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Quizzes > Health & Medicine > Human Anatomy & Medicine

Select the Statement That Accurately Describes the Muscular System

Think you can select the statement that accurately describes the muscular system? Dive in now!

Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art muscle illustration on teal background with quiz banner prompting test of muscular system knowledge

This muscular system quiz helps you pick the correct statement about how muscles work. Get instant feedback as you practice concepts like fiber types, contraction, and neuromuscular signals so you can spot gaps before an exam; when you finish, try a short practice set or tackle the advanced quiz .

Which muscle type is under voluntary control?
Cardiac muscle
Myofibroblast
Skeletal muscle
Smooth muscle
Skeletal muscle fibers are consciously controlled by the somatic nervous system and enable voluntary movements. Cardiac and smooth muscles are involuntary, regulated by the autonomic nervous system. Skeletal muscles are attached to bones via tendons and contract to move the skeleton.
What is the primary protein responsible for muscle contraction?
Actin
Collagen
Keratin
Myosin
Myosin heads bind to actin filaments and use ATP to generate force, causing muscle contraction. Actin is the thin filament but requires myosin for movement. Keratin and collagen are structural proteins in skin and connective tissue, not contractile.
Which structure separates individual muscle fibers into fascicles?
Epimysium
Endomysium
Sarcolemma
Perimysium
The perimysium is connective tissue that groups muscle fibers into bundles called fascicles. Endomysium surrounds individual fibers and epimysium encases the whole muscle. Sarcolemma is the muscle cell membrane.
What ion initiates muscle contraction by binding to troponin?
Calcium
Potassium
Magnesium
Sodium
Calcium binds to troponin, causing conformational change that moves tropomyosin off actin sites so myosin can bind. Sodium and potassium are critical for action potentials but not directly for contraction. Magnesium is a cofactor for ATPases.
Which energy molecule is directly used by myosin during the power stroke?
GTP
NADH
FADH2
ATP
Myosin ATPase hydrolyzes ATP to ADP and inorganic phosphate to power the cross-bridge cycle. GTP is used in signaling, NADH and FADH2 in respiration but not directly for contraction.
Which movement reduces the angle between two bones?
Abduction
Rotation
Flexion
Extension
Flexion decreases the joint angle, such as bending the elbow. Extension increases the angle. Abduction moves a limb away from midline and rotation turns around an axis.
What type of muscle fiber is fatigue-resistant and uses aerobic metabolism?
Type I (slow-twitch)
Type IIb
Type IIx (fast-twitch)
Type IIa
Type I fibers have abundant mitochondria and myoglobin, supporting aerobic metabolism and endurance. Type II fibers are faster but fatigue more quickly. IIa are intermediate, IIx/IIb are glycolytic.
Which neurotransmitter stimulates skeletal muscle contraction at the neuromuscular junction?
Dopamine
Acetylcholine
Norepinephrine
Serotonin
Acetylcholine released from motor neurons binds nicotinic receptors on the sarcolemma, triggering an action potential. Dopamine, norepinephrine, and serotonin are central neurotransmitters, not at the neuromuscular junction.
Which term describes the minimal stimulus needed to elicit a muscle contraction?
Maximal stimulus
Subthreshold stimulus
Threshold stimulus
Supramaximal stimulus
Threshold stimulus is the smallest voltage that triggers an action potential and muscle twitch. Subthreshold fails to produce contraction; maximal elicits maximum response; supramaximal exceeds necessary levels.
During muscle shortening, which band of the sarcomere decreases in length?
A band
I band
Both I band and H zone
H zone
Both the I band and H zone shorten during contraction as actin and myosin overlap more. The A band remains constant length. (Note: only one correct - I band is specific to actin overlap reduction.)
Which connective tissue layer surrounds the entire muscle organ?
Perimysium
Epimysium
Fascia
Endomysium
Epimysium is dense irregular connective tissue that wraps the whole muscle. Endomysium and perimysium encase fibers and fascicles, respectively. Fascia is a broader layer outside the epimysium.
Which term describes the ability of muscle to stretch without damage?
Elasticity
Irritability
Contractility
Extensibility
Extensibility is the capacity of muscle to be stretched beyond its resting length. Elasticity is the ability to recoil to original length. Contractility is to shorten forcefully, and irritability refers to responsiveness to stimuli.
What is the functional unit of a muscle fiber?
Sarcolemma
T-tubule
Myofibril
Sarcomere
The sarcomere, defined by Z discs, is the contractile unit where actin and myosin interact. Myofibrils are chains of sarcomeres. Sarcolemma is the cell membrane, T-tubules are invaginations.
Which process describes a sustained muscle contraction without relaxation?
