Organisation of the Spinal Cord Flashcards
What is the spinal cord
- This is the connection between the brainstem and the spinal nerves
what makes up the peripheral nerves in the body
- The spinal and cranial nerves make up all the peripheral nerves in the body
what are the 3 meninges in the spinal cord
- Dura mater – tough and thick fibrous layer
- Arachnoid mater – looks like a spidner web
- Pia mater – innermost layer this is on the brain or on the spinal cord itself
what are the spaces in the spinal cord
- There is a big space between the dura mater and the spinal cord this space is filled with fat, this is called extra or epidural space
- Between the dura mater and arachnoid mater there is the subdural space
- Between the arachnoid and pia mater there is the subarchanoid space
where is the CSF in
subarchanoid space
what is the aim of a lumbar puncture
aim to take a sample of CSF, therefore the needle is inserted into the subarachnoid space, this is used in diagnosis of meningitis
what is the aim of an epidural
aim to anaesthetise spinal nerves, this diffuses across the spinal nerves
describe the structure of motor neurones
- Cell body at one end of the neurone
- Dendrites stick out of the cell body and the nucleus is within the cell body
- There is a long axon and then axon terminals at the end
- Covered by a myelin sheath
describe the structure of sensory neurones
- Dendrites at one end,
- Long axon
- Cell body sticks out of the edge of the axon
- Then you have the axon terminates
- Axon is covered by a myelin sheath
where is the grey and white matter in the spinal cord
- The grey matter is a spinal cord is arranged internally whereas the white matter is towards the outside
describe the structure of the grey matter
- There are posterior and anterior horn of grey
- in the thoracic region of the spinal cord there is a lateral horn of grey – this is where the sympathetic nerves leave the spinal cord therefore it is only in the thoracic region
describe the structure of the white matter
posterior, lateral and anterior funcilus
why is there larger anterior horn in the spine
- Sensory neurones travel towards the posterior part of the spinal cord whereas the cell bodies of the motor neurone are towards the anterior horn of the spinal cord, therefore there is a larger anterior horn of the spine as this is where all of the cell bodies of the motor neurones originate here
where does information going to the brain go up in
- goes up or down the spinal cord in the white matter then it synapses in the anterior part of the grey hour with a motor neurone
describe where the grey and white matter is in the brain
- Grey matter is on the outside of the brain and makes up the cerebral cortex, whereas the white matter is on the inside of the brain
what is in grey matter
cell bodies and synapses
what is in white matter
myelinated axons
how many pairs of spinal nerves are there
31
describe the breakdown of spinal nerves
- 8 cervical – C1 travels between the skull and the vertrebeae, in the cervical region the spinal nerve is named according to the veretebrae below
- In the rest of the body the spinal nerve is named according to the vertebrae above
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
How do you name the spinal nerves
– C1 travels between the skull and the vertrebeae, in the cervical region the spinal nerve is named according to the veretebrae below
• In the rest of the body the spinal nerve is named according to the vertebrae
where does the spinal cord end
at the level of L1/2
what happens below the level of L1/2
Below L1/2 the spinal nerves are bunched together, forming the cauda equina.
