Adaptation to sensory modalities:

Correct Answer: A

Rationale: Adaptation involves receptor fatigue (A, correct) or central inhibition. Rates vary (not B), Na+ channel inactivation (C) is partial, and inhibitory transmitters (D) are secondary. A is most accurate.

Correct Answer: A

Rationale: The neural crest (A) gives rise to the peripheral nervous system (PNS), including sensory and autonomic ganglia. The neuraxis (B) is the central nervous system (CNS) axis, rhombencephalon (C) forms brainstem and cerebellum (CNS), and neural tube (D) forms the CNS. A is correct.

Correct Answer: A

Rationale: The dura mater (A) forms and supports venous sinuses (e.g., superior sagittal) for CNS blood drainage. The arachnoid mater (B) and subarachnoid space (C) handle CSF, and pia mater (D) adheres to the brain. A is correct.

Correct Answer: A

Rationale: The peripheral nervous system (PNS) controls peripheral structures. The trigeminal ganglion (A) is a sensory relay, not directly controlled by PNS motor output. Gastric plexus (B), sympathetic chain (C), and cervical plexus (D) are PNS autonomic/somatic effectors. A is the least directly controlled.

Correct Answer: B

Rationale: The soma, or cell body, of a neuron contains the nucleus, which houses the cell’s genetic material. Dendrites receive signals, axons transmit them, and the synaptic end bulb releases neurotransmitters, but only the soma contains the nucleus.