What two types of macromolecules are the main components of myelin?

Correct Answer: C

Rationale: Myelin is primarily composed of lipids (e.g., cholesterol) and proteins (e.g., myelin basic protein), which form the insulating sheath around axons. Carbohydrates and nucleic acids are not major components.

Correct Answer: D

Rationale: Metabotropic receptors require effector proteins (e.g., G-proteins) to initiate intracellular signaling cascades. Ionotropic receptors are ligand-gated channels that don’t use effector proteins.

Correct Answer: B

Rationale: The superior colliculus in the midbrain coordinates visual reflexes, including light reflexes (e.g., pupillary response via pretectal nuclei). The red nucleus and substantia nigra are motor-related, and the inferior colliculus processes sound.

Correct Answer: D

Rationale: The lumbar plexus (L1-L4) forms the femoral nerve from L2-L3-L4, innervating thigh muscles. It’s lateral to the inferior vena cava, formed from anterior rami, and includes more than the last three lumbar nerves.

Correct Answer: D

Rationale: The facial nerve (CN VII) motor nucleus is in the pons, controlling facial muscles. The midbrain houses CN III/IV nuclei, and the cerebellum coordinates movement.