Spinal Cord and Pathways Flashcards
Name the 2 enlargements of the spinal cord and what they relate to.
Cervical - UPPER limb
Lumbar - LOWER limb
What happens at each segment of the spinal cord?
Rootlets emerge from the dorsal and ventral parts
Where do roots pass? When do they stop?
Through the subarachnoid space
They stop when they reach the appropriate intervertebral space
What happens to the posterior root as it passes through the intervertebral space?
It enlarges by the posterior root ganglion
What do anterior and posterior roots fuse to form?
Mixed spinal nerve
What arises from the mixed spinal nerve?
Anterior and posterior rami
How does the spinal cord terminate?
Conus medullaris
At what level does the spinal cord terminate?
L1/L2
What are the spinal meninges continuous with?
Cranial meninges
What do meninges pass through?
Foramen magnum
Name the 3 layers of meninges.
Dura
Arachnoid
Pia
In the spinal canal, what suspends the spinal cord?
DENTICULATE LIGAMENT
What is the denticulate ligament made of?
Pia and arachnoid
The denticulate ligament never joins to the dura
False - it does at some points
What is different about the dura in the spinal canal?
It is not attached to the periosteum like in the brain
Describe the anatomy of the spinal cord.
OUTER - WHITE
INNER - GREY - ‘H’ shape
What does white matter in the spinal cord consist of?
Axons, blood vessels and glial cells
All arranged longitudinally
What does grey matter contain?
Nerve cell body, synapses, glial cells and blood vessels
What extends throughout the spinal cord?
A small canal that opens in the 4th ventricle
What is the white matter said to be made of?
Anterior, posterior and lateral funiculus
What is the grey matter of the spinal cord divided into?
4 parts
Left and right anterior and posterior
Where are lateral horns found?
T1-L2
What does the lateral horn contain?
Presynaptic sympathetic nerve fibres
Name the 2 veins that drain the spinal cord.
Longitudnal
+
Segmental
Name the space between the dura and the periosteum in the spinal canal.
Epidural space
What is contained within the epidural space?
Adipose tissue
Anterior and posterior epidural venous plexus
What arteries are derived from vertebral, intercostal and lumbar arteries?
SEGMENTAL
What arteries travel along dorsal and ventral roots?
RADICULAR
3 longitudinal arteries arise from the ……… arteries
VERTEBRAL
There is 2 anterior and 1 posterior longitudinal arteries
FALSE
2 posterior
1 anterior
How do we perceive sensation?
Primary somatosensory cortex
Sensory fibres cross the midline, the left side of the body is represented by the right cortex
TRUE
How does info from the periphery reach the somatosensory cortex?
They travel in the spinal cord
What happens to the amount of white matter as you descend the spinal cord?
DECREASES
What is responsible for fine touch and conscious proprioception
Dorsal column
Where do dorsal column fibres cross?
In the medulla
What tract carries the sensation of pain, temperature and DEEP PRESSURE?
Spinothalamic
How do spinothalamic fibres cross?
Segmentally
How does info from the motor cortex reach the motor neurone?
Corticospinal tract extends down from the cortex all the way to the spinal cord
What tract is responsible for fine, precise movement of distal limbs e.g digits?
Corticospinal
How do motor commands reach the appropriate muscles?
Motor fibres cross at the midline
Left cortex controls the right side of the body and vice versa
What does the corticospinal tract form? And what are they known as?
Visible ridges
Pyramids
Where are the ‘pyramids’ seen?
On the anterior surface of the medulla
What is the corticospinal tract also known as?
Pyramidal tract
Where do 85% of fibres of the corticospinal tract cross?
In the caudal medulla at the decussation of the pyramids
What do crossed fibres of the corticospinal tract form?
Lateral CST
What do uncrossed fibres of the corticospinal tract form?
Ventral CST
How do crossed fibres of the corticospinal tract cross?
Segmentally
What can a CVA of the internal capsule of the pyramidal tract result in?
A lack of descending control of the CST
What does a lack of descending control of the CST result in?
Spastic paralysis
Hyperflexion of the upper limbs
What is lack of descending control of the CST also called?
Decoriate posturing
What are motor systems outside the pyramidal tract known as?
Extra-pyramidal system
What provides input to cervical segments?
Tectospinal tract
What does the tectospinal tract do?
Mediate head and neck reflex in response to visual stimuli
What forms the central core of the brainstem?
Reticular formation
What is reticular formation?
A highly organised network of nuclei in the brainstem
Describe the reticular formation.
It has MANY NUCLEI, and receives INPUT FROM virtually ALL parts of the CNS
What is the function of the reticular formation?
Influences voluntary movement
What area of the brainstem can you find reticular formation?
Pons
Medulla
In general, what do fibres originating in the i) pons ii) medulla facilitate and inhibit?
i) facilitate extensor, inhibit flexor
ii) facilitate flexor, inhibit extensor
What does the vestibulospinal tract provide excitatory input to?
‘Antigravity’ extensor muscles
Where do fibres of the vestibulospinal tract originate?
In vestibular nuclei of the pons and medulla
What does the vestibulospinal tract play an important role in?
Patients exhibiting decerebrate rigidity and paraplegia in extension
What can lesions in the brainstem at the level of the midbrain result in?
A lack of descending cortical control of this tract
What does lack of descending cortical control lead to?
Domination of extensor muscle tone and hyperextended spastic paralysis
What condition occurs after hemisection of the spinal cord e.g from a stab?
Brown-Sequard Syndrome
Describe Brown-Sequard Syndrome.
If there is damage to the right side, there is IPSILATERAL loss of FINE TOUCH, but CONTRALATERAL loss of pain and temperature sensation
