Unit 4 Flashcards
The average length of the spinal cord is?
16-18 inches
The maximum diameter of the cord is?
about 1.3cm at the cervical enlargement
At what cord level is the cervical enlaregment the biggest?
at C5-C6
Approximately what does the spinal cord weigh?
27-35 grams
What is the superior boundary of spinal cord?
the foramen magnum; or superior most ventral rootlet of C1 spinal nerve
What is the inferior boundary of the spinal cord?
The disc between L1-L2; or conus medullaris
How many spinal nerve pairs exist in the PNS?
31
Dorsal roots contain what type of fibers?
sensory or afferent
Ventral roots contain what type of fibers?
motor or efferent fibers
How are cervical nerves named?
the nerve is named for the vertebrae below
Give an example of a cervical nerve naming
C4 nerve exits between C3 and C4 vertebrae
How are thoracic nerves named?
the nerve is named for the vertebrae above
Give an example of a thoracic nerve naming
T1 nerve exits between T1 and T2 vertebrae
How are lumbar nerves named?
the nerve is named for the vertebrae above
Give an example of a lumbar nerve naming
L1 nerve exits between L1 and L2 vertebrae
Where do sacral nerves S1-S4 exit?
through dorsal and ventral sacral foramina
Where does sacral nerve S5 exit?
through the sacral hiatus
What other nerve exits through the sacral hiatus besides S5?
coccygeal nerve 1
At what point of development is the spinal cord and vertebral column the same length?
the first three months
At birth what level is the Co1 nerve at?
L1-L3
In adulthood what level is the Co1 nerve found?
about L1-L2
At what cord level injury is considered quadriplegic ?
C8 and above
At what cord level injury is considered paraplegic?
T1 and below
At what area are cord and vertebral level the same?
in the cervical area
As the cord descends, past the cervical area, what happens to the cord levels and vertebral levels?
they progressively become separated, and roots travel inferiorly to exit
At what level does a burst fracture typically happen?
T6
What happens to gray matter as you descend the cord?
Gray matter % increases
Is funiculi white or gray matter?
white matter
Are horns white or gray matter?
gray matter
Which part of the horn carries sensory information and has lots of cell bodies?
the posterior/dorsal horn
At what levels is the lateral horn present?
T1-L2 and S2-S4
What is the significance of the lateral horn?
it is filled with preganglionic autonomic cell bodies
What is the significance of the anterior/ventral horn?
its the somatic/motor horn that has cell bodies to provide the PNS with skeletal muscle information
Describe what a funiculus is
its a longitudinal bundle of white matter fibers
Describe the composition of gray matter
Dense concentrations of neuron cell bodies with thick dendritic mats which supports glial cells and has dense capillary beds
What parts of the white matter in the cord are myelinated?
only long processes
Describe Lamina I
its the cap over the dorsal/posterior horn and has lots of synaptic activity
Describe Lamina II
near a pain center called the “Substantia Gelantinosa”
so lamina II is associated with pain interpretation
Describe Lamina III and IV
because these two lamina are closely associated they can be grouped together
Collectively called the Nucleus Propius
associated with temperature, touch, and pressure
Describe Lamina V
in the cervical area only on the lateral edge is a formation called the Formatio reticularis
this lamina contains cell bodies carrying pain info to the contralateral spinothalamic tract (ascending tract)
Describe Lamina VI
carries sensory info and is missing at some cord levels
Describe Lamina VII
Its in the lateral horn when present and contains preganglionic autonomic neurons (T1-T12 or L1-L2 and S2-4)
it carries many descending tract fibers
Lamina VII contains Clarke’s Nucleus,describe it
It runs from C8-L3 and contributes axons to the posterior spinocerebellar tract
Lamina VII also contains the interomediolateral nucleus, describe it
it forms most cell bodies from T1-T12.
Its also present at L1,2 and S2,3,4 but without a distinct horn
if lateral horn is present the cell bodies are preganglionic sympathetic
At what level of the interomediolateral nucleus are preganglionic sympathetic neurons located?
