Seven Flashcards
What are three brainstem motor centers?
Vestibular Nuclei, Reticular Formation, and Red Nuclei
What do vestibular nuclei influence? What information do the vestibular nuclei receive? How many groups of neurons does a vestibular nuclei have? Where is it located? Where does the lateral vestibulospinal tract end up? Where does the medial vestibulospinal tract end up? What does each control more or less?
Vestibular Nuclei Influence Extensor Activities
Receptor organs for balance or equilibrium in the internal ear, project information pertaining to the position of the head via the vestibular nerve to the vestibular nuclei. The vestibular nuclei consist of four groups of neurons (medial, lateral, superior, and inferior) deep to the vestibular area in the floor of the fourth ventricle at the pontomedullary junction. The lateral vestibular nucleus gives rise to the lateral vestibulospinal tract which descends ipsilaterally through the length of the spinal cord and facilitates the extensor muscles of the limbs, especially the lower. The medial vestibulospinal tract arises from the medial and inferior vestibular nuclei and descends bilaterally into the anterior funiculus of the spinal cord. It influences the paravertebral and neck muscles controlling movements of the head.
What does the reticular formation influence through spinal motor neurons? Where do lateral reticulospinal fibers come from? Where do medial reticulospinal fibers arise from? With respect to voluntary movements, where does the reticular formation receive input from? Where do the fibers end up in the spinal cord?
The Reticular Formation Influences Posture and Muscle Tone
Two regions of the reticular formation influence spinal motor neurons. From the medullary reticular formation arises lateral reticulospinal fibers and from the pontine reticular formation arises medial reticulospinal fibers.
Although the reticular formation receives input from many sources, it appears that with respect to its role in voluntary movements, the projections from the cerebral cortex are
especially important. Thus, both the pontine and medullary groups of reticulospinal neurons are influenced directly by the cerebral cortex. In addition to the strong cortical input these reticular nuclei are also influenced by the cerebellum, the vestibular nuclei, and the anterolateral quadrants of the spinal cord.
The fibers run more or less with the medial and lateral vestibulospinal tracts.
What does the red nucleus influence? Where is the red nucleus located? Where does input to the red nucleus come from? What is the pathway for rubrobulbar and rubrospinal tracts? Where do they end up in the spinal cord? What movements do they influence?
The Red Nucleus Influences Flexor Activities
The red nucleus is in the tegmentum of the midbrain at the levels of the superior colliculus and pretectum. Input to the red nucleus comes from two main sources, the cerebral cortex and the cerebellum. The main outputs of the red nucleus are rubrobulbar and rubrospinal tracts which cross immediately after their origin and descend through the brainstem. They end up near the lateral vestibulospinal tracts, near the corticospinal tract. The red nucleus influences flexor movements in the upper limb.
Do brainstem motor centers directly synapse with LMNs? What allows multiple LMNs to be influenced at a time?
They do not. They first synapse with propriospinal neurons, which allow information to be integrated to influence LMNs at multiple segments at a time.
List 3 things included in a functional summary of the pyramidal system? What are the medial supraspinal/brain stem motor centers involved in? Lateral? What do propriospinal neurons do?
Pyramidal System
- Commands All Movements
- Exclusive for Highly Skilled and Rapid Distal Limb Movements
- Commands Largely Contralateral Movements
Supraspinal/Brainstem Motor Centers
• Medial – Commands Bilateral Trunk and Head Movements
• Lateral - Commands Girdle, Proximal and Intermediate Limb Movements
Propriospinal Neurons
• Interneuron Between Descending Motor Pathways and LMNs
• Integrates and Distributes Descending Commands for
Movements
