Tracts and Nuclei Flashcards
Marginal zone
Contains spinothalamic tract neurons that relay to ventral posterior thalamic nucleus.
All levels of spinal cord.
Substantia gelatinosa
Contains interneurons modulating pain and temperature inputs.
All levels of spinal cord.
Nucleus proprius
Where somatosensory inputs are processed and relayed to ventral horn (for reflexes) and brain.
All levels of spinal cord.
Dorsolateral fasciculus
Dorsal root entry zone for pain and temperature fibres.
All levels of spinal cord.
Nucleus dorsalis
Clarke’s column.
Contains tract neurons relaying proprioceptive input from LOWER limbs to cerebellum.
T1-L2 (all thoracic, some lumbar)
Intermediolateral nucleus
Contains preganglionic sympathetic neurons.
In lateral horn, only T1-L3.
Sacral autonomic nucleus
Contains preganglionic PARAsympathetic neurons (autonomic neurons to pelvic viscera).
Only S2-S4.
Medial motor nucleus
Contains motor neurons of axial musculature.
All spinal levels.
Lateral motor nucleus
Contains motor neurons of distal musculature.
Only at spinal enlargements.
Spinal cord sensory/motor organisation?
Sensory: above sulcus limitans.
Motor: below sulcus limitans.
Spinal cord somatic/visceral organisation?
Somatic: closer to sulcus limitans
Visceral: further from sulcus limitans
Gracile fasciculus
Function: discriminative touch, vibration, proprioception for LOWER LIMBS.
Start: dorsal root ganglion from below T6.
End: gracile nucleus.
Cross: uncrossed.
Cuneate fasciculus
Function: discriminative touch, vibration and proprioception for UPPER LIMBS.
Start: dorsal root ganglion above T6.
End: cuneate nucleus.
Cross: uncrossed.
Spinothalamic tract
Function: pain (sharp), temperature, some light touch.
Start: marginal zone, nucleus proprius (and sometimes modulated in substantia gelatinosa)
End: thalamus
Cross: at level of spinal cord.
Dorsal spinocerebellar tract
Function: proprioception and some touch of LOWER limbs.
Start: nucleus dorsalis.
End: cerebellum.
Cross: uncrossed.
Ventral spinocerebellar tract
Function: proprioceptive info (incl. reflexes) of LOWER limbs.
Start: nucleus proprius and intermediate zone of lumbosacral cord.
End: cerebellum.
Cross: crosses ventral white commisure, crosses back to ipsilateral as it enters cerebellum.
Cuneocerebellar tract
Function: proprioception and some touch for UPPER limbs.
Start: lateral cuneate nucleus in caudal medulla.
End: cerebellum (v. short tract).
Cross: uncrossed.
Lateral corticospinal tract
Function: motor, skilled voluntary movements of distal muscles.
Start: M1 and premotor areas of cortex.
End: spinal enlargements.
Cross: at pyramidal decussation in caudal medulla.
Ventral corticospinal tract
Function: motor, skilled voluntary movements of trunk and proximal limbs.
Start: M1 and premotor areas of cortex.
End: throughout spinal cord.
Cross: uncrossed.
Rubrospinal tract
Function: autonomic motor, muscle tone in distal muscles of upper limbs.
Start: red nucleus.
End: lateral motor column (spinal enlargements).
Cross: early in midbrain.
Vestibulospinal tract
Function: autonomic motor, controls postural muscles for balance and posture.
Start: lateral vestibular nucleus in medulla.
End: interneurons in ventral horn at all levels.
Cross: uncrossed.
Anterolateral system
Spinothalamic tract + spinoreticulothalamic tract.
Light touch, pain and temperature.
Runs between inferior olivary nucleus and spinal trigeminal nucleus in medulla, then dorsolaterally to medial meniscus in pons and midbrain.
Reticulospinal tract
Function: autonomic motor, stereotyped movements in axial and distal muscles, muscle tone, visceral smooth muscle.
Start: reticular formation of pons and medulla.
End: interneurons in ventral horn at all spinal levels, as well as lateral horn and sacral autonomic nucleus.
Cross: uncrossed.
Upper motor neuron lesion
Spastic paralysis:
- loss of voluntary control to muscles
- hypertonia
- hyperreflexia
- Babinski sign (extensor plantar response)
Lower motor neuron lesion
Flaccid paralysis:
- loss of neural input to muscle
- hypotonia
- hyporeflexia
- muscle wasting
Brown-Sequard Syndrome
- hemisection of spinal cord
- spastic paralysis on contralateral side
- loss of sensation on ipsilateral side
- loss of pain and temp. sensation on contralateral side
Lumbar cistern
A reservoir of CSF between L1-2 to S1-2. It is where spinal cord ends.
Cerebral peduncles
- aka. crus cerebri
- attach cerebrum to brainstem
- contain corticopontine, corticobulbar and corticospinal tracts
- arises from ventral pons
Middle cerebellar peduncle
- largest
- contains pontocerebellar fibres
- originates in basis pontis
Superior cerebellar peduncle
- smallest
- originates in cerebellum
- decussates in midbrain
- terminates in thalamus
- contains cerebellothalamic, cerebellorubral and ventral spinocerebellar tracts
Inferior cerebellar peduncle
- originates in medulla
- terminates in cerebellum
- contains spinocerebellar fibres (cuneocerebellar, olivocerebellar and dorsal spinocerebellar)
Inferior olivary nucleus
Coordinates signals from spinal cord to cerebellum.
Regulates motor coordination and learning.
Superior colliculi
Involved in incorporating environmental stimuli and coordinating gaze shifts with head movements.
Inferior colliculi
Involved in sound localisation, frequency determination and integration of auditory and non-auditory inputs.
Medial lemniscus
Function: discriminative touch, vibration and proprioception.
Start: gracile and cuneate nuclei in medulla.
End: ventral posterior nucleus in thalamus.
Cross: sensory decussation of medulla.
Medial longitudinal fasciculus
Function: coordinating eye movements with head position (connects the abducens, trochlear, occulomotor and vestibular nuclei).
Cross: crossed and uncrossed.
Lateral lemniscus
Function: carries auditory information, part of auditory pathway.
Start: superior olivary nucleus and cochlear nuclei.
End: inferior colliculi.
Cross: posterior tegmental commissure.
Central tegmental tract
- between red nucleus (midbrain) and inferior olivary nucleus (medulla)
- contains fibres of RF
Corticopontine fibres
- synapse with pontine nuclei in basis pontis
- form pontocerebellar fibres post-synapse
- then ascend to cerebellum via MCP
- don’t enter pons or medulla
Corticobulbar tract
- target motor nuclei of cranial nerves (trigeminal, facial, hypoglossal) and nucleus ambiguus in pons and medulla
- enters pons but not medulla or spinal cord
