AANN Core Curriculum, 7th Edition, Ch. 3 Anatomy of the Nervous System: Digital Version-Chapter 3

Chapter 3

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The nervous system comprises the central nervous system (CNS)—brain and spinal cord—and the peripheral nervous system (PNS), consisting of cranial and spinal nerves. The supratentorial compartment contains the cerebral hemispheres and diencephalon; the infratentorial compartment contains the cerebellum and brainstem (midbrain, pons, and medulla).<br /><br />The meninges are the dura mater, a tough outer covering; the arachnoid, a thin web-like middle layer; and the pia mater, a delicate membrane adhering to the CNS. Cerebrospinal fluid (CSF) cushions the brain and spinal cord. It is produced mainly by the choroid plexus at about 500 mL daily, flows from the lateral ventricles through the third and fourth ventricles into the subarachnoid space, and is reabsorbed into venous sinuses. Normal CSF is clear and colorless, with few cells and low protein.<br /><br />The cerebral lobes support distinct functions: frontal (judgment, planning, voluntary movement, speech production), parietal (somatic sensation), temporal (hearing, language comprehension, memory), occipital (vision), insular (sensory and visceral integration), and limbic (emotion and memory). Basal ganglia regulate movement; the diencephalon includes the thalamus, a major information relay, and hypothalamus, which regulates visceral and endocrine functions. The limbic system, including hippocampus and amygdala, contributes to memory, emotion, and survival responses.<br /><br />The internal carotid and vertebrobasilar systems form the cerebral arterial circulation. The anterior and middle cerebral arteries principally supply medial and lateral cerebral surfaces, respectively; posterior cerebral arteries supply occipital and inferior temporal regions and parts of the thalamus and midbrain. Cerebellar and spinal arteries supply the posterior fossa and spinal cord.<br /><br />Spinal white-matter tracts carry sensory information upward (including dorsal columns and spinothalamic pathways) and motor commands downward (especially corticospinal pathways). Peripheral nerves contain axons, fascicles, and connective-tissue coverings; dermatomes map skin sensation to spinal roots. Reflex arcs link receptors, sensory neurons, spinal processing, and motor or visceral effectors.<br /><br />The involuntary autonomic nervous system maintains homeostasis: sympathetic thoracolumbar pathways mobilize the body, while parasympathetic craniosacral pathways support restorative functions. CNS, PNS, and autonomic pathways work together to integrate sensation, movement, and internal regulation.

Keywords

central nervous system

peripheral nervous system

cerebrospinal fluid

meninges

cerebral lobes

basal ganglia

diencephalon

cerebral circulation

spinal tracts

autonomic nervous system