Peripheral Nervous System: Spinal Cord & Spinal Nerve – Key Vocabulary

Vocabulary flashcards covering essential terms related to the peripheral nervous system, spinal cord anatomy, neural pathways, and clinical correlates from the lecture.

Central Nervous System (CNS)

Consists of the brain and spinal cord.

Peripheral Nervous System (PNS)

All neural structures outside the CNS; includes 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Afferent

Sensory fibers that carry information toward the CNS.

Efferent

Motor fibers that carry information away from the CNS.

Somatic Nervous System

Voluntary division that supplies skin, skeletal muscle, and joints.

Visceral (Autonomic) Nervous System

Involuntary division that supplies glands, smooth muscle, and internal organs.

General Somatic Afferent (GSA)

Sensory fibers conveying conscious, sharp, well-localized input from somatic structures.

General Visceral Afferent (GVA)

Sensory fibers conveying usually unconscious, dull, poorly-localized input from visceral organs.

General Somatic Efferent (GSE)

Motor fibers innervating skeletal (somatic) muscle.

General Visceral Efferent (GVE)

Motor (autonomic) fibers innervating smooth muscle, cardiac muscle, and glands.

Body Wall

Tissues mostly somatic (skin, fascia, muscles, bones) plus some visceral components such as glands and arrector pili.

Body Cavity

Contains only visceral structures (internal organs).

Somatic Sensation

Conscious, sharp, well-localized perception of touch, pain, temperature, pressure, or proprioception.

Visceral Sensation

Often unconscious; conscious perception is dull and poorly localized (e.g., distension, cramping).

Conus Medullaris

Tapered terminal end of the spinal cord, typically at vertebral levels L1–L2.

Cauda Equina

Bundle of lumbar, sacral, and coccygeal nerve roots descending below the conus medullaris inside the vertebral canal.

Meninges

Protective connective-tissue coverings of the CNS: dura mater, arachnoid mater, and pia mater.

Dura Mater

Outermost meningeal layer; tough and fibrous.

Arachnoid Mater

Middle, web-like meningeal layer lying against the dura.

Pia Mater

Innermost meningeal layer tightly adherent to the surface of the brain and spinal cord.

Filum Terminale

Pia mater extension anchoring the conus medullaris to the coccyx.

Denticulate Ligament

Lateral pia mater specializations that anchor the spinal cord to the dura, stabilizing it within the vertebral canal.

Epidural Space

Space between vertebral canal and dura mater; contains fat and blood vessels.

Subdural Space

Potential space between dura and arachnoid mater.

Subarachnoid Space

Space between arachnoid and pia mater filled with cerebrospinal fluid (CSF).

Lumbar Puncture

Needle access to the subarachnoid space (typically between L3-L4 or L4-L5) to sample CSF or deliver anesthesia.

Multipolar Neuron

Motor (efferent) neuron type with many dendrites and a single axon; cell bodies in CNS gray matter.

Pseudounipolar Neuron

Sensory (afferent) neuron with a single process that splits into peripheral and central branches; cell bodies in dorsal root ganglia.

Gray Matter

Central H-shaped region of the spinal cord containing neuronal cell bodies; transmits information laterally to/from spinal nerves.

White Matter

Peripheral region of the spinal cord containing myelinated axons; transmits information up and down the cord.

Dorsal Root

Spinal root carrying afferent (sensory) fibers only.

Ventral Root

Spinal root carrying efferent (motor) fibers only.

Dorsal Root Ganglion (DRG)

Cluster of pseudounipolar sensory neuron cell bodies on the dorsal root.

Dorsal Ramus

Mixed branch supplying skin and intrinsic muscles of the back and neck.

Ventral Ramus

Mixed branch supplying the remainder of the body wall and limbs; often forms plexuses.

Spinal Nerve (sensu stricto)

Short mixed segment formed by fusion of a dorsal and a ventral root before splitting into rami.

Dermatome

Strip of skin supplied by sensory fibers from a single spinal cord segment.

Plexus

Network where ventral rami merge and re-form to create new peripheral nerves with mixed segmental contributions.

Brachial Plexus

Somatic plexus from C5–T1 ventral rami that innervates the upper limb.

Cervical Plexus

Somatic plexus from C1–C5 ventral rami that innervates the neck region.

Intercostal Nerves

Ventral rami of T1–T12 that run segmentally along the thoracic wall without forming a plexus.

Lumbar & Sacral Plexuses

Networks of L1–S4 ventral rami supplying pelvis, perineum, and lower limb.

White Ramus Communicans

Myelinated preganglionic sympathetic fibers connecting a spinal nerve to a sympathetic ganglion (T1–L2).

Gray Ramus Communicans

Unmyelinated postganglionic sympathetic fibers returning from a sympathetic ganglion to every spinal nerve.

Sympathetic Ganglion

Paravertebral autonomic ganglion containing cell bodies of postganglionic sympathetic neurons.

Meningeal Ramus

Small branch re-entering the vertebral canal to supply meninges, ligaments, and blood vessels.

Segmental Innervation

Organization of the spinal cord into repeating units; aids diagnosis by mapping deficits to specific cord levels.

Cutaneous Sensory Field

Area of skin supplied by a particular peripheral nerve after redistribution within a plexus.