Ascending and Descending Pathways Flashcards
What is the name given to the end of the spinal cord situated at L1/2?
Conus medullaris
What connects the spinal cord to the dura?
Denticulate ligament
What is present in the white matter?
Longitudinally oriented axons, glial cells and blood vessels
What is present in the grey matter?
Neuronal soma Cell process Synapses Glia Blood vessels
What is an extra addition to the grey matter at T1-L2?
Lateral horn containing the preganglionic sympathetic neurones
What is the arterial supply to the spinal cord?
3 major longitudinal arteries
Segmental arteries
Radicular arteries
What is the origin of the major longitudinal arteries supplying the spinal cord?
Vertebral arteries
What is the origin of the segmental arteries supplying the spinal cord?
Vertebral
Intercostal
Lumbar arteries
What is the venous drainage of the spinal cord?
Longitudinal and segmental veins
What do the radicular arteries supply?
The dorsal and ventral roots
What is the epidural space?
Space between the dura and bone which contains adipose tissue and the anterior and posterior epidural venous plexuses
Where is the primary somatosensory cortex and the sensory cortical homunculus?
Post central gyrus
What does the dorsal column/medial lemniscus system detect?
Fine touch
Proprioception
Where do fibres from the dorsal column decussate?
Medulla
Describe the dorsal column
Fibres enter dorsal root ganglion where they will project into dorsal column
Ascend to the medulla where they will synapse at the nucleus gracilis/cuneatus
Decussate after synapse and ascend to the thalamus via the medial lemniscus
Synapse in thalamus and ascend to the postcentral gyrus at the somatosensory cortex
What does the spinothalamic tract detect?
Pain
Temperature
Deep pressure
Describe the spinothalamic tract
Nervce cell bodies in dorsal root ganglion
Enter spinal cord and synapse in the posterior horn in tract cells
Decussate and ascend up the spinal cord on the contralateral side
Synapse in thalamus
Ascend to the postcentral gyrus of at the somatosensory cortex
Where is the primary motor cortex found?
Precentral gyrus
What is the main motor tract?
Descending corticospinal tract which is divided into the lateral and ventral tracts
What movements will the corticospinal tract control?
Fine, precise movements particularly of distal limb
Where will the corticospinal tract decussate?
85% at the caudal medulla called the decussation of the pyramids
What will crossed fibres of the corticospinal tract form?
Lateral CST
What will uncrossed fibres form?
Ventral CST
What will the motor fibres pass through whilst in the brain from the motor cortex to the thalamus?
Internal capsule
Where are the pyramids of the medulla found?
Anterior surface of medulla
What can a CVA of the internal capsule result in?
Lack of descending control of the corticospinal tract resulting in spastic paralysis with hyperflexion of upper limbs
Decortical posturing
What is the tectospinal tract?
Input to cervical segments
Mediates reflex head and neck movement due to visual stimuli
Where is the tectum found?
Posterior area of midbrain
Where does the reticulospinal tract originate?
Areas of reticular formation in pons and medulla
What is the function of the reticular system?
Integrate cranial nerve reflexes
Participate in conduction and modulation of pain
Influence voluntary movement
Regulate autonomic activity
Integrate basic functions like respiration and sleep
Activate the cerebral cortex
What is the vestibulospinal tract?
Excitatory input to antigravity extensor muscles
Where do the vestibulospinal fibres originate?
Medial and lateral vestibular nuclei in the pons
From where do the medial and lateral vestibular nuclei receive input?
Vestibular apparatus and cerebellum
Describe decerebrate rigidity
Vestibulospinal tract; lesions of the brainstem at level of midbrain can result in a lack of descending cortical control of this tract resulting in domination of extensor muscle tone and hyperextended spastic paralysis
