Flashcards in Neurophysiology (Part 3) Deck (94)
Descending motor pathways are divided among what 2 tracts?
pyramidal and extrapyramidal tracts
What are the 2 types of pyramidal tracts?
- corticospinal tract
- corticobulbar tract
Where do the pyramidal tracts descend down to?
They pass through the medullary pyramids and descend directly onto lower motor neurons in the spinal cord
What are the 5 types of extrapyramidal tracts?
- rubrospinal tract
- potine reticulospinal tract
- medullary reticulospinal tract
- lateral vestibulospinal tract
- tectospinal tract
Where does the rubrospinal tract originate from and where does it project to?
It originates in the red nucleus and projects to the motoneurons in the lateral spinal cord
Stimulation of the red nucleus (rubrospinal tract) produces what?
activation of flexor muscles and inhibition of extensor muscles
Where does the pontine reticulospinal tract originate from and where does it project to?
It originates in nuclei of the pons and projects to the ventromedial spinal cord
Stimulation of the pontine reticulospinal tract produces what?
General activation of both flexor and extensor muscles, with its predominant effect on extensors
Where does the medullary reticulospinal tract originate from and where does it project to?
It originates in the medullary reticular formation and projects to motoneurons in the spinal cord
Stimulation of the medullary reticulospinal tract produces what?
General inhibition of both flexor and extensor muscles, with its predominant effect on extensors
Where does the lateral vestibulospinal tract originate from and where does it project to?
It originates in the lateral vestibular nucleus and projects to the ipsilateral motoneurons in the spinal cord
Stimulation of the lateral vestibulospinal tract produces what?
Activation of extensors and inhibition of flexors
Where does the tectospinal tract originate from and where does it project to?
It originates in the superior colliculus and projects to the cervical spine
What is the tectospinal tract involved in?
Control of neck muscles
If a brainstem lesion occurs above the pontine reticular formation and lateral vestibular nucleus, but below the midbrain what will occur and why?
It will cause a dramatic increase in extensor tone (called decerebrate rigidity) because the pontine reticular formation and lateral vestibular nucleus have powerful excitatory effects on extensor muscles
Will lesions above the midbrain cause decerebrate rigidity?
What does the cerebellum regulate and play a role in?
movement and posture and plays a role in certain kinds of motor learning
What does the cerebellum help to control?
The rate, range, force, and direction of movements (collectively called synergy)
The cerebellum is connected to the brainstem via what?
3 cerebellar peduncles that contain both afferent and efferent nerve fibers
What are the 3 main divisions of the cerebellum?
What is the vestibulocerebellum dominated by and what does it control?
It is dominated by vestibular input and controls balance and eye movements
What is the spinocerebellum dominated by and what does it control?
It is dominated by spinal cord input and controls synergy of movement
What is the pontocerebellum dominated by and what does it control?
It is dominated by cerebral input and controls the planning and initiation of movements
How many layers are there to the cerebellar cortex and how are they described?
3, all of which are described in relaation to its output cells, the Purkinje fibers
List the 3 layers of the cerebellar cortex staring with the innermost layer
- granular layer
- Purkinje cell layer
- molecular layer
What does the granular layer contain?
the granule cells, Golgi II cells, and glomeruli
Mossy fibers from which 2 tracts synapse on dendrites of the granule and Golgi type II cells in the granular layer of the cerebellar cortex?
spinocerebellum and pontocerebellum tracts
What does the Purkinje cell layer contain?
Output from the Purkinje cell layer is always ______.