32

none

Question 33

torque = load

Answer 33

isometric

Question 34

torque > load

Answer 34

concentric

Question 35

torque < load

Answer 35

eccentric

Question 36

_____ conduction velocities are recruited 1st

Answer 36

slow

Question 37

______ the number of MU fibers, the faster to maximum tension

Answer 37

(the greater the size, the greater the tension)

Question 38

the _____ the size of muscle fibers the greater the tension

Answer 38

greater

Question 39

the higher the MU firing frequency the ______ the tension

Answer 39

greater

Question 40

the ________ to resting length, the greater the tension

Answer 40

closer

Question 41

the _____ # of cross bridges, the greater the tension

Answer 41

greater

Question 42

fiber orientations effect on the magnitude of active muscle tension

Answer 42

pennate muscles tension is greater than strap muscles tension

Question 43

contraction type & magnitude of active muscle tension

Answer 43

eccentric > isometric > concentric

Question 44

contraction type: increased speed & decreased tension

Answer 44

concentric

Question 45

contraction type: increased speed & increased tension

Answer 45

eccentric

Question 46

agonist

Answer 46

prime mover - responsible for desired action

Question 47

antagonist

Answer 47

muscle that counteracts desired action (reciprocal inhibition)

Question 48

synergists

Answer 48

muscle that assist the agonist in performing the desired action

Question 49

cocontraction

Answer 49

contraction of agonist & antagonist to provide joint stability

Question 50

spurt muscle

Answer 50

- PROXIMAL attachment is FAR from joint axis of rotation - DISTAL attachment is CLOSE to joint AOR - relatively large ROTARY component (mobility)

Question 51

example of spurt muscle

Answer 51

hamstrings, biceps brachii

Question 52

shunt muscle

Answer 52

- PROXIMAL attachment is CLOSE to joint axis of rotation - DISTAL attachment is FAR from joint AOR - relatively large TRANSLATORY component (stability)

Question 53

example of shunt muscle

Answer 53

brachioradialis

Question 54

muscle type with a rotary component ( & purpose of component)

Answer 54

spurt muscle | purpose = mobility

Question 55

muscle type with a translatory component (& purpose of component)

Answer 55

shunt muscle | purpose = stability

Question 56

Passive insufficiency

Answer 56

- inactive, antagonist muscle is of sufficient length to permit full ROM at joints crossed by the muscle - this elongates muscles to reach a limit where they don't stretch anymore (flex wrist vs flex wrist in a fist)

Question 57

tenodesis

Answer 57

tendon action - passive tendon may produce movements of joints when muscle is elongated over 2 or more joints - EXAMPLE wrist extension & flexion: causes passive finger flexion

Question 58

GTOs

Answer 58

golgi tendon organs - in tendons near muscultendinous function - sensitive to tension - excessive tension = muscle inhibition

Question 59

muscle spindles

Answer 59

sensitive to muscle length & velocity of lengthening - quick stretch of muscle causes muscle contraction (doctor hits you with reflex hammer on knee -- tendon tap)

Question 60

effects of immobilization on muscle function

Answer 60

- decrease # of sarcomeres & increase in sarcomere length which causes a displaced length tension curve - thickening & increase CT - increase collagen - muscle atrophy

Question 61

effects of aging on muscle function

Answer 61

- increase CT causes an increase in muscle stiffness | - resistance training decreases deleterious effects (hypertrophy)