Midterm Study Guide - Muscle Chapter Flashcards
To achieve a given joint motion, do muscles work independently or alone?
Muscles work in groups, not independently to achieve a given joint motion, this is an example of aggregate muscle action.
(Slide 72, 100)
What are the different types of fiber arrangements in skeletal muscles (5)?
Parallel, Fusiform, Pennate, Convergent, Circular
Slide 73
What are the characteristics of Pennate muscles (3)?
- Shorter fibers
- Arranged obliquely to their tendons (like a feather)
- Arrangement increases the cross-sectional area of a muscle (increasing the power/tension)
(Slide 76)
What are the three types of Pennate muscles?
Unipennate, Bipennate, Multipennate
Slide 76
What is muscle “strength”?
Maximal force a muscle can generate for a single maximal effort (amount of tension a muscle produces).
(Slide 81)
What is muscle “power”?
Work done over a given period of time (muscle contracting in a brief amount of time).
(Slide 81)
What is muscle “torque”?
Muscle force causing rotary movement of a body around an axis (turning/twisting force).
(Slide 81)
What are the characteristics of Circular muscles?
Concentric fibers adjust an opening (sphincter).
Slide 79
What is the definition of contraction in regard to muscles?
Tension developed in a muscle as a result of a stimulus; all are either isometric/isotonic.
(Slide 82)
What can muscle contractions be used for?
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)
What is an isometric contraction, when does it occur, and why?
- Iso (same) metric (measure/length); Tension developed w/in muscle w/o joint motion (static contraction, no movement) (muscle contracts w/o changing length).
- Occurs when tension a muscle develops = force applied to the muscle.
- Used to stabilized joints
(Slide 84)
What is the ‘line of pull’?
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)
What is the ‘line of pull’ a function of (3)?
- Muscle’s attachment
- Plant of joint motion
- Muscle’s distance from the joint’s axis of rotation
(Slide 89)
What will happen if the line of pull is altered from its optimal position due to muscle weakness or poor posture?
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)
What does ‘range of motion’ depend on?
Length of muscle fibers (long fibers = large range of motion, parallel & fusiform muscles)
(Slide 98)
What does ‘power’ depend on?
Total # of muscle fibers (many fibers = great power, convergent/unipennate/bipennate/multipennate)
(Slide 98)
What are the properties of muscle force production and movement (4)?
Irritibility/Excitability, Contractility, Extensibility, Elasticity
(Slide 98)
What is ‘interdigitation’?
Muscle may be innervated by 1+ nerves & particular nerve may innervate 1+ muscles.
(Slide 100)
True/False. Two+ muscles may share a common tendon.
TRUE!
i.e. Achielles T - Gastrocnemius & Soleus OR 3 proximal attachements of Biceps brachii
(Slide 100)
What are the 4 roles that muscles may work in?
Prime mover (agonist), Antagonist, Synergist, Stabilizer (fixator) (Slide 101)
What is the role of a muscle acting as a prime mover (agonist)?
Muscles that assume the major responsibility for producing a specific movement
(Slide 101)
What is the role of a muscle acting as a synergist?
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)
What is the role of a muscle acting as a stabilizer (fixator) & what is an example of it?
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)
What is muscle ‘irritability/excitability’?
Property of muscle being sensitive/responsive to chemical/mechanical/electrical stimuli.
(Slide 99)
What is muscle ‘contractility’?
Ability of muscle to contract & develop tension (internal force) against resistance when stimulated
(Slide 99)
What is muscle ‘extensibility’?
Ability of muscle to be passively stretched beyond its normal resting length
(Slide 99)
What is muscle ‘elasticity’?
Ability of muscle to return to its original length following stretching
(Slide 99)
What is the role of a muscle acting as a antagonist & give an example?
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)
What is a lever?
Rigid bar that moves on a fixed point (bones of skeleton)
Slide 111
What is a Mechanical Advantage (Power Level)?
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)
What is a musculoskeletal lever?
Lever allows a muscle to move a heavier load or to move a load farther/faster than it otherwise could.
(Slide 114)
What are the three classes of levers in the body?
First, Second, and Third :-)
Slide 114
What are second class levers in the body & give an example?
