Spinal cord & ascending + descending pathways Flashcards
Describe the relationship of the spinal cord and associated roots with the spinal canal and meninges
Anterior + posterior rootlets -> anterior and posterior root -> roots pass through subarachnoid space until they reach the appropriate intervertebral foramina -> as they pass through the foramina the posterior root is enlarged by the posterior root ganlgion -> roots fuse to form mixed spinal nerve -> anterior and posterior rami
What is the spinal cord called when it terminates?
Conus medullaris which in turn continues as a thin connective tissue cord called the filum terminale which is anchored to the dorsum of the coccyx
Where do the spinal cord and filum terminale end respectively?
L2 & S2
What structure anchors the spinal cord in the spinal canal?
The denticulate ligament suspends the lateral aspects of the spinal cord in the canal
What is the denitculate ligament composed of?
Pial and arachnoid tissue and attaches to the dura at various points along the length of the cord
At which spinal segments is there an additional lateral horn in the grey matter?
Levels T1-L2. The lateral horn contains preganglionic sympathetic neurons
Describe the central canal of the spinal cord
The central canal is small and runs the entire length of the spinal cord. Rostrally it opens into the 4th ventricle and caudally it is blind ending
Name the 3 types of artery that supply the spinal cord
Longitudinal (x3), segmental and radicular
Describe the longitudinal arteries of the spinal cord
3 major arteries - one anterior and 2 posterior that all originate from the vertebral arteries. These run the length of the spinal cord
Describe the segmental arteries of the spinal cord
Derived from vertebral, intercostal and lumbar arteries
Describe the radicular arteries of the spinal cord
Travel along the dorsal and ventral roots
Describe the venous drainage of the spinal cord
Similar to arterial supply with both longitudinal and segmental veins
How does the dura in the cranial cavity differ from that in the spinal canal?
In the cranial cavity the dura is directly attached to the periosteum whereas in the spinal canal there is a space between the dura and the bone, the epidural space, which contains adipose tissue and the anterior and posterior epidural venous plexuses. This space is utilised in epidural anaesthesia
Where is the primary somatosensory cortex?
Post-central gyrus
Sensory fibres cross the midline of the brain - what does this mean?
It means that the left side of the body is represented on the right cortex and vice versa
In which regions is the spinal cord larger?
Cervical and lumbar
What is the function of the dorsal column/medial lemniscus (DCML)?
Fine touch and conscious proprioception - particularly in the upper limb
Where do the fibres of the DCML cross?
Medulla oblongata
What is the function of the spinothalamic tract?
Pain, temperature and deep pressure
Where do the fibres of the spinothalamic tract cross?
They cross segmentally!
What is the function of the corticospinal tract?
Fine, precise movement particularly of distal limb movements e.g. digits
Where do the corticospinal/pyramidal tract fibres cross?
About 85% of fibres cross in the caudal medulla at the decussation of the pyramids
What can happen as a result of CVA of the internal capsule?
Can result in a lack of descending control of the corticospinal tract which results in a spastic paralysis with hyperflexion of the upper limbs. This is sometimes referred to as decorticate posturing
What is the function of the tectospinal tract?
Thought to mediate reflex head and neck movements in response to visual stimuli
Where do fibres from the vestibulospinal tract originate?
Fibres originate in the vestibular nuclei of pons and medulla (these in turn receive input from vestibular apparatus and cerebellum).
