Spinal Cord Flashcards
Where are motor and sensory primarily found in brain
Cerebrum (longitudinal)
What is at the C8 level
NO C8 vertebra
Where does the sacral cord end
L2
Conus medularis
What is the cauda equina formed by
Descending roots
What does the dural sleeve cover?
Spinal cord, roots and DRG
This spans from dura to pia/cord and help to stabilize the spinal cord in the horizontal plane. Arachnoid trabecula have similar effect
Denticulate ligament
Where is the CSF in the spinal cord?
Subarachnoid space
What is the only thing present from L3 and caudally
Cauda equina
Space between the dura and the bone
Epidural space
Space between the arachnoid and pia
Subarachnoid space
What’s the difference between the roots and the horns?
The roots are the beginnings of the spinal cords, and horns are the projections of gray matter within the spinal cord
What cell or cell parts are present in the gray matter
- neuronal cell bodies
- glia (mostly astrocytes, microglia)
- dorsal/posterior horn
- ventral/anterior horn
- intermediate gray zone
- some myelinated and unmyelinated axons
What cells or cell parts are present in the white matter
- glia (astrocytes, microglia, and oligodendrocytes)
- axons
- highly myelinated
- no neuronal cell bodies
What are the parts of hte fluid filled neural tube
- central canal
- gray matter
- white matter
Where is glia found
In both gray and white
Where are neurons found
Only in grey
Why is there a lot more gray matter on levels of the spinal cord close to extremities?
Because of the different plexuses
C5-T1
L1-L4
What lamina/nuclei are in the dorsal horn of gray matter?
- substantia glatinosa (lamina II) pain/temp
- nucleus proprius of posterior horn (III, IV, V) crude touch
- nucleus dorsalis
What lamina/nuclei are in the intermediate gray?
Intermediolateral cell column; sympathetic preganglionic neurons (VII)
What lamina/nuclei are in the ventral gray horn
- VII, IX motorneurons
- of limbs and lumbar enlargements
Nuclei names and lamina # where pain/temp fibers terminate and synapse
Lamina II
Substantial gelatinosa
Part of anterolateral system
Nuclei names and lamina number where crude pain touch fibers terminate and synapse
Lamina III, IV, V
- Nucleus proprius of posterior horn
- nucleus dorsalis
Part of anterolateral systme
Where are preganglionic sympathetic and parasympathetic fibers located
Lamina VII
Where is the central canal?
Right down the central longitudinally through spinal cord
Where is the posterior funiculus and what kind of matter
- white matter
- located from the posterior median sulcus to the posterolateral sulcus
Where is the lateral funiculus located and what kind of matter is it
- white
- located from the posteriolateral sulcus/tract to about the line of the denticulate ligament
Where is the anterior funiculus and what kind of matter is it
- white
- located from the anterior median fissure to about the denticulate ligament
What divides the posterior funiculus up?
Posterior median sulcus/septum and the posterior intermediate sulcus
What is the fasiclus gracilis?
It s a subdivision of the posterior fasiculus that is most medial
Bordered by the posterior median sulcus/septum and the posterior intermediate sulcus/septum
What is the fasiculus cuneatus
Division of the postieor funiculus that is more lateral
Bordered by the posterior intermediate sulcus/septum and the posterolateral tract/sulcus
What is the anterior white commissure?
Bundle of nerve fibers which cross midline of the spinal cord just anterior to the gray commissure
What cord level mediates the patellar tendon reflex?
L4
What level of spinal cord is the biceps reflex located
C5
What level of spinal cord is the brachioradialis reflex located
C6
What level of spinal cord is the triceps reflex located
C7
What level of the spinal cord is the ankle jerk reflex located
S1
How would the patellar reflex be affected if there was only damage to the dorsal horn?
Descending projections to motoneurons regulate the stretch reflex and myotatic reflex usually inhibitory. Disruption of this inhibitory input leads to exaggerated reflexes
What is clonus
Hyperactive extensions.felxions
How are stretch reflexes tested?
Circuit function on side of tendon tap
- mimics knee flexion
- sensory arc of reflex activated (DRG)
- sensory input activates motoneurons for knee extension
- knee extends
- sensory arc also inhibits knee flexion
Can also be activated by passive stretch by examiner, whihc activates the muscle spindle
Stretch reflex rating
2/4 is considered normal
4/4:clonus 3/4: increased, brisk 2/4: normal 1/4: reduced 0/4: absent
What is damaged if clonus happens?
