#1
Which molecule is responsible for storing and providing energy in muscle cells?
Adenosine triphosphate (ATP)
ExplanationATP serves as the primary energy carrier in muscle cells, releasing energy during its conversion to ADP.
#2
What is the term for the increase in muscle size resulting from resistance training and an increase in the size of individual muscle fibers?
Muscle hypertrophy
ExplanationMuscle hypertrophy is the enlargement of muscles due to increased fiber size, often resulting from resistance training.
#3
What is the term for the minimal stimulus required to elicit a muscle contraction?
Threshold stimulus
ExplanationThreshold stimulus is the minimum stimulus needed to initiate a muscle contraction.
#4
What is the term for the muscle's ability to return to its original length and shape after contraction or extension?
Elasticity
ExplanationElasticity is the ability of muscles to return to their original length and shape after contraction or extension.
#5
What is the term for the brief contraction of all muscle fibers in a motor unit in response to a single action potential?
Twitch
ExplanationA twitch is the brief contraction of all muscle fibers in a motor unit in response to a single action potential.
#6
What is the primary function of the sarcoplasmic reticulum in muscle cells?
Calcium ion storage and release
ExplanationThe sarcoplasmic reticulum stores and releases calcium ions, crucial for muscle contraction and relaxation.
#7
Which neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?
Acetylcholine
ExplanationAcetylcholine is released at the neuromuscular junction, triggering muscle fiber depolarization and contraction.
#8
What is the role of tropomyosin in muscle contraction?
Blocking myosin-binding sites on actin
ExplanationTropomyosin blocks myosin-binding sites on actin, preventing muscle contraction in the absence of calcium.
#9
Which type of muscle fibers are fatigue-resistant and primarily use oxidative metabolism for energy production?
Type I (slow-twitch) fibers
ExplanationType I fibers are fatigue-resistant and rely on oxidative metabolism for sustained energy production.
#10
Which enzyme breaks down acetylcholine to terminate its action at the neuromuscular junction?
Acetylcholinesterase
ExplanationAcetylcholinesterase breaks down acetylcholine, terminating its action and allowing muscle relaxation.
#11
What is the term for the contractile unit of a muscle fiber, consisting of overlapping actin and myosin filaments?
Sarcomere
ExplanationA sarcomere is the functional unit of muscle contraction, formed by the arrangement of actin and myosin filaments.
#12
During which phase of muscle contraction do the actin and myosin filaments slide past each other, causing the muscle to shorten?
Concentric contraction
ExplanationConcentric contraction involves the shortening of muscles as actin and myosin filaments overlap.
#13
What is the phenomenon where a muscle contracts with increasing force in response to repeated stimulation at a constant intensity?
Twitch summation
ExplanationTwitch summation refers to the increased force of muscle contraction due to repeated stimulation without complete relaxation.
#14
Which ion directly binds to troponin, leading to the exposure of myosin-binding sites on actin during muscle contraction?
Calcium (Ca2+)
ExplanationCalcium ions directly bind to troponin, allowing the myosin-binding sites on actin to be exposed and initiating muscle contraction.
#15
In which phase of muscle contraction does the muscle generate force without changing its length?
Isometric contraction
ExplanationIsometric contraction involves muscle force generation without a change in muscle length.