Spinal cord & tracts Flashcards
Where in the spine is white matter largest? Where is grey matter largest?
White matter is biggest in the cervical spine.
Grey matter is biggest within the cervical and lumbar enlargements, corresponding to the arms and legs.
What are funiculi?
Divisions of the white matter of the spinal cord composed of longitudinal bundles of axons
What functional components are found within the posterior horn of the spine?
Sensory: GSA and GVA
*GSA is found most posterior column, GVA is anterior to that
What functional components are found within the lateral horn of the spine?
GVE
Preganglionic sympathetics
What functional components are found within the anterior horn of the spine?
Motor efferents: GSE
Where is the substantia gelatinosa, and what is its function?
Nucleus within the posterior horn of the spine that modulates pain. Analogous to the spinal trigeminal nucleus.
Where is the nucleus proprius and what is its function?
Nucleus within the posterior horn that receives many sensory inputs. Axons project from this nucleus to form the spinothalamic tract (STT)
Where is the nucleus dorsalis and what is its function?
Found in the intermediate zone of the spinal cord. Receives muscle spindle information and projects to the cerebellum via the dorsalspinocerebellar tract (DSCT)
Where is the intermediolateral nucleus and what is its function?
IML is found in the lateral horn, and contains cells that make up the preganglionic sympathetic efferents (GVE)
Where are the medial and lateral motor nuclei and what are their functions?
Motor nuclei found in the anterior horn. Innervate skeletal muscle. Largest in the cervical and lumbar enlargements.
Which nerve receptors are not encapsulated?
Free nerve endings (pain/temp)
Merkel’s disks (touch)
Hair follicles (touch)
What receptors are fast adapting?
Hair follicles (touch) Meissner's corpuscle (2 point discrimination) Pacinian corpuscle (vibration)
What is the difference between neuromuscular spindles and golgi tendon organs?
Spindles are found within muscles and sense muscle stretch/length. GTOs are found within tendons and sense muscle tension.
What information is relayed by the dorsal column pathway?
2 point discrimination
Vibration sense
Proprioception
All GSA
Describe the path of the dorsal column pathway
Peripheral sensory neurons have cell bodies in the dorsal root ganglion, enters spinal cord and ascends in the dorsal column (fasiculus cuneatus or gracilis).
Synapse in the ipsilateral nucleus cuneatus/gracilis of the lower medulla. Crosses in medulla and ascends to VPL of thalamus via the medial lemniscus. VPL neurons project to area 312.
What physical exam test can detect posterior column damage?
Romberg sign: positive if patient requires vision to stand steadily with feet together
What is the major spinal nucleus associated with the STT?
Nucleus proprius
Describe the path of the STT
Primary neurons sense pain/temp, synapse in ipsilateral nucleus proprius. Secondary neuron crosses at that level and ascends in the contralateral anterolateral funiculus. Synapses in VPL of thalamus, which projects to area 312.
What is sacral sparing?
Because of the somatotopic organization within the anterolateral funiculus, central lesions (like syringomyelia) will affect the upper body first, thus sparing the lower body.
What is a Brown-Sequard lesion?
Spinal cord hemisection. Results in ipsilateral loss of proprioception below lesion and contralateral loss of pain/temp below lesion.
What is the major spinal nucleus associated with the dorsal spinocerebellar tract?
Nucleus dorsalis (Clark’s nucleus) between C8-L2
Describe the path of the dorsal spinocerebellar tract
Lower extremity neurons (C8-L2) from muscle spindles and golgi tendon organs synapse in nucleus dorsalis, ascend in ipsilateral lateral funiculus, pass through the inferior cerebellar peduncle and end in the ipsilateral cerebellum.
Describe the path of the cuneocerebellar tract
Upper extremity neurons (C7-C1) from muscle spindles and golgi tendon organs synapse in the cuneate nucleus, passes through the inferior cerebellar peduncle and into the ipsilateral cerebellum.
Describe the path of the ventral spinocerebellar tract
Samples interneuron activity in the intermediate spinal gray matter, crosses immediately and ascends in the contralateral anterolateral funiculus. After passing through the superior cerebellar peduncle, it crosses back over to end in the ipsilateral cerebellum.
