Which of the following means Collection of axon in the central nervous system:

Correct Answer: D

Rationale: Tract . In the central nervous system (CNS), a tract refers to a bundle or collection of axons (nerve fibers) that transmit similar typof information, such as motor or sensory signals, within the brain or spinal cord. For example, the corticospinal tract carrimotor signals from the brain to the spinal cord. Choice A, Ganglion, is incorrect because it refers to a cluster of neuron cell bodies, typically found in the peripheral nervous system (PNS), not a collection of axons in the CNS. Choice B, Nerve, is also incorrect as it describa bundle of axons in the PNS, not the CNS, where the term tract is used instead. Choice C, Nucleus, refers to a group of neuron cell bodiwithin the CNS, not axons, making it an unsuitable answer. Thus, Tract is the precise term for a collection of axons in the CNS, making D the correct choice.

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: Autonomic nuclei in the lateral horn gray matter , which is not part of the pathway. Parasympathetic stimulation of the parotid gland involvthe glossopharyngeal nerve (CN IX). The pathway starts with preganglionic neurons in the inferior salivatory nucleus (brainstem, not hypothalamus as in A), exits via CN IX, synapsin the otic ganglion (outside CNS, as in C), and uspreganglionic neurons with cell bodiin the CNS . Choice B refers to the lateral horn (T1-L2), which is for sympathetic outflow (e.g., to sweat glands), not parasympathetic to the parotid. Thus, B is not part of this parasympathetic pathway, making it the correct 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.