Spinal cord Flashcards
What forms the cauda equina?
Roots of lower 4 pairs lumbar nerves, 5 pairs of sacral nerves, and pair of coccygeal nerves
What are the two enlargements of the spinal cord?
Cervical enlargement for upper limbs
Lumbosacral enlargement for lower limbs
What is the anterior/ventral median fissure of the spinal cord?
Deep anterior midline groove where the anterior spinal A lies
What is the anterior/ventral lateral sulcus of the spinal cord?
Shallow groove where the anterior rootlets emerge
What is the posterior/dorsal lateral sulcus of the spinal cord?
Shallow groove where the posterior rootlets enter
What is the posterior/dorsal intermediate sulcus of the spinal cord?
Shallow groove continuous with posterior intermediate septum rostral to T6
What is separated by the posterior intermediate sulcus of the spinal cord?
Fasciculus gracilis from fasciculus cuneatus
What is the posterior/dorsal median sulcus?
Shallow posterior midline groove continuous with the posterior median septum
What are the structures pierced during a lumbar pucture?
Skin
Subcutaneous tissue and fascia
Supraspinatus ligament
Interspinous ligament
Ligamentum flavum
Dura mater
Arachnoid mater
Into subarachnoid space
What are reasons for a lumbar puncture?
CSF obtained for diagnostic or therapeutic processes
Spinal tap and spinal anaesthesia
What forms the spinal nerve?
Posterior and anterior roots joined within intervertebral foramen
How many spinal nerves are there?
8 cervical pairs
12 thoracic pairs
5 lumbar pairs
5 sacral pairs
1 coccygeal pair
What is conveyed in the posterior/dorsal root of the spinal nerve?
Sensory input from body
What is conveyed in the spinal/dorsal root ganglion?
Synapses with posterior root from periphery
What is conveyed in the anterior/ventral root?
Motor output from visceral and somatic motor neurons
What is innervated by posterior rami of spinal nerves?
Skin and muscles of back
What is innervated by anterior rami of spinal nerves?
Ant and lat muscles and skin of the trunk, extremities, and viscera
What is innervated by the meningeal rami of the spinal nerves?
Meninges and vertebral column
What is the gray communicating rami of spinal nerves?
Unmyelinated postganglionic sympathetic fibers of all spinal nerves
What is the white communicating rami of the spinal nerves?
Myelinated preganglionic sympathetic fibers and myelinated visceral fibers (splanchnic nerves) only found from segments T1-L2
Where are the cervical segments 1-8 of the spinal cord located?
Foramen magnum to C6 vertebra
Where are the thoracic segments 1-6 located?
C6 vertebra to T4 vertebra
Where are the thoracic segments 7-12 located?
T4 vertebra to T9 vertebra
Where are the lumbar and sacral spinal segments located?
T10 vertebra to L1 vertebra
What are the 3 general divisions of the spinal cord white matter?
Dorsal funiculus
Lateral funiculus
Ventral funiculus
When is white matter in the spinal cord the greatest?
Cervical levels
What are the parts of the ventral gray horn of the spinal cord?
Medial group
Lateral group
Central group
What are characteristics of the medial group of the ventral gray horn of the spinal cord?
Innervates axial musculature of neck and trunk
Subdivided into ventromedial and dorsomedial parts
What are characteristics of the lateral group of the ventral gray horn of the spinal cord?
Confines cervical and lumbar enlargements
Supplies limb muscles
What are the two nuclei in the central group of the ventral gray horn of the spinal cord?
Phrenic nucleus in cervical region for diaphragm
Spinal nucleus of CN XI in cervical region
What are the nerve cell groups on the posterior gray horn from most posterior?
Substantia gelatinosa
Nucleus propius
Nucleus dorsalis - Clarke’s column
Visceral afferent nucleus
What is the function of the substantia gelatinosa?
Receives afferents for pain and temperature
What is the function of nucleus proprius?
Receives fibers from posterior white column associated with proprioception, two-point discrimination, and vibration
What is the function of the nucleus dorsalis (Clarke’s column)?
Projects somewhat into the posterior funiculus
Receives proprioceptive, touch, and pressure afferents from trunk and lower limbs
At what levels is the nucleus dorsalis located?
C8/T1 to L2/L3
What is the function of the visceral afferent nucleus?