T1-L2
At what level of the interomediolateral nucleus are preganglionic parasympathetic neurons found?
S2-4
What is another name for the nucleus at S2-4?
Sacral parasympathetic Nucleus
Describe Lamina VIII
its located at the medial aspect of the ventral horn and contains delta motor neurons
What are delta motor neurons?
they play a role in skeletal muscle and extend into the periphery
Describe Lamina IX
most skeletal muscle is innervated from neurons here
Class A alpha motor neurons are prominent here
Describe Class A alpha motor nerurons
they are the fastest, largest motor neurons and travel from cord-PNS-muscle
Describe Lamina X
it surrounds the central canal and holds anterior and posterior gray commisures
unmyelinated fibers are common here
Describe Fasciculi
bundles of functionally related axons within a white column
Describe the Gracilis fasciculi
Its present at all cord levels, but only carries information that occurs below T6
Its fibers synapse in the gracilis nucleus of the M.O.
Describe the Cuneatus fasciculi
Its present at T5 or 6 and up and all sensory info above T6 goes to this tract
Its fibers synapse in the cuneatus nucleus of the M.O.
Describe the functions of Gracilis and Cuneatus
two point touch, vibratory sensations, and kinesthetic sensation
Describe how to give the Romberg’s test and what it tests
have feet close together, arms out, eyes closed, and if they fall over they fail.
this test for posterior column issues
How many neurons are in the Gracilis and Cuneatus pathway?
3.
Describe the path of a 3 neuron pathway
periphery to M.O., M.O. to thalamus, thalamus to cerebral cortex
Where do fibers for gracilis and cuneatus cross?
At the internal arcuate fibers of the M.O.
Where do fibers of gracilis and cuneatus go to in the thalamus?
the VPL
Where do fibers of gracilis and cuneatus terminate?
the post central gyrus of the cerebral cortex
If sensory information is picked up on the right big toe and travels through gracilis, what side of the brain will interpret this info?
the right side
Describe the Lateral Spinothalamic tract
its present at all cord levels
it carries pain/temp info
it crosses quickly in the spinal cord
Describe the Anterior Spinothalamic tract
its located at all cord levels
it carries light touch/pressure
it crosses slowly, in about 2-3 cord levels
Describe the Anterior Spinothalamic tract
its located at all cord levels
it carries light touch/pressure
it crosses slowly, in about 2-3 cord levels
What lamina would the Lat. Spinothalamic tract be associated with?
lamina 2/the pain lamina
Where do fibers of the Anterior and Lateral Spinothalamic tracts go to in the M.O.?
the VPL
Are the Spinothalamics contralateral or ipsilateral?
contralateral
What lamina would the Ant. Spinothalamic tract be associated with?
likely 3 and 4
What do lesions of the spinothalamics lead to?
Analgesia (loss of pain senstion) and thermatoanaesthesia (loss of temp sensation) on the opposite side of the body
The anterior and lateral spinothalamics are sometimes considered as one tract, what is it called?
the anterolateral system
Describe the fiber crossing of the Anterior Spinocerebellar tract
its fibers cross in the cord, but cross one more time in the M.O.
Is the anterior spinocerebellar tract contralateral or ipsilateral?
ipsilateral
Where do fibers of the Anterior spinocerebellar tract terminate?
the cerebullum via the superior cerebellar penduncle
What info does the Anterior spinocerebellar tract carry?
general state of gross movements of the lower body and what is about to happenq
What are the fiber origins of the Anterior spinocerebellar tract?
mostly in the lumbosacral cord’s gray laminae
Do most fibers of the Posterior Spinocerebellar tract cross?
no
What are the fiber origins of the Posterior Spinocerebellar tract?
nucleus dorsalis (C8-L3)
At what level does the Posterior Spinocerebellar tract stop?
