GRE Subject Test: Biology : Understanding Musculoskeletal Functions

Study concepts, example questions & explanations for GRE Subject Test: Biology

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Example Questions

Example Question #1 : Understanding Musculoskeletal Functions

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?

Possible Answers:

White fibers have less myoglobin than red fibers

Red fibers have more mitochondria than white fibers

White fibers fatigue more quickly than red fibers

White fibers utilize aerobic respiration more than red fibers

Correct answer:

White fibers utilize aerobic respiration more than red fibers

Explanation:

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 #2 : Understanding Musculoskeletal Functions

Influx of which ion through the T-tubules will cause calcium release from the sarcoplasmic reticulum?

Possible Answers:

Potassium

Calcium

Sodium

Chloride

Correct answer:

Calcium

Explanation:

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 #3 : Understanding Musculoskeletal Functions

The triceps brachii extends the arm, while the biceps brachii flexes the arm. How is the biceps brachii related to the triceps brachii?

Possible Answers:

They are antagonists

They are agonists

It is a fixator of the triceps brachii

They are synergists

Correct answer:

They are antagonists

Explanation:

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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