S10-Topography of the major motor systems Flashcards
What are the main features of upper motor neurones?
They have cell bodies in the cerebral cortex and synapse with lower motor neurones. These modulate and stimulate thtte activity of lower motor neurones.
What are the main functions of descending tracts?
- Control of movement
- Muscle tone
- Spinal reflexes
- Spinal autonoic function
- Modulation of sensory transmission
What are the 7 main descending tracts?
Ventromedial tracts:
- Corticospinal - Voluntary, discrete, skilled movement of limbs
- Corticobulbar- Movement of face, head and neck muscles
- Rubrospinal- Facilitate activity of flexors, inhibits activity of extensors
Lateral tracts
- Tectospinal - Reflex postural movements in response to visual stimuli
- Vestibulospinal - Facilitates activity of extensor muscles, inhibits flexor muscles, concerned with postural activity associated with balance
- Reticulospinal-Facilitates or inhibits alpha and gamma motor neurones and can thus fascilitate or inhibit voluntary movement or reflex activity.
- descending autonomic fibres-Control visceral activity
What does the corticospinal tract do?
Discrete voluntary and skilled movements of limbs.
What does the corticobulbar tract do?
Movements of the head, face and neck muscles
What does the rubrospinal tract do?
Facilitates activity of flexors, inhibits activity of extensors.
What does the tectospinal tract do?
Reflex postural movements in response to visual stimuli
What does the vestibulospinal tract do?
Facilitates activity of extensor muscles, inhibits flexors and concerned with postural activity associated with balance.
What does the reticulospinal tract do?
Fascilitates or inhibits alpha and gamma motor neurones and can fascilitate or inhibit voluntary movement.
What does the descending autonomic tract do?
Control visceral activity
How is motor activity modulated in the brain?
Some descending fibres terminate in the VLN thalamus, basal ganglia and cerebellum to send sensory information back to the cerebrum to modify motormovement.
What is the pathway of the corticospinal tract?
The neurones arise in the sensorimotor cortex before leaving through the corona radiata and internal capsule. They enter the crus cerebri of the midbrain and travel to the medulla. Here 85% decussate to form the lateral corticospinal tract. 15% remain ipsilateral to form the ventral corticospinal tract. This decussates in the spinal cord near its synapse.
What is the pathway of the corticobulbar tract?
It arises in the sensorimotor complex before passing through the corona radiata and internal capsule. It then runs into the brainstem to synapse with cranial motor nuclei. It directly innervate V, VII, XI, XII and indirectly innervates III, IV and VI by interneurones.
What is the result of damage to the genu of the internal capsule?
It results in damage to the corticobulbar tracts so will have problems with muscles of head and neck.
What is the pathway of the the rubrospinal tract?
Originates in the red nucleus of the midbrain tegmentum. Decussates at the central tegmentum. Descends spinal cord in ventrolateral part.