Recruitment
Summation
Tetanus
Twitch
Tetanus is a smooth, sustained contraction due to high-frequency stimuli. A twitch is a single contraction-relaxation cycle. Summation increases force by overlapping twitches; recruitment adds more fibers.
Which metabolic pathway provides the fastest ATP for short bursts of muscle activity?
Creatine phosphate system
Beta-oxidation
Oxidative phosphorylation
Glycolysis
The creatine phosphate system donates phosphate to ADP to rapidly regenerate ATP for about 10 seconds of high-intensity effort. Glycolysis is slower and oxidative phosphorylation is aerobic. Beta-oxidation is fatty acid breakdown.
Which ion channel opens in response to depolarization of the T-tubule membrane?
Dihydropyridine receptor
Ryanodine receptor
Potassium leak channel
Voltage-gated sodium channel
Dihydropyridine receptors in T-tubules sense voltage changes and mechanically activate ryanodine receptors on the SR to release calcium. Ryanodine receptors release calcium but are not voltage sensors. Sodium channels initiate the action potential.
During sustained exercise, which fuel source becomes predominant after muscle glycogen is depleted?
Plasma glucose
Amino acids
Fatty acids
Lactate
As exercise continues past glycogen depletion, muscles increasingly oxidize fatty acids from adipose tissue. Plasma glucose plays a role but is secondary. Amino acids are minor fuels, lactate is a byproduct.
Which muscle action involves generating force while lengthening?
Isometric contraction
Eccentric contraction
Isokinetic contraction
Concentric contraction
Eccentric contractions occur when a muscle lengthens under tension, such as lowering a weight. Concentric shortens, isometric holds length, isokinetic controls speed. Eccentric actions produce high force with less energy.
Which condition results from autoimmune attack on acetylcholine receptors?
Lambert-Eaton syndrome
Myasthenia gravis
Duchenne muscular dystrophy
Polymyositis
Myasthenia gravis features antibodies against nicotinic receptors, causing muscle weakness that worsens with use. Lambert-Eaton affects presynaptic calcium channels. Duchenne is a dystrophin deficiency. Polymyositis is inflammatory.
Which enzyme degrades acetylcholine in the synaptic cleft?
Butyrylcholinesterase
Acetylcholinesterase
Monoamine oxidase
Choline acetyltransferase
Acetylcholinesterase rapidly hydrolyzes ACh to acetate and choline, terminating the signal. Choline acetyltransferase synthesizes ACh. MAO degrades monoamines. Butyrylcholinesterase acts on other esters.
Which cytoskeletal protein connects Z discs and maintains resting tension?
Nebulin
Dystrophin
Titin
Desmin
Titin spans half the sarcomere, stabilizing myosin and contributing to passive elasticity. Nebulin regulates actin length. Dystrophin links cytoskeleton to extracellular matrix. Desmin maintains alignment.
Which mechanism describes increased force by recruiting more motor units?
Summation
Recruitment
Tetanus
Rate coding
Recruitment refers to activating additional motor units to increase strength. Rate coding changes firing frequency. Summation and tetanus depend on stimulus timing, not number of units.
Which pathological feature characterizes Duchenne muscular dystrophy?
Loss of dystrophin
Excess acetylcholine
Autoimmune necrosis
Mitochondrial proliferation
Duchenne is caused by dystrophin gene mutations leading to absent dystrophin and muscle fiber degeneration. Other options describe different disorders. Loss of dystrophin weakens cell membrane.
Which fiber type is most abundant in marathon runners?
Type IIb fibers
Type IIx fibers
Type I fibers
Type IIa fibers
Endurance athletes have a higher proportion of Type I slow-twitch fibers for aerobic performance and fatigue resistance. Fast-twitch types are more common in sprinters.
Which phenomenon explains why a motor unit fires at higher frequencies before fatigue sets in?
Motor unit remodeling
Twitch potentiation
Rate coding
Recruitment
Rate coding increases the firing frequency of a motor unit to enhance force output. Twitch potentiation is increased force in successive twitches. Recruitment adds units. Remodeling is structural change.
Which clinical test measures the electrical activity of muscle?
ECG
EOG
EMG
EEG
Electromyography (EMG) records muscle electrical signals to diagnose neuromuscular conditions. ECG monitors heart, EEG brain, EOG eye movements.
Which signaling molecule activates protein kinase A to enhance glycogen breakdown in muscle?
Glucagon
Adenosine
Epinephrine
Insulin
Epinephrine binds ?-adrenergic receptors, increasing cAMP and activating PKA, which phosphorylates and activates glycogen phosphorylase. Glucagon acts mainly in liver. Insulin inhibits glycogen breakdown.
Which transcriptional coactivator regulates mitochondrial biogenesis in muscle?
PGC-1?
NF-?B
AP-1
CREB
Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1?) drives the expression of genes involved in mitochondrial replication and oxidative metabolism in muscle. NF-?B, AP-1, CREB have other roles.
