Week 3 Pt.1: Test 1 Flashcards
Stable posture is a result of what
Balance of Competing forces
Movement results from
Unbalanced competing forces
Skeletal muscles adapt to what
Immediate and long term external forces that can destabilize the body
Describe the force range of skeletal muscles
Wide range
Fine motor to large lifting
Skeletal muscles respond to what
Both external environment to internal control mechanisms (I.e. nervous system)
Each muscle fiber is an individual …
Multinucleated cell
What is responsible for contraction of a whole muscle
Contraction at the muscle fiber level
Muscle shortening occurs because of shortening of what
Sarcomere
Describe the length of muscle fibers
Varying length
Can be tendon to tendon or much shorter
What contains many myofibrils that include tiny cylinders consisting of bundles of myofilaments
Cytoplasm or sarcoplasm
What is responsible for holding the components of the cell, storing the molecules for cellular processes, and responsible for giving the cells its shape
Sarcoplasm
Specialized membrane that surrounds striated muscle fiber cells; how calcium enters and leaves cells
Sarcolenna
What is the endomysium? External to? Partially attached to? Helps to…?
Thin layer of connective tissue that surrounds individual muscle fiber
Immediately external to sarcolemma
Partially attached to perimysium
Help transfer actin myosin contractile force
What is perimysium
Sheath of connective tissue surrounding bundle of muscle fibers
Contractile proteins of muscle
Actin
Myosin
Describe the noncontractile muscle structural proteins
Cytoskeleton with muscle fibers
Supportive structures between fibers
Contract but no role for force transmission
Titindoes provides what
Passive tension within muscle fiber
Desmin does what
Stabilizes alignment of adjacent sarcomeres
Describe fusiform fibers
Run parallel to one another and central tendon
Fusiform designed for what
Mobility and low force over long range
Pennate fibers run how
Approach central tendon obliquely
Describe pennate fibers
Large number of fibers
Generate larger forces
Most muscles fall in this group
Unipennate, Bipennate, and multipennate types
How does muscle architecture impact amount of force that can be created
Physiological cross sectional area and pen nation angle
Describe the purpose of understanding physiological cross sectional area
Determines amount of active proteins available to generate force
Max force potential proportional to CSA
I.e. thicker muscles have more force that thinner
Describe pennation angle
Fibers run at different angles
CSA needs to be perpendicular to fiber direction
Angle of orientation between fibers and tendons
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)
what are series elastic components
tissues attached en dot end with active proteins
i.e. tendon, titan
what are parallel elastic components? Examples?
tissues that lie parallel with active proteins
i.e. epi, peri, endomysium
what is elongated when you stretch the whole muscle
elongates both parallel and series components
what is the critical length
all slack tissue much be brought to this initial level of tension
what happens past the point of critical length
tension increases until muscle reaches high level of stiffness and fails
role of passive tension within stretched muscles
can stabilize or assist movement
what does it mean that muscle is viscoelastic
time changes its behavior
quick stretch elicits (increased velocity) increases its stiffness
elasticity is a dampening mechanism that can help
protect a muscle
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
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
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)
what does the term amortization describe
time from cessation of eccentric prestretch to the onset of concentric muscle action
“time to rebound”
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
what is the ultimate force generator in the muscle
sarcomere
what does the dark band of a muscle fiber represent
A band
thick myosin
what does the light band of the muscle fiber represent
I bands
actin (thin)
describe actin and myosin in resting muscle
slightly overlapping
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
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)
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)
describe the relationship between load and velocity for eccentric and concentric contraction
eccentric = increase load, increase contraction speed
concentric = increase load, decrease contraction speed
what are isokinetics
torque joint angle velocity relationship
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
what is a motor unit
a single motor alpha neuron with its entire family of muscle fibers
what are excitation sources
cortical descending neurons, spinal interneurons, and afferent (sensory neurons)
what is rate coding
rate of sequential activation of motor units?
what do alpha motor neurons innervate
extra fusal fibers
not intrafusal fibers
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
smaller motor units control what
less force and more fine motor control
low innervation ratio
larger motor units control what
larger forces
high innervation ratio present
describe slow oxidative motor units
slower contractile characteristics
little loss of force during sustained activation (remain more constant; endurance)
describe fast glycol motor units
larger motor neuron units
recruited after the slow oxidative units when large forces are required
describe fast oxidative glycolytic fibers
in between slow oxidative and fast glycolytic
what is unfused tetanus
summated mechanical twitches
what is fused tetanus
as time interval shortens between action potentials greater force is generated and the twitches fuse into a stable muscle force
what two things operate in the rise of muscle force and are highly specific to demand
rate coding and recruitment
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
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
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)
describe the fatigue difference between older and younger individuals
older = less fatiguable with isometrics, but more fatiguable with concentrics and fast velocities
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)
strength training can cause the greatest change in what type of fibers
fast twitch II
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
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)
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
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
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
