Skeletal Muscle Flashcards
T-tubule
deep invaginations of sarcolemma; extend into sacroplasm
sacromere
the functional contractile unit in a skeletal muscle fiber
The sarcomere is defined by the area between
2 adjacent Z discs
myofibrils
composed of short bundles of myofilaments
Myofilaments are of 2 types
actin and myosin
Individual actin molecules
G-actin (globular actin monomers)
Strands of actin molecules
F-actin; filamentous actin polymers
two primary regulatory proteins are also part of the thin filaments
tropomyosin, troponin-C
Myosin heads form crossbridges…
with actin thin filaments during contraction
sliding filament theory
thin filaments slide across thick filaments toward the center of the sacromere (shortening of the H zone and I zone, A band does not change, Z-lines move closer together)
explain the molecular basis of muscle contraction (in relation to ADP Pi, ATP)
myosin heads contain bound ADP and Pi (weak affinity for actin), when 1 of the myosin heads stops on the actin subunit- Pi is released which binds myosin to actin +triggers force stroke that moves the actin filament, ADP dissociates, ATP forms and binds to the anti-nucleotide binding site, myosin head deteched from actin; ATP is hydrolyzed
explain the molecular basis of muscle contraction (in relation to ca2+ and tropinin)
ca levels rise, ca binds to troponin, troponin-C moves tropomyosin away from actin’s myosin binding site and myosin and actin bind strongly and creates powerstroke, actin filaments move
what is DHPR?
An L-type Ca channel that detects voltage
In skeletal muscle, when DHPR is activated, what does it do?
It opens RyR
What is RyR
RyR is a calcium channel in the sarcoplasmic reticulum
is cardiac muscle neurogenic or myogenic?
myogenic: the cells within the heart muscle itself are dictating where/when/how the cardiac muscle contracts
pacemaker cells
modified muscle cells whose job is to set the pace
In cardiac muscle, is the L-type calcium channel real or is it voltage gated
it is a real calcium channel
In cardiac muscle, what activates RyR?
calcium from the L-type calcium channel (calcium induced calcium release)
In cardiac muscle what do the SERCA and PMCA pumps do
pumps Ca out against its gradient (relax muscle)