Which ion accumulation triggers muscle fatigue during high-intensity exercise?
Calcium
Sodium
Chloride
Potassium
Excess extracellular K+ during high-frequency firing reduces membrane potential and impairs action potential propagation, contributing to fatigue. Calcium is essential for contraction; sodium and chloride less implicated.
Which dystroglycan complex component links the cytoskeleton to the extracellular matrix?
Desmin
Nebulin
Titin
Dystrophin
Dystrophin binds F-actin internally and connects to dystroglycan and extracellular laminin, stabilizing the sarcolemma. Other proteins have structural roles but not ECM linkage.
Which pathway is upregulated in muscle atrophy to degrade proteins?
mTOR
Glycolysis
Oxidative phosphorylation
Ubiquitin-proteasome
Muscle atrophy activates ubiquitin ligases (e.g., MuRF1) that tag proteins for proteasomal degradation. mTOR promotes growth, not atrophy. Glycolysis and oxidative phosphorylation are metabolic.
Which genetic mutation leads to myotonic dystrophy type 1?
CAG repeat expansion
CGG repeat expansion
CTG repeat expansion
GAA repeat expansion
Myotonic dystrophy type 1 is caused by CTG trinucleotide repeat expansions in the DMPK gene, leading to multisystemic symptoms. GAA causes Friedreich ataxia; CGG Fragile X; CAG Huntington disease.
Which signaling cascade promotes fast-to-slow fiber type transformation with endurance training?
JAK-STAT
mTORC1-S6K
Calcineurin-NFAT
MAPK-ERK
Calcineurin dephosphorylates NFAT, which translocates to the nucleus and induces slow fiber gene expression. mTORC1-S6K drives hypertrophy. MAPK-ERK and JAK-STAT have other roles.
Which drug class inhibits acetylcholinesterase to treat myasthenia gravis?
ACE inhibitors
Beta blockers
Calcium channel blockers
Cholinesterase inhibitors
Cholinesterase inhibitors like pyridostigmine increase acetylcholine availability at the neuromuscular junction, improving muscle strength. Other drug classes have different targets.
Which biopsy finding is characteristic of polymyositis?
Dystrophin deficiency
Perifascicular atrophy
Rimmed vacuoles
Endomysial inflammation
Polymyositis shows endomysial inflammatory infiltrates of CD8+ T cells attacking fibers. Dermatomyositis has perifascicular atrophy. Dystrophin deficiency is Duchenne, rimmed vacuoles are inclusion body myositis.
Which process regulates muscle glucose uptake during exercise?
Insulin-mediated GLUT4 translocation
AMPK-mediated GLUT4 translocation
PKA-mediated glucose uptake
mTOR-mediated glucose transport
Exercise activates AMPK, which promotes GLUT4 translocation and glucose uptake independently of insulin. Insulin also triggers GLUT4 but is not the primary driver during exercise.
Which molecule buffers hydrogen ions in active muscle to delay fatigue?
Creatine
Carnosine
ATP
Lactic acid
Carnosine, a dipeptide in muscle, buffers H+ generated by metabolism, stabilizing pH and delaying fatigue. Creatine stores high-energy phosphate. Lactic acid contributes to acidity; ATP is energy currency.
Which microRNA is implicated in skeletal muscle hypertrophy by targeting myostatin expression?
miR-133a
miR-1
miR-206
miR-486
miR-486 downregulates PTEN and indirectly suppresses myostatin signaling, promoting hypertrophy. Other miRNAs regulate differentiation but not directly myostatin in adult muscle.
Which advanced imaging technique quantifies muscle fiber orientation and architecture?
Dual-energy X-ray absorptiometry
FDG-PET
Ultrasound elastography
Diffusion tensor MRI
Diffusion tensor MRI measures directional water diffusion, revealing fiber tracts and pennation angles in muscle. Elastography measures stiffness, FDG-PET metabolism, DEXA body composition.
Which splice variant of titin is upregulated in cardiac muscle but not in skeletal muscle?
N2BA
Universal titin
N2A
N2B
Cardiac muscle expresses the shorter N2B isoform of titin, contributing to higher stiffness. N2A is skeletal, N2BA is a mixture, and universal titin is not a variant.
Which receptor tyrosine kinase mediates satellite cell activation for muscle repair?
PDGFR-?
ErbB2
VEGFR2
c-Met
c-Met is the receptor for hepatocyte growth factor (HGF) and triggers satellite cell activation after injury. ErbB2/VEGFR2/PDGFR-? have roles in other tissues.
Which transcription factor is essential for myogenic determination during embryonic development?
NFATc1
MyoD
SRF
MEF2C
MyoD is a master regulator gene that commits cells to the myogenic lineage in embryogenesis. MEF2C and SRF modulate differentiation; NFATc1 is involved in fiber type regulation.
Which advanced proteomic approach quantifies phosphorylation changes in contracting muscle?
SILAC-based phosphoproteomics
Western blot only
2D gel electrophoresis
Label-free shotgun proteomics
SILAC uses isotope labeling for accurate quantitation of phosphorylation sites during contraction. Shotgun can detect proteins but less precise quantitation, 2D gels and Western blot are lower throughput.
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Study Outcomes

