Flashcards in Muscle Deck (61):
What are the components of thin filaments?
1. F-actin2. Troponin3. Tropomyosin
Actin, troponin, and tropomyosin are components of what muscle filament?
What constitutes thick filaments?
What is F-actin made up of?
Two G-actin polymers twisted to form a double stranded helix
Two G-actin polymers twisted to form a double stranded helix forms ___________
What are the components of troponin?
1. TnT2. TnC3. TnI
What is the function of TnT?
Troponin subunit that binds to tropomyosin
What is the function of TnC?
Troponin subunit that binds calcium
What is the function of TnI?
Troponin subunit that binds troponin to actin molecule; inhibits actin-myosin interaction
Where does the Tn complex bind to tropomyosin?
Grooves of actin filaments
What constitutes a tropomyosin molecule?
1. Two polypeptide chains in an a-helix2. Each a-helix rests on 7 G-actin molecules, covering active site3. Head to tail of tropomyosins form tropomyosin filaments
What does trypsin do to myosin molecules?
Breaks them into heavy meromyosin and light meromyosin
What is the molecular composition of myosin?
2 heavy chains and 4 light chains
What constitutes heavy meromyosin?
1. 4 light chains2. 2 globular chains3. Short twisted tail (a-helix)
What constitutes light meromyosin?
The shafts of the heavy chains wrapped around each other
What makes up a sarcomere?
Overlapping thick and thin myofilaments
Overlapping thick and thin myofilaments make up a _______________
A series of sarcomeres joined end-to-end makes up a _______________
What makes up a myofibril?
A series of sarcomeres joined end-to-end
What makes up a muscle fiber (muscle cell)?
Many parallel myofibrils
Many parallel myofibrils make up a ______________
Muscle fiber (muscle cell)
What are the characteristics of the A band?
1. Dark band - thick and thin filaments2. Widest band
What are the characteristics of the H band?
1. Thick filaments only2. Bisects the A band
What are the characteristics of the I band?
1. Thin filaments only2. Light band3. Made up of portions of adjacent sarcomeres
What are the characteristics of the Z disc?
1. Attachment for thin filaments2. Contains a-actinin3. Bisects I band
What are the characteristics of the M line?
1. Consists of protein structures lying between thick and thin filaments, holding them together2. Creatine kinase is major protein3. Bisects H band
What is the role of a-actinin?
Anchors thin filaments to Z disc
What anchors thick filaments to the Z disc?
What is the role of titin?
Anchors thick filaments to Z disc
What is the role of myomesin and C protein?
Secures thick filaments at M line
What is the role of dystrophin?
Cytoplasmic protein that binds actin filaments to laminin
What makes up the sarcolemma?
Cell membrane + external lamina + reticular lamina
What is endomysium?
Surrounds muscle fiber, consists of delicate layer of reticular fibers
What is a fascicle?
Many muscle fibers bundled together
What connective tissue surrounds a fascicle?
What is perimysium?
Collagenous connective tissue that surrounds a fascicle
What is epimysium?
Deep fascia, surrounds many fascicles
What is the term for deep fascia taht surrounds many fascicles?
What are T tubules?
Invaginations of sarcolemma which are continuous with extracellular space
What is the function of T tubules?
Carry nerve impulses deep into cell
What is the terminal cisterna of the sarcoplasmic reticulum?
Stores calcium in its lumen
What is the triad located at the A-I junction of the sarcomere?
1 T tubule + 2 terminal cisternae
What are satellite cells?
Regenerative cells that lie between the skeletal muscle cell and its external lamina
New myoblasts are derived from ___________
What components make up the innervation of skeletal muscle?
1. Motor unit2. Motor end plate
What constitutes the motor unit?
A lower motor neuron and all muscle fibers it innervates
What constitutes the motor end plate?
1. Axon terminal2. Synaptic cleft3. Muscle cell sarcolemma
What is myesthenia gravis?
Autoimmune disease causing muscle weakness
What is the cause of myesthenia gravis?
Antibodies attack Ach receptors on sarcolemma of skeletal muscle, forming Ab-receptor complexes
What is muscular dystrophy?
Genetic, degenerative disease affecting striated muscles
What is the protein affected in Duchenne's muscular dystrophy?
Which muscle type contains a lot of glycogen?
What are some characteristics of cardiac muscle?
1. Weakly striated2. Short and branched cells3. Cells contain glycogen, lipid droplets, and lipofuscin4. 1-2 nuclei5. Atrial granules6. Many mitochondria7. Intercalated discs
What are atrial granules?
Membrane-bound granules: 1. Contain atrial natriuretic factor and brain natriuretic factor2. Most common in right atrium
What are intercalated discs?
Specialized intercellular junctions
Are T tubules of the cardiac (ventricular) muscle larger or smaller than in skeletal muscle?
What are Purkinje fibers?
Specialized cardiac muscle cells in the endocardium that act as batteries which relay electrical impulses to cardiac muscle fibers
What are some characteristics of smooth muscle?
1. Forms sheets2. No striations3. Mononuclear - nucleus is in center4. Dense bodies - crossing of myofilament bundles5. No T tubules6. Poorly developed SR
What are dense bodies?
Criss-crossing of myofilament bundles
What is a common component of dense bodies?
a-actinin (similar to Z discs)