2 - Organisation of the Spinal Cord Flashcards
What are the 3 layers of meninges surrounding the brain and spinal cord?
Dura mater, arachnoid mater and pia mater
How many pairs of spinal nerves are there?
31
Where are the two regions of enlargement on the spinal nerves? What do they represent?
Cervical enlargement at C4-T1 represents the origin of the brachial plexus
Lumbar enlargement at T11-S1 represents the origin of the lumbar and sacral plexus
What is the name of the region where the spinal cord tapers off?
Cauda equine at L2
What is the name of the region which anchors the spinal cord in place?
Filum Terminale
What are the dermatomes for the shoulder, thumb, middle finger, little finger, nipples, umbilicus, inguinal, medial knee, big toe, little toe, gluteal and anal canal?
C4 – shoulder L1 - Inguinal C6 – thumb L3 - Medial knee C7 – middle finger L5 - Big toe C8 – little finger S1 - Little toe T4 – nipples S3 - Gluteal T10 - umbilicus S5 - Anal Canal
What is a dorsal root ganglion?
A collection of nerve cell bodies of sensory neurons
What is the difference between the proportion of white and grey matter in the cervical, thoracic, lumbar and sacral regions?
Cervical - Large amount of white matter, large ventral and dorsal horns
Thoracic - Large amount of white matter, lateral horn of grey
Lumbar - Little white matter, large ventral and dorsal
Sacral - very little white matter, predominantly grey matter
What is the blood supply to the spinal cord?
The anterior spinal artery which is formed by the vertebral arteries
Two posterior spinal arteries which are formed by the vertebral and cerebellar artery
Also reinforced by radiculospinal arteries of the body wall
What are names of the 4 sensory ascending tracts?
Spinocerebellar, Fasciculus cuneatus, fasciculus gracilis, spinothalamic
Where does the spinothalamic tract decussate?
At the segmental level which dorsal root enters the spinal cord
Which sensations does the spinothalamic tract send from the spinal cord to the thalamus?
Crude touch, pain, temperature
What is the function of the first, second and third order neuron in the spinothalamic tract?
1st order - Sensation from sensory receptors to spinal cord, travelling via the dorsal root
2nd order - 1st order synapses with the second order in the dorsal horn of grey, travels via spinothalamic tract to thalamus
3rd order - 2nd order synapses with third order in the thalamus, travels via the internal capsule to the primary somatosensory cortex
Where does the DCML decussate?
Medulla of the brainstem
What sensations does the DCML send from the periphery to the brain?
Vibration, proprioception, discriminative touch
What is the function of the first, second and third order neurons of the DCML tract?
1st order - Sensation from receptors to spinal cord, runs into fasciculus gracilis or cuneatus
2nd order - 1st order synapses with the 2nd order in the medulla - in the cuneate or gracile nucleus, travels via the medial lemniscus to the thalamus
3rd order - 2nd synapses with the 3rd in the thalamus, travels via the internal capsule to the primary somatosensory cortex
What is the difference between the fasciculus gracilis and fasciculus cuneate?
Gracilis - Lower limbs
Cuneate - Upper limbs
Does the spinocerebellar tract decussate?
No
. What sensations does the spinocerebellar tract send from the spinal cord to the cerebellum?
Subconscious proprioception
What is the function of the first and second order neurones of the spinocerebellar tract?
1st - Sensation along spinal nerve via dorsal root to spinal cord, synapse in the dorsal horn of grey
2nd - Enters the ipslateral spinocerebellar tract towards the cerebellum
What is the name of the descending motor tract?
Corticospinal tract
Where does the corticospinal tract transmit motor signals to and from?
Cortex to the spinal cord
Where does the corticospinal tract decussate?
Spino-medullary junction
What is the function of the first and second order neuron in the corticospinal tract?
1st - Enter the medullary pyramid from the primary motor cortex, this is where decussation occurs
2nd - 1st synapse with 2nd in the ventral horn of grey, the second order neuron travels out of the spinal cord via the ventral root and into the spinal nerve to reach the skeletal muscle
What is the difference between a complete and incomplete spinal cord injury?
Complete spinal cord injury - spinal cord is fully compressed or severed - complete loss of sensory and motor information below the lesion
Incomplete spinal cord injury - spinal cord is compressed or injured - brain’s ability to send signals to the site of injury is not completely removed
What is Brown-Sequard syndrome?
One side of the spinal cord is affected, Contralateral loss of pain and temperature sensation on one side, Ipsilateral paralysis and loss of proprioception on the opposite side
