The outer layer of connective tissue that surrounds the nerve is called:

Correct Answer: A

Rationale: Epineurium . The epineurium is the outermost layer of connective tissue that surrounds an entire nerve, providing structural support and protection to the nerve fibers within. It encasthe fascicl(bundlof nerve fibers) and contains blood vessels that nourish the nerve. Choice B, Epithelium, is incorrect because it refers to a layer of cells lining body surfacor cavities, not a connective tissue layer around nerves. Choice C, Glial cells, is wrong as these are supportive cells in the nervous system (e.g., Schwann cells or astrocytes) and not a connective tissue layer. Choice D, Endoneurium, is also incorrect because it is the innermost connective tissue layer that surrounds individual nerve fibers within a fascicle, not the outer layer of the nerve as a whole. Therefore, Epineurium is the accurate term for the outer connective tissue layer of a nerve, confirming A as the correct answer.

Correct Answer: A

Rationale: The arachnoid mater ends at S2 . The arachnoid mater, along with the dura mater, forms the dural sac, which ends at the S2 level, containing the subarachnoid space with CSF. Choice B is true but not the only correct option, as the spinal cord dohave cervical and lumbosacral enlargements. Choice C is incorrect because CSF is in the subarachnoid space (between arachnoid and pia), not between dura and arachnoid (the subdural space is potential). Choice D is wrong as the bundle of nerve roots below the conus medullaris is the cauda equina, not the conus itself. Since the question asks for a true statement and A is accurate and specific, it is the correct answer.

Correct Answer: C

Rationale: A delta fibers . Fast pain, which is sharp and well-localized, is transmitted by A delta fibers, which are small, myelinated axons with rapid conduction (5-30 m/s). They respond to mechanical and thermal stimuli, quickly signaling acute pain. Choice A, A alpha fibers, is incorrect as these large, myelinated fibers transmit proprioception and motor signals, not pain. Choice B, A beta fibers, is wrong because they carry touch and pressure sensations, not pain. Choice D, C fibers, transmits slow, dull, poorly localized pain, not fast pain. Thus, A delta fibers are specifically responsible for fast pain sensation, making C the correct answer.

Correct Answer: A

Rationale: If the disc between L4 / L5 is herniated sensory changwill likely occur at the medial border of leg , which is false. An L4-L5 disc herniation typically affects the L5 nerve root, causing sensory changin the anterolateral leg and dorsum of the foot, not the medial leg (L4 dermatome). Choice B is true (S1 tests tiptoe standing via gastrocnemius). Choice C is correct (L4 compression affects knee jerk). Choice D is accurate (S1 compression weakens gastrocnemius). Thus, A misattributsensory changes, making it the exception and the correct answer.

Correct Answer: B

Rationale: Substantia gelatinosa of spinal cord . The lateral spinothalamic tracts second-order neurons are in the substantia gelatinosa (Rexed lamina II) of the spinal cords dorsal horn, where first-order neurons from dorsal root ganglia synapse after crossing via the anterior white commissure. Choice A (thalamus) is the third-order neuron site (VPL). Choice C (dorsal root ganglia) is first-order. Choice D (medulla) is unrelated to this tracts second-order site. Thus, B correctly identifithe location, making it the right answer.