T2 L4 Motor learning Flashcards
Describe a simple motor pathway
Motor cortex of the brain –> upper motor neurone –> lower motor neurone –> muscle
What are the descending motor pathways?
Rubrospinal Corticospinal Reticulospinal Tectospinal Vestibulospinal
What descending pathways are ventromedial?
Reticulospinal
Tectospinal
Vestibulospinal
What descending pathways are lateral?
Rubrospinal
Corticospinal
Describe the reticulospinal pathway
From brainstem
Reticular formation just under cerebral aqueduct & 4th ventricle
Descends in 2 separate pathways: pontine (medial) & medullary (lateral)
Facilitates extension of limbs
Describe the tectospinal pathway
Originates in superior colliculus in midbrain which receives direct input from retina & insula cortex
Used to construct map of world around us
Direct her & eye to move so appropriate point of space is imaged on fovea
Projections decussate immediately & lie close to midline into cervical regions to help control muscles of neck, upper trunk & shoulders
Describe the vestibulospinal pathway
Originate in vestibular nuclei of medulla which relay sensory information from vestibular labyrinth in inner ear
Medial pathway projects down to spinal cord. Active spinal circuits that control neck & back muscles & guide head muscles
Lateral pathway projects ipsilaterally down to spinal cord to maintain upright & balanced posture by facilitating extensor muscles of the leg
Describe rubrospinal pathway
From red nucleus
Innervate flexor muscles in upper limbs
Involuntary
Describe corticospinal pathway
Only cortical tract to directly synapse with motor neurons
Predominantly derived from cells in layer V
90% fibres cross but individual variation may account for differences in deficits in stroke
What stimuli can be used to induce posturing in coma?
Supraorbital pressure
Nail bed stimulation
Sternal rub
What causes decorticate posturing?
Lesion above red nucleus
Rubrospinal pathways are disinhibited & therefore facilitate flexors in upper limbs
Flexion of arms, extension of legs
What causes decerebrate posturing?
Lesion below red nucleus
Rubrospinal pathways are disrupted & therefore upper limbs are extended
Extension of all 4 limbs
What happens if there is damage to the motor Cortex &. corticospinal tract?
Typical posture
Increased tone, brisk reflexxes
Extensor plantar
What is the evidence of damage to motor neurons?
Reduced tone
Loss of reflexes
Muscle wasting
Why does the babinski reflex occur in babies?
Corticospinal tracts aren’t fully developed which would inhibit spinal extensor response
What are the symptoms of Bells palsy?
Weakness in entire half of face as damage is to lower motor neuron
Describe innervation to lower 1/2 of the face
Contralaterally innervated
Describe innervation to upper 1/2 of face
Bilaterally innervated
Describe area 4
Primary motor cortex
Anterior to central sulcus in pre-frontal gyrus
Stimulating this area leads to simple movements on contralateral side
Describe area 6
Complex movements on either side of the body
Describe area 5 & 7
In posterior parietal cortex
Targets for inputs from primary somatosensory cortex
What will a middle cerebral artery occlusion cause?
Proximal lesion affects internal capsule
Complete hemiparesis
Distal lesion may spare leg area of motor cortex but secondary swelling & ischaemia may compromise function
A more proximal blockage will take out all fibres from leg, hand & face
What are the consequences of an anterior cerebral artery stroke?
ACA supplies medial part of frontal lobe including leg area of motor cortex
Crural paresis
Frontal signs e.g. aboulia
What is a seizure ‘march’ (Jacksonian seizure)?
Partial onset simple motor seizure becoming secondarily generalised
