Week 2: Nerve Supply Flashcards
What types of nervous tissue contribute to grey and white matter?
Grey matter: Cell bodies of neurons
White matter: Axons
What is the function of white matter columns?
To carry signals from the PNS to CNS or vice versa
What information passes through the dorsal columns?
Sensory
What information passes through the ventral columns?
Motor and sensory
What information passes through the lateral columns?
Motor and sensory
How many points of attachment does each spinal nerve have to the spinal cord?
2
Where do the dorsal rootlets enter the spinal cord and how many are there?
6-8 rootlets from the dorsal root enter dorsally (from the back)
What is the dorsal root ganglion, and what does it contain?
It is a swelling on the dorsal root that contains the cell bodies of afferent (sensory) neurons
How many rootlets form the ventral root of a spinal nerve?
6-8
What forms when the dorsal and ventral roots merge?
They form the spinal nerve proper
Where does the spinal nerve proper enter after merging?
The intervertebral foramen
What happens to the spinal nerves after emerging from the vertebral column?
Each spinal nerve divides into a dorsal ramus and a ventral ramus (ramus=branch)
In general, which structures are innervated by the dorsal rami?
Joints and muscles of the surrounding (dorsal) region and skin of the back
The ventral rami anastomose to form what type of structures?
Nerve plexuses
Note: there is one exception for the thoracic ventral rami, which form the intercostal nerves
What is the likely effect of a lesion to a dorsal root?
Dorsal root - sensory information
* Loss of sensation from areas innervated by the specific spinal nerve
What is the likely effect of a lesion to a ventral root?
Ventral root - motor information
* Loss of voluntary movement to areas innervated by the specific spinal nerve
What is the likely effect of a lesion to a spinal nerve?
Spinal nerve - mixed information
* Loss of both sensation and voluntary movement
Is the spinal cord part of the central nervous system or the peripheral nervous
system?
Central nervous system
What are the 31 segments of the spinal cord?
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal (in most humans)
Why do enlargements develop in the cervical and lumbar regions of the spinal cord?
They contain the cell bodies of the motor neurons that innervate the muscles of the upper (cervical) and lower (lumbar) extremities
What is the conus medularis?
The tapering caudalmost extremity of the spinal cord
What level does the conus medullaris extend to in the adult and infant?
It extends to L1/L2 vertebrae in the adult, and 1 – 2 levels more caudally in the infant
How would you explain the disparity between the respective cord and vertebral levels that one sees in an adult?
- In the early embryo the segments of the spinal cord and the vertebral levels are in register
- However, the spinal cord stops elongating during development, while the vertebral column continues to elongate as the body grows.
Explain the formation of the cauda equina:
- Collection of spinal nerve roots distal to the conus medullaris
- Early in development they pass through the intervertebral foramina to exit the vertebral column
- As the vertebral column grows, the spinal nerve roots elongate along with it