EX1; Skeletal Muscle Flashcards
What is the organization of the skeletal muscle (7)
whole muscle fascicle muscle fiber (cell) myofibril sarcomere filament protein
What is the shape of actin molecules
Two intertwined helical chains of actin molecules (like pearls)
These two things are found on the actin chains
troponin
tropomyosin
Troponin comprised of what three subunits
TnC (calcium)
TnI (inhibits muscle function)
TnT (binds tropomyosin)
Troponin also contains what specific site
Ca binding site
A troponin is found every how many actin molecules
7
What is the structure of the myosin filament
2 pairs light chains per myosin
2 heavy chains
What is the orientation of the cross bridges of the myosin filament
opposite for the left and right
heads away from the center, tails toward
This represents the same protein but slightly different amino acid sequence; similar function
isoform
True or False
You are born with all your muscle cells, they just undergo isoform changes
True
This is the functional unit of the contractile apparatus, which can shorten and generate force
sarcomere
What three things compose the sarcomere
thick filaments, thin filaments, and Z-lines (or Z disks)
True or False
There is one sarcomere to one muscle cell
False; there are many sarcomeres in every muscle cell
This anchors the thin filaments
Z line
This large protein extends from Z line to the thick filaments, aiding the thick filaments to remain in the center of the sarcomere
titan
This is a thin filament protein; possibly a molecular ruler to determine filament length
nebulin
True or False
A major difference between skeletal and cardiac muscle is that cardiac muscle does not contain nebulin
True
This is the mechanism by which AP in sarcolemma initiates muscle contraction
excitation-contraction coupling
This ion plays a pivotal role in the activation of skeletal muscle
calcium
What is the design of the excitation contraction coupling
toward achieving a rapid and very large increase in the free calcium ion concentration inside muscle cells
This binds Ca ions in the lateral sacs
calsequestrin
Ca is pumped here before it diffuses into the lateral sac
fenestrated collar
The lateral sacs and the fenestrated collar are found where
in the sarcoplasmic reticulum
Ca ions are released from the lateral sacs of the SR to initiate what
contraction
Ca ions re sequestered by the fenestrated collar of the SR to cause what
relaxation
What is used to transport Ca in and out of the SR
Ca-ATPase pump
This moves deeper into the actin groove upon the introduction of calcium to expose the myosin binding sites on actin
tropomyosin
This states that muscles shorten by a relative sliding of thick and thin filaments; the filaments do not change in length
sliding filament theory
Using the cross bridge theory; thick and thin filaments are or are not connected at rest
they are NOT
These form between the two types of filaments following an increase in free Ca
cross-links (cross-bridges)
What two things constitute a cross bridge
actin and myosin
Which one, actin or myosin, regulates the cross bridge cycle
myosin
the light chain actin are modulatory
What is the first step of the cross bridge theory
cross bridge binds to actin
Upon the cross bridge binding to actin, what then happens
the power stroke; cross bridge moves (z-line decrease) release of ADP and P
When ADP and P is released during the movement of the power stroke, what happens to the myosin
it undergoes a conformational change
What binds to the myosin causing the cross bridge to detach
ATP
What energizes the cross bridge
the hydrolysis of ATP
The energized cross bridge then does what
bind to actin, and the cycle repeats again and again
The amount of force generated is proportional to what
the number of attached cross bridges
The rate of the cross bridge cycle determines the rate (velocity) of what
muscle shortening; different types of myosin go through the cycle at different rates
True or False
muscle shortening and force generation are energy-consuming events
True
The source of energy for force generation and muscle shortening is what
ATP
Why is there no change in ATP during muscle contraction
phosocrestine buffering
Where in the sarcomere is the creatine kinase found; of which deals with ATP and phosphocreatine
at the M line; right in the center of energy consumption
How much ATP is consumed per cross bridge
one cross bridge = one ATP
What are the consumers of ATP and how much ATP do they consume
myosin ATPase; contraction (70)
Ca ATPase; relaxation (30)
This is a fundamental property of striated muscle that reflects the arrangement and length of thick and thin filaments
length-tension relationship
The amount of tension (force) that a muscle can generate when it is activated is dependent upon what
its length
This states that a muscle can shorten at a higher velocity when moving a lighter load
load-velocity (force-velocity) relationship
What does the load-velocity relationship show us about the cross bridge cycle
the cross bridge cycle to cause shortening since the rate of cycling determines shortening velocity
Velocity of skeletal-muscle fiber shortening and lengthening is a function of what
load
Generally in mammalian muscles, the amount of ten sun generated by a muscle, per unit of cross-sectional area, is fairly consistent, this shows us what
the difference in the power generated by different muscles is determined mainly by the speed (velocity) of contraction
What is different about the latent period when comparing moving a light, intermediate or heavy load
the latent period is longer for heavier loads because you need to build up enough energy to move said load
A single muscle is composed of an assembly of this; a single motor neuron and all of the muscle fibers it innervates
motor units
True or False
most muscle fibers have one NMJ and are innervated by a single motoneuron
True
True or False
Motoneurons can innervate more than one muscle fiber
True
How many different muscle fibers can be controlled by a single motor unit
it varies from 100 in muscles controlling fine movement and up to 2,000 muscle fibers in large muscles of the leg
What three things can each muscle fiber type be distinguished from other types by
structural, biochemical, and physiological
True or False
The types of fibers comprising a muscle are developed from birth and are unchanging
False; they may change during developments, some disease, and in some cases following exercise training
What two classifications are used in distinguishing muscle fibers
fast or slow
Which fiber, fast or slow has smaller neuromuscular junctions
slow
Which fiber, fast or slow are larger in diameter
fast
Which fiber, fast or slow contains different sarcomere protein isoforms
slow
Which fiber, fast or slow are more fatigue resistant
slow
Which fibers, IIA or IIB are smaller
IIA
Which fibers, IIA or IIB depends more on an oxidative metabolism
IIA
Which fibers, IIA or IIB are less fatigable and contract a little slower
IIA
Which fibers, IIA or IIB depends more on glycolytic metabolism
IIB
Muscles that are utilized for maintaining posture have a high proportion of what fibers
type I
Muscles that are utilized to perform tasks rapidly and with a lot of dexterity contain primarily which fibers
type II
This type II fiber are faster and generate more power but are less efficient
IIB
Which fibers are most efficient overall (among skeletal fiber types)
type I
What are 5 systemic disorders are associated with muscle cramps
dehydration
metabolic; low sodium, magnesium, ca, glucose, potassium
endocrine; thyroid, adrenal insufficiency
pregnancy
drugs and toxins
This is a deficiency or defect in dystrophin; links cytoskeletal (structural) proteins to membrane leading to membrane tears and weakness in skeletal and cardiac muscle
muscular dystrophy
