Unit IV: Spinal Cord Flashcards
How long is the spinal cord?
16-18 inches
At what vertebral level does the spinal cord occupy 75% of the vertebral canal?
C5-C6
What is the superior boundary of the SC for convenience?
Foramen magnum
What is the superior boundary of the SC being precise?
1st cervical spinal nerve
What is the inferior boundary of the SC?
L1-L2: conus medullaris
*How many pairs of spinal nerves are there?
31
*What does the Bell-Magendi Law state?
Dorsal roots contain sensory (afferent) fibers and ventral roots are motor (efferent) fibers
*Where are cervical spinal nerves found in position to its corresponding vertebra?
One above
*Where are thoracic spinal nerves found in position to its corresponding vertebra?
One below
*Where are lumbar spinal nerves found in position to its corresponding vertebra?
One below
*S5 exits at the ___
Sacral hiatus
*___ exits at the sacral hiatus
Co1-> may be missing
*During the first 3 months of the embryonic development, the cord and the vertebral column are approximately the ___
Same length
At birth, the Co1 cord level is at the same level as ___
L1-L3
By adulthood, the Co1 cord level is found at ___
L1-L2
The end of the SC is called the ___
Conus medullaris
Through the lumbar cistern, the formation of the SC is called the ___
Cauda equina
The ___ is continuous with the MO and 4th ventricle
Central canal
The central canal expands in the conus medullar is as a ___
Terminal ventricle
*Terminal vs. lumbar cistern
- both contain CSF
- T- within the cord
- L- outside the cord
The dorsal horn of gray matter functions in ___
Sensory
The lateral horns of gray matter functions in ___
Autonomic-> preganglionic
The ventral horn of gray matter functions in ___
Motor
What is a funiculus?
A longitudinal bundle of white matter fibers-> columns
White matter composition
- dense concentrations of neuron cell bodies
- many synaptic areas
- support glial cells
- dense capillary beds
*Rexed lamina I
Forms a thin cap over the dorsal horn
*RL II
- “substantia gelatinosa”
2. important pain reception center
*RL III and IV
- “nucleus proprius”
2. sensory receptors
*RL V
- cervical area only
- reticular formation
- axons cross to the other side of the cord
*Which tract is found in RL V?
Lateral spinothalamic
*RL VI
- missing at some cord levels
2. most anterior aspect of dorsal horn
*RL VII
- intermediate gray area
- descending fibers
- C8-L3
- lateral horn-> T1-L2
- “sacral parasympathetic nucleus”
*Which tract is found in RL VII?
Posterior spinocerebellar tract
*RL VIII
- anterior horn
- delta motor neurons
- most medial
*RL IX
- skeletal muscles
- “somatic motor horn”
- class A alpha motor neurons
- series of disconnected islands
*RL X
- surrounds the central canal
- gray commissures
- crosses midline
- Blood vessels are ___ dense in white matter than in gray matter
Less
Fibers associate and stay together by surface proteins are called ___
NCAMs
*Are tracts observable by general staining techniques?
No
Sensory input enters the SC as ___ at the dorsal later sulcus
Dorsal root ganglion axons
Most axon will synapse in the ___ when entering the cord
Dorsal gray horn laminae
*Where is gracilis located?
Dorsal funiculus-> medial aspect
*Where is gracilis present?
In all cord levels
*Where do fibers synapse in gracilis?
MO
- Functions of gracilis
- 2 point touch discrimination
- vibratory sensations
- kinesthetic sensation
*Pathway of gracilis
- DRG at all cord levels-> MO
- medial lemniscus-> thalamus
- post. central gyrus
*Where is cuneatus located?
Dorsal funiculus-> lateral aspect
*Where is cuneatus present?
T6 and up
*Where do fibers synapse in cuneatus?
MO
*Functions of cuneatus
- 2 point touch discrimination
- vibratory sensations
- kinesthetic sensation
*Pathway of cuneatus
- DRG: T6 and up-> MO
- medial lemniscus-> thalamus
- post. central gyrus
*Where is the lateral spinothalamic tract located?
