His: Skeletal Muscle and Nerve Tissue Flashcards
Myofibers are separated by _________.
Endomysium
Fascicles are separated by __________.
Perimysium
Entire muscle is covered by ____________.
Epimysium
Group of muscles are called ______.
Fascicles
- ______ is located in the periphery of a skeletal upscale cell. 2. ______ is occupied by myofibrils.
- Nucleus 2. Cytoplasm
Myofibrils are composed of _____ and _____ filaments.
Thin and thick filaments
Basic structural unit of the myofibrils
Sarcomere
Calcium storage site and sleeves around each myofibrils
Sarcolemma and SR
Invaginations of the sarcolemma
Transverse tubules (T-tubules)
Dilated ends of SR that release Ca2+ and trigger muscle contraction
Terminal cisternae
Anchor site for actin (thin) microfilaments
Z-line
Contains actin thin filaments
I-band
Anchor site for thick myosin filaments
M-line
Contains only thick myosin filaments
H-zone
Overlap of thick and thin filaments plus H-zone
A-band
When a muscle cell contracts, the ____ filaments slide past the ___ filaments toward the center of the sarcomere. The ____ are brought closer together.
- Thin filaments 2. Thick filaments 3. Z-lines
- ___ provides the driving force for movement. 2. ____ drives the movement of myosin heads along actin filaments.
- Myosin II heads 2. ATP
Contains a long alpha-helical coiled-coil tail that enables several molecules to assemble into large bipolar aggregate or filament
Myosin II
- runs in the grooved formed by F-actin strands - binds to troponin complex - extends for the length of 7 actin monomers - consists of 2 nearly identical alpha-helical polypeptides twisted around each other
Tropomyosin
Complex of 3 proteins: - troponin T - troponin I - troponin C
Troponin
Binds the troponin complex to tropomyosin
Troponin T
Inhibits the binding of myosin to actin (relative to the troponin complex)
Troponin I
Binds Ca2+ in the troponin complex
Troponin C
- slow ATPase - red (high myoglobin) - slow, less powerful contraction - contract for long periods without fatigue
Type I fibers (slow oxidative)
- largest and most prevalent type of skeletal muscle fiber - intermediate ATPase - provides power - primarily aerobic - intermediate fatigue
Type IIa fibers (oxidative glycolysis)
- fast ATPase produces fast contractions - largely anaerobic - rapid fatigue - lower myoglobin content
Type IIb fibers (fast glycolytic)
Types of nerve tissue
- Neuron 2. Neuroglia (neuron supporting cells)