1.9 Descending Pathways Flashcards
What are the symptoms of lower motor neuron damage?
• Paralysis - loss of movement • Paresis - weakness of affected muscles • Loss of reflexes • Loss of muscle tone Fibrillations and fasciculation
Define distal and proximal musculature?
Distal musculature - controls fine movements e.g. fingertips - lateral
Proximal and axial musculature - controls postions - medial
How many descending pathways are there, and what are they called?
5 Lateral and anterior corticospinal reticulospinal rubrospinal tectospinal vestibulospinal
Explain the functions of each of these?
Lateral corticospinal - voluntary control ofdistal musculature
Anterior corticospinal - voluntary control of proximal vasculature
Reticulospinal - regulate flexor reflexes and initiate patterned activity such locomotion
Rubrospinal - Upper flexion
Tectospinal - visual stimuli and coordination
Vestibulospinal - balance and head movements etc.
Explain the direct upper motor pathways…
Corticospinal tract;
Corticobulbar tract
What can damage to these result in?
Damage result in Babinski sign; Paralysis, Paresis exclusively fine skilled movements
Segmental reflexes remain unaffected
Explain the indirect upper motor pathways…
From brainstem nuclei to LMN
Damage to these can result in what?
Damage result in spastic paralysis, hyperreflexia etc….
Where does the lateral corticospinal tract decussate?
Rostral medulla - pyramid
Where does does the anterior corticospinal tract decussate?
Spinal level
With which nuclei are corticobulbar fibres associated with?
V, VII, XI & XII
Which ones are bilateral and unilateral?
V &XI are bilateral
VII & XII are unilateral
Are the muscles of the face below the eye innervated bilaterally or unilaterally?
Unilaterally
What effects would an upper motor lesion in the corticobulbar tract have?
Facial Paralysis - contralateral below the eye
What would a lower motor lesion in the same tract result in?
Facial Paralysis - ipsilateral whole face
What is the pathway of the rubrospinal tract? What is its function?
Red nucleus - mesencephalon - decussates quickly - upper flexor activity
Where does the tectospinal tract arise from?
Tectum - superior colliculus
Where does the reticulospinal tract originate from and what is its function?
Reticular formation - midbrain - ipsilateral - locomotion and pain modulation
Where does the vestibulospinal tract originate from and what is its function?
Vestibular nucleus - balance and coordination
Explain the Babinski sign…
Fanning of toes - upper motor neurone damage (direct)
Describe Decorticate Posturing…
Lesion above the red nucleus - including thalamus or internal capsule.
It involves the involuntary flexion of the upper extremeties in response to external stimuli - excess red nucleus influence. Arms are flexed and bent inwards, fists are clenched and feet are turned inwards.
Explain Decerbrate Posturing…
Brainstem damage at or below the level of the red nucleus e.g, a pontine stroke or uncal herniation. It describes the involuntary extension of the upper extremities in response to external stimuli. the head is arched back, the arms are extended by the sides and rotated internally, the legs are extended and rotated internally the patient is rigid, with the teeth clenched
Explain the structure of the internal capsule…
Centre - face, arms, torso, legs