Ventral horn
Explain how sensory fibers enter the spinal cord and what the dermatome means
To the dorsal horn
Dermatomes are areas on the skin that correlate to the level of the spinal cord where the sensory nerve receives information enter through
Loss of sensation in a dermatome
A sign of a focal or segmental pathology of the spinal cord, dorsal root, or proximal spinal nerves at the same level corresponding segmental level
Explain the function of the nociceptive withdrawal reflex?
Ipsilateral withdrawal
- pain input activates ipsilateral knee flexion and ipsilateral Doris flexion of foot
- pain input INHIBITS ipsilateral leg extensors
Contralateral anti-gravity
-sensory input activates contralateral motoneurons for anti gravity response: activates hip and knee extension and inhibits knee flexor motoneurons
What is the nociceptive withdrawal reflex clinically significant
Because reflexes do not require conscious state, the nociceptive reflex can be used to test the arousability and motor system of a patient with an impairment of loss of consciousness
Describe how a muscle spindle works and how it can be tested by examiner
- tap mimics knee flexion
- tap detected as mild muscle stretch by the muscle spindle
- sensory arc of reflex is activated (DRG)
- sensory input activates motoneurons for knee extension
- knee extends
- sensory arc also inhibits knee flexion
Tested by knee tap or passive stretch
What does muscle tone mean and why is it clinically significant?
Degree of resistance to passive stretch
- Provide clues about the neurological basis causing motor weakness or paralysis
- excitability of muscle itself
- excitability of lower neurons
- status of upper neurons that synapse on lower motorneurons
- status of reflex circuitry: stretch and myotatic reflex circuits
Describe different definitions and locations of upper motor neurons and lower motor neurons
- Upper motor neurons are in precentral gyrus and synapse onto lower motorneurons in the anterior horn
- lower motorneurons actually project onto muscles
What aspects of motor function is served by the corticospinal system?
Voluntary movement
-control cranial motor nerves, contralateral limbs, and axial bilaterally
Describe how strength or power is evaluated
Measured on a 1-5 scale, 5 being normal
Describe an example of stretch reflex circuit and explain how it works.
- tap mimics knee flexion
- tap detected as mild muscle stretch by muscle spindle
- sensory arc involves DRG
- sensory input activates motorneurons for knee extension
- knee extends
- sensory arc also inhibits knee flexion by activating an interneuron whihc inhibits the motor neuron for flexion
How is a stretch reflex response evaluated
On a scale of 1-4, 2/4 being normal
Explain how autonomic nervous system and sacral spinal cord can activate or inhibit urinary voiding (micturition)
Sympathetic
- inhibits detrusor
- activates external sphincter
Parasympathetic
- activates detrusor
- inhibits external sphincter
Long reflex circuit
- stimulates detrusor
- inhibits sphincter
Short reflex circuit
-stimulates detrusor
What is the origin of blood to the spinal cord outside the vertebral column?
Blood is supplied from the basilar artery which gets its supply for the ICA
Where are spinal veins found
Subarachnoid
Where is the internal venous plexus found (meningeal layer)
Epidural space
What meningeal layer is the external venous plexus found
Outside dura
How would the patellar reflex be affected if there was damage to the ventral horn only
No reflex would occur
How would the patellar reflex be affected if there was damage to the dorsal horn only?
Impaired reflex
Where are all of the upper motorneurons located?
Precentral gyrus or brain stem, mostly the precentral gyrus though
Where in the spinal cord are lower motorneurons located?
Ventral horn of the spinal cord
How many times do the axons of upper motorneurons cross the midline?
One time at the pyramidal decussation
What side of the body doe s the left precentral gyrus control
Right
Which side of the body does the right precentral gyrus control?
Left
Describe the clinical rating scale for scoring motor strength (from cases)
On a 1-5 scale with 5 being normal, can overcome resistance from examiner
Does anterior horn damage produce lower motor neuron signs or upper motorneuron signs?
Lower motorneuron signs (segmental deficits)
Does damage to the lateral corticospinal tract produce lower motorneuron signs or upper motorneuron signs
Upper motor neuron signs (with level down paresis) suprasegmental
Does damage to the anterior corticospinal tract produce produce upper motorneuron sign or lower motor neuron sign
Lower
If both the anterior horn and the lateral corticospinal tracts on one side are damaged, are there lower motorneuron signs or upper motorneuron signs
Paresis on opposite side of body
