Tissues of Sharks Are Isotonic to Seawater, but Their Concentrations

question 36

Multiple Choice

Tissues of sharks are isotonic to seawater, but their concentrations of sodium ions, potassium ions, and chloride ions in cells and extracellular fluids are similar to those of freshwater fishes. What can you infer about the movement of sodium and chloride in these animals?

• A) To maintain homeostasis of sodium and chloride levels, the shark must take up additional sodium and chloride from seawater.
• B) Sodium and chloride will diffuse into shark gills from seawater down their concentration gradient.
• C) Sharks conserve sodium and chloride, limiting excretion.
• D) Sodium and chloride must be eliminated through the gills.

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Definitions:

Single Sarcomere

The smallest contractile unit of a muscle fiber, consisting of actin and myosin filaments, responsible for muscle contraction.

Sarcolemma

The cell membrane surrounding a muscle fiber, crucial in muscle contraction and conduction of nerve impulses.

Labeled Structure

A term indicating a diagram or image where specific parts have been marked with labels to identify them.

Acetylcholine

A neurotransmitter in both the central and peripheral nervous systems that is involved in muscle contraction, memory formation, and various other functions.