Musculoskeletal System Flashcards
What is the basic contractile unit of a muscle fiber?
C. Sarcomere
The sarcomere is defined by Z discs and contains thick (myosin) and thin (actin) filaments.
Which of the following structures stores calcium ions that are released during muscle contraction?
B. Sarcoplasmic reticulum
The sarcoplasmic reticulum stores calcium ions, which are released when the muscle is stimulated to contract.
The neurotransmitter that stimulates muscle contraction at the neuromuscular junction is:
B. Acetylcholine
Acetylcholine stimulates muscle contraction by binding to receptors at the neuromuscular junction.
What role do calcium ions play in muscle contraction?
C. They expose the binding sites on actin filaments.
Calcium ions bind to troponin, causing a conformational change that exposes the binding sites on actin filaments for myosin to bind.
Which connective tissue layer surrounds individual muscle fibers?
A. Endomysium
The endomysium provides structural support and electrical isolation.
Which of the following describes an isotonic contraction?
A. The muscle shortens and movement occurs.
In isotonic contractions, the muscle shortens and movement occurs, such as during lifting weights.
ATP is regenerated in muscle fibers through which of the following processes?
D. Direct phosphorylation by creatine phosphate
Direct phosphorylation by creatine phosphate quickly regenerates ATP during short bursts of muscle activity.
What is the role of the perimysium in skeletal muscle?
B. It separates and surrounds bundles of muscle fibers (fascicles).
The perimysium surrounds and separates bundles of muscle fibers, known as fascicles.
What type of muscle contraction occurs when the muscle generates force but does not change length?
A. Isometric contraction
In isometric contractions, the muscle generates force but does not shorten or change length.
During muscle contraction, what happens to the sarcomere?
B. It shortens as actin filaments slide past myosin filaments.
During contraction, the sarcomere shortens as actin filaments slide past myosin filaments.
The release of calcium from the sarcoplasmic reticulum results in which of the following?
C. Exposure of binding sites on actin
Calcium ions bind to troponin, exposing binding sites on actin filaments for myosin to attach and initiate contraction.
Which muscle type is controlled involuntarily and is found in the walls of internal organs?
C. Smooth muscle
Smooth muscle is involuntary and found in the walls of internal organs such as the stomach and intestines.
Which of the following best describes the function of the myosin heads during muscle contraction?
B. They bind to actin, flex, and pull the thin filaments toward the center of the sarcomere.
The myosin heads cause muscle contraction by pulling the actin filaments toward the center of the sarcomere.
Which process produces ATP in muscle fibers during prolonged, oxygen-dependent activity?
C. Aerobic respiration
Aerobic respiration is the primary source of ATP during prolonged activity, as it efficiently uses oxygen to produce ATP.
What type of muscle contraction occurs when the muscle lengthens while generating force?
B. Eccentric contraction
In eccentric contractions, the muscle lengthens while generating force, such as lowering a weight.
The sarcoplasmic reticulum’s primary role is to:
B. Store calcium ions for muscle contraction.
The sarcoplasmic reticulum stores calcium ions, which are released to trigger muscle contraction.
The direct source of energy for muscle contraction is:
C. ATP
ATP is the direct source of energy for muscle contraction.
Which of the following types of muscle fibers are best suited for short bursts of activity?
B. Fast-twitch fibers
Fast-twitch fibers are better suited for short bursts of high-intensity activity, as they quickly generate energy through anaerobic glycolysis.
What occurs when a muscle fiber contracts?
B. Myosin filaments slide past actin filaments.
During contraction, myosin filaments pull the actin filaments toward the center of the sarcomere, shortening the muscle.
Which of the following muscle types is characterized by striations and involuntary control?
C. Cardiac muscle
Cardiac muscle is striated and under involuntary control, found in the heart.
