nervousindepth

Dorsal Column-Medial Lemniscal Pathway (DCML)

Ascending pathway; carries fine touch, vibration, and proprioception.

First-Order Neuron (DCML)

From peripheral receptors to dorsal root ganglion to dorsal column nuclei (gracile/cuneate).

Second-Order Neuron (DCML)

From nucleus gracilis/cuneatus; decussates in medulla (internal arcuate fibers) to medial lemniscus; ascends to thalamus.

Third-Order Neuron (DCML)

From ventral posterolateral (VPL) nucleus of thalamus to primary somatosensory cortex (postcentral gyrus).

Fasciculus Gracilis

Part of DCML; carries sensory information from lower body (below T6).

Fasciculus Cuneatus

Part of DCML; carries sensory information from upper body (above T6).

Spinothalamic Tract

Ascending pathway; carries pain, temperature, crude touch.

Anterior Spinothalamic Tract

Carries crude touch and pressure.

Lateral Spinothalamic Tract

Carries pain and temperature sensations.

First-Order Neuron (Spinothalamic)

Enters spinal cord; synapses in dorsal horn (substantia gelatinosa).

Second-Order Neuron (Spinothalamic)

Decussates immediately at level of entry via anterior white commissure; ascends in contralateral spinothalamic tract.

Third-Order Neuron (Spinothalamic)

From VPL of thalamus to primary somatosensory cortex.

Spinocerebellar Tracts

Ascending tracts; carry proprioceptive information to cerebellum.

Dorsal Spinocerebellar Tract

Unconscious proprioception from lower limbs; remains ipsilateral.

Ventral Spinocerebellar Tract

Unconscious proprioception from lower limbs; double decussation; ipsilateral final projection.

Cuneocerebellar Tract

Upper limb equivalent of dorsal spinocerebellar tract; fibers enter via fasciculus cuneatus to external cuneate nucleus.

Rubrospinal Tract

Descending pathway; originates from red nucleus; facilitates flexor muscles; inhibits extensors.

Lateral Corticospinal Tract

Main motor tract; decussates in pyramids (medulla); controls distal voluntary movements.

Anterior Corticospinal Tract

Controls axial (trunk) muscles; fibers remain mostly uncrossed.

Corticobulbar Tract

Motor pathway; controls muscles of face, head via cranial nerves.

Vestibulospinal Tract

Descends from vestibular nuclei; controls balance and posture.

Tectospinal Tract

Originates in superior colliculus; coordinates head and eye movements.

Reticulospinal Tract

From reticular formation; influences voluntary movements and reflexes.

Dorsal Horn

Gray matter of spinal cord; contains sensory neuron synapses.

Ventral Horn

Gray matter of spinal cord; contains lower motor neurons.

Lateral Horn

Present in T1-L2; contains preganglionic sympathetic neurons.

Substantia Gelatinosa

Part of dorsal horn; modulates pain transmission.

Nucleus Proprius

Located in dorsal horn; relays mechanical and temperature sensations.

Clarke's Column (Nucleus Dorsalis)

Located from T1-L2; relay for dorsal spinocerebellar tract.

Decussation

Crossing of nerve fibers from one side to the other.

Internal Arcuate Fibers

Axons that cross (decussate) from nucleus gracilis/cuneatus in DCML.

Medial Lemniscus

Bundle of second-order DCML fibers after decussation; ascends to thalamus.

Ventral Posterolateral (VPL) Nucleus

Thalamic relay for sensory information from body (spinothalamic and DCML).

Ventral Posteromedial (VPM) Nucleus

Thalamic relay for sensory information from the face (trigeminal system).

Spinoreticular Tract

Carries pain information to reticular formation; involved in arousal and alertness.

Spinohypothalamic Tract

Carries pain information to hypothalamus; mediates autonomic and emotional responses to pain.

Spinomesencephalic Tract

Projects to midbrain; involved in pain modulation (periaqueductal gray).

Brown-Séquard Syndrome

Hemisection of spinal cord; ipsilateral loss of DCML, contralateral loss of spinothalamic function.

Upper Motor Neuron (UMN) Lesion

Weakness, hyperreflexia, spasticity, Babinski sign positive.

Lower Motor Neuron (LMN) Lesion

Weakness, hyporeflexia, atrophy, fasciculations.

Babinski Sign

Upgoing plantar reflex; indicates UMN lesion.

Proprioception

Sense of limb position and movement; mediated by muscle spindles, Golgi tendon organs.

Muscle Spindle

Sensory receptor for muscle stretch; involved in reflex arcs.

Golgi Tendon Organ

Sensory receptor detecting tension in tendons.

Monosynaptic Reflex

Simple reflex arc involving one synapse (e.g., patellar reflex).

Polysynaptic Reflex

Reflex involving interneurons (e.g., withdrawal reflex).

Dermatome

Area of skin supplied by a single spinal nerve.

Myotome

Group of muscles supplied by a single spinal nerve.

Posterior Column Syndrome (Tabes Dorsalis)

Loss of DCML pathway; sensory ataxia and positive Romberg sign.

Romberg Sign

Instability with eyes closed; indicates loss of proprioception.

Anterior Cord Syndrome

Damage to anterior spinal cord; motor and pain/temp loss, preserved proprioception.

Posterior Cord Syndrome

Damage to dorsal columns; loss of fine touch, proprioception, vibration.

Lateral Cord Syndrome

Damage to corticospinal tract and spinothalamic tract on one side; combination of motor and sensory deficits.

Periaqueductal Gray (PAG)

Midbrain structure; involved in endogenous pain suppression.

Spinovestibular Tract

Carries proprioceptive information to vestibular nuclei for balance control.

Pyramidal Decussation

Crossing of corticospinal fibers at medullary pyramids.

Anterior White Commissure

Site where spinothalamic tract fibers decussate in spinal cord.

Dorsal Root Ganglion

Contains cell bodies of sensory (afferent) neurons.

Anterior (Ventral) Root

Contains motor (efferent) axons leaving spinal cord.

Posterior (Dorsal) Root

Contains sensory (afferent) axons entering spinal cord.

Rexed Laminae

Layers of neurons in spinal gray matter; laminae I-X.

Lamina II (Substantia Gelatinosa)

Processes pain and temperature information.

Lamina IX

Contains lower motor neurons.

Central Canal

Small canal in center of spinal cord; filled with cerebrospinal fluid.

Pyramidal Tracts

Corticospinal and corticobulbar tracts; voluntary movement pathways.

Extrapyramidal System

Includes rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts; regulates involuntary and automatic movements.

Spinocervical Tract

Carries touch and pressure to the cervical region; lesser known sensory pathway.