Lateral funiculus
*Where is the lateral spinothalamic tract present?
All cord levels
*What is the function of the lateral spinothalamic tract?
Pain/temperature
*Do fibers cross quickly or gradually in the lateral spinothalamic tract?
Quickly
*Pathway of the lateral spinothalamic tract
- DRG-> cord level
- (crosses quickly)-> VPL of the thalamus
- post. central gyrus
*Where is the anterior spinothalamic tract located?
Anterior funiculus
*Where is the anterior spinothalamic tract found?
All cord levels
*What is the function of the anterior spinothalamic tract?
Light touch/pressure
*Do fibers cross quickly or gradually in the anterior spinothalamic tract?
Gradually
*Pathway of the anterior spinothalamic tract
- DRG-> cord level
- (crosses gradually)-> VPL of the thalamus
- post. central gyrus
Lesions in the spinothalamic tracts lead to ___ and ___ on the opposite side of the body
Analgesia and thermoanaesthesia
What is analgesia?
Loss of pain sensation
What is thermoanaesthesia?
Loss of temperature sensation
*In the spinothalamic tracts, fibers terminate in the ___
VPL of the thalamus
*Where is the anterior spinocerebellar tract located?
Lateral funiculus
*Do fibers cross in the anterior spinocerebellar tract?
Yes, and cross back again in cerebellum
*Where are the fiber origins in the anterior spinocerebellar tract?
Lumbosacral cord’s gray laminae
*Where do fibers terminate in the anterior spinocerebellar tract?
Cerebellum-> superior cerebellar peduncle
*What is the function of the anterior spinocerebellar tract?
- gross movements of lower body
2. general activity of what is about to happen
*Where is the posterior spinocerebellar tract located?
Lateral funiculus
*Do fibers in the posterior spinocerebellar tract cross?
No
*Where are the fiber origins of the posterior spinocerebellar tract?
Nucleus dorsalis-> C8-L3
*Where do fibers terminate in the posterior spinocerebellar tract?
Cerebellum-> inferior cerebellar peduncle
*What is the function of the posterior spinocerebellar tract?
- proprioceptive input dealing with mainly fine movements
2. what has just happened
*Pathway of the anterior spinocerebellar tract
- DRG-> cord level
2. (crosses quickly)-> superior cerebellar peduncle-> crosses back-> opposite side of cerebellum
*Pathway of the posterior spinocerebellar tract
- DRG (C8-L3)-> cord level-> inferior cerebellar peduncle-> cerebellum
*Proprioceptive fibers dealing with fine movements from the lower extremity may enter the cord ___
Below the nucleus dorsalis
*If proprioceptive fibers come from below the nucleus dorsals, which tract takes over and carries them to the designated spinal tract?
Gracilis
*Function of the cuneocerebellar tract
Fine movement proprioceptive fibers from the lower extremity
*Pathway of the cuneocerebellar tract
- DRG (upper extremity)-> inferior cerebellar peduncle
2. cerebellum
6 ascending tracts
- gracilis
- cuneatus
- lateral spinothalamic
- anterior spinothalamic
- anterior spinocerebellar
- posterior spinocerebellar
*Where is the anterior corticospinal tract located?
Anterior funiculus
*How many fibers does the anterior corticospinal tract carry?
5-15%
*Where do fibers cross in the anterior corticospinal tract?
In the cord
*Where does the anterior corticospinal tract terminate?
By mid thoracic cord level
*What is the function of the corticospinal tract
Trick question- function is unclear
*Where is the lateral corticospinal tract located?
Lateral funiculus
*How many fibers does the lateral corticospinal tract carry?
85-95%
*Where do fibers in the lateral corticospinal tract cross?
Pyramids of the MO
*What level is the lateral corticospinal tract found at?
All cord levels
*What is the function of the lateral corticospinal tract?
