In the dorsal horn-medial lemniscal pathway, the cell bodiof the first, second, and third order neurons are located in, respectively:

Correct Answer: D

Rationale: Dorsal root ganglia, brain stem, diencephalon . In the dorsal column-medial lemniscal pathway: first-order neuron cell bodiare in the dorsal root ganglia (DRG), sensing stimuli; second-order are in the medulla (brainstem, nucleus gracilis/cuneatus), where they decussate; third-order are in the thalamus (diencephalon, VPL), relaying to cortex. Choice A misplacfirst-order (dorsal column is axons). Choice B usvague terms (hindbrain/forebrain). Choice C misnamregions. Thus, D accurately locatthe neurons, making it correct.

Correct Answer: C

Rationale: Inferior cerebellar peduncle . The posterior spinocerebellar tracts second-order neurons, originating in Clarknucleus (dorsal nucleus), ascend ipsilaterally and enter the cerebellum via the inferior cerebellar peduncle, relaying unconscious proprioception from lower limbs. Choice A (superior cerebellar peduncle) is for efferent cerebellar output. Choice B (middle cerebellar peduncle) is for pontocerebellar fibers. Choice D (crus cerebri) is midbrain motor tracts. Thus, C accurately identifithe entry route, making it correct.

Correct Answer: D

Rationale: Contralateral loss of sensation occurs as a result of a hemisection above the level of the medulla . Both pathways anterolateral (pain/temperature, crossin spinal cord) and dorsal column-medial lemniscal (touch/proprioception, crossin medulla) ascend contralaterally above the medulla. A hemisection there disrupts crossed fibers, causing contralateral loss. Choice A is wrong (dorsal column decussatin medulla). Choice B is false (first synapse is spinal cord or medulla, not DRG). Choice C is incorrect (free nerve endings are spinothalamic, not dorsal column). Thus, D is true for both, making it correct.

Correct Answer: B

Rationale: Gracile . The posterior (dorsal) horn contains sensory nuclei: nucleus dorsalis (Clarkes, A) for spinocerebellar tracts, nucleus proprius for touch, and substantia gelatinosa for pain/temperature. The gracile nucleus is in the medulla, not the spinal cords posterior horn, processing dorsal column input. Thus, B is the exception, making it correct.

Correct Answer: D

Rationale: Medullary reticulospinal tracts is tonically active . The medullary reticulospinal tract inhibits extensors and is not tonically active (pontine reticulospinal is). Choice A is true (vestibulospinal supports antigravity). Choice B is correct (pontine is uncrossed). Choice C is accurate (rubrospinal is lateral). Thus, D misattributtonic activity, making it the wrong statement and the correct answer.