GRE Subject Test: Biology : Understanding Musculoskeletal Functions
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Example Questions
Example Question #271 : Biology
Skeletal muscle fibers are made up of white and red fibers. White fibers are considered fast-twitch and red fibers are considered slow-twitch.
Which of these statements INCORRECTLY describes a difference between white and red fibers?
White fibers fatigue more quickly than red fibers
Red fibers have more mitochondria than white fibers
White fibers have less myoglobin than red fibers
White fibers utilize aerobic respiration more than red fibers
White fibers utilize aerobic respiration more than red fibers
White fibers have less myoglobin than red fibers. White fibers have less mitochondria than red fibers. White fibers fatigue more quickly than red fibers.
White fibers primarily use anaerobic respiration (red primarily uses aerobic). Remember that red fibers are active over long periods of sustained stress, while white fibers are more explosive. Red fibers require oxygen from respiration and myoglobin to maintain activity.
Example Question #1 : Understanding Musculoskeletal Functions
Influx of which ion through the T-tubules will cause calcium release from the sarcoplasmic reticulum?
Chloride
Sodium
Potassium
Calcium
Calcium
When acetylcholine binds to its receptors at the neuromuscular junction, it stimulates an initial influx of sodium ions that cause a localized depolarization of the muscle cell. This depolarization causes voltage-gated calcium channels to open within the T-tubules, carrying the signal into the cell interior. Proteins in the wall of the T-tubules directly interact with the internal sarcoplasmic reticulum, stimulating the organelle to release intracellular calcium. This release liberates myosin-binding sites on actin, allowing contraction to occur.
Sodium ions, potassium ions, and chloride ions play important roles in maintaining membrane potential at the neuromuscular junction, but the T-tubules rely heavily on calcium to interact with the sarcoplasmic reticulum.
Example Question #8 : Musculoskeletal System
The triceps brachii extends the arm, while the biceps brachii flexes the arm. How is the biceps brachii related to the triceps brachii?
They are agonists
It is a fixator of the triceps brachii
They are antagonists
They are synergists
They are antagonists
Since the triceps and biceps produce opposing motions in the arm, they can be considered antagonists of one another. An antagonist will stretch, while the agonist contracts, and vice versa. Extensors, such as the triceps brachii, will act as antagonists of flexors, such as the biceps brachii.
A synergist assists the agonist by stabilizing the origin bone.
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