Upper motor neurones and control of movement Flashcards
Motor control hierarchy involved which three levels?
High level- strategy
Middle level- tactics
Low- execution
Which structures are responsible for strategy in motor control?
Neocortical association areas, Basal Ganglia
Which structures are responsible for tactics in motor control?
Motor cortex, Cerebellum
Which structures are responsible for execution in motor control?
Brain stem, spinal cord
Describe strategy in motor control
What is the aim of the movement? How can it best be achieved?
What are the tactics involved in motor control?
What sequence of muscle contractions and relaxations in time and space will fulfil the strategic aim
What is involved in execution of motor control?
Activation of motor pools and interneurone pools that command the desired movement and make essential postural adjustments
Controlled movements of the body (motor control) are initiated/influenced by (2)?
Multiple sensory inputs
A need to move using internal mechanisms
Descending spinal tracts arise from ______ _____ and _____ ____
Descending spinal tracts arise from cerebral cortex and brain stem
Descending spinal tracts are concerned with;
_____ of movement
_______ tone
_____ reflexes
spinal _______ functions
_______ of sensory transmission to _____ centres
Descending spinal tracts are concerned with;
control of movement
muscle tone
spinal reflexes
spinal autonomic functions
modulation of sensory transmission to higher centres
What are the two important pathway divisions in descending spinal tracts?
Lateral and ventromedial
Lateral pathways are under control from the ______ _____.
They are important for ________ control of distal ________, partially discrete, ______ movements (hands and fingers)
Lateral pathways are under control from the cerebral cortex.
They are important for voluntary control of distal musculature, partially discrete, skilled movements (hands and fingers)
Lateral pathways include;
Lateral corticospinal tract
Rubrospinal tract
Ventromedial pathways are under control from the ______ and are important for the control of _______ and ________.
Ventromedial pathways are under control from the brainstem and are important for the control of posture and locomotion.
The ventromedial pathways include;
- pontine reticulospinal tract
- medullary reticulospinal tract
- lateral vestibulospinal tract
- tectospinal tract
- ventral corticospinal tract
The major lateral pathway is the _______ (or _____) tract
The major lateral pathway is the corticospinal (or pyramidal) tract
The corticospinal tract is one of the ______ and ____ CNS tracts
The corticospinal tract is one of the longest and largest CNS tracts
Cell bodies of the CST are located in?
The motor cortex (BA4 and BA6) and somatosensort areas of the parietal cortex
Axons of the CST course to the base of the ______ forming a tract- the _________ pyramid
Axons of the CST course to the base of the medulla forming a tract- the medullary pyramid
Most fibres of the CST cross at the ________ ________ to form the _______ ______ _____- remainder stay ipsilateral to form the _______ ________ _____ and decussate more caudally
Most fibres of the CST cross at the pyramidal decussation to form the lateral corticospinal tract- remainder stay ipsilateral to form the ventral corticospinal tract and decussate more caudally
Axons of the CST terminate where?
In the dorsolateral region of the ventral horn and intermediate grey.
Irrespective of the level of decussation of the CST fibres, _____ hemisphere controls _____ musculature
Irrespective of the level of decussation of the CST fibres, left hemisphere controls right musculature
The rubrospinal tract is _________ older than the CST
The rubrospinal tract is phylogenetically older than the CST
Cell bodies of the rubrospinal tract are located where?
Where does the input come from?
In the red nucleus
Input is from the motor cortex and the cerebellum
Axons of the rubrospinal tract decussate at the ____ ______ _________ and descend the spinal cord ventrolateral to the _______ ________ ______, terminating in the ____ ____
Axons of the rubrospinal tract decussate at the ventral tegmental decussation and descend the spinal cord ventrolateral to the lateral corticospinal tract, terminating in the ventral horn
The rubrospinal tract exerts control over limb _____ muscle, exciting LMNs of those muscles
The rubrospinal tract exerts control over limb flexor muscle, exciting LMNs of those muscles
Lesions of the lateral columns are associated with;
- loss of ______ movements
- slowing and impairment of accuracy of ______ _______
- _____ effect on normal posture
Lesions of the lateral columns are associated with;
- loss of fractionated movements
- slowing and impairment of accuracy of voluntary movements
- little effect on normal posture
Give an example of fractionated movement
Shoulders, elbow, wrist and fingers moving independently
Why can recovery from lesion of the CST occur?
As the rubrospinal tract can compensate- weaness will persist.
Where do cell bodies of the vestibulospinal tract lie?
Vestibular nuclei (lateral and medial)
Where do cell bodies of the vestibulospinal tract recieve input from?
Input via CN VIII from the vestibular labytinths
Cerebellar input is also important
Axons from the lateral vestibular nucleus (______ nucleus) descend ipsilaterally as the ______ _________ ____ as far as the ____ ___ ____
Axons from the lateral vestibular nucleus (Deiter’ nucleus) descend ipsilaterally as the lateral vestibulospinal tract as far as the lumbar spinal cord
How does the vestibulospinal tract help to hold upright and balanced posture?
By facilitating extensor MNs of antigravity muscles
Axons from the medial vestibular nucleus descend as the _____ _________ ____ as far as the _____ ______ ____
Axons from the medial vestibular nucleus descend as the medial vestibulospinal tract as far as the cervical spinal cord
What is the role of the medial vestibulospinal tracts?
Activate the cervical spinal circuits that control neck and back movements guiding head muscles
Where do cell bodies of the tectospinal tract reside?
Superior colliculus (aka optic tectum)
Where does the optic tectum recieve input from?
Direct input from the retina and from the visual cortex and afferents conveying somatosensory and auditory information
Where do axons of the tectospinal tract decussate?
In the dorsal tegmental decussation
How do the axons of the tectospinal tract descend?
Descend close to the midline as the tectospinal tract to the cervical spinal cord
What do axons of the tectospinal tract influence?
Muscles of the neck, upper trunk and shoulders
What does the superior colliculus act as?
A map of the external world guiding the orientation of the head and eyes to an important, new, visual stimulus
Where do pontine and medullary reticulospinal tracts originate from?
From the reticular formation
What is the reticular formation?
Diffuse mesh of neurones that are located along the length and at the core of the brainstam
The pontine (_____) reticulospinal tract;
- descends _________
- _______ antigravity reflexes of the _____ ____
- helps to maintain a standing posture by facilitating the ________ of the ________ of the _____ _____
The pontine (medial) reticulospinal tract;
- descends ipsilaterally
- enhances antigravity reflexes of the spinal cord
- helps to maintain a standing posture by facilitating the contraction of the extensors of the lower limbs
The medullary (_____) reticulospinal tract;
- descends _______
- _______ the action of the medial _____
- _______ antigravity muscles from _____ ______
The medullary (lateral) reticulospinal tract;
- descends bilaterally
- opposes the action of the medial tract
- releases antigravity muscles from reflex control
Activity in both the medial and lateral reticulospinal tract is controlled by what?
Descending signals from the cortex