L3
Where do the fibers of the Posterior Spinocerebellar tract terminate?
the cerebellum via the inferior cerebellar peduncle
What information does the Posterior Spinocerebellar tract carry?
proprioceptive info of fine movements of what just happened from inside a muscle
Is the Posterior Spinocerebellar tract ipsilateral or contralateral?
ipsilateral
What lamina would be associated with the Posterior Spinocerebellar tract?
lamina 7
In what tract is info of fine movements of the lower body carried in, when its below nucleus dorsalis, until it reaches the posterior spinocerebellar tract?
gracilis
Where do the fibers for the cuneocerebellar tract originate?
from the pectoral girdle and extremity
Once in the spinal cord, where do fibers of the cuneocerebellar tract go to?
to the Cuneate nucleus in the M.O.
Where do fibers of the cuneocerebellar tract enter the cerebellum?
the inferior cerebellar peduncle
What information does the cuneocerebellar tract carry?
fine movement proprioception for our arms and hands
Is the cuneocerebellar tract ipsilateral or contralateral?
ipsilateral
Of the ascending tracts, which ones are found at all cord levels?
Gracilis, Anterior Spinothalmaic, lateral Spinothalamic, and Anterior Spinocerebellar
Which ascending tract crosses twice?
the Anterior spinocrerebellar
Which ascending tract crosses twice?
the Anterior spinocrerebellar
What percentage of fibers does the Anterior Corticospinal tract carry?
only 5-15%
Where do fibers of the Anterior Corticospinal tract cross?
in the spinal cord after theyve came out of the tract just prior to their destination
At what level does the Anterior Corticospinal tract terminate?
it terminates at T6
What does the Anterior corticospinal tract influence?
axial muscles of neck and shoulder
What percentage of fibers does the Lateral corticospinal tract carry?
about 90%
Where do fibers of the Lateral Corticospinal tract cross?
in the pyramids of the M.O.
Where does the Lateral corticospinal tract terminate?
it actually runs the length of the whole cord
What does the Lateral corticospinal tract influence?
initiating and completing precise skilled voluntary muscle movements, especially in distal extremities
What lamina are the Corticospinals associated with?
Lamine VII and IX
Describe Lower Motor Neurons (LMN’S)
they originate in the spinal cord or brain stem and extend into PNS to innervate somatic muscles
Describe Upper Motor Neruons (UMN’s)
come from higher brain centers which influence LMN’s
Describe the result of lesions to UMN’s
Reduction or absence of voluntary movement
hyperreflexia-exaggerated reflexes
increased muscle tone
babinski sign-toes flare out and extend
Clonus-jerking against resistance
What would be an example of a pathology that affects UMN’s?
Cerebral Palsy
Describe the result of lesions to LMN’s
reduction or absence of voluntary movement
Hyporreflexia
decreased muscle tone or atrophy
muscle fibrillations
What would be an example of a pathology that affects LMN’s?
Polio
What would be an example of a pathology that affects LMN’s?
Polio
Describe pyramidal neurons
associated with the initiation of skilled voluntary movements; in the cord are corticospinal fibers
Describe extrapyramidal neurons?
they originate in the brain stem and influence posture, muscle tone, enhances reflexes, and allows voluntary movement to be smooth and effective
What 3 tracts are strongly associated with extrapyramidal neurons?
vestibulospinal, rubrospinal, and tectospinal tracts
Where does the tectospinal tract originate?
from the superior colliculus of the tectum
Describe the fiber crossing of the tectospinal tract
they cross as the descend
Where do most fibers of the tectospinal tract terminate?
in the upper 4 cervicals
What is the function of tectospinal tract?
postural reflex enhancement dealing with sight and auditory stimuli which is accomplished by adjustments to the trapezius and steinocleidomastoid
What would be an example of the tectospinal tract being used?
when one hears a loud boom or sound and they avert their gaze as a reflex
What lamina is associated with the tectospinal tract?
Lamina VII
