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DPT 702: Biomechanics > Week 3 Pt.1: Test 1 > Flashcards

Week 3 Pt.1: Test 1 Flashcards

1
Q

Stable posture is a result of what

A

Balance of Competing forces

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2
Q

Movement results from

A

Unbalanced competing forces

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3
Q

Skeletal muscles adapt to what

A

Immediate and long term external forces that can destabilize the body

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4
Q

Describe the force range of skeletal muscles

A

Wide range

Fine motor to large lifting

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5
Q

Skeletal muscles respond to what

A

Both external environment to internal control mechanisms (I.e. nervous system)

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6
Q

Each muscle fiber is an individual …

A

Multinucleated cell

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7
Q

What is responsible for contraction of a whole muscle

A

Contraction at the muscle fiber level

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8
Q

Muscle shortening occurs because of shortening of what

A

Sarcomere

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9
Q

Describe the length of muscle fibers

A

Varying length

Can be tendon to tendon or much shorter

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10
Q

What contains many myofibrils that include tiny cylinders consisting of bundles of myofilaments

A

Cytoplasm or sarcoplasm

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11
Q

What is responsible for holding the components of the cell, storing the molecules for cellular processes, and responsible for giving the cells its shape

A

Sarcoplasm

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12
Q

Specialized membrane that surrounds striated muscle fiber cells; how calcium enters and leaves cells

A

Sarcolenna

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13
Q

What is the endomysium? External to? Partially attached to? Helps to…?

A

Thin layer of connective tissue that surrounds individual muscle fiber

Immediately external to sarcolemma

Partially attached to perimysium

Help transfer actin myosin contractile force

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14
Q

What is perimysium

A

Sheath of connective tissue surrounding bundle of muscle fibers

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15
Q

Contractile proteins of muscle

A

Actin

Myosin

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16
Q

Describe the noncontractile muscle structural proteins

A

Cytoskeleton with muscle fibers

Supportive structures between fibers

Contract but no role for force transmission

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17
Q

Titindoes provides what

A

Passive tension within muscle fiber

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18
Q

Desmin does what

A

Stabilizes alignment of adjacent sarcomeres

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19
Q

Describe fusiform fibers

A

Run parallel to one another and central tendon

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20
Q

Fusiform designed for what

A

Mobility and low force over long range

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21
Q

Pennate fibers run how

A

Approach central tendon obliquely

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22
Q

Describe pennate fibers

A

Large number of fibers
Generate larger forces
Most muscles fall in this group
Unipennate, Bipennate, and multipennate types