  1. Identify muscle classifications -

    Describe the characteristics of skeletal, cardiac, and smooth muscles, and differentiate their roles within the muscular system.

  2. Analyze muscle fiber functions -

    Evaluate how different muscle fiber types contribute to strength, endurance, and speed in various physiological activities.

  3. Select accurate muscular system statements -

    Apply critical thinking to select the statement that accurately describes the muscular system from multiple-choice options.

  4. Explain muscle-posture control -

    Understand the mechanisms by which muscles maintain posture and stability during static and dynamic movements.

  5. Apply muscle nomenclature rules -

    Use standardized naming conventions to identify muscles based on location, shape, and function.

  6. Illustrate contraction roles in movement -

    Explain how a muscle contracts on demand to provide posture and movement, integrating knowledge of actin-myosin interactions.

Cheat Sheet

  1. Muscle Fiber Types -

    Muscle fibers are classified as slow-oxidative (type I) or fast-glycolytic (type II), each suited for endurance or power respectively, as described in Tortora & Derrickson's Principles of Anatomy and Physiology. A handy mnemonic is "SOFT" (Slow, Oxidative, Fatigue-resistant, for Posture and endurance). Understanding these differences will help you select the statement that accurately describes the muscular system in any quiz scenario.

  2. Sliding Filament Mechanism -

    The contraction cycle is driven by actin and myosin cross-bridges pulling filaments past each other, powered by ATP hydrolysis (Alberts et al., Molecular Biology of the Cell). Visualizing this process with the "attach-pivot-detach" steps cements your grasp of contraction physics. Mastering this cycle ensures you choose the correct answer when asked to select the statement that accurately describes the muscular system's molecular function.

  3. Neuromuscular Junction Essentials -

    At the neuromuscular junction, acetylcholine release triggers an action potential that travels down T-tubules, causing Ca2+ release from the sarcoplasmic reticulum and initiating contraction (Guyton & Hall, Textbook of Medical Physiology). Remember "A-T-C" (ACh, T-tubule, Ca2+) to quickly recall the sequence. This sequence is often tested, so knowing it by heart helps you select the statement that accurately describes the muscular system's activation process.

  4. Muscle Naming Conventions -

    Muscles are named by criteria like location (e.g., brachialis), shape (e.g., deltoid), size (e.g., gluteus maximus), and fiber direction (e.g., rectus abdominis) based on Gray's Anatomy. An easy acronym is "LSFDS": Location, Shape, Fiber, Depth, and Size. Recognizing these patterns is key when you select the statement that accurately describes the muscular system's nomenclature rules.

  5. Posture vs. Movement Roles -

    Skeletal muscles perform isometric contractions to maintain posture and isotonic contractions (concentric and eccentric) to generate movement (American College of Sports Medicine guidelines). Think "PIO" (Posture-Isometric, Isotonic-Movement, Opposition-Eccentric control) to recall each type. This distinction is critical for selecting the statement that accurately describes the muscular system's functional roles in maintaining stability and motion.

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