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Striated Muscle

Terms

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Specialized cell membrane of muscle
Sarcolemma
Cytoplasm of muscle is called
Sarcoplasm
Why is striated muscle called Thin filament regulated
Activation is via Ca binding to troponin which along with tropomyosin is one of regulatory proteins found on thin filament
Name 3 fibers types of skeletal muscle
Type I - slow twitch, oxidative, red
Type IIb- fast twitch, glycolytic, white
Type IIa- fast twitch, nixed oxidative and glycolytic, white
Difference between cardiac muscle and striated muscle
Cardiac muscle is only in heart
-Has gap junctions
-highest sustainable metabolic rate
-Auto rhythmic
Difference between striated and smooth
No striations in smooth muscle
-Thick filament regulated, activation through phosphorylation of muscle proteins found in thick filaments
Describe skeletal muscle fibers
-Multinucleated
-Electrically isolated
-Packed with contractile proteins
Thick filament contains
Myosin
Thin filament contains
Actin
Tropomyosin
Troponin
I band
Isotropic - allows polarized light to pass through
-primarily thin filaments
-runs from A to A band
A band
-primarily thick filaments (can contain overlapping thin and intermediate filaments)
H zone
THICK filaments only
Can be part of or include whole A band
Z line
Structure demarcating separation of sarcomeres
M line
Central line of sarcomere
What happens in sarcomere when muscle is activated
-Sarcomeres shorten, Z lines get closer
-A band remains CONSTANT
-I band and H zone shorten
-Myofilament length remains constant
Phase I of muscle contraction
Transient increase in Ca relieves natural block by troponin and tropomyosin of actin/myosin interaction - increases ATPase activity of myosin by 1000 times
Phase II of muscle contraction
Power stroke, S1 goes from 90 degrees to 45 - primary force generation step
Phase III
Myosin detaches from actin upon release of ADP, to which it has higher affinity
Describe what happens in rigor mortis
Muscle relaxes when ADP replaces actin in myosin. When ATP is not available, crossbridge will remain attached in high stiffness/low force position causing rigor mortis
T tubules
central to excitation contraction coupling
Invaginations of sarcolemma near A-I band
Feet of t tubules are
voltage sensing elements, lead to release of Ca

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