Exam 4, Chapter 12: The Spinal Cord Flashcards
dorsal root ganglia are?
Sensory neurons
Surrounding the Neural tube,
Interneurons (assosiciation neurons), which receive sensory input from sensory neurons come from?
dorsal cells
Surrounding the Neural tube,
Motor neurons from?
ventral cells!
enclosed within the vertebral column from the foramen magnum to L1 / L2
Spinal Cord Gross Anatomy
afferent fibers (sensory)
Spinal Cord Gross Anatomy
Ascending fibers
efferent fibers (motor)
Spinal Cord Gross Anatomy
Descending fibers
protected by bone, meninges, and CSF
Spinal Cord Gross Anatomy
space between the vertebrae and the dural sheath (dura mater) which isfilled with fat and a network of veins
Spinal Cord Gross Anatomy
Epidural Space
Epidural anesthesia is delivered into this space via flexible cannula
Spinal Cord Gross Anatomy
Epidural space
terminal portion of the spinal cord
Spinal Cord Gross Anatomy
Conus medullaris
End of cord narrows to a cone shape between L1 and L2
Spinal Cord Gross Anatomy
Conus Medullaris
fibrous extension of the pia mater; anchors the spinal cord to the coccyx
Spinal Cord Gross Anatomy
Filum terminale
delicate shelves of pia mater; attach the spinal cord to the vertebrae
Spinal Cord Gross Anatomy
Denticulate ligaments
31 pairs attach to the cord by paired roots
Spinal Cord Gross Anatomy
Spinal nerves
8 cervical pair; 12 thoracic pair; 5 lumbar pair; 5 sacral pair; 1 coccygeal
Spinal Cord Gross Anatomy
Spinal Nerves
sites where nerves serving the upper and lower limbs emerge, so large ventral horns and multiple nerve roots leaving the cord in these regions
Spinal Cord Gross Anatomy
Cervical and Lumbar Enlargements
collection of nerve roots at the inferior end (below L2)
Spinal Cord Gross Anatomy Cauda equina (horse tail)
- Dura mater (single layer only; no periosteal attachment)
- Arachnoid mater with CSF in subarachnoid space
- Pia mater
Spinal Cord Gross Anatomy
Meninges
also circulates in the central canal which continues superiorly into the medulla oblongata
Spinal Cord Gross Anatomy
CSF
separates ventral funiculi (white matter tract regions)
Cross-Sectional Anatomy of Spinal Cord
Ventral median fissure
divides dorsal funiculi (white matter tract regions)
Cross-Sectional Anatomy of Spinal Cord
Dorsal median sulcus
consists of soma, unmyelinated processes and neuroglia
Cross-Sectional Anatomy of Spinal Cord
Gray Matter Columns
Gray Matter
connects R / L masses of gray matter; encloses central canal
Cross-Sectional Anatomy of Spinal Cord
Gray Matter Columns
Gray Commissure
Interneurons (Therefore, a sensory synapse will occur here)
Cross-Sectional Anatomy of Spinal Cord
Gray Matter Columns
Dorsal Horns
Somatic (voluntary) motor neurons & some interneurons
Cross-Sectional Anatomy of Spinal Cord
Gray Matter Columns
Ventral Horns
Contain sympathetic motor fibers; this column is present in T1-L2 only
Cross-Sectional Anatomy of Spinal Cord
Gray Matter Columns
Lateral Horns
dorsal root ganglion (sensory nerve cell bodies) lead to dorsal roots which
expand into rootlets before entering the spinal cord
Cross-Sectional Anatomy of Spinal Cord
Spinal Roots
Dorsal half
May synapse at a dorsal horn interneuron or continue via axons in the white matter
columns towards the brain
Cross-Sectional Anatomy of Spinal Cord
Spinal Roots
Dorsal Half
motor rootlets join to form motor roots
Cross-Sectional Anatomy of Spinal Cord
Spinal Roots
Ventral half
fuse laterally to form short spinal nerves
Cross-Sectional Anatomy of Spinal Cord
Spinal Roots
Dorsal and ventral roots
Body representation in four zones (maintain spatial relationships)
Cross-Sectional Anatomy of Spinal Cord
Spinal Roots
Gray matter Somatotopy
visceral sensory (VS), visceral motor (VM)
Cross-Sectional Anatomy of Spinal Cord
Visceral representation on the internal aspect
Gray matter Somatotopy
Somatic representation on the external aspect
Cross-Sectional Anatomy of Spinal Cord
Gray matter Somatotopy
somatic sensory (SS), somatic motor (SM)
ascending, descending, and transversely
Cross-Sectional Anatomy of Spinal Cord
White Matter Columns
Three Directions of Fiber movement
dorsal, ventral, lateral (T1-L2 only)
Cross-Sectional Anatomy of Spinal Cord
White Matter Columns
are Divided into three columns (funiculi)
Each white matter column contains several fiber tracts
- Fiber tract names reveal their origin and destination
- Fiber tracts are composed of bundled axons with similar sensory functions
Cross-Sectional Anatomy of Spinal Cord
White Matter Columns
All pathways decussate at some point
- Most consist of two or three neurons (relays)
- Most maintain somatotopy (organizational mapping)
- Pathways are paired (one on each side of the spinal cord or brain)
Neuron Pathways: Sensory (Afferent-Ascending)
General Features
(of two or more things) cross or intersect each other to form an X.
Neuron Pathways: Sensory (Afferent-Ascending)
decussate
The central processes of “first-order neurons” branch diffusely as they enter the spinal cord
and medulla
-conduct impulsees and proprioceptors
-most synapse with 2nd-order neurons (interneuron) in the spinal cord or medullary nuclei
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
conduct impulses from cutaneous receptors (discriminative touch, pressure, vibration , temperature, pain)
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Conduct impulses
First Order Neuron
(feedback on position of joints & relative movement of joints)
-other branches take part in “spinal cord reflexes”
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Proprioceptors
most branches synapse with these, aka “interneuron” in the spinal cord or medullary nuclei
(nuclei in medulla oblongata)
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Second-order neurons
“red nucleus”
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Medulla oblongata nuclei
Location of third order-(inter)neuron
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Axons extend to thalamus
Extension of Third Order Neuron Axons
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Primary Somatosensory Cortex
Subconscious Second Order Axons where?
Neuron Pathways: Sensory (Afferent-Ascending)
Ascending Pathway Organization
Cerebellum
no additional synapses