The dorsal root ganglion:

Correct Answer: D

Rationale: Contains visceral sensory and somatic sensory cell bodi. The dorsal root ganglion (DRG) is a structure outside the spinal cord containing the cell bodiof sensory neurons, including somatic sensory (e.g., touch, pain) and visceral sensory (e.g., organ sensation) neurons, which send axons into the spinal cord via the dorsal roots. Choice A is incorrect because somatic motor cell bodiare in the ventral horn, not the DRG. Choice B is wrong as parasympathetic cell bodiare located in the brainstem or sacral spinal cord, not the DRG. Choice C is false since the lateral horn (not DRG) contains autonomic neurons in the thoracolumbar region. Thus, D correctly identifithe sensory role of the DRG, making it the right answer.

Correct Answer: B

Rationale: L4 . The knee jerk reflex (patellar reflex) tests the integrity of the L3-L4 nerve roots, primarily L4, via the femoral nerve, which innervatthe quadriceps femoris. Loss of this reflex indicatL4 root dysfunction, often due to disc herniation (e.g., L3-L4). Choice A, L3, contributbut is less dominant than L4. Choice C, S1, affects ankle jerk and plantar flexion, not knee jerk. Choice D, S2, is unrelated (e.g., affects plantar muscles). Thus, L4 is the most likely affected root, making B the correct answer.

Correct Answer: C

Rationale: Conscious Proprioception . The posterior white column-medial lemniscal pathway transmits fine touch, vibration, and conscious proprioception (position sense) from the body to the brain. It involvdorsal columns (fasciculus gracilis and cuneatus), medial lemniscus, and VPL thalamus. Choice A (temperature) and B (pain) are incorrect as these are carried by the spinothalamic tract. Choice D (crude touch) is wrong because fine, discriminative touch is via this pathway, while crude touch is spinothalamic. Thus, C accurately reflects the pathways role, making it correct.

Correct Answer: B

Rationale: Fasciculus cuneatus transmits information coming from areas inferior to T6 . The fasciculus cuneatus carriproprioception, vibration, and fine touch from the upper body (above T6), while the fasciculus gracilis handlbelow T6. Choice A is true (faster myelinated fibers). Choice C is correct (ipsilateral loss below lesion). Choice D is accurate (excludfree nerve endings, used by spinothalamic). Thus, B misattributcuneatus function, making it the wrong statement and the correct answer.

Correct Answer: C

Rationale: It is concerned with proprioception (muscle-joint sense) . The medial lemniscus, formed by decussating fibers from the nucleus gracilis and cuneatus in the medulla, carriproprioception, vibration, and fine touch to the thalamus (VPL), then cortex. Choice A is wrong (begins in medulla, not spinal cord). Choice B is false (spinothalamic tracts are separate). Choice D is incorrect (ends in thalamus, not cortex directly). Thus, C accurately describits role, making it correct.