Beta receptors are stimulated by:

Correct Answer: C

Rationale: Isoproterenol (isoproteranol) is a beta-adrenergic agonist, stimulating β receptors (e.g., heart, lungs). Methoxamine is α₁-specific, acetylcholine is cholinergic, atropine blocks muscarinic.

Correct Answer: D

Rationale: Abducens (VI) innervates the lateral rectus eye muscle, not facial muscles (facial nerve, VII). Other pairings are correct.

Correct Answer: C

Rationale: The neuron is the fundamental structural and functional unit of the nervous system, encompassing axons, dendrites, and cell body. Synapses are junctions between neurons.

Correct Answer: B

Rationale: Neurotransmitters (e.g., acetylcholine) are stored in synaptic vesicles (neuron vesicles) in the presynaptic terminal, released into the cleft upon signal.

Correct Answer: A

Rationale: The myelin sheath is formed by Schwann cells (PNS) wrapping around axons. Neurilemma is the outer Schwann cell layer, nodes are gaps, gray matter is unmyelinated.