Skeletal Muscle Contraction Flashcards
myofibrils consist of repeating units of _____
sarcomeres
each myofibril contains _____
myofilaments (myosin and actin)
one sarcomere ends at the ___ line
Z line
I bands consist of ___
actin
A bands consist of ____
myosin (including the portion that overlaps with actin)
H zone consists of ____
ONLY myosin (no overlapping actin)
The troponin complex consists of which binding sites?
1) binding site for tropomyosin
2) binding site for Ca2+ that initiates contraction
3) binding site for MYOSIN heads to actin in a resting muscle
the ____ ___ surrounds each ____ and stores Ca2+
the SARCOPLASMIC RETICULUM surrounds a MYOFIBRIL and stores Ca2+
What are the transverse invaginations of sarcolemma
T TUbules
3 factors a contraction requires
1) stimulation by motor neuron
2) increase in cytoplasmic Ca2+
3) ATP
What is the sliding filament thoery?
the idea that when a sarcomere contracts, Z lines move closer togeher, I bands (actin) and H bands (myosin only) decrease.
Skeletal muscle contraction requires stimulation by a ___ ___ at the ___ ____
stimulation by a motor neuron at the neuromuscular junction.
neurons at the neuromuscular junction secrete _____, which diffuses across the neuromuscular junction and binds to sarcolemma
ACETYLCHOLINE
Explain the activation of a muscle contraction starting at the neuromuscular junction
Skeletal muscle contraction requires stimulation by a motor neuron at neuromuscular junction.
The neurons secrete the neurotransmitter acetylcholine, which diffuses across the neuromuscular junction and binds to sarcolemma.
Depolarization of the sarcolemma will spread down T tubules, and depolarize SR which results in the release of Ca++ into sarcoplasm.
Ca2+ binds to troponin on thin filaments, and expose the myosin binding sites that allow myosin heads to bind to actin.
if ATP is present, a power stroke can occur.
