Which term describes a bundle of axons in the peripheral nervous system?

Correct Answer: D

Rationale: In the peripheral nervous system (PNS), a bundle of axons is called a nerve. A nucleus refers to a cluster of cell bodies in the CNS, a ganglion is a cluster of cell bodies in the PNS, and a tract is a bundle of axons in the CNS.

Correct Answer: A

Rationale: Mechanically gated channels open in response to physical stimuli, such as pressure or stretch (e.g., in touch receptors). Chemical stimuli affect ligand-gated channels.

Correct Answer: A

Rationale: GABA (gamma-aminobutyric acid) is the primary inhibitory neurotransmitter in the CNS, causing hyperpolarization. Acetylcholine, glutamate (excitatory), and norepinephrine have varied effects.

Correct Answer: D

Rationale: The medulla oblongata extends through the foramen magnum, connecting the brain to the spinal cord. It lies below the pons, not between midbrain and pons, and has multiple cranial nerves (e.g., IX, X, XII), not just trigeminal (V). Pyramids are medial to olives.

Correct Answer: A

Rationale: Parasympathetic innervation via pelvic splanchnic nerves (S2-S4) relaxes the sphincter and contracts the detrusor for urination. Sympathetic innervation (T11-L2, not L3-L4) inhibits the bladder, and sensation travels via both systems.