Skeletal Muscle Quiz

Skeletal Muscle

• Voluntary muscle with striations
• Multinucleated muscle fibers
• Contains mitochondria for energy production
• Sarcolemma is the plasma membrane
• Sarcoplasm is the cytoplasm
• Sarcoplasmic reticulum stores calcium
• Myofibrils are contractile structures
• Sarcomeres are the basic contractile units
• Myosin is a thick filament protein with actin-binding sites
• Actin is a thin filament protein with myosin-binding sites
• Tropomyosin inhibits actin-myosin interaction
• Troponin binds calcium and moves tropomyosin
• Motor units consist of a motor neuron and the muscle fibers it innervates
• Neuromuscular junction is the synapse between a motor neuron and muscle fiber
• Acetylcholine is a neurotransmitter released at the neuromuscular junction
• Motor end plate is the region of the muscle fiber membrane under the axon terminal
• Acetylcholinesterase breaks down acetylcholine
• Curare blocks ACh receptors
• Organophosphates inhibit acetylcholinesterase
• Nerve gases also inhibit ACh breakdown
• Pralidoxime is an antidote that reactivates acetylcholinesterase
• Atropine is a muscarinic receptor antagonist
• Succinylcholine acts as an ACh receptor agonist
• Rocuronium and vecuronium are nondepolarizing neuromuscular blockers
• Botulinum toxin blocks acetylcholine release
• SNARE complex is needed for neurotransmitter vesicle fusion
• Cross-bridge cycling occurs due to Ca2+ and is a process for muscle contraction
• Excitation-contraction coupling links action potential to muscle contraction.
• Sliding-filament mechanism is how muscle contraction occurs
• Twitch is the mechanical response to a single action potential
• Latent period is between action potential and contraction
• Contraction phase is when tension develops
• Relaxation phase is when tension decreases
• Isometric twitches generate tension without shortening
• Isotonic twitches shorten while generating tension
• Summation is increased tension from successive action potentials leading to tetanus
• Titin provides passive elasticity in muscles
• Optimal length (L0) is for maximum isometric tension
• ATP production via creatine phosphate, oxidative phosphorylation, and glycolysis
• Muscle fatigue is due to repeated stimulation
• Central command fatigue is cerebral cortex failing to signal motor neurons
• Fatigue factors include ATP decrease and ion concentration changes
• Shortening velocity is the rate of muscle fiber shortening
• Skeletal muscle fibers vary in characteristics
• Fibers are classified by velocity and ATP synthesis pathway
• Oxidative fibers have high mitochondria, dark meat, and are for endurance
• Glycolytic fibers have few mitochondria, high glycogen, and are for quick bursts
• Slow-oxidative (Type I), fast-oxidative-glycolytic (Type IIa), and fast-glycolytic (Type IIb) fibers make up muscle fiber types
• Whole-muscle tension depends on fiber tension and fiber count
• Shortening velocity control depends on load and motor unit recruitment
• Muscle adaptation is increased activity leading to larger fibers and ATP capacity
• Disuse atrophy is muscle wasting from inactivity
• Denervation atrophy is muscle wasting from nerve damage
• Skeletal muscle disorders include conditions affecting muscle contraction control
• Poliomyelitis is a viral disease destroying motor neurons
• Muscle cramps are involuntary contractions due to high action potentials
• Electrolyte imbalances cause muscle cramps from dehydration
• Hypocalcemic tetany causes involuntary contractions from low extracellular Ca2+
• Muscular dystrophy is a genetic disease causing muscle degeneration
• Duchenne muscular dystrophy is an X-linked disorder due to a dystrophin deficiency
• Myasthenia gravis is an autoimmune disorder affecting ACh receptors
• Acetylcholinesterase inhibitors prolong acetylcholine availability
• Plasmapheresis is a blood treatment replacing antibodies

Smooth Muscle

• Involuntary muscle, found in organs, non-striated
• Spindle-shaped, single nucleus, smaller than skeletal muscle
• Thick myosin and thin actin filaments, no troponin
• Dense bodies anchor thin filaments
• Motor units are groups of fibers controlled by a single neuron
• Myosin light chain kinase (MLCK) phosphorylates myosin for cross-bridge cycling
• Myosin light chain phosphatase (MLCP) dephosphorylates myosin to induce relaxation
• Cytosolic Ca2+ comes from sarcoplasmic reticulum and extracellular fluid
• Pacemaker potential leads to spontaneous action potentials
• Slow waves are fluctuations in membrane potential
• Varicosities are swollen regions of autonomic neurons
• Norepinephrine influences smooth muscle contraction
• Local factors are paracrine signals affecting tension
• Single-unit smooth muscle acts as a single unit via gap junctions
• Multi-unit smooth muscle cells respond independently

Cardiac Muscle

• Involuntary muscle, found in the heart, striated
• Automaticity is its ability to generate action potentials independently
• Absolute refractory period is the time preventing tetanic contractions

Additional Information

• Myoglobin is an oxygen-binding protein
• Calcium channels allow Ca2+ entry during contraction
• Mechanosensitive ion channels open in response to mechanical stretching
• Desmosomes provide mechanical strength in cardiac muscle
• Rhabdomyolysis is the rapid breakdown of muscle tissue from myoglobin release
• Acidosis (increased acidity in blood) affects muscle function
• Malignant hyperthermia causes muscle rigidity and hypermetabolism

Test your knowledge on skeletal muscle structure and function with this quiz. Explore essential concepts such as myofibrils, neurotransmission at the neuromuscular junction, and protein interactions in muscle contraction. Perfect for students of anatomy and physiology.