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23
Q

How does muscle architecture impact amount of force that can be created

A

Physiological cross sectional area and pen nation angle

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24
Q

Describe the purpose of understanding physiological cross sectional area

A

Determines amount of active proteins available to generate force

Max force potential proportional to CSA

I.e. thicker muscles have more force that thinner

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25
Describe pennation angle
Fibers run at different angles CSA needs to be perpendicular to fiber direction Angle of orientation between fibers and tendons
26
What is the difference between alignment in series or in parallel
Parallel = all components connected across each other (bigger muscle) Series = all components connected end to end forming a single path (longer)
27
what are series elastic components
tissues attached en dot end with active proteins i.e. tendon, titan
28
what are parallel elastic components? Examples?
tissues that lie parallel with active proteins i.e. epi, peri, endomysium
29
what is elongated when you stretch the whole muscle
elongates both parallel and series components
30
what is the critical length
all slack tissue much be brought to this initial level of tension
31
what happens past the point of critical length
tension increases until muscle reaches high level of stiffness and fails
32
role of passive tension within stretched muscles
can stabilize or assist movement
33
what does it mean that muscle is viscoelastic
time changes its behavior quick stretch elicits (increased velocity) increases its stiffness
34
elasticity is a dampening mechanism that can help
protect a muscle
35
how can passive tension affect force production
stretched muscle has elasticity and temporarily stores some of that energy (i.e. a spring) releasing that stored energy can assist in force production
36
what are two components of plyometric exercise
elasticity and viscoelasticity muscles are loaded by eccentric action followed immediately by concentric action to reach optimum force increasing stress load increases intensity
37
the eccentric prestretch phase of a plyometric activity does what (stretches what)?
stretches muscle spindle of the muscle tendon unit and noncontractile tissue within muscle (SEC and PEC components)
38
what does the term amortization describe
time from cessation of eccentric prestretch to the onset of concentric muscle action "time to rebound"
39
what happens if amortization phase is delayed? What isn’t activated?
stored energy lost as heat stretch reflex not activated resultant positive work of concentric contraction not as effective
40
what is the ultimate force generator in the muscle
sarcomere
41
what does the dark band of a muscle fiber represent
A band thick myosin
42
what does the light band of the muscle fiber represent
I bands actin (thin)
43
describe actin and myosin in resting muscle
slightly overlapping
44
describe the sliding filament hypothesis
active force generated when actin filaments slide past myosin pulling Z discs within a sarcomere (narrows H band) if sarcomere shortens, muscle shortens H band = area of only myosin Z discs = end of sarcomeres
45
do active proteins themselves shorten? Describe
no myosin heads attach to actin filament and form cross bridge amount of force in given sarcomere depends on simultaneously formed cross bridges force also depends on length at any moment (alters amount of potential overlap)
46
describe the results of summation of active and passive tension
all force is generated actively passive tension begins to contribute when muscle is stretched beyond resting length passive tension then accounts for must of the force as the muscle is stretched further (i.e. length tension curve)
47
describe the relationship between load and velocity for eccentric and concentric contraction
eccentric = increase load, increase contraction speed concentric = increase load, decrease contraction speed
48
what are isokinetics
torque joint angle velocity relationship
49
what are alpha motor neurons
lower motor neurons whose cell bodies are found in the anterior horn of the spinal cord ' axons travel down body to innervate skeletal muscle to cause contraction
50
what is a motor unit
a single motor alpha neuron with its entire family of muscle fibers
51
what are excitation sources
cortical descending neurons, spinal interneurons, and afferent (sensory neurons)
52
what is rate coding
rate of sequential activation of motor units?
53
what do alpha motor neurons innervate
extra fusal fibers not intrafusal fibers
54
what is an action potential and where/how does it travel
sum of all competing inhibitory and excitatory inputs at critical voltage signal is propagated down the icon to the motor endplate at the neuromuscular junction twitch occurs
55
smaller motor units control what
less force and more fine motor control low innervation ratio
56
larger motor units control what
larger forces high innervation ratio present
57
describe slow oxidative motor units
slower contractile characteristics little loss of force during sustained activation (remain more constant; endurance)
58
describe fast glycol motor units
larger motor neuron units recruited after the slow oxidative units when large forces are required
59
describe fast oxidative glycolytic fibers
in between slow oxidative and fast glycolytic
60
what is unfused tetanus
summated mechanical twitches
61
what is fused tetanus
as time interval shortens between action potentials greater force is generated and the twitches fuse into a stable muscle force
62
what two things operate in the rise of muscle force and are highly specific to demand
rate coding and recruitment
63
do concentric or eccentric contractions require more motor units
at the same level of force, eccentric contractions require less units B/c more cross bridges are occurring
64
what is muscle fatigue
exercise induced decline in Max voluntary muscle force despite max effort basis of neuromuscular overload and adaptation necessary for training reversible with normal rest
65
compare fatigue between men and women
women are less fatiguable than men for concentric/isometric when intensity is the same (more type I slow twitch)
66
describe the fatigue difference between older and younger individuals
older = less fatiguable with isometrics, but more fatiguable with concentrics and fast velocities
67
does eccentric or concentric contractions create more muscle fatigue
at same load/velocity eccentric produces less muscle fatigue BUT repeated eccentric training can lead to delayed onset muscle soreness that peaks at 24-72 hours (caused by damage to sarcomeres and cytoskeleton)
68
strength training can cause the greatest change in what type of fibers
fast twitch II
69
why might an individual experience gains in strength within the first few days of starting a resistance training program
adaptation of nervous system increased activity in brain cortex, supraspinal drive, motor neuron excitability, greater discharge of Motor units, and less neural inhibition
70
describe the physiological changes that take place during muscle hypertrophy
increased protein synthesis within muscle fibers increased physiological cross sectional area of whole muscle sarcomeres added in parallel serial addition of sarcomeres increase of speed in contraction and elongation limited evidence of hyperplasia (added number of fibers/cells)
71
describe the changes in muscle with reduced use
3-6% atrophy within the first week 10 days of immobilization = 40% less of 1RM 20% less cross sectional area = 40% reduction in strength greater number of slow twitch fibers (because fast twitch are the first to be lost) postural/single joint muscles show greater atrophy
72
describe the changes in muscle with advanced age
**changes are highly variable** greater loss of power than just the peak force 10% decline per decade after age 60 greater decline after 75 greatest in lower limb
73
main mechanism for age related muscle changes
sarcopenia loss of muscle tissue and infiltration of connective tissue, fat, and decrease in fibers and size loss of alpha motor neurons reduce fivers resistive exercise can help

DPT 702: Biomechanics (13 decks)

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