Spinal Pathways I and II Flashcards
where the spinal cord ends at birth; where it ends in adults
L3//L1-L2 interspace due to the vertebral column maturing after the spinal cord.
what causes the spinal roots below L3 that form the cauda equina?
differential growth of the spinal cord and vertebral column
the space where the blood vessels enter and exit the spinal cord
the perivascular space (extension of subarachnoid)
space filled with CSF
subarachnoid space
what forms the external glial membrane on the surface of the CNS?
astrocytes and their processes
the internal glial membrane exists between the..
parenchyma of spinal cord and ependymal cells that line the ventricles and central canal (these cells are part of the limiting membrane between the CSF and brain.)
vertebral levels of the cervical enlargement; vertebral levels of the lumbosacral enlargements, and what they form
C5-T1 (forms brachial plexus); L3-S1 (forms lumbosacral plexus)
the funiculi of white matter, and where they’re located
posterior funiculus (dorsal column)- between the posterior median septum and the dorsal root fibers lateral funiculus- between the dorsal and ventral roots anterior funiculus (ventral funiculus)- between the ventral roots and the anterior median fissure
describe the location of fasciculus gracilis and fasciculus cuneatus
gracilis is posteromedial, cuneatus is posterolateral
where is Lissauer’s tract?
immediately dorsal to the apex of the dorsal horn
lamina II is the
substantia gelatinosa
lamina VIII is called the..//function?
commissural nucleus (many of its neurons project to the opposite side through the ant. commissure)
dorsal nucleus (Clarke’s/nucleus dorsalis) is only present..
levels T1-L2/L3
the sacral autonomic nucleus’s cells give rise to..
preganglionic autonomic fibers to parasympathetic ganglia
the intermediolateral nucleus cells give rise to..
preganglionic autonomic fibers to the sympathetic ganglia
which lamina contains the motor neurons to skeletal musculature?
lamina IX
what are tract cells?
have axons which enter the white matter and ascend into the brain stem
what is the function of commissural neurons?
axons cross to the opposite side of the spinal cord in the anterior white commissure
what is the fasciculus proprius (propriospinal tract)?
axons ascend or descend in the white matter and synapse somewhere along the spinal cord
a peripheral afferent fiber having its origin in a DRG cell
primary neuron
tracts are usually composed of what type of neuron?
secondary (or tertiary)
what sensory modalities does the dorsal column- medial lemniscus pathway carry?
two point touch, pressure, vibration, and joint position, to the cerebral cortex
if the afferent fiber enters below the T6 level, it joins…./if it enters above the T6 level it joins…
fasciculus gracilis; fasciculus cuneatus.
in this ascending pathway, the secondary neuron is located..
in the caudal medulla
secondary fibers from the dorsal column nuclei decussate to the opposite side of the medulla as..
internal arcuate fibers
internal arcuate fibers coalesce to form the
medial lemniscus (flat band of fibers, which synapse on third order neurons in the ventral posteriorlateral nucleus of the thalamus)
from lateral to medial of the fasciculus cuneatus and gracilis, they are made of fibers from the..
cervical region, thorax (fasciculus cuneatus from above T6), lower body (fasciculus gracilis).
the tract that carries pain and temperature information
lateral spinothalamic tract division of the spinothalamic tract
the primary neurons of the lateral spinothalamic tract
unmyelinated C fibers, smallest myelinated A-delta peripheral fibers.
where do these afferent fibers of the lateral spinothalamic tract pass after entering the dorsal root of the spinal cord?
dorsolateral fasciculus (Lissauer’s tract)
what is substance P? where is it found?
a peptide transmitter of many afferent fibers. abundant in the lateral spinothalamic tract
an endogenous opioid peptide that is abundant in the lateral spinothalamic tract
encephalin (pain suppression system)
where are the spinothalamic tract cells located?
laminae I, IV, V in man.
where to the spinothalamic tract axons decussate?
in the anterior white commissure just a few synapses up from the site of entry, and then enter the anterior part of the lateral funiculus on the contralateral side.
where does crossing to the contralateral side occur for spinothalamic tract cells?
