Skeletal Muscle Flashcards
The ______ is the basic contractile unit of a muscle
sarcomere
sarcomere encompasses an organized bundle of contractile proteins between two______
Z-disks
the Z-disks form an anchor point for an array of _____ that extend inward towards the center from both ends
actin filaments
_____ are located centrally without extending to either Z-disk
myosin filaments
each myosin filament makes multiple contacts with surrounding actin filaments via molecular ______
cross-bridges
______ consists of two strands of G-actin monomers which form a helical structure
F-actin “thin” filament
_____ and _____ are regulatory protein complexes spaced along the actin filament
tropomyosin and troponin
_____ consists of a chain of light meromyosin (tail portion), and heavy meromyosin (S2 region), that terminates in a globular head portion (S1 region)
myosin “thick” filament
the ____ region (myosin) serves as a flexible link between the head and tail portions
the S2 region
_______ (myosin) contains binding sites for actin and ATP
head portion (S1 region)
Cross-bridge interactions between myosin and actin generates ______ ” (force) along the myofibril
“active tension
Active tension forces are transmitted from individual sarcomeres linearly from what 2 protiens
nebulIN
And titan
Active tension forces are transmitted from individual sarcomeres Laterally between adjacent fibrils from what 2 protiens
Destin and skelemin
Active tension forces are transmitted from individual sarcomeres Laterally between Extracellular matrix from what 2 protiens
Costumers (dystrophin)
What transfers tension to other sarcomeres
Costumers (dystrophin)
actin-myosin binding is regulated by _____
calcium
_____ of troponin has a binding site for Ca+
he C-subunit
______ between the myosin and actin filaments generates “active” tension within the sarcomeres
“cross-bridge cycling”
What are the 4 steps of cross-bridge cycling
Formation of the cross-bridge
Rotation of the myosin head
Detachment of myosin head from actin
Resting of the myosin head
this step requires the presence of Ca++, and causes the ADP attached to the myosin head to be released
Formation of the cross-bridge
this step serves as the “power stroke” that generates “active tension” within the sarcomere
Rotation of the myosin head
this step requires the availability of ATP to bind to the myosin head
Detachment of myosin head from actin
this step requires the hydrolysis of ATP to ADP
Resting of the myosin head
The release of ____ triggers recoil
ADP
at the end of the power stroke, the attached myosin-actin cross-bridge is called the “______
rigor complex”
without sufficient _____the filaments will remain in this state rigor
ATP
the initiation and continuation of cross-bridge cycling is dependent upon _____`
Ca++ availability
The sarcolemma and sarcoplasmic reticulum provide structure for an “_______ that makes Ca++ available
activation system”
the signal that triggers Ca++ release from the SR is coupled to ______ of the sarcolemma …
depolarization
receptors are embedded within the T-tubule membrane
dihydropyridine (DHP) receptor
RyR receptors are embedded e of the terminal cistern within the membran
ryanodine (RyR) receptor
the ryanodine Ca++ channels remain open for just a brief interva
“calcium spark”
the quantity of Ca++ released per “spark” remains consistent, regardless of the frequency of repeated “sparks” triggered by _________
a train of arriving action potentials
cytosolic [Ca++] will vary in proportion to the_____ of action potentials
frequency
the level of ______ determines the strength of contraction
activation
the number of cross bridges that form and start cycling
Level of activation
“pulling force” generated by the stretching of the longitudinal filaments
Tension
stretching of the longitudinal filaments (nebulin and titan) caused by sarcomere shortening
elastic
a single action potential will generate a single ______
twitch
the strength of the _____ contraction is measured as the peak developed tension
isometric
summation allows the ______ to vary with the frequency of stimulation
maximum force
reflects an accumulation of cytosolic free Ca++
Summation of force
Changes in the ______ will also affect the developed force
pattern of stimulation
one extra impulse inserted into what is otherwise a steady train of action potentials can ______
greatly increase the tension
one extra impulse at the very start of a train of action potentials can provide _____
tension at the very outset of the train
one missing impulse in a train of action potentials will _______
reduce the tension for the remainder of the train
By altering the length you also____
Alter the fore
Length dependent muscle activation is due to what
misaligning myosin heads at crossbridges
optimal amount of initial _________ will allow the greatest number of cross-bridges
overlap between the actin and myosin filaments that
Passive tension, and active force generation by a muscle fiber, are both_____
“length dependent”
external force pulling against a relaxed muscle generates
preload
determines the peak force generated by a single twitch by determining the initial overlap between the actin and myosin filaments
preload
contraction will cause the muscle to shorten only when the active force is greater than the external load
afterload
The extent to which a muscle will shorten will vary _____ to its afterload
inverse
