Spinal Cord Flashcards
How many pairs of spinal nerves are there?
31
What root do ALL sensory axons pass in a spinal cord?
Spinal nerve –> Posterior root –> posterior rootlet –> posterior horn of spinal cord
How do all motor axons pass into the spinal nerve?
Anterior horn of spinal cord–> anterior rootlet –> anterior root –> spinal nerve
What does a spinal nerve pair supply to a body segment?
General sensory to ALL structures
Somatic motor supply to skeletal muscles
Sympathetic supply to skin and smooth muscle
Name for an area of skin supplied by sensory innervation from a single spinal nerve?
Dermatome
Define Myotome:
Collection of skeletal muscles all supplied by one spinal nerve. Often underlies the dermatome of the nerve but not always.
What fibres are contained in the cervical enlargement?
Brachial plexus
from C4-T1
What nerves are contained in the lumbar enlargement?
Lumbosacral plexus - responsible for the innervation of the lower limb
What is the name of the connective tissue that attaches from the conus medullaris to the dorsal surface of the 1st coccygeal vertebra?
The filum terminale
Where does the spinal cord end?
L1-L2
The dorsal roots carry afferent/efferent neurons?
Afferent
sensory receptors
The ventral roots carry afferent/efferent neurons?
Efferent
motor neurons
The dorsal/ventral ramus supplies the muscles and skin of the back region?
Dorsal
The dorsal/ventral ramus supplies muscle and skin of the front and limbs?
Ventral
Is the dorsal or ventral ramus larger?
Ventral
It supplies a larger region
Where is CSF contained?
In the subarachnoid space
What separates the dura from the bony wall of the vertebral body?
The epidural space
Following its termination at L1/2, what does the spinal cord then become?
The cauda equina
What is the name for the small continuous structure of the spinal cord, which follows on from the cerebral ventricular system?
The central canal
Is grey or white matter found internally in the spinal cord?
Grey matter
Why do the higher levels of the spinal cord contain more white matter?
As the ascending tracts go up they gain more fibres, whereas the opposite is true for descending tracts
What do thoracic and upper lumbar segments possess?
Lateral horns
What is contained in the lateral horns?
Preganglionic sympathetic neurons
What is the name given for the 10 divisions of he spinal cord (at each layer)?
Rexed’s Laminae
What sensory spinal tract lies near the superficial tip of the dorsal horn?
Lissauer’s Tract
aka dorsolateral fasciculus
Define a ganglion:
A group of neuron cell bodies living outwith the CNS
known as a nucleus in the CNS
What are the three main blood supplies to the spinal cord?
- 3 major longitudinal arteries
- Segmental arteries
- Radicular Arteries
Where are the longitudinal arteries found?
Run the length of the spinal cord
Originate from the vertebral arteries
Where are the segmental arteries found?
Derived from the vertebral, intercostal and lumbar arteries
Where are the radicular arteries found
Travel along the dorsal and ventral roots
What is the main venous drainage of the spinal cord?
Similar to the arterial
Longitudinal and segmental veins
What sensory tract is responsible for fine touch and proprioception?
Dorsal column / medial lemniscus system
Where do the fibres cross in the dorsal column / medial lemniscus tract?
Medullar
Which sensory spinal tract carried pain, temperature and deep pressure?
Spinothalamic tract
Where do the fibres of the spinothalamic tract cross?
Segmentally (i.e. at each level)
Where do the fibres of the corticospinal tract decussate?
Pyramids of the medulla
85%
Where do the remaining 15% of fibres in the corticospinal tract decussate?
They don’t.
They form the anterior tract instead
What tract to the crossed fibres (85%) form?
The lateral corticospinal tract
What is the corticospinal tract responsible for?
Fine precise movement
especially of distal limb muscles e.g. digits
A CVA of the ____ ______ can result in lack of descending control of the CST
internal capsule
Spastic paralysis and hyperflexion of the upper limbs is also referred to as what?
Decorticate posturing (caused by a CVA of the internal capsule)
What extrapyramidal tract is mainly responsible for mediating the head and neck movement in response to visual stimuli?
Tectospinal tract
Where does the tectospinal tract mainly input?
The cervical spine
Which tract has fibres originating from both the pons and the medulla?
The reticulospinal tract
What formation forms a central core of the brainstem?
The reticular formation
Fibres originating from the _____ of the reticulospinal tract are responsible for the inhibition of flexor movements and facilitate extensor?
Pons
Fibres of the reticulospinal tract which originate in the _____ are responsible for the inhibition of extension and facilitate flexion?
Medulla
What tract is responsible for the excitatory input to ‘anti-gravity’ extensor muscles?
Vestibulospinal tract
Where does the vestibulospinal tract receive its input from?
Vestibular apparatus
Cerebellum
Is the vestibulospinal tract contra or ipsilateral?
Ipsilateral
The fibres do not cross at any point
What spinal tract is thought to play an important role in decerebrate rigidity and extension paraplegia?
Vestibulospinal tract
What is decerebrate rigidity and extension paraplegia?
Domination of extensor muscle tone and hyperextended spastic paralysis
What syndrome will a lateral hemisection of the spinal cord cause?
Brown-Sequard’s Syndrome
What are the clinical features of Brown-Sequard’s syndrome
Ipsilateral paralysis
Ipsilateral hyperreflexia and extensor plantar reflex
Ipsilateral loss of vibratory sense and proprioception
Contralateral loss of pain and deep temperature sense
What is an acute viral infection of the neurons which leads to rapid paralysis and wasting of limb and respiratory muscles?
Poliomyelitis
Is the disability in poliomyelitis bilateral or asymmetrical?
Asymmetrical
Where does poliomyelitis mainly affect?
Legs
What reflex is repsonisble for the maintenance of muscle tone and posture?
Stretch reflex
What neurons are responsible for the regulation of the stretch reflex?
Gamma motor neurons
What are the two main tracts of the dorsal column tract?
Fasciculus cuneatus
Fasciculus Gracilis
Which tract of the dorsal tract has more influence over the lower limb?
Fasciculus gracilis
What is Romberg’s sign?
High stepping, unsteady gait when eyes are closed
What does a positive Romberg’s test mean?
Patient has a problem with their dorsal column of the spinal cord
Loss of proprioception
What disease can selectively damage the spinothalamic tract?
Syringomyelia
Where does the rubrospinal tract originate?
The red nucleus of the midbrain
What is the main purpose of the rubrospinal tract?
Non pyramidal control of spinal motor activity
Limb flexor muscles
