Flashcards in Exam #1: Organization of the Spinal Cord Deck (36):
Where is the cervical enlargement of the spinal cord?
C5- T1; this is the origin of the nerves destined for the upper limb i.e. the roots of the brachial plexus
Where is the lumbosacral enlargement?
L2-S3; this is the origin of the nerves destined for the lower limb i.e. the lumbosacral plexus
Where is the common site for a LP? Why?
L3-4 or L4-5
****Cord ends at L2 (conus medullaris)--not going to hit the spinal cord; this space below the conus medullaris is known as the lumbar cistern
Where do the cervical nerve roots emerge?
Above the vertebrae
*****Remember that there are 8 cervical spinal nerves, but only 7 cervical vertebrae
Where do the lumbar nerve roots emerge?
Below the vertebrae
What is the spinal nerve?
The distal continuation of the dorsal & ventral roots, once they join together
What is the gray matter of the spinal cord?
"H" or butterfly in the center of the cord
What is the white matter of the spinal cord?
Outside of the H
- Tracts, fasiculi, commisures
What are the cross sectional differences between the cervical and sacral regions?
- Cervical region has the most white matter/ highest white:gray ratio
- Descending the spinal cord, the amount of white matter generally decreases
- In the sacrum, white matter is the least
What are the three general areas of the gary matter?
Dorsal horn/ column
Lateral horn/ column
What is the dorsal horn of the gray matter?
Cell bodies of the pseudounipolar neurons
What is the ventral horn of the gray matter?
Cell bodies of the motor neurons
What is the lateral horn of the gray matter?
Preganglionic sympathetic neurons
What levels of the spinal cord contain a lateral horn?
T1- L2 i.e. the levels that contain sympatheitc ganglia
What does the intermediate zone contain? Where is the intermediate zone?
This is the area between the dorsal & ventral horns of the gray matter that contains interneurons
Describe the arrangement of the ventral motor neurons in terms of function.
The regions that are innervated & the corresponding functions have a spatial arrangement in the ventral cord:
Lateral nuclei= limbs
Medial nuclei= trunk
What are "Rexed Laminae" of the spinal cord?
The gray matter of the spinal cord is divided into nine different regions referred to as "Rexed Laminae"
*Note that there is a 10th laminae (X), which is the gray commissure around the central canal of the cord
How are the nerve cells in the dorsal horn divided? What lamina does the substantia gelatinosa correspond to & what is its function?
The nerve cells in the dorsal horn are divided into four groups:
1) Substantia gelatinosa= II
- Unmyelinated axons mostly dealing with nociception
2) Nucleus proprius
3) Nucelus dorsalis
What lamina does the nucleus proprius correspond to? What is the function f the nucleus proprius?
IV, V, VI
- Receives central processes of the majority of unipolar neurons from the DRG
- Transmits pain, temperature, & light touch
What is Clarke's Column ? What lamina does it correspond to? What is the function?
- Clarke's Column is also referred to as the nucleus dorsalis, & corresponds to lamina VII
- Receives signals from proprioceptive fibers
What is contained in the intermediolateral cell column from T1-L2? What is contained between S2-S4 in relation to the ANS?
Interomediolateral Cell Column= T1-L2
- preganglionic sympathetic cell bodies
S2-S4= preganglionic parasympathetic nerve cell bodies
What is the general function of Rexed Lamina IX?
Motor--this is the lamina associated with the ventral horn
How is the white matter of the spinal cord divided?
The white matter of the spinal cord is divided into three general columns:
1) Dorsal faniculi
2) Lateral faniculi
3) Ventral faniculi
Describe the locations of the dorsal, lateral, & ventral faniculi
Dorsal= dorsal median fissure-->dorsolateral sulcus i.e. between the dorsal midline & dorsal nerve rootlets
Lateral= Dorsolateral-->ventrolateral sulci i.e. between the nerve rootlets
Ventral= Ventrolateral sulcus--> ventral median fissure i.e. between the ventral rootlets & ventral midline
What are the two subdivisions of the dorsal faniculus? Are these divisions present throughout the entire length of the spinal cord?
Medial= fasiculus gracilis
- Input from lower trunk & lower limb
Lateral= fasiculus cuneatus
- All spinal cord levels
- Input from upper trunk & upper limb
What are the different tracts of the lateral funiculus?
1) Lateral corticospinal tract
2) Ventral spinocerebellar tract
3) Dorsal spinocerebellar tract
4) Spinothalamic tract
5) Rubrospinal tract
What is the function of the Lateral Corticospinal Tract?
What is the function of the Ventral Spinocerebellar Tract?
What is the function of the Dorsal Spinocerebellar Tract?
What is the function of the Spinothalamic tract?
What is the function of the Rubrospinal tract?
What is the major tract of the ventral faniculus?
Anterior corticospinal tract--motor
What is the ventral white commisure?
Location of crossing over in the spinal cord
What is the dorsolateral tract of Lissauer? Where is it located?
Located at the tip of the wing of the butterfly, just distal of the gray matter, this white matter tract consists of the central processes of sensory unipolar neurons conveying pain & temperature sensation
Clinically, how does the outcome differ from complete transection of the spinal cord in the cervical region vs. the lumbar region?