where are there swellings of the spinal cord
- Swelling in the cervical and lubrosacral region of the spinal cord
why is there a swelling in the cervical region
- In the cervical region this is where all the nerves innervating the upper limb form the brachial plexus
why is there a swelling in the lubrosacral region
- In the lumbarsaral region this is where all the nerves innervating the lower limb come out of
where is lumbar puncture and epidural performed
- Lumbar puncture and epidural anaesthesia are both performed below the level of L3 to avoid damage to the spinal cord
- The proportion of white and grey matter …
varies along the spinal cord
describe the cervical region
- Spinal cord itself is the widest
- Large amount of white matter
- Large ventral and dorsal horns
describe the thoracic region
- Large proportion of white matter
- Lateral horn of grey
describe the lumbar region
- Little white matter
- Larger ventral and dorsal
describe the sacral region
- Very little white matter
- Predominantly grey matter
what is a dermatome
- A dermatome is an area of skin which receives its sensory supply from a single spinal nerve dermatomes are useful to help localise neurologic levels
where does the spinal cord receive its blood supply
anterior and posterior spinal arteries
- These arteries are not enough to supply the whole cord, so they are reinforced by radiculospinal arteries which are derived from arteries of the body wall
describe the structure of how the anterior and posterior spinal arteries form
- Vertebral arteries stems from the subclavian artery, they run through the transverse foramen and then pass through the foramen magnum to enter the skull
- The two arteries anastomose to form the basilar artery
- The two vertebral arteries join together to from the basilar artery
- 2 vertebral arteries come up the neck join together in the skull and form the anterior spinal artery
- The vertebral artery on each side gives of the posterior spinal artery as well
how does the vertebral artery go into the skull
they run through the transverse foramen and then pass through the foramen magnum to enter the skull
what is the venous drainage of the anterior and posterior spinal arteries
- 3 anterior spinal veins
- 2-3 posterior spinal veins
what are the 3 ascending tracts
Spinothalamic tract
Dorsal column medial leminsicus
Spinocerebellar pathway
what is the descending tract
Corticospinal
describe the pathway of the spinothalmic tract
- The first order neuron transmits the sensation along the spinal nerve and travels via the dorsal root into the spinal cord.
- In the spinal cord the first order neuron synapses with the second order neuron in the dorsal horn of grey
- The second order neuron then decussates to reach the contralateral spinothalamic tract
- The second order neuron travels via the spinothalamic tract up to the thalamus
- In the thalamus the secondary order neuron synapses with the third order neuron
- The third order neuron travels via the internal capsule to the primary somatosensory cortex
describe the pathway of the dorsal column medial reminisces
- The first order neuron transmits the sensation along the spinal nerve and travels via the dorsal root into the spinal cord.
- In the spinal cord the first order neuron does not synapse but runs into the dorsal column (fasiculus gracilis from the lower limb, fasciculus cuneatus from the upper limb)
- The first order neuron ascends in the spinal cord along the ipsilateral dorsal column to enter the medulla
- In the medulla the first order neuron synapses with the second order neuron within the cunate or gracile nucleus respectively and then decussates to reach the medial lemnisus
- The second order neuron travels via the medial lemnisus to reach the thalamus
- In the thalamus the secondary order neuron synapses with the third order neuron
- The third order neuron travels via the internal capsule to the primary somatosensory cortex
describe the pathway of the spinecerebellar tract
- The first order neuron transmits the sensation along the spinal nerve and travels via the dorsal root into the spinal cord.
- In the spinal cord the first order neuron synapses in the dorsal horn of grey
- The second order neuron enters the ipsilateral spinocerebellar tract and ascends to the cerebellum
describe the pathway of the corticospinal tract
- The first order neuron has its cell body in the primary motor cortex and the axon projects along the internal capsule to reach the brainstem
- The first order neurons run anteriorly in the brainstem, and enter the medullary pyramids
- In the pyramids the majority of fibres decussate to enter the corticospinal tract.
- From the corticospinal tract the first order neurons descend to the level of innervation and enter the ventral horn of grey and synapse with the second order neurons
- The second order neuron travels out of the spinal cord via the ventral root and into the spinal nerve to reach skeletal muscle
what are the two types of spinal cord injury
- either have a incomplete or complete spinal cord injury
wha tis an incomplete spinal cord injury
Incomplete spinal cord injuries occur when the spinal cord is compressed or injured, but the brain’s ability to send signals below the site of the injury is not completely removed.
what is a complete spinal cord injury
Complete spinal cord injuries occur when the spinal cord is fully compressed or severed. A complete injury will result in a complete loss of sensory and motor information below the level of the lesion.
what are the presentations of the central cord injury
- Patients present with upper limb weakness and sensory loss below the level of the injury
- the upper extremities are classically more affected than lower extremitites
- motor function more severely Impaired than sensory function
what are the presentations of Brown- Sequard
- Paralysis and loss of proprioception, vibration, discriminative touch on the ipsilateral side as the injury
- Loss of pain and temperature sensation on the opposite or contralateral side as the lesion
