Spinal cord function and dysfunction Flashcards
Recall the segments of the spinal cord
31 total
- 8 cervical
- 12 thoracic
- 5 lumbar
- 5 sacral
- 1 coccygeal
How do nerves exit the spinal cord?
Through intervertebral foramina
Recall the relationship between each spinal nerve and its point of exit from the spinal cord
- C1-C7 emerge above their corresponding vertebrae
- C8 comes out below C7
- T1 onwards emerge below their corresponding vertebra
What is the white matter of the spinal cord made up of?
Ascending and descending tracts
Within the nervous system, what words replace the anatomical descriptions of “superior” and “inferior”?
Superior = rostral
Inferior = caudal
What is the grey matter of the spinal cord made up of?
Neuronal cell bodies
What are the main sensory and motor tracts of the spinal cord?
Sensory - spinothalamic and dorsal columns
Motor - corticospinal
Summarise how sensory information is sent to the brain.
3 neurons (primary, secondary, tertiary) are needed to trasnmit sensory information to the cerebral cortex
Where 1st order synapses with 2nd order = crossing to other side of spinal cord
What is the consequence of a disruption in brain influence over reflex action?
Spasticity due to lack of higher control
What feature is unique to the thoracic segments of the spinal cord?
Intermediate lateral horn
Describe the distribution of sensory and motor fibres in the spinal cord?
Motor = ventral
Sensory = dorsal
Both = lateral
Name the dorsal and ventral fissures in each spinal segment and recall which is wider
Dorsal = posterior median sulcus
Ventral = anterior median fissure (wider)
These divide the anterior and posterior surfaces of the spinal cord into two halves.
At which vertebral level does the spinal cord end?
L2
Recall the regions of enlarged spinal cord
For upper limbs: cervical enlargement: C3–> T1
For lower limbs: lumbar enlargementL L1–> S3
Where are the motor neuronal cell bodies located?
Grey matter
Where are herniated discs most likely to occur, and why?
L5/S1
Discs are present posteriorly but not anteriorly
Which 2 layers of the meninges extend past the end of the spinal cord?
Dura and arachoid
What part of the spinal cord is most amenable to CSF removal and why?
Between L2 and S2 as there is a large volume of CSF and some floating neurons but no spinal cord
Recall the 3 factors affecting the severity of a spinal cord lesion
- Amount of neural tissue lost
- Vertical level - the higher the lesion the greater the disability
- Transverse plane
Recall the expected pathology following an injury to the lateral corticospinal tract.
- Spinal shock - loss of reflex activity below the lesion lastinc for days or weeks= flaccid paralysis
- Return of reflexes leading to hyperreflexia and/or spasticity = rigid paralysis
What is a spinal segment?
A portion of the spinal cord which gives rise to spinal nerves
What is the space that is present in the spinal cord but not in the brain?
Epidural space (between dura and vertebral periosteum and is filled with fat and venous plexus)
Define dermatome and myotome.
Dermatome - an area of skin innervated by a single spinal segment or nerve.
Myotome - muscles innervated by one single spinal nerve or segment
Why are the aterior and posterior rami referred to as “mixed spinal nerves”?
They contain both sensory and motor nerve fibres
What is the difference between gyrii, sulci and fissures?
Fissure at the front , sulcus at the back.
Sulcus is a less deep fissure.
Fissure differentiates between the left and right side of the cord.
How do the fissures and sulci divide the spinal cord into different columns?
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What are the functions of the posterolateral sulcus and anterolateral sulcus?
Posterolateral sulcus - entry point for the posterior (sensory) root
Anterolateral sulcus - exit point for the anterior (motor) root
What information do the anterior and posterior roots carry?
Anterior root - carries motor information
Posterior root - carries sensory information
Where are the cell bodies of 1o sensory afferents located?
Spinal ganglion(/dorsal root ganglion) - both the cell bodies of first order neurons of the spinothalamic and dorsal column pathways.
