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Biomechanics > Midterm Study Guide - Muscle Chapter > Flashcards

Midterm Study Guide - Muscle Chapter Flashcards

1
Q

To achieve a given joint motion, do muscles work independently or alone?

A

Muscles work in groups, not independently to achieve a given joint motion, this is an example of aggregate muscle action.
(Slide 72, 100)

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2
Q

What are the different types of fiber arrangements in skeletal muscles (5)?

A

Parallel, Fusiform, Pennate, Convergent, Circular

Slide 73

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3
Q

What are the characteristics of Pennate muscles (3)?

A
  1. Shorter fibers
  2. Arranged obliquely to their tendons (like a feather)
  3. Arrangement increases the cross-sectional area of a muscle (increasing the power/tension)
    (Slide 76)
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4
Q

What are the three types of Pennate muscles?

A

Unipennate, Bipennate, Multipennate

Slide 76

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5
Q

What is muscle “strength”?

A

Maximal force a muscle can generate for a single maximal effort (amount of tension a muscle produces).
(Slide 81)

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6
Q

What is muscle “power”?

A

Work done over a given period of time (muscle contracting in a brief amount of time).
(Slide 81)

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7
Q

What is muscle “torque”?

A

Muscle force causing rotary movement of a body around an axis (turning/twisting force).
(Slide 81)

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8
Q

What are the characteristics of Circular muscles?

A

Concentric fibers adjust an opening (sphincter).

Slide 79

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9
Q

What is the definition of contraction in regard to muscles?

A

Tension developed in a muscle as a result of a stimulus; all are either isometric/isotonic.
(Slide 82)

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10
Q

What can muscle contractions be used for?

A

Cause, control, or prevent joint movement.
1. Initiate/Accelerate movement of a body segment
2. Slow down/Decelerate movement of a body segment
3. Prevent movement of a body segment by external forces
(Slide 82)

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11
Q

What is an isometric contraction, when does it occur, and why?

A
  1. Iso (same) metric (measure/length); Tension developed w/in muscle w/o joint motion (static contraction, no movement) (muscle contracts w/o changing length).
  2. Occurs when tension a muscle develops = force applied to the muscle.
  3. Used to stabilized joints
    (Slide 84)
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12
Q

What is the ‘line of pull’?

A

Direction of movement produced by the contracting muscle, pull of a muscle from its origin to insertion (it can change during joint motion).
(Slide 89)

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13
Q

What is the ‘line of pull’ a function of (3)?

A
  1. Muscle’s attachment
  2. Plant of joint motion
  3. Muscle’s distance from the joint’s axis of rotation
    (Slide 89)
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14
Q

What will happen if the line of pull is altered from its optimal position due to muscle weakness or poor posture?

A

Muscle will be inefficient, work harder, and have strain put upon it. Can lead to muscle/joint injury, muscle weakness, hypertonicity, or trigger points. It also can lead to aberrant sensory input, which may result in muscle imbalance & joint dysfunction.
(Slide 89, 91)

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15
Q

What does ‘range of motion’ depend on?

A

Length of muscle fibers (long fibers = large range of motion, parallel & fusiform muscles)
(Slide 98)

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16
Q

What does ‘power’ depend on?

A

Total # of muscle fibers (many fibers = great power, convergent/unipennate/bipennate/multipennate)
(Slide 98)

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17
Q

What are the properties of muscle force production and movement (4)?

A

Irritibility/Excitability, Contractility, Extensibility, Elasticity
(Slide 98)

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18
Q

What is ‘interdigitation’?

A

Muscle may be innervated by 1+ nerves & particular nerve may innervate 1+ muscles.
(Slide 100)

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19
Q

True/False. Two+ muscles may share a common tendon.

A

TRUE!
i.e. Achielles T - Gastrocnemius & Soleus OR 3 proximal attachements of Biceps brachii
(Slide 100)

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20
Q

What are the 4 roles that muscles may work in?

A 
Prime mover (agonist), Antagonist, Synergist, Stabilizer (fixator)
(Slide 101)
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21
Q

What is the role of a muscle acting as a prime mover (agonist)?

A

Muscles that assume the major responsibility for producing a specific movement
(Slide 101)

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22
Q

What is the role of a muscle acting as a synergist?

A

Muscle which performs/assists the same joint motion as the agonist (2 muscles called synergists if their contraction causes movement in the same direction).
(Slide 103)

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23
Q

What is the role of a muscle acting as a stabilizer (fixator) & what is an example of it?

