Motor control - Corticobulbospinal terminations
10 important questions on Motor control - Corticobulbospinal terminations
What is bilateral innervation?
--> less vulnerable to lesions
Where do the axons that innervate the bilateral areas cross over?
Which areas are bilaterally innervated?
- Dorsal facial motor nucleus (mimical musculature upper half face)
- Ambiguous nucleus (swallowing)
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Which areas do not receive information from the primary motor cortex?
What is the difference between the crossed and uncrossed corticospinal tract?
Crossed - crossed over to the other side
Uncrossed - not crossed over and projects bilaterally
What are the secondary motor control pathways?
- reticulo-spinal tract
- vestibulo-spinal tract
- tecto-spinal tract
--> all influence through interneurons, never directly to motor neurons
What is the rubro-spinal tract (secondary motor control pathway)?
- Cross over
- The red nucleus receives input from the cerebellum and (motor) cortex.
- This tract plays an important role in motor learning.
- It projects mainly to cervical intumescence flexor motorneurons (held responsible for partly recovery after lesions).
- Eventually, terminates in ventral root (anterior grey column)
Evolution: more corticospinal and less rubrospinal
What is the reticulo-spinal tract (2nd motor control pathway)?
- axons originate from reticular formation in pons or medulla
- cross over
- regulation of postural reflexes
- control of tone of muscles in relation to stance
- control of general excitability of motor neuron pools
- all muscles need a little bit of stimulation before they can be activated by the corticospinal tract
- Medial reticulospinal tract
- increases activity of reflexes (stimulates excitatory neurons)
- Lateral reticulospinal tract
- decreases activity of reflexes (stimulates inhibitory neurons)
- terminate in ventral horn
What is the vestibulo-spinal tract (equilibrium, 2nd motor control pathway)?
- Descend uncrossed
- Synapse with neurons in ventral horn
- Information about the head position -> maintenance of equilibrium
- Coordination of eye and neck/trunk movements
- Vestibulo-collic reflex stabilizes head through neck movements
- Vestibulo-spinal refect stabilizes body through postural movements
What is the tecto-spinal tract (2nd motor control pathway)?
- Descend crossed
- Terminates in ventral horn
- Visual (and auditory) information to neck and upper trunk; coordination of the eye and neck/trunk movements
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