10 High-Frequency Traps in Neural Control (NEET)

Trap 1: Resting Potential Sign Error

Wrong: "Resting membrane potential is +70 mV" Correct: -70 mV. The INSIDE is NEGATIVE. Why students fall: They confuse the magnitude (70) with the sign. Remember: at REST, inside is NEGATIVE (-).

Trap 2: Cerebellum Initiates Movement

Wrong: "The cerebellum initiates voluntary movements" Correct: The CEREBRUM (motor cortex) initiates; cerebellum only COORDINATES. NEET question stem: "Which brain region is responsible for initiating voluntary movement?" → Answer: Cerebrum (motor cortex), NOT cerebellum.

Trap 3: Na+/K+ Pump Ratio Reversal

Wrong: "The pump moves 2 Na+ out and 3 K+ in" Correct: 3 Na+ OUT, 2 K+ IN (more sodium pumped out than potassium pumped in). Memory trick: "3 out, 2 in" — the LARGER number goes OUT.

Trap 4: Depolarization = K+ efflux

Wrong: "K+ flowing out causes depolarization" Correct: Na+ influx causes depolarization. K+ efflux causes REPOLARIZATION. Mnemonic: NDKR = Na Depolarizes, K Repolarizes.

Trap 5: Stapes Connects to Round Window

Wrong: "Stapes connects to the round window" Correct: Stapes connects to the OVAL window. The round window is a pressure-relief valve.

Trap 6: Rods for Colour Vision

Wrong: "Rods detect colour; cones detect dim light" Correct: RODS (rhodopsin) = dim light (scotopic). CONES (iodopsin) = colour (photopic), at fovea.

Trap 7: Myopia Corrected by Convex Lens

Wrong: "Myopia (short-sightedness) is corrected by a convex (converging) lens" Correct: Myopia → concave $\frac{diverging}{minus}$ lens. Hypermetropia → convex $\frac{converging}{plus}$ lens. Rule: Myopia = Minus (concave). Hypermetropia = H-ype = H-convex.

Trap 8: Thalamus Relays Smell

Wrong: "The thalamus relays ALL sensory information to the cerebral cortex" Correct: ALL senses EXCEPT SMELL bypass the thalamus. Olfactory fibres project directly to the olfactory cortex.

Trap 9: Cerebellum Damage Causes Paralysis

Wrong: "Cerebellar damage causes paralysis (loss of movement)" Correct: Cerebellar damage causes ATAXIA (loss of coordination). Muscle strength is PRESERVED (motor cortex and corticospinal tract are intact).

Trap 10: Presbyopia is the Same as Myopia

Wrong: "Presbyopia occurs due to elongated eyeball in old age" Correct: Presbyopia is age-related LOSS OF LENS ELASTICITY → reduced accommodation. Myopia is elongated eyeball (not age-related). Presbyopia is corrected by bifocals (not just concave or convex).