Spinal Cord function Flashcards
How many spinal segments and spinal nerves does a human have?
31
spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal
Discrepancy between spinal levels and vertebral levels (emerge from spinal cord vs vertebrae)
where do spinal nerves exit the spinal cord
Through the intervertebral foramen
Which spinal nerves are enlarged?
For the limbs - C3-T1
L1-S3
How does the patterns of nerve exit changes at the cervical level?
8 nerves but 7 vertebrae
C1-C7, nerves exit above the corresponding vertebrae
BUT C8 comes out below
And from there on out, nerve exit under corresponding vertebrae
Where do nerves L1 to S1 originate from in the cord?
The cord is much shorter than the vertebral column-the nerves descend from the chord (cauda equina) and the exit later-
The further down you go (even on thoracic levels), the more the distance between spinal chord and nerve-More discrepancy as you go down
(made use to administer anesthetics -underneath the cord)
What is the organisation of meninges around the spinal chord? How does it differ from the brain and why does it matter?
Dura mater, arachnoid matter and pia matter (in brain as well)
in brain, no space between skull and dura
BUT in spine, epidural space between bone and dura (used to inject anesthetics-under the end of chord tho)
Still subarachnoid space (sample CSF) - between arachnoid and Pia (Pia ends with spinal chord)
What anchors the spinal cord
Fillum terminale reaches out of end of chord down with cauda equina and anchors at the bottom
What is the difference between an epidural and a spinal aneathetic
Epidurals are aimed between the Dura and the arachnoid
Spinal are aimed to bypass and aim for the subarachnoid space
Describe the general look of a spinal cord section, inculing the immediate surroudings
Butterfly shape - grey matter in the center (cell bodies)-dorsal and ventral horns
Outside of the butterfly-white matter-towards brain (superior/rostral), and down (inferior/caudal)
generally says same all the way down-
Exiting from the horns, rootlets join to form the ventral and dorsal root respectively
Dorsal/posterior root has a ganglia
Roots join to form SPINAL NERVE (then ramus can exit)-this is where meninges end
Explain myotomes and dermatomes
Dermatomes is an area of skin that is only serves by a single spinal nerve segment (eg: umbilicus is around T9/10)
Myotome-an area/collection of muscle that is only served by one spinal nerve segment
Describe the splitting of spinal nerve as they exit the chord
Posterior ramus-small and innervates the back muscle of the spine
Anterior ramus-much larger and usually is what has the main role
Describe the roots of pain versus touch on a single spinal level
Touch and proprioception enters via the dorsal horn and go straigt up
Temperature and pain enter the horn, then signals to another neuron which crosses to the other side of the chord and then run up
Describe the location of the grey matter used in limb touch and motor
In the dorsal regions-sensory: fasciculatus gracilis (closer to median)-for ipsilateral lower limb. Fasciculatus cuneatus-upper limbs
Motor: Lateral region has spinocerebella region (to cerebellum)
And lateral corticospinal tract (ispsilatteral motor innervation of limbs
also lateral spinothalamic tract-pain and temperature
Frontal side also has area of motor innervation-anterior corticospinal tract
Describe how motor fibres descend from the brain
Descending motor fibres can split-into the anterior corticospinal tract (IPSILATERAL) and split to the other side (15%) and 85% becomes the lateral corticospinal tract (CONTRALATERAL)
Describe the principal pathway of sensory neurons
For touch-1st sensory neuron passes into the spinal cord and goes up immediately (no switching around)-and synapses around the medulla (WHERE THEY SWITCH SIDE) -the 2ndary neuron (which goes to thalamus)
For pain, synapse to 2ndary neuron crosses at the SAME LEVEL at which it enters
General rule- 2ndary neuron are always the ones that cross over
3rd sensory neuron are same for both pathway-up to cortex from hypothalamus