Which adult structure(s) arises from the diencephalon?

Correct Answer: A

Rationale: The diencephalon develops into the thalamus, hypothalamus, and parts of the retina (A). Midbrain (B) arises from the mesencephalon, pons and cerebellum (C) from the rhombencephalon (metencephalon), and cerebrum (D) from the telencephalon. A is correct.

Correct Answer: A

Rationale: A fascicle (A) is a bundle of axons within a peripheral nerve. Tracts (B) are CNS axon bundles, nerve roots (C) are spinal nerve origins, and epineurium (D) is the nerve’s outer layer. A is correct.

Correct Answer: A

Rationale: Oligodendrocytes provide myelin for axons in the central nervous system (CNS), where tracts are located. Schwann cells myelinate axons in the peripheral nervous system (PNS), astrocytes support neurons, and satellite cells support cell bodies in the PNS.

Correct Answer: C

Rationale: Neural signaling, including sensory input, CNS processing, and motor output, occurs in a fraction of a second (milliseconds) due to the speed of action potentials and synaptic transmission.

Correct Answer: D

Rationale: A thick, myelinated axon propagates action potentials fastest due to saltatory conduction (myelin) and lower resistance (thickness). Myelination speeds conduction more than diameter alone.