Receives visceral afferents from dorsal nerve roots
What is the extent of the visceral afferent nucleus?
T1 to L2 and S2 to S4
What are the two nuclei of the intermediate/lateral gray column?
Intermediolateral nucleus
Intermediomedial nucleus
What is the function of the intermediolateral nucleus?
Origin of preganglionic fibers of SyNS
What is the function of the intermediomedial nucleus?
Origin to preganglionic fibers of PsNS
What is the extent of the intermediomedial nucleus?
S2 to S4 segments
What are the parts of the dorsal column tracts of the spinal cord?
Fasciculus gracilis
Fasciculus cuneatus
What are the ascending tracts of the spinal cord?
Dorsal column tracts
Spinothalamic tract
Spinocerebellar tract
What are the descending tracts of the spinal cord?
Corticospinal tract
Rubrospinal tract
Vestibulospinal tract
Olivospinal tract
Descending autonomic fibers
What are the divisions of the spinothalamic tract of the spinal cord?
Lateral
Ventral
What are the divisions of the spinocerebellar tract of the spinal cord?
Ventral
Dorsal
Cuneocerebellar
Rostral
What are the divisions of the corticospinal tract of the spinal cord?
Lateral
anterior
Where do the fasciculus gracilis and fasciculus cuneatus synapse?
Gracile and cuneate nuclei in caudal medulla forming medial lemniscus which terminates in the VPL of thalamus
What is the function of the spinothalamic tract?
Crude touch, pain, and temperature sensation
Where does the spinothalamic tract synapse?
Decussate in anterior white commissure and ascend in anterolateral funiculus to terminate in VPL and intralaminar nuclei of thalamus
What is the function of the dorsal part of the spinocerebellar tracts?
Uncrossed
Unconscious proprioception of lower limb
What is the function of the cuneocerebellar part of the spinocerebellar tracts?
Uncrossed
Unconscious proprioception of the upper limb and trunk
What is the main function of the ventral and rostral parts of the spinocerebellar tracts?
Crossed
Monitor state of activity of spinal reflex arcs for upper and lower limbs
What are the two major pathways involved in somatic sensory perception?
Dorsal column-medial lemniscal pathway
Spinothalamic tract
What is the origin of the fibers of the corticospinal tracts?
Majority from pyramidal cells of the motor cortex
Some from premotor cortex, somatosensory cortex, and parietal lobe
What fibers form the lateral corticospinal tract?
Fibers that cross at the pyramidal decussation in the medulla
What fibers form the anterior corticospinal tract?
Fibers that do not cross
Where do the majority of fibers in the corticospinal tracts terminate?
Interneurons in spinal cord that project to motor neurons in the anterior horn
What are the signs of a UMN lesion?
Decreased strength
Hypertonia
Hyperreflexia
Mild atrophy
Clonus
Babinski reflex present
What are the signs of a LMN lesion?
Decreased strength
Hypotonia
Hyporeflexia
Severe atrophy
Fasciculations
Fibrillations
What arteries supply the spinal cord?
Two posterior spinal As
Anterior spinal A
Reinforced by segmental arteries at each intervertebral foramen
What are characteristics of veins of the spinal cord?
Mirror arteries
Lack valves
What are characteristics of syringomyleia?
Development of fusiform cyst/syrinx in or around the central canal of spinal cord
Obliterates spinothalamic fibers decussating in white commissure
What are symptoms of syringomyelia?
Dissociated sensory loss - pain and temp lost, but proprioception and touch remain
What are characteristics of tabes dorsalis?
Late manifestation of neurosyphilis
Affects lumbosacral dorsal spinal roots and spinal columns
What are symptoms of tabes dorsalis?
Loss proprioception leading to sensory ataxia
Positive Romberg’s sign
What are characteristics of subacute combined degeneration of the spinal cord?
Deficiency of vit B12
Associated with pernicious anemia
What are symptoms of subacute combined degeneration of the spinal cord?
Sensory ataxia
Weakness and spasticity of limbs
What are symptoms of MS into the spinal cord?
Loss of proprioception in hands and fingers
What are characteristics of the ALS?
Involves both LMNs and UMNs
Progressive spinal muscular atrophy or progressive bulbar palsy - LMN component
Pseudobulbar palsy or primary lateral sclerosis refers to UMN component