A

Synergists that act to control motion of the prime mover (agonist). Immobilize the origin of the agonist so that it can act more efficiently. Continuous low-level muscle activity w/isometric/eccentric pull.

i.e. deltoid = agonist of arm abduction (originates on scapula), when it contracts the pectoralis minor/rhomboids/trapezius hold the scapula in place
(Slide 103)

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24
Q

What is muscle ‘irritability/excitability’?

A

Property of muscle being sensitive/responsive to chemical/mechanical/electrical stimuli.
(Slide 99)

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25
Q

What is muscle ‘contractility’?

A

Ability of muscle to contract & develop tension (internal force) against resistance when stimulated
(Slide 99)

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26
Q

What is muscle ‘extensibility’?

A

Ability of muscle to be passively stretched beyond its normal resting length
(Slide 99)

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27
Q

What is muscle ‘elasticity’?

A

Ability of muscle to return to its original length following stretching
(Slide 99)

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28
Q

What is the role of a muscle acting as a antagonist & give an example?

A

Muscles that oppose/reverse the movement by a agonist. When agonist active, antagonist is relaxed allowing the movement of the joint. Help regulate the action of the agonist by partially contracting to provide some resistance or to slow/stop action.

i.e. During running, as knee extends, hamstring relaxes/slowly releases to control momentum
(Slide 101)

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29
Q

What is a lever?

A

Rigid bar that moves on a fixed point (bones of skeleton)

Slide 111

30
Q

What is a Mechanical Advantage (Power Level)?

A

Load is close to fulcrum, effort applied far from fulcrum, small effort applied to relatively long distance (used to move large load over small distance).
Advantage: lift heavy loads!
(Slide 112)

31
Q

What is a musculoskeletal lever?

A

Lever allows a muscle to move a heavier load or to move a load farther/faster than it otherwise could.
(Slide 114)

32
Q

What are the three classes of levers in the body?

A

First, Second, and Third :-)

Slide 114

33
Q

What are second class levers in the body & give an example?

A

Load (resistance) lies btwn the fulcrum & the effort. Great strength, less speed & ROM. Effort applied at 1 end, fulcrum at other end, load in btwn. Rare, but work at mechanical advantage.

i.e. Planter flexion of foot
(Slide 116)

34
Q

In general, skeletal muscle is always attached to _____?

A

Bone

Slide 71

35
Q

In general, skeletal muscle is responsible for & it aids in?

A

Movement of the body & all of its joints & aids fluid & blood movement w/in the body
(Slide 71)

36
Q

Muscle contraction produces ______ that causes _________ ____________.

A

Force (torque), joint movement

Slide 71

37
Q

Besides causing movement, muscle also provide….

A

protection & posture/support

Slide 71

38
Q

There are over _____ skeletal muscles that make up approximately _____% of body weight.

A

600, 40-50%

Slide 71

39
Q

True/False. Pairs of skeletal muscles (215) work in cooperation w/each other to perform opposite actions at the joints which they cross.

A

TRUE!

Slide 71

40
Q

Different shapes and fiber arrangements of muscles affect what (2)?

A
  1. Muscle’s ability to exert force
  2. Range through which a muscle can effectively exert force onto a bone
    (Slide 72)
41
Q

Cross section diameter of a muscle affects what?

A

Muscle’s ability to exert force (greater cross section diameter yields greater force exertion)
(Slide 72)

42
Q

What type of muscles are able to shorten the most and effect the most movement?

A

Longer muscles can shorten through a greater range & are more effective in moving joints through large ranges of motion.
(Slide 72)

43
Q

What are the characteristics of parallel muscle?

A

Fibers arranged parallel to the length of muscle. Produce greater RoM than similar sized muscles w/pennate arrangement.
(Slide 74)

44
Q

What are the characteristics of fusiform muscles (spindle shaped)?

A

Fibers arranged parallel & w/large cross section diameter. Produce greater ROM than similar sized muscles w/pennate arrangement.
(Slide 75)

45
Q

What is an example of a unipennate, bipennate, & multipennate muscle?

A

Extensory digitorum, rectus femoris, deltoid

Slide 77

46
Q

What are the characteristics of convergent muscles?

A

Broad origin, pointed insertion, direction of pull can be varied (versatile).
(Slide 78)

47
Q

What are the types of muscle contraction (tension) in general (4)?

A

Isometric
Isotonic = Concentric & Eccentric
(Slide 83)

48
Q

What is isotonic contraction?

A

Iso = same, tonic = tone/tension
Muscle contraction w/o appreciable change in the force of contraction… maintains tension under a constant load (tension developed w/in muscle for either initiating/controlling movement - dynamic contractions).
(Slide 85)

49
Q

Isotonic contractions are either ______ or _____.

A

Concentric = shortening contraction
Eccentric = lengthening contraction
(Slide 85)

50
Q

What is a concentric contraction & when does it occur & what is it used for?

