Spinal Cord and Spinal Nerves – Key Vocabulary

A comprehensive set of vocabulary flashcards covering anatomy, physiology, reflexes, nerve plexuses and disorders of the spinal cord and spinal nerves.

Spinal Cord

CNS structure that processes reflexes and conducts sensory and motor impulses between body and brain.

Spinal Nerves

31 paired peripheral nerves that connect the spinal cord to sensory receptors, muscles and glands.

Meninges

Three protective connective-tissue layers (dura mater, arachnoid mater, pia mater) surrounding the CNS.

Dura Mater

Outermost, tough meningeal layer enveloping the spinal cord and brain.

Arachnoid Mater

Middle meningeal layer; web-like and avascular, lying deep to the dura mater.

Pia Mater

Innermost, delicate meningeal layer that adheres directly to the spinal cord surface.

Epidural Space

Fat‐filled space between vertebral bone and dura mater; site for epidural anesthesia.

Subdural Space

Narrow potential space between dura and arachnoid mater.

Subarachnoid Space

Region between arachnoid and pia mater that contains cerebrospinal fluid (CSF).

Cerebrospinal Fluid (CSF)

Protective fluid that cushions the spinal cord and brain and circulates nutrients.

White Matter

Myelinated axon tracts (anterior, lateral, posterior columns) conducting impulses up and down the cord.

Gray Matter

Unmyelinated neuronal cell bodies forming anterior, posterior and lateral horns that integrate signals.

Anterior (Ventral) Horn

Gray matter region containing somatic motor neuron cell bodies.

Posterior (Dorsal) Horn

Gray matter region receiving sensory information from peripheral receptors.

Lateral Horn

Gray matter area (T1–L2 segments) housing autonomic motor neuron bodies.

Anterior Funiculus

White-matter column on ventral side of cord carrying mixed tracts.

Posterior Funiculus

White-matter column on dorsal side mainly containing ascending sensory tracts.

Lateral Funiculus

White-matter column on each lateral side containing both ascending and descending tracts.

Central Canal

CSF-filled channel running the length of the spinal cord within the gray commissure.

Cervical Enlargement

Bulge of spinal cord (C4–T1) supplying upper limbs.

Lumbar Enlargement

Bulge of spinal cord (T9–T12) supplying lower limbs.

Conus Medullaris

Tapered lower end of spinal cord around L1–L2 vertebral level.

Cauda Equina

Bundle of lumbar, sacral and coccygeal nerve roots resembling a horse’s tail below conus medullaris.

Filum Terminale

Thin strand of pia mater anchoring conus medullaris to coccyx.

Dermatome

Skin segment supplied by a single spinal nerve’s sensory fibers.

Plexus

Network of interweaving anterior rami of spinal nerves (except T2-T12).

Cervical Plexus

Anterior rami of C1–C4 (and part of C5); supplies head, neck, diaphragm (via phrenic nerve).

Brachial Plexus

Anterior rami of C5–T1; innervates shoulders and upper limbs.

Lumbar Plexus

Anterior rami of L1–L4; supplies anterolateral abdominal wall, external genitalia, parts of lower limb.

Sacral Plexus

Anterior rami of L4–S4; supplies buttocks, perineum and most of lower limb including sciatic nerve.

Coccygeal Plexus

Anterior rami of S4–S5 and coccygeal nerves; gives rise to anococcygeal nerve to coccygeal skin.

Phrenic Nerve

Branch of cervical plexus (C3–C5) that innervates the diaphragm for breathing.

Musculocutaneous Nerve

Brachial plexus nerve (C5–C7) to arm flexors and lateral forearm skin.

Median Nerve

Brachial plexus nerve (C5–T1) to most forearm flexors and lateral palm/digits sensation.

Radial Nerve

Brachial plexus nerve (C5–T1) to extensor muscles of arm/forearm and posterior limb skin.

Ulnar Nerve

Brachial plexus nerve (C8–T1) to intrinsic hand muscles, medial forearm flexors and medial hand skin.

