SAT - Biology Subject Human Anatomy and Physiology Questions and Answers

Question 1

Which of the following describes the primary role of calcium ions (Ca2+) in the contraction of a skeletal muscle fiber?

Accepted Answer

To bind to troponin, which causes tropomyosin to shift and expose the myosin-binding sites on actin.

Answer

In skeletal muscle contraction, an action potential triggers the release of Ca2+ from the sarcoplasmic reticulum. These calcium ions then bind to troponin, a protein complex on the actin filament. This binding causes a conformational change that moves the tropomyosin protein, uncovering the sites on actin where myosin heads can bind, thus initiating the cross-bridge cycle and muscle contraction.

Question 2

A patient is found to have a consistently high level of blood calcium (hypercalcemia). A defect in which of the following glands or hormones would most likely contribute to this condition through a failure of negative feedback?

Accepted Answer

Overproduction of parathyroid hormone (PTH) by the parathyroid glands.

Answer

Parathyroid hormone (PTH) is responsible for raising blood calcium levels by stimulating its release from bones, increasing its reabsorption in the kidneys, and promoting the activation of Vitamin D to enhance intestinal absorption. In a normal negative feedback loop, high blood calcium would suppress PTH secretion. An overproduction of PTH would override this feedback, leading to chronically high blood calcium levels (hypercalcemia).

Question 3

Which of the following correctly traces the path of deoxygenated blood as it enters the heart and is pumped toward the lungs?

Accepted Answer

Superior Vena Cava → Right Atrium → Right Ventricle → Pulmonary Artery

Answer

Deoxygenated blood from the systemic circuit returns to the heart via the superior and inferior vena cavae, entering the right atrium. From there, it passes through the tricuspid valve into the right ventricle. The right ventricle then contracts, pumping the deoxygenated blood through the pulmonary valve into the pulmonary artery, which carries it to the lungs for oxygenation.

Question 4

The primary function of the Loop of Henle within the nephron of the kidney is to:

Accepted Answer

create a salt concentration gradient in the renal medulla.

Answer

The Loop of Henle establishes a hypertonic (high salt) concentration gradient in the interstitial fluid of the renal medulla. This gradient is critical for the final step of urine concentration, as it allows the collecting ducts to reabsorb water from the filtrate under the influence of antidiuretic hormone (ADH), thereby conserving water for the body.

Question 5

During the transmission of a nerve impulse, the rapid depolarization of the neuron's membrane is primarily caused by which event?

Accepted Answer

The influx of sodium ions (Na+).

Answer

When a neuron reaches its threshold potential, voltage-gated sodium channels open rapidly. This allows a massive influx of positively charged sodium ions (Na+) to rush into the cell, down their electrochemical gradient. This rapid influx of positive charge causes the membrane potential to shoot up from negative to positive, an event known as depolarization, which is the rising phase of the action potential.

SAT - Biology Subject Test Practice Test

SAT - Biology Subject Test Practice Test

SAT - Biology Subject Human Anatomy and Physiology Questions and Answers