Describe the meningeal coverings of the spinal cord.
Pia mater - adheres tightly to the surface of the spinal cord
Arachnoid mater - ballooned up against the dura
Dura mater - continuous with the inner sheet of dura in the cranium. Forms the dural sac which extends to S2
What is in the subarachnoid space?
CSF - this is continuous with the subarachnoid space of the cranium
What is the name of the extensions of the pia mater which anchor the spinal cord to the dura?
Denticulate ligaments - they also serparate the anterior and posterior roots
Where are spinal nerve blocks administered? Which part is anaesthesised in child birth?
Spinal nerve blocks - subarachnoid space (L2-S2)
Epidural nerve blocks - anaesthetics for childbirth in epidural space
What do spinal nerves branch into once they leave the intervertebral foramen?
Anterior(ventral) ramus, posterior(dorsal) ramus, rami communicantes
Describe the route for pain and temperature afferents.
- Fibres enter the dorsal horn
- They travel up or down 1-2 segments in the LISSAUER TRACT
- Then they synapse in the nucleus proprius
- Fibres cross the midline in the anterior commissure and travel in the SPINOTHALAMIC TRACT
Describe the route for discriminative touch and proprioception.
Sensory fibres enter the dorsal horn and then travel in the dorsal columns without synapsing in the posterior horn.
They go straight up into the medulla where they then synapse
What is the point in the spinal cord where pain and temperature neurons cross the midline?
Anterior commisure
Where are alpha-motor neurons located in the spinal cord and what are they involved in?
Located in the anterior horn and involed in reflex circuits (modulated by interneurons)
Desribe the sensory loss that would result from a lesion in a hemisection of the spinal cord.
There will be ipsilateral loss of tactile sensation and proprioception and contralateral loss of pain and temperature sensation.
Which tracts in the spinal cord carry sensory information from ipsilateral lower limbs?
Fasciculus gracillis
Which tracts in the spinal cord carry sensory infromation from ipsilateral upper limbs?
Fasciculus cuneatus
What is the spinocerebellar tract responsible for?
Proprioception from limbs to cerebellum
What information does the spinothalamic tract carry?
Pain and temperature from contralateral side of the body
What information do the anterior and lateral corticospinal tracts carry?
Corticospinal tract is involved in volunatry movement.
- Anterior = motor info to ipsilateral AND contralateral anterior horn (mostly axial muscles)
- Lateral = motor into to ipsilateral anterior horn (mostly limb muscles)
What are the main 3 spinal tracts and what information do they carry?
Spinothalamic – pain and temperature.
Coticospinal – voluntary movement
Dorsal tracts – fine touch, discriminative ability.
Describe the pathway of corticospinal tracts.
Start at motor cortex
- Descending fibers arise from cells in the motor area of the cerebral cortex.
- The impulse travels through the anterior column.
- Lateral corticospinal tract fibres decussate at the level of the medulla oblongata
- Fibers of the anterior corticospinal tract do not decussate at the level of the medulla, but they cross over in the spinal level they innervate.
- So motor neurons from the motor cortex will supply the contralateral side of the body.
What information fo the dorsal column pathways carry? Where do they decussate?
Dicriminate touch, vibration and proprioception - these cross at the medulla.
Describe the reflex pathway to muscle stretching e.g. patellar reflex.
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Describe the reflex pathway in response to a noxious stimulus.
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What nerves are affected in a person with no reflex actions after trauma?
Peripheral nerves
Describe the autonomic outflow from the spinal cord.
Sympathetic - thoracolumbar T1-L2
Parasympathetic - craniosacral (brainstem cranial nerves III, IV, IX, X and S2-4 spinal segments)
In what situations is loss of neural tissue extensive?
Degenerative conditions (but usually small in trauma)
What is Brown-Sequard syndrome?
A lesion in the spinal cord –> weakness or paralysis (hemiparaplegia) on one side of the body and a loss of sensation (hemianesthesia) on the opposite side.
