Biology Human Anatomy & Physiology Flashcards

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

Answer: A motor neuron action potential propagated via T-tubules

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

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

Answer: Ball-and-socket joint

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

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

Answer: Create a concentration gradient in the renal medulla

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

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

Answer: Cytotoxic T cells (CD8+)

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

Gas exchange in the lungs occurs primarily by which mechanism?

Answer: Simple diffusion along partial pressure gradients

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

Which hormone, secreted by adipose tissue, signals satiety and suppresses appetite by acting on the hypothalamus?

Answer: Leptin

Leptin is released by adipocytes proportional to fat stores and signals the hypothalamus to suppress hunger.

The olfactory receptors that detect smell are classified as which type of sensory receptor based on stimulus origin?

Answer: Chemoreceptor

Olfactory receptors are chemoreceptors that respond to dissolved chemical molecules binding to receptor proteins in the nasal epithelium.