1-2 spinal cord segments rostral to the soma of the tract cell.
sensory pathway that conveys a light touch
anterior/ventral spinothalamic tract
which is better at localizing touch: dorsal column pathway or anterior spinothalamic tract?
dorsal column pathway
location of the anterior spinothalamic tract cells
lamina I, IV, V
where the fibers of the anterior spinothalamic tract cross after entering through lamina I, IV, or V?
cross in the anterior commissure, take position in the anterior part of the lateral funiculus
how does referred pain work?
spinothalamic tract cells are activated b heart pain, the brain is tricked into perceiving left arm pain due to convergence of afferent pain info from both visceral and somatic origins onto the same spinothalamic tract cell
tract that carries unconscious sensation to the cerebellum from the lower half of the body for motor control
dorsal spinocerebellar tract
types of afferents that carry info to the dorsal spinocerebellar tract
muscle spindle organs, Golgi tendon organs, touch and pressure receptors
where do the afferents of the dorsal spinocerebellar tract travel?
in the fasciculus gracilis, and make monosynaptic contact with cells of the dorsal nucleus of Clarke on the same side of the body
fibers from Clarke’s nucleus turn laterally and form the..
dorsal spinocerebellar tract along the border of the lateral funiculus immediately anterior to the dorsolateral fasciculus (Lissauer’s tract)
where does the dorsal spinocerebellar tract enter after continuing into the medulla?
inferior cerebellar peduncle, where they terminate as mossy fibers ipsilaterally
the dorsal spinocerebellar tract conveys info to the cerebellum about the performance of ________, following a voluntary movement
single muscles
this tract conveys info from the Golgi tendon organ and forms a variety of cutaneous afferents from the lower half of the body to the cerebellum (T1 and below)
ventral spinocerebellar tract (movement control)
cells of origin of the ventral spinocerebellar tract are located in..
lamina V, VI, VII
where do the axons from the ventral spinocerebellar tracts decussate?
immediately in the anterior white commissure, and form a tract in the contralateral funiculus immediately anterior to the dorsal spinocerebellar tract
where in the brainstem does the ventral spinocerebellar tract enter?
superior cerebellar peduncle
the majority of the fibers of the ventral spinocerebellar tract in the cerebellum..
decussate again (double crossing) in the cerebellum to terminate as mossy fibers on the same side as the cells of origin, although some terminate contralaterally
this tract conveys info about LARGE groups of muscles; also provides an internal feedback to the cerebellum concerning the voluntary movement of limbs
ventral spinocerebellar tract
tract that conveys upper half of the body info that’s analogous to the dorsal spinalcerebellar tract for the lower half of the body
cuneocerebellar tract
tract that conveys info for the upper half of the body, that’s analogous to the ventral spinocerebellar tract
rostal spinocerebellar tract
an internal communication system of the spinal cord
propriospinal tracts
axons of these neurons enter the white matter of all 3 funiculi, and ascend or descend
propriospinal tract
these types of pathways are concerned with somatic and visceral motor activities and modulating central transmission of sensory impulses
descending pathways
this is a motor tract which has its origin in neurons in the primary motor cortex, premotor cortex, and primary somatosensory cortex
corticospinal (pyramidal) tract
where do the fibers of the corticospinal (pyramidal) tract course?
through the internal capsule and continue into the cerebral peduncles and the pons. they then from the pyramids in the medulla
at the lower end of the medulla, 80% of the pyramidal tract fibers cross in the..
pyramidal decussation
in the contralateral spinal cord, the pyramidal tract fibers cross in the pyramidal decussation in the medulla and form the..
lateral corticospinal tract
lateral corticospinal tact fibers terminate mainly on..
interneurons in the intermediate gray
these fibers directly control somatic motor function*, esp. those of distal flexor muscles in voluntary movements
lateral corticospinal tract
the function of those pyramidal tract fibers originating in the primary somatosensory cortex that terminate on interneurons in laminae IV-VIII
*to modulate sensory information entering the spinal cord
the other 20% of pyramidal tract fibers continue ipsilaterally to form the
anterior corticospinal tract
fibers of this tract are concerned with the control of..
axial muscles