A

Coming to the center. Muscle develops tension as it shortens.
Occurs when muscle develops enough tension to overcome the resistance being applied to it.
Used to initiate movement against gravity/resistance
(Slide 86)

51
Q

What is a eccentric contraction & what is it used for?

A

Away from the center. Muscle lengthens under tension (tension less than resistance applied to it). Results in controlled joint motion.
Used to decelerate body segment movement.
(Slide 87)

52
Q

Describe the line of pull in terms of the Pectoralis Major and its multiple actions on the humerus.

A

Pectoralis major = primarily a flexor of the humerus, but it also adducts it due to its line of pull in certain arm positions. When arm = abducted, the line of pull moves & the pec. major contributes to abduction of the humerus.
(Slide 91)

53
Q

What is the angle of pull?

A

Angle btwn the line of pull of the muscle & the bone on which it inserts
(Slide 92)

54
Q

When does the angle of pull change on a muscle?

A

W/every degree of joint motion

Slide 92

55
Q

A vertical component of the angle of pull is always _______ to the lever (attachment) and causes _______ movement at the joint axis.

A

Perpendicular, rotational
When angle of pull is 90 the force is 100% rotational.
(Slide 92)

56
Q

A horizontal component of the angle of pull is always _______ to the lever (attachment) and causes _______ movement at the joint axis.

A

Parallel, non-rotational
When angle of pull is 45, rotational & stabilizing forces are equal
(Slide 92)

57
Q

True/False. When a muscle contracts (concentric) it pulls both ends toward the center of the muscle.

A

True, if neither of the bone’s attachments are stabilized, then the muscle contraction pulls both bones toward each other
(Slide 95)

58
Q

True/False. Usually, neither bone’s attachments is more stabile than the other (during concentric contraction).

A

FALSE! Usually, one of the bone’s attachments is more stabilized & the less stabilized bone usually moves toward the more stabilized one.
(Slide 95)

59
Q

What is a open or closed kinetic chain regarding concentric contraction of muscle?

A

Open chain:
During Bicep Curl: Biceps brachii origin (least movable bone) on scapula & insertion (most movable bone) on radius. Moves distal to proximal

Closed chain:
During Pull Up: Radius (least movable bone) is stable & scapula moves. Moves proximal to distal.
(Slide 95, 96)

60
Q

True/False. Any of the muscles in the group can contribute to the action being performed, meaning only ONE may be involved in an injury/dysfunction.

A

FALSE!
Any of the muscles in the group can contribute to the action being performed, meaning that more than one muscle may be involved in an injury/dysfunction.
(Slide 100)

61
Q

True/False. A muscle may cause more than one action either at the same joint or at a different joint depending upon the characteristics of the joints.

A

True!

Slide 100

62
Q

What is a fulcrum?

A

Fixed point of leverage (joints of the body)

Slide 111

63
Q

What is effort?

A

Force applied to move a resistance tension (torque) of the muscles
(Slide 111)

64
Q

What is load?

A

Resistance to be moved (bone, tissue mass, & objects to be moved)
(Slide 111)

65
Q

What is the function of a lever?

A

Convert force to torque, work of contracting muscle to the force of rotating bone
(Slide 111)

66
Q

What are the forces involved w/musculoskeletal levers?

A

Internal & external forces produce torque throughout the body through a system of bony levers. This force is produced by muscle, gravity, & external physical contacts
(Slide 111)

67
Q

What is a mechanical disadvantage lever (speed lever)? Why are they useful?

A

Load is far from fulcrum, effort is applied near the fulcrum, force exerted must be greater than load moved.
Useful because they allow the load to move rapidly through a larger ROM, called speed levers.
(Slide 113)

68
Q

True/False. Small difference in site of a muscle’s insertion can translate into small differences in the amount of force that must be generated to move a given load.

A

FALSE!
Small difference in site of a muscle’s insertion can translate into LARGE differences in the amount of force that must be generated to move a given load.
(Slide 114)

69
Q

What is a first class musculoskeletal lever?

A

Fulcrum lies btwn the effort & the load (resistance), effort applied @ 1 end of lever & load lies on other end w/fulcrum in btwn.
i.e. Atlanto-occipital joints lies btwn post. cervical muscles & weight of forehead & face.
(Slide 115)

70
Q

What is a third class musculoskeletal lever?

A

Effort applied @ point btwn the load & fulcrum. Most levers in body are these! Great speed w/mechanical disadvantage. Allow rapid movement w/little shortening of muscle, produce fast/large movement w/little effort.
i.e. Biceps muscle effort applied to forearm btwn elbow joint & weight of hand & forearm.
(Slide 117)

Biomechanics (5 decks)

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