Exam 3: Lecture 14 Flashcards
What is the hierarchical structure of a muscle?
Fasiculus->Fascile->Myofiber->Myofibril->Sarcomere->Filaments
List the distinctive characteristics of skeletal, cardiac, & smooth muscle.
Skeletal- Voluntary, striated
Smooth- Involuntary
Cardiac- Cardiac
What does the epimysium cover?
Entire muscle
What does the perimysium cover?
Fascicle
What does the sarcolemma cover?
Myofiber (muscle cell)
What does the endomysium cover and consist of?
Muscle fiber (including sarcolemma)
Consists of basal lamina & reticular collagen fibers
Basal lamina helps distribute force of contraction
T/F: The width of the A band decreases during contraction.
False, the width of the A band does not change during contraction
What are the characteristics of myosin thick filaments?
Two identical heavy chains
Head at each end
Actin, ATP, & light-chain binding regions
Essential/regulatory light chains
What are the characteristics of thin myosin filaments?
Polymer of G actin
Two polymers wound in alpha-helix
Plus end inserts on Z-disk
Troponin/tropomyosin
What are the 3 portions of the troponin complex and what are their functions?
Troponin I- Inhibits action/myosin binding
Troponin C- Binds to Ca++ ions
Troponin T- Binds to tropomyosin
What does titin do?
Provides myosin with elasticity
What does desmin do?
Provides structural strength to myofibril
What does plectin do?
Binds desmin filaments
What does nebulin do?
Controls how long actin filament gets/is
What are the cytoskeleton components?
AlphaBeta-crystallin
Dystrophin
Dystroglycan complex
What does AlphaBeta-crystallin do?
It’s a heat shock protein that protects desmin from mechanical stress
What does dystrophin do?
Anchors actin to sarcolemma
Reinforces sarcolemma during contraction
What does the dystroglycan complex do?
Links dystrophin (intracellular) to laminin-2 (extracellular)
What is muscular dystrophy?
X-linked disease resulting in progressive degeneration of skeletal muscle
What is the difference between Duchenne’s and Becker’s muscular dystrophy?
In Duchenne’s the dystrophin is absent
In Becker’s the dystophin is abnormal
Describe the characteristics of satellite cells.
Become mitotic in times of stress
Found in basal lamina
Give rise to myogenic precursor cells
Describe the characteristics of skeletal muscle
Peripheral, multinucleated Sarcomeric arrangement Single neuron innervation "all-or-none" Contains troponin C
Describe the characteristics of smooth muscle.
Central, mononucleated No sarcomeric arrangement Innervated by ANS Not "all-or-none" Connected via gap junctions
Describe the characteristics of cardiac muscle.
Central, mononucleated
Connected via gap junctions
Not directly innervated
Sarcomeric arrangement
Describe Type I myofibers
Slow twitch, aerobic respiration
Many mitochondria
High NADH/ATPase/myoglobin
Dark/red
Describe Type IIA myofibers.
Between slow/fast twitch
Both aerobic and anaerobic respiration
Resistance to fatigue
Describe Type IIB myofibers.
Fast twitch, anaerobic respiration
Fatigue quickly
White/light fibers
Describe the structure of a neuromuscular spindle.
Extrafusal (skeletal muscle fibers) and intrafusal fibers
What are intrafusal fibers?
Nuclear bag/chain fibers
Nuclear bag contains sensory region
Alpha-motor neurons go to _________ fibers and gamma-motor neurons go to _________ fibers.
Extrafusal
Intrafusal
