Overview of the Nervous System Flashcards
How many paired elements of the spinal cord are there?
31
How many of each vertebrae are there?
8 C 12 T 5 L 5 S 1 C
What is a segmental level?
Each spinal vertebrae
Where are there two enlargements? What is the purpose of these enlargements?
Cervical enlargement
thoracolumbar Enlargement
These are regions that allow a very large amount of neurons to pass in/out of the upper/lower limb
Conus Medullaris
Ill defined ‘cone’ where the TL enlargement transforms posteriorly into a tip. Here the spinal cord ends, around the level of L1/L2
Cauda Equina
a ‘horsetail’ of fibres that run from both the conus medullaris and TL enlargement.
Where in the subarachnoid space the largest?
Where it surround the cauda equine, in the lumbar region.
Where is the best olace to do a spinal puncture and why?
In the lower lumbar region where there is
a) a large subarachnoid space so lots of CSF and
b) here the spinal cord is in individual fibres of the ‘cauda equina’. The needle is far more likely to glance off and avoid damage to these fibres, unlike higher up, where the single SC could easily be pierced.
What are the three protective layers of the spinal cord
Pia Mater
Arachnoid Mater
Dura Mater
Pia Mater…
Tightly adhered to the spinal cord, can only be distinguished with a microscope. Stops fluid moving in/out of the spinal cord, acts as a seal
Arachnoid Mater
Shimmery, spider like, leaves a virtual subdural space as it lies against the dura mater
Dura Mater
‘hard mother’, thicker, tough protective layer. Provides resistance to injections. Is thicker posterior, as this region lacks the protect of the vertebral bodies
What is in the epidural space, and what is it’s clinical relevance
Between the spine and dura mater, the ED space contains, fat, veins and arteries. there are large deposits of fat, one at each level of the spinal cord, that are retained even at extremely low weights. This allows the veins to move up and down.
What would happen in relation to the epidural space if someone underwent huge weight loss
There would be a decrease in the fat pads, less protection for the veins and there could damage/tear. This could result in small bleeds, causing confusion and loss of consciousness
Sub arachnoid space
between pia-arachnoid mater. Contains CSF, that acts like a ‘cushion’ against impact. The CSF also ensure that the spinal cord is bathed in nutrients (glucose/salts). Has a few cells.
What produces CSF
produced by the brain in the coroplexus, flows down the spinal cord
General rule of the spinal cord?
Ventral/anterior = sensory info dorsal/posterior = motor info
Whats a ganglia
bundle of cell bodies
whats a plexus
bundle of nerve fibres. Ensures nerve fibres dont have to ;find their own way’
Dorsal root ganglion
Contain the cell bodies of sensory neurons
Epineurium is
a ‘unity’ of the 3 protective sheaths (pia, arachnoid and dura mater). Not individual layers but a ‘better sheath’ that runs into the periphery
What is within the peripheral nerve?
Elements of the sensory, motor and autonomic nervous system.
Posterior Ramus
The PNs posterior division that supplies/supports the musculature of the back
Anterior Ramus
Goes anteriorly to support the front, eg) roots of plexus. Is much bigger then the posterior as the SC is positioned more posterior
Anterior Ramus communicans
Links into the autonomic system, and runs up and down the vertebrae, feeding the Autonomic NS.
Rootlets
come directly off the spinal cord, feed together to form a root.
Denticulate Ligament
piece of arachnoid that goes back and forth between the pia and arachnoid mater. Holds the subarachnoid space open
Filum Terminale
an extension of the pia mater that forms a ‘string’. this continues inferiorly from the conus medullaris to attach to the coccyx. At the level S1/2, the duralarachnoid sac encloses around the filum terminale, helping it anchor to the coccyx. This stops the streching of the SC/nerves during movements of the back
