Spinal Cord Anatomy, Brainstem, and Cranial Nerves

Comprehensive practice flashcards defining essential structural, functional, and neuroanatomical vocabulary covering the spinal cord, spinal nerves, brainstem, cranial nerves, and cranial nerve nuclei.

Conus medullaris

The tapering terminal end of the spinal cord, located at the L1/L2 vertebral level in an adult.

Cauda equina

A collection of nerve roots (L3 to S5) extending inferiorly below the conus medullaris within the subarachnoid space, resembling a horse's tail.

Filum terminale

A thin strand of pia mater that extends from the tip of the conus medullaris and attaches to the coccyx, anchoring the spinal cord inferiorly.

Denticulate ligament

Lateral shelf-like extensions of pia mater that attach to the dura mater to anchor the spinal cord laterally, serving as a landmark separating dorsal from ventral rootlets.

Cervical enlargement

The expanded region of the spinal cord spanning segments C5 to T1 characterized by increased gray matter and neuronal cell bodies that innervate the upper limbs.

Lumbar enlargement

The expanded region of the spinal cord spanning segments L1 to S3 that contains high numbers of neuronal cell bodies to innervate the lower limbs.

Epidural space

The space located between the bony vertebral canal and the spinal dura mater (dural sheath), containing fat and blood vessels.

Subdural space

A potential space between the dura mater and the arachnoid mater that opens only when abnormal bleeding or fluid separates the two membranes.

Subarachnoid space

A true anatomical space situated between the arachnoid mater and the pia mater that contains cerebrospinal fluid (CSF).

Lumbar puncture (Spinal tap)

A diagnostic or therapeutic procedure where a needle is inserted into the subarachnoid space below L2 (typically between L3 and L4) while the patient is in a lateral recumbent position to access CSF without injuring the spinal cord.

Posterior (dorsal) horn

The gray matter region of the spinal cord containing interneurons that receive and process sensory input transmitted by sensory axons entering through the dorsal roots.

Anterior (ventral) horn

The gray matter region of the spinal cord containing somatic motor neuron cell bodies whose axons exit through ventral roots to innervate skeletal muscles.

Lateral horn

The small gray matter projection found exclusively in the thoracic, upper lumbar, and sacral segments of the spinal cord, housing preganglionic autonomic motor cell bodies of the sympathetic division.

Dorsal root ganglion (DRG)

A nodular swelling along each dorsal root containing cell bodies of pseudounipolar sensory neurons, where axons pass through without forming any synapses.

Dorsal primary ramus (DPR)

A mixed branch of the spinal nerve containing both motor and sensory fibers that innervates the deep muscles and skin of the back.

Ventral primary ramus (VPR)

A mixed branch of the spinal nerve containing both motor and sensory fibers that innervates the muscles and skin of the anterolateral body walls and the limbs.

Dermatome

A specific strip or cutaneous area of skin that receives sensory innervation from the fibers of a single spinal nerve root.

Anterior spinal artery

A single longitudinal artery derived from branches of the vertebral arteries that travels along the anterior median fissure to supply the anterior portion of the spinal cord.

Posterior spinal arteries

Two longitudinal arterial vessels arising from the vertebral arteries that descend along the dorsal aspects of the cord to supply its posterior portions.

Midbrain (Mesencephalon)

The most rostral division of the brainstem, connecting the diencephalon rostrally with the pons caudally, and housing visual and auditory reflex centers.

Pons

The middle component of the brainstem, part of the metencephalon, that connects the midbrain with the medulla and relays information between the cerebrum and cerebellum.

Medulla oblongata (Myelencephalon)

The most caudal component of the brainstem extending from the lower border of the pons to the foramen magnum, containing vital cardiovascular, respiratory, and autonomic reflex centers.

Crus cerebri

The prominent ventral column of descending motor tracts on each cerebral peduncle of the midbrain, medial to which the oculomotor nerve (CN III) emerges.

Superior colliculi

Paired elevations on the dorsal midbrain that integrate visual, auditory, and somatosensory information to serve as visual reflex centers orienting eye and head movements.

Inferior colliculi

Paired dorsal midbrain elevations that act as auditory reflex centers specializing in auditory location and sound orientation.

Pyramids of the medulla

Paired longitudinal elevations situated on either side of the ventral median fissure of the medulla, formed by descending corticospinal motor tracts.

Decussation of the pyramids

The crossover point of corticospinal motor tract fibers located at the caudal boundary of the medulla oblongata.

Olives

Paired oval swellings situated lateral to the medullary pyramids that relay input from the spinal cord, cerebral cortex, and brainstem to the cerebellum.

Fasciculus gracilis

A dorsal column ascending tract carrying fine touch, vibration, and conscious proprioception from the lower body below spinal level T6.

Fasciculus cuneatus

A dorsal column ascending tract carrying fine touch, vibration, and conscious proprioception from the upper body above spinal level T6.

General Somatic Efferent (GSE)

A motor fiber modality that carries voluntary motor commands from the CNS to somite-derived skeletal muscles, found in CN III, IV, VI, XI, and XII.