Initiating and accomplishing precise skilled voluntary movements
*Pathway of the anterior corticospinal tract
- motor cortex-> (crosses in cord)-> level of synapse
2. DRG
*Pathway of the lateral corticospinal tract
- motor cortex-> (crosses in MO)-> level of synapse
2. DRG
*Tract that has the only axons that begin in the cerebral cortex and run uninterrupted to the spinal cord
Corticospinals
*Where do corticospinal tracts synapse?
Laminas VII and IX
*Most axons from the corticospinals are ___ from the pre central gyrus of the frontal lobe
Giant pyramidal (Betz) cells
What are lower motor neurons?
Originate in the spinal cord or brain stem and extend into the PNS
What are upper motor neurons?
Neurons that come from the cortex or brainstem that influence LMNs
Example of a UMN lesion
Cerebral Palsy
Example of a LMN lesion
Polio
*What are pyramidal neurons?
UMNs involved with the initiation of skilled voluntary movements
Example of a tract in the cord that is pyramidal?
Corticospinals
*What are extrapyramidal neurons?
- UMNs which originate in the brain stem and extend down to the cord
- influence posture, muscle tone, reflexes, smooth and effective voluntary movments
Examples of tracts that are extrapyramidal
- tectospinal
- rubrospinal
- vestibulospinal
*Origin of the tectospinal tract
Superior colliculus of midbrain’s tectum
*Do fibers cross in the tectospinal tract?
Yes- as they descend
*Where do fibers terminate in the tectospinal tract?
Upper 4 cervical cord levels
*What is the function of the tectospinal tract
Sight and auditory stimuli-> trapezius and SCM
*Pathway of the tectospinal tract
- tectum-> (cross in MO)-> synapse before C4
*Origin of the rubrospinal tract
Red nucleus
*Do fibers cross in the rubrospinal tract?
Yes- in the midbrain
*Where is the rubrospinal tract found?
All cord levels
*What is the function of the rubrospinal tract?
Muscle tone control in the hand and foot
*Pathway of the rubrospinal tract
- red nucleus-> (crosses in MO)-> level of synapse
*Origin of the vestibulospinal tract
MO-> Deiters’ nucleus
*Do fibers cross in the vestibulospinal tract?
No
*Where is the vestibulospinal tract found?
All cord levels
*Function of the vestibulospinal tract
- muscle tone and postural adjustment in extensor musculature
- falling
*Pathway of the vestibulospinal tract
- Deiters’ nucleus-> level of synapse
*What is the function of the reticulospinal tract
Heart, blood pressure, and respiratory rates and rhythms
*Where is the fasciculus proprius found at?
Spinospinal fibers
*Function of the fasciculus propruis
Spinal reflexes
What fibers are the first to be myelinated in the fetus?
Fasciculus proprius
*Where is the dorsolateral located?
Between RL I and posterior lateral sulcus of the cord
Symptoms of UMN lesions
- skeletal muscle becomes rigid
2. spasticity
Symptoms of LMN lesions
- skeletal muscle wastes away
2. flaccidity
What vertebral levels are most common sites for severe injury?
C5/C6 and T12/L1
What is Brown-Sequard Syndrome?
Total loss of either the right or left side of the spinal cord
What is Tabes Dorsals?
Bacteria that wastes away the dorsal funiculus-> fasciculus gracilis
*What is multiple sclerosis?
Destruction of the CNS myelin-> interfascicular oligodendrocytes
*What is amyotrophic lateral sclerosis?
Destruction of UMNs and LMNs-> lateral corticospinal tracts
Toxins and myelin features
- myelin alteration
2. hexachlorophene
What is pernicious anemia
- deficiency of vitamin B12 due to intrinsic factor problems
- CNS and PNS changes
What is syringomeylia?
The cord’s central canal or adjacent areas begin to hollow out
What is poliomyelitis?
- a virus altering of the sytoplasm of the neuron’s cell body until cell death
- scar tissue follows
- upper cervicals-> respiratory failure
- retrograde
Neoplasm and compression features
- most common cord tumor-> ependymoma in the conus medullaris
- most common vertebral canal tumor-> meningioma
- glioblastoma multiforma