Biology Test Biology Human Anatomy & Physiology 5

Question 1

In the sliding filament theory, what triggers the release of calcium from the sarcoplasmic reticulum?

Accepted Answer

A motor neuron action potential propagated via T-tubules

Answer

Action potentials travel down T-tubules and trigger calcium release from the sarcoplasmic reticulum via ryanodine receptors.

Question 2

Which type of joint allows the greatest range of motion in multiple planes?

Accepted Answer

Ball-and-socket joint

Answer

Ball-and-socket joints, like the hip and shoulder, allow flexion, extension, abduction, adduction, and circumduction.

Question 3

The countercurrent multiplier mechanism in the loop of Henle primarily serves to:

Accepted Answer

Create a concentration gradient in the renal medulla

Answer

The loop of Henle establishes a hypertonic medullary gradient that allows the collecting duct to concentrate urine under ADH influence.

Question 4

Which immune cells are responsible for directly killing virus-infected cells and tumor cells?

Accepted Answer

Cytotoxic T cells (CD8+)

Answer

CD8+ cytotoxic T cells recognize and destroy cells displaying foreign antigens on MHC class I molecules via perforin and granzymes.

Question 5

Gas exchange in the lungs occurs primarily by which mechanism?

Accepted Answer

Simple diffusion along partial pressure gradients

Answer

O2 and CO2 move across the alveolar-capillary membrane by simple diffusion down their respective partial pressure gradients.

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