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)
In general, skeletal muscle is always attached to _____?
Bone
Slide 71
In general, skeletal muscle is responsible for & it aids in?
Movement of the body & all of its joints & aids fluid & blood movement w/in the body
(Slide 71)
Muscle contraction produces ______ that causes _________ ____________.
Force (torque), joint movement
Slide 71
Besides causing movement, muscle also provide….
protection & posture/support
Slide 71
There are over _____ skeletal muscles that make up approximately _____% of body weight.
600, 40-50%
Slide 71
True/False. Pairs of skeletal muscles (215) work in cooperation w/each other to perform opposite actions at the joints which they cross.
TRUE!
Slide 71
Different shapes and fiber arrangements of muscles affect what (2)?
- Muscle’s ability to exert force
- Range through which a muscle can effectively exert force onto a bone
(Slide 72)
Cross section diameter of a muscle affects what?
Muscle’s ability to exert force (greater cross section diameter yields greater force exertion)
(Slide 72)
What type of muscles are able to shorten the most and effect the most movement?
Longer muscles can shorten through a greater range & are more effective in moving joints through large ranges of motion.
(Slide 72)
What are the characteristics of parallel muscle?
Fibers arranged parallel to the length of muscle. Produce greater RoM than similar sized muscles w/pennate arrangement.
(Slide 74)
What are the characteristics of fusiform muscles (spindle shaped)?
Fibers arranged parallel & w/large cross section diameter. Produce greater ROM than similar sized muscles w/pennate arrangement.
(Slide 75)
What is an example of a unipennate, bipennate, & multipennate muscle?
Extensory digitorum, rectus femoris, deltoid
Slide 77
What are the characteristics of convergent muscles?
Broad origin, pointed insertion, direction of pull can be varied (versatile).
(Slide 78)
What are the types of muscle contraction (tension) in general (4)?
Isometric
Isotonic = Concentric & Eccentric
(Slide 83)
What is isotonic contraction?
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)
Isotonic contractions are either ______ or _____.
Concentric = shortening contraction
Eccentric = lengthening contraction
(Slide 85)
What is a concentric contraction & when does it occur & what is it used for?
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)
What is a eccentric contraction & what is it used for?
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)
Describe the line of pull in terms of the Pectoralis Major and its multiple actions on the humerus.
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)
What is the angle of pull?
Angle btwn the line of pull of the muscle & the bone on which it inserts
(Slide 92)
When does the angle of pull change on a muscle?
W/every degree of joint motion
Slide 92
A vertical component of the angle of pull is always _______ to the lever (attachment) and causes _______ movement at the joint axis.
Perpendicular, rotational
When angle of pull is 90 the force is 100% rotational.
(Slide 92)
A horizontal component of the angle of pull is always _______ to the lever (attachment) and causes _______ movement at the joint axis.
Parallel, non-rotational
When angle of pull is 45, rotational & stabilizing forces are equal
(Slide 92)
True/False. When a muscle contracts (concentric) it pulls both ends toward the center of the muscle.
True, if neither of the bone’s attachments are stabilized, then the muscle contraction pulls both bones toward each other
(Slide 95)
True/False. Usually, neither bone’s attachments is more stabile than the other (during concentric contraction).
FALSE! Usually, one of the bone’s attachments is more stabilized & the less stabilized bone usually moves toward the more stabilized one.
(Slide 95)
What is a open or closed kinetic chain regarding concentric contraction of muscle?
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)
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.
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)
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.
True!
Slide 100
What is a fulcrum?
Fixed point of leverage (joints of the body)
Slide 111
What is effort?
Force applied to move a resistance tension (torque) of the muscles
(Slide 111)
What is load?
Resistance to be moved (bone, tissue mass, & objects to be moved)
(Slide 111)
What is the function of a lever?
Convert force to torque, work of contracting muscle to the force of rotating bone
(Slide 111)
What are the forces involved w/musculoskeletal levers?
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)
What is a mechanical disadvantage lever (speed lever)? Why are they useful?
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)
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.
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)
What is a first class musculoskeletal lever?
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)
What is a third class musculoskeletal lever?
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)