Femoral Nerve

Lumbar plexus nerve (L2–L4) to hip flexors, knee extensors and anterior thigh/medial leg skin.

Obturator Nerve

Lumbar plexus nerve (L2–L4) to hip adductors and medial thigh skin.

Sciatic Nerve

Largest body nerve (L4–S3); splits into tibial and common fibular nerves to supply posterior thigh and entire leg/foot.

Tibial Nerve

Branch of sciatic; innervates posterior leg muscles and plantar foot.

Common Fibular (Peroneal) Nerve

Branch of sciatic; divides into superficial and deep fibular nerves serving anterior/lateral leg and dorsum foot.

Anterior (Ventral) Ramus

Branch of a spinal nerve that supplies limbs and anterior/lateral trunk; participates in plexuses.

Posterior (Dorsal) Ramus

Branch of a spinal nerve that supplies deep back muscles and skin of posterior trunk.

Meningeal Branch

Small spinal nerve branch that re-enters vertebral canal to supply vertebrae, ligaments and meninges.

Rami Communicantes

Small branches connecting spinal nerves to sympathetic trunk ganglia.

Intercostal Nerves

Anterior rami of T2–T12 that travel alone (no plexus) to supply thoracic wall structures.

Reflex

Fast, involuntary, unplanned response to a specific stimulus helping maintain homeostasis.

Reflex Arc

Neural pathway of receptor → sensory neuron → integration center → motor neuron → effector.

Stretch Reflex

Monosynaptic, ipsilateral reflex causing contraction of a muscle that is suddenly stretched (knee-jerk).

Tendon Reflex

Polysynaptic, ipsilateral reflex that causes relaxation of a muscle experiencing excessive tension.

Flexor (Withdrawal) Reflex

Polysynaptic, ipsilateral reflex withdrawing a limb from painful stimulus.

Crossed-Extensor Reflex

Polysynaptic, contralateral reflex that extends opposite limb to maintain balance during withdrawal.

Muscle Spindle

Proprioceptive receptor detecting muscle stretch; initiates stretch reflex.

Golgi Tendon Organ

Proprioceptive receptor in tendons sensing tension; initiates tendon reflex.

Ipsilateral

Refers to reflexes or pathways occurring on the same side of the body as the stimulus.

Contralateral

Refers to reflexes or pathways affecting the side opposite the stimulus.

Monosynaptic

Reflex pathway containing a single synapse between sensory and motor neurons.

Polysynaptic

Reflex pathway involving two or more synapses and one or more interneurons.

Reciprocal Innervation

Neural circuitry that simultaneously excites one muscle and inhibits its antagonist during a reflex.

Anterior Root (Motor Root)

Bundle of axons of motor neurons leaving the spinal cord to form part of a spinal nerve.

Posterior Root (Sensory Root)

Bundle of sensory neuron axons entering the spinal cord; contains dorsal root ganglion.

Spinal (Dorsal Root) Ganglion

Swelling on posterior root housing cell bodies of sensory neurons.

Homeostasis (Spinal Cord)

Balance maintained through sensory input, integration, motor output and reflex activity of the cord.

Traumatic Spinal Cord Injury

Damage to spinal cord via section or compression leading to sensory and motor deficits.

Monoplegia

Paralysis of a single limb.

Paraplegia

Paralysis of both lower limbs (and possibly lower trunk).

Hemiplegia

Paralysis of one side of the body (arm and leg on same side).

Quadriplegia (Tetraplegia)

Paralysis of all four limbs and torso.

Shingles

Reactivation of varicella-zoster virus causing painful dermatomal rash and possible neural complications.

Multiple Sclerosis (MS)

Autoimmune demyelinating disease of CNS leading to varied neurological symptoms.

Poliomyelitis (Polio)

Viral disease attacking motor neurons; can cause paralysis; preventable by vaccination.

Spinal Cord Compression

Pressure on spinal cord from tumor, fracture, etc., producing neurological deficits.