General Visceral Efferent (GVE)

An autonomic motor fiber modality carrying parasympathetic impulses from the CNS to smooth muscle, cardiac muscle, and glandular tissue, found in CN III, VII, IX, and X.

Special Visceral Efferent (SVE)

A branchial motor fiber modality that supplies skeletal muscles derived from embryonic pharyngeal (branchial) arches, found in CN V, VII, IX, and X.

General Somatic Afferent (GSA)

A sensory fiber modality transmitting touch, pain, temperature, and proprioception from somatic structures such as skin, muscles, and joints, found in CN V, VII, IX, and X.

Special Somatic Afferent (SSA)

A sensory fiber modality carrying special exteroceptive senses of vision (CN II) as well as hearing and equilibrium/balance (CN VIII).

General Visceral Afferent (GVA)

A sensory fiber modality that conveys stretch, distention, pain, baroreception, and chemoreception from internal organs, found in CN VII, IX, and X.

Special Visceral Afferent (SVA)

A sensory fiber modality that conveys chemical senses from specialized receptor organs, namely smell (CN I) and taste (CN VII, IX, and X).

Olfactory nerve (CN I)

A sensory cranial nerve carrying SVA fibers for smell from receptors in the upper nasal cavity through the cribriform plate of the ethmoid bone to the olfactory bulb.

Optic nerve (CN II)

A sensory cranial nerve carrying SSA fibers for vision arising from the retina of the eye.

Oculomotor nerve (CN III)

A motor cranial nerve emerging from the interpeduncular fossa of the midbrain carrying GSE fibers to most extraocular eye muscles and GVE parasympathetic fibers for pupillary constriction and accommodation.

Trochlear nerve (CN IV)

A motor cranial nerve carrying GSE fibers to the superior oblique muscle of the eye, uniquely emerging from the dorsal (posterior) surface of the brainstem caudal to the inferior colliculi.

Trigeminal nerve (CN V)

The largest cranial nerve, emerging from the ventrolateral pons and dividing into ophthalmic (V1), maxillary (V2), and mandibular (V3) branches to provide GSA sensory innervation to the face and SVE motor innervation to muscles of mastication.

Abducens nerve (CN VI)

A motor cranial nerve carrying GSE fibers to the lateral rectus muscle of the eye, emerging at the pontomedullary junction medially between the pons and the medullary pyramid.

Facial nerve (CN VII)

A mixed cranial nerve emerging at the pontocerebellar angle that provides motor innervation to the muscles of facial expression (SVE), parasympathetic supply to lacrimal, sublingual, and submandibular glands (GVE), and taste to the anterior 2/3 of the tongue (SVA).

Vestibulocochlear nerve (CN VIII)

A sensory cranial nerve emerging at the junction between the medulla, pons, and cerebellum, carrying SSA fibers via vestibular and cochlear divisions for balance and hearing.

Glossopharyngeal nerve (CN IX)

A mixed cranial nerve emerging posterior to the medullary olive that provides SVE motor fibers to the stylopharyngeus, GVE parasympathetic fibers to the parotid gland, and taste and general sensation to the posterior 1/3 of the tongue.

Vagus nerve (CN X)

A mixed cranial nerve emerging posterior to the medullary olive that provides extensive parasympathetic innervation (GVE) to thoracic and abdominal organs, and somatic motor branches (SVE) to muscles of the pharynx, larynx, and palate.

Spinal accessory nerve (CN XI)

A motor cranial nerve emerging from spinal rootlets of C1-C5 and the medulla that provides motor supply (classified as GSE for the exam) to the sternocleidomastoid and trapezius muscles.

Hypoglossal nerve (CN XII)

A motor cranial nerve emerging from the sulcus anterior to the olive (preolivary sulcus) carrying GSE fibers to innervate the intrinsic and extrinsic muscles of the tongue.

Edinger-Westphal (EW) nucleus

A parasympathetic preganglionic motor nucleus located in the midbrain that provides GVE fibers to CN III for pupillary sphincter constriction and ciliary muscle accommodation.

Nucleus ambiguus

A medullary motor nucleus that houses SVE cell bodies supplying muscles of the soft palate, pharynx, and larynx via CN IX and CN X.

Nucleus of the solitary tract (NST)

A sensory nucleus in the medulla where visceral sensory fibers (GVA) and taste afferents (SVA) carried by CN VII, IX, and X terminate.

Superior salivatory nucleus

A pontine parasympathetic nucleus providing GVE preganglionic fibers via CN VII to the lacrimal gland, submandibular gland, and sublingual gland.

Inferior salivatory nucleus

A parasympathetic nucleus in the brainstem providing GVE preganglionic fibers via CN IX to innervate the parotid salivary gland.

Chorda tympani

A specialized branch of CN VII that carries special visceral afferent (taste) fibers from the anterior two-thirds of the tongue and hitchhikes along the lingual nerve.

Lingual nerve

A branch of the mandibular nerve (CN V3) that mediates general somatic sensation (temperature, pain, touch) from the anterior two-thirds of the tongue.