Wrong about disk on L4 root:

Correct Answer: C

Rationale: It is the most common disk . Herniation at the L4 root (typically L3-L4 disc) affects the L4 nerve, impacting knee jerk (via quadriceps, A), sensation in the anteromedial leg , and knee extension , all correct. However, the most common disc herniation is at L5-S1, not L3-L4 or L4-L5, due to greater mechanical stress lower in the spine. Thus, C inaccurately claims L4 is the most common site, making it the wrong statement and the correct answer.

Correct Answer: C

Rationale: Nucleus proprius . Laminae III and IV of the spinal cord gray matter contain the nucleus proprius, which processsensory input like fine touch and pressure, relaying it to ascending pathways. Choice A (intermedio-medial nucleus) is in lamina VII, for visceral functions. Choice B (intermedio-lateral nucleus) is in lamina VII (T1-L2), for sympathetic neurons. Choice D (substantia gelatinosa) is in lamina II, for pain and temperature. Thus, C correctly identifithe nucleus proprius in laminae III-IV, making it the right answer.

Correct Answer: C

Rationale: They form internal arcuate fibers as they decussate , which is false for first-order neurons. In the dorsal column pathway, first-order neurons from the arm (pseudounipolar, D) ascend in the fasciculus cuneatus and synapse in the nucleus cuneatus . Second-order neurons from the nucleus cuneatus form internal arcuate fibers and decussate. Choice C attributthis to first-order neurons, which dont decussate they end in the medulla. Thus, C is the exception, making it the correct answer.

Correct Answer: D

Rationale: the gracile tract. The fasciculus gracilis (gracile tract) in the dorsal column carriconscious proprioception from the lower limbs, synapsing in the nucleus gracilis, then via medial lemniscus to the cortex. Choice A (medial lemniscus) is part but not the initial structure. Choice B (dorsal spinocerebellar) is for unconscious proprioception to cerebellum. Choice C (spinothalamic) is for pain/temperature. Choice D (ventral spinocerebellar) is also unconscious. Thus, D (gracile tract) is specific for lower limb position sense, making it correct.

Correct Answer: B

Rationale: The anterior spinothalamic tract is found in the anterior white column . The anterior spinothalamic tract, carrying crude touch, ascends in the anterior (ventral) white column of the spinal cord after crossing. Choice A is wrong (posterior spinocerebellar is in the lateral column). Choice C is incorrect (lateral spinothalamic is in the lateral column). Choice D is false (fasciculus gracilis is in the posterior column). Thus, B correctly locatthe anterior spinothalamic tract, making it the right answer.