MCQs

Bitter taste evolved as a protective mechanism against ingesting plant toxins, which are frequently alkaloids (like quinine, caffeine, and nicotine) or other nitrogenous compounds.

Otoliths (or otoconia) are heavy calcium carbonate crystals in the maculae of the utricle and saccule. Gravity pulls on them, shifting the gelatinous membrane and bending the underlying hair cells.

Many rod cells converge onto a single bipolar cell (and many bipolar cells onto a ganglion cell), increasing light sensitivity through spatial summation but sacrificing visual acuity. Cones have a 1:1 ratio in the fovea.

Lateral inhibition occurs when a strongly stimulated central neuron inhibits its less-stimulated neighbors via interneurons. This isolates the signal, improving stimulus localization and contrast.

The fingertips have extremely high densities of Meissner's corpuscles and Merkel discs with very small receptive fields, allowing for precise two-point discrimination and fine tactile resolution.

The axons of primary olfactory sensory neurons travel through the porous cribriform plate of the ethmoid bone to synapse with mitral and tufted cells in the olfactory bulb.

Pulmonary stretch receptors are a type of mechanoreceptor located in the smooth muscle of the airways. They detect mechanical deformation (stretching) during inspiration (Hering-Breuer reflex).

The organ of Corti sits on the basilar membrane within the cochlear duct (scala media), which is filled with endolymph. The scala vestibuli and scala tympani contain perilymph.

Meissner's corpuscles are rapidly adapting, encapsulated receptors found just beneath the epidermis in hairless skin, specializing in fine, discriminative touch.

Fast, sharp pain (like a needle prick) is transmitted rapidly by myelinated A-delta fibers. Slow, dull, aching pain is transmitted by unmyelinated C fibers.

Rhodopsin consists of opsin protein bound to retinal. Retinal is a light-absorbing molecule synthesized directly from Vitamin A (retinol). Vitamin A deficiency leads to night blindness.

A generator potential is a graded depolarization in the sensory nerve ending itself. If it reaches threshold, it opens voltage-gated sodium channels at the first node of Ranvier, firing an action potential.

The adequate stimulus is the specific form of energy (light, mechanical, chemical) to which a receptor is uniquely adapted and most sensitive, having the lowest threshold for activation. It is not the only energy that can activate it (e.g., a hard punch to the eye causes seeing "stars").

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.

Blocking the kinetochores prevents microtubule attachment at the centromere, interrupting mitotic checkpoints and halting orderly chromosome separation.