chapter 11 Flashcards
What protein is found in thin filaments?
actin
What protein is found in thick filaments?
myosin II
What is the cytoplasm of muscles cells called?
sarcoplasm
this type of muscle is attached to bone and is responsible for movement of the axial and appendicular skeleton and for maintenance of body posture and position
skeletal muscle
muscle that is restricted to the soft tissues like the tongue, pharynx, lumbar part of the diaphragm, and upper part of the esophagus
visceral striated muscle
type of striated muscle found in the wall of the heart and in the base of the large veins that empty into the heart
cardiac muscle
A muscle cell is a multinucleated ____________________________
syncytium
A muscle fiber is formed during development by the fusion of small, individual muscle cells called ______________________________
myoblasts
consists of the plasma membrane of the muscle cell, its external lamina, and the surrounding reticular lamina
sarcolemma
the delicate layer of reticular fibers that immediately surrounds individual muscle fibers
endomysium
a thicker connective tissue layer that surrounds a group of fibers to form a fascicle
perimysium
functional units of muscle fibers that tend to work together to perform a specific function
fascicle
the sheath of dense connective tissue that surrounds a collection of fascicles that constitutes the muscle
epimysium
functions primarily to store oxygen in muscle fibers and provides a ready source of oxygen for muscle metabolism
myoglobin
-contain many mitochondria and large amounts of myoglobin
-these fibers have great resistance to fatigue but generate less tension than other fibers
-their myosin ATPase reaction velocity is the slowest of all of the fiber types
-typically found in the limb muscles of mammals and in the breast muscle of migrating birds
Type I or slow oxidative fibers
-medium size with many mitochondria and high myoglobin content
-contain large amounts of glycogen and are capable of anaerobic glycolysis
-generate high peak muscle tension
Type IIa or fast oxidative glycolytic fibers
-contain less myoglobin and fewer mitochondria
-have a low level of oxidative enzymes but exhibit high anaerobic enzyme activity and store a considerable amount of glycogen
-high peak muscle tension
-myosin ATPase velocity is the fastest of all the fiber types
-fatigue rapidly as a result of production of lactic acid
Type IIb or fast glycolytic fibers
the structural and functional subunit of the muscle fiber
myofibril
forms a highly organized tubular network around the contractile elements in all striated muscle cells
sarcoplasmic reticulum
The basic contractile unit of striated muscle
-the portion of a myofibril between 2 adjacent Z lines
Sarcomere
Which portion of the sarcomere are thick filaments restricted to?
central portion or A band
What portion of the sarcomere are thin filaments found?
attached to the Z line and extend into the A band to the edge of the H band
The Z line and its matrix material anchor the thin filaments from adjacent sarcomeres to the angles of the zigzag by _______________________________, and actin-binding protein.
a-actinin
-small molecule that polymerizes to form a double-stranded helix, the F-actin filament
-polar, oriented in the same direction
-has a binding site for myosin
G-actin
-64 kDa protein that consists of a double helix of two polypeptides
-forms filaments that run in the groove between the F-actin molecules in the thin filament
tropomyosin
-the smallest subunit of the troponin complex
-binds calcium which is an essential step in the initiation of contraction
Troponin-C (TnC)
binds to tropomyosin, anchoring the troponin complex
Troponin-T (TnT)
binds to actin, thus inhibiting actin-myosin interaction
Troponin-I (TnI)
-small actin-binding protein that is attached to the free end of the thin filament
-maintains and regulates the length of the actin filament in the sarcomere
Tropomodulin
-an elongated, inelastic protein attached to the Z lines that spans most of the length of the thin filament except for its minus pointed end
-acts as a “molecular ruler” for the length of the thin filament because the molecular weight of different isoforms correlates to the length of thin filaments during muscle development
-adds stability to the thin filaments anchored by the a-actinin in Z lines
Nebulin
Myosin II is composed of _________heavy polypeptide chains and _______light chains
2 heavy 4 light
Each globular myosin head represents a heavy chain ___________________________that projects at an approximate right angle at one end of the myosin molecule.
motor domain
zone in the middle of thick myosin filaments that does not have globular projections
bare zone
-large protein that spans half of the sarcomere
-2 spring-like portions of this protein help center the thick filament in the middle between two Z lines
-springs prevent excessive stretching of the sarcomere by developing a passive restoring force that helps with its shortening
Titin
-short, bipolar, rod-shaped, actin-binding protein that bundles thin filaments into parallel arrays and anchors them at the Z-line
a-actinin
intermediate filament that forms a lattice that surrounds the sarcomere at the level of the Z lines, attaching them to one another and to the plasma membrane via linkage protein ankyrin
Desmin
What are the names of the M line proteins that hold thick filaments in register at the M line and attach titin molecules to the thick filament?
-myomesin
-M-protein
-obscurin
-muscle creatine phosphatase
-protein that contributes to normal assembly and to stabilization of thick filaments
-forms several distinct transverse stripes on both sides of the M line that interact with titin molecules
Myosin-binding protein C
protein that is thought to link laminin, which resides in the external lamina of the muscle cells, to actin filaments
Dystrophin
When a muscle contracts, each sarcomere ______________________, but the myofilaments ___________________________.
shorten
remain the same length
