Spinal Cord Flashcards
What is the neural tube derived from?
Ectoderm
What substance is secreted by the notocord that converts it to the neural tube?
Sonic Hedgehog
What nutrient affects neural tube development?
Folic acid
What structure precedes the neural tube?
The neural plate
Describe neural tube formation
A groove forms in the neural plate
The inner walls form into inner + intermediate mantle and outer marginal layers
The mantle layer forms dorsal (alar) and ventral (basal) plates
Tissues at the sides of the tube form the neural crest cells
What part of the neural tube forms sensory neurons in the dorsal horn of the grey matter?
Alar plate
What part of the neural tube forms motor neurons in the ventral horn of the grey matter?
Basal plate
What does the innermost layer of the neural tube develop into?
Ependymal cells
What do the neural crest cells give rise to?
DRG, adrenal medulla, melanocytes, enteric ganglia, schwann cells, sympathetic ganglia
What CNS cell is mesodermally derived?
Microglia
Where does the spinal cord begin and end?
Foramen magnum and L1/L2 in an adult
What are the 2 enlargements of the cord?
Cervical and lumbosacral
Where is the cervical enlargement largest?
C6
What is the dilated end of the spinal cord?
Conus medullaris
What are nerves that exit the end of the spinal cord called?
Cauda equina
What is structures of the cord are derived from pia mater?
Dentate ligaments, filum terminale
What is the function of the dentate ligaments?
They anchor the cord to the dura
Where is the filum terminale internum?
From conus medullaris to the end of the dural sac
Where is the end of the dural sac?
S2
Where is the filum terminale externum?
anchored to the coccyx, continuous witht he coccygeal ligament
What are fasciculi?
Fast conducting white matter that ascend and descend
What spinal tracts are associated with 2 point discrimination, vibration, and joint position sense?
Cuneatus and gracilis tracts
Where do cuneatus and gracillis cross
In the medulla
What is the destination of a third order neuron in tracts gracilis and cuneatus?
VPL of the thalamus
What do cuneatus and gracilis tracts differ in control of?
Which set of limbs
Between cuneatus and gracilis, which tract controls upper limbs?
Tracts gracilis
What two spinal tracts are collectively known as the “anterolateral” system?
Ventral and lateral spinothalamic tracts
What type of information is carried by the spinothalamic tracts?
Crude pressure, nociception, and thermoreceptors
Where do the spinothalamic tracts cross?
In the cord
Which crosses quicker the ventral or lateral spinothalamic tract?
Lateral
Which ascending cord controls proprioception?
Spinocerebellar tract
Where does the the spinocerebellar tract cross?
Dorsal - no crossing
Ventral - twice once in the cord and pons
Which tract controls only proprioception in the lower limbs?
Dorsal spinal cerebellar
What Rexed lamina is the anterolateral system carried in?
I and II
What Rexed lamina are the spinocerebellar tracts carried in?
VII
Where does the dorsal and ventral spinocerebellar enter the cerebellum at?
Dorsal - Inferior cerebellar peduncle
Ventral - Superior cerebellar peduncle
What does the lateral corticospinal tract control?
Voluntary muscle control of the limbs
Where does the lateral corticospinal tract originate?
Pre-central gyrus
Where does the lateral corticospinal tract cross?
The medulla
What does the ventral corticospinal tract control?
Voluntary muscles of head, neck, and trunk
Where does the ventral corticospinal tract cross?
Spinal cord at the level of exit
What does the rubrospinal tract control?
Excitation of proximal flexors and inhibition of extensors
Where does the rubrospinal tract cross?
The midbrain
Where does the rubrospinal tract originate?
The nucleus ruber
What does the vestibulospinal tract control?
Postural neck reflexes, extensors of the back and limbs
Where does the vestibulospinal tract originate?
Vestibular nuclei
Where does the vestibulospinal tract cross?
It doesn’t
Where does the reticulospinal tract originate?
Reticular formation
Where does the reticulospinal tract cross?
Many levels
What is the function of the reticulospinal tract?
Restricts voluntary movements through the gamma motor neurons
Where does the raphespinal tract originate at?
Raphe nucleus
Where does the raphespinal tract cross at?
It does not
What is the function of the raphespinal tract?
Inhibits nociception by releasing serotonin; this acts on C fibers
What is located in Rexed lamina I?
Fibers from sensory first order neurons; contributes to contralateral spinothalamics
What is located in Rexed lamina II?
Small neurons that respond to substance P
What is located in Rexed lamina III and IV?
Nucleus proprius, main input is from mechanoreception and light touch
What is located in Rexed lamina V?
Neurons that respond to noxious and visceral stimuli
What is located in Rexed lamina VI?
Neurons that receive mechanical signals from the skin and joints
What is located in Rexed lamina VII?
Clarke’s column (dorsal nucleus) for proprioception; Intermediolateral horn is in T1-L2
What is in Rexed lamina VIII and IX?
Alpha motor neurons to extrafusal skeletal muscles and Gamma motor neurons to intrafusal fibers in the muscle spindle
What is in Rexed laminae X?
Grey commissure surrounding the central canal
What supplies blood to the cord?
Segmental spine arteries derived from: ascending cervical, deep cervical, posterior intercostal, lumbar
What do segmental spinal arteries give rise to?
Radicular and segmental medullary artery
What do segmental spinal arteries supplement?
Anterior and posterior spinal arteries
What does the anterior spinal artery supply?
The anterior 2/3
What does the posterior spinal arteries supply?
The posterior 1/3
