Exam 3, Set 1 Flashcards
Muscle Cell/ Muscle Fiber
A cell that has differentiated for the specialized function of contraction
Functions of the muscular system
Heat, Movement, Posture, Structure
Myofibril
The long thin contracting protein subunits of a muscle cell that are composed of actin and myosin filaments.
Thick Filament
Myosin, essentially a molecule with 2 round heads and chain-like tail.
Thin Filament
A polymer of actin with tightly bound regulatory proteins troponin and tropomyosin
function and location of myosin heads
Function: Bind and hydrolyze ATP,
Location: attached to elongated tail region
Function and location of myosin head binding sites
Function: Facilates binding so cross-bridges can form
Location: on the actin filaments
Function and location of actin
Function: Shortens the sarcomere
Location: attached at their plus ends to the Z disc
Function and location of troponin
function: sarcomeric Ca2+ regulator
location: attached to the protein tropomyosin and lies within the groove between actin filaments
Function and location of tropomyosin
Function: Stabilizes actin filaments but also regulates muscle contraction
Location: in each of the two long-pitch helical grooves of actin
Function and location of Ca2+
Function: induces skeletal muscle contraction
Location: the cytosol
Sliding filament model of contraction
Within the sarcomere, myosin slides along actin to contract the muscle fiber
Excitation-contraction coupling
The rapid communication between electrical events occurring in the plasma membrane of skeletal muscle fibres and Ca2+ release from the SR, which leads to contraction
Steps in the process of excitation-contraction coupling
Step 1
AP spreads along the sarcolemma to the T-tubules
Step 2
Calcium is released into the SR
Step 3
Calcium binds to actin and blocking action of tropomyosin is removed
Step 4
Myosin heads attach to begin contraction
Step 5
Calcium is removed and binding sites on actin become blocked again by tropomyosin
Step 6
Muscle relaxes
Steps in cross bridge cycling, and the involvement of ATP, cross bridges, and the myosin head ATPase
Step 1
cross bridge formation: myosin head attaches to actin myofilament
Step 2
the power stroke:
ADP and Pi are released from myosin head
Myosin head bends,changes to low-energy state
Shape change pulls actin towards the M line
Step 3
cross bridge detachment: ATP attaches to myosin, breaking cross bridge
Step 4
cocking of the myosin head: attached ADP is hydrolyzed by myosin ATPase —-> ADP + Pi, bringing it back to a high-energy state
How a muscle cell obtains the ATP it needs
Using creatine phosphate
Using glycogen (no oxygen)
Using aerobic respiration
isotonic Contractions
Tension remains the same in the contraction
concentric contractions
total length of the muscle shortens as tension is produced
