Unit 3_Descending Pathways Flashcards
Where do the descending pathways originate?
Some originate in cerebral cortex and others originate in the brainstem.
What pathways are for voluntary activity and modulating brainstem pathways?
Cortical originating pathways
What pathways are important for postural control under the influence of cortex and sensory inputs?
Brainstem originating pathways
What pathways regulate distal, proximal and postural muscles directly to the spinal cord and/or through brainstem pathways?
Cortical descending pathways
What are the two types of the cortical descending pathways?
Ventral Corticospinal Tract
Lateral Corticospinal Tract
Where does the crossing occur in the cortical descending pathway?
At the Medulla
What pathways are important for postural control and as a group do a lot of bilateral control?
Ventromedial brainstem originating pathways
What are the two types of Ventromedial brainstem originating pathways?
Medial brainstem pathway
Lateral brainstem pathway
What is bringing center of mass back over base of support?
Postural support
What is extending base of support to capture center of mass?
Postural support
Responses to postural perturbations are normally what and automatic and involved in brainstem originating pathways?
Adaptable so that they are functional
What are the following functions support for?
- Regulate muscle tone: Background muscle activity (stiffness)
- Coordinate balance by utilizing vestibular, visual and proprioceptive inputs
Maintaining postural control
What kind of pathways are the following?
Tectospinal (only travels to cervical spine)
Pontine reticulospinal
Medullary reticulospinal
Ventromedial Pathways: Brainstem
What pathway includes when neurons in the medullary reticular nuclei send axons bilaterally into the lateral columns of the spinal cord to form the lateral or medullary reticulospinal pathways? These axons affect alpha motor neurons mostly through interneurons. The strongest synaptic connections are on alpha motor neurons (through interneurons) that control proximal muscles.
Medullary Reticulospinal Pathway
What pathway includes neurons in the pontine reticular nuclei send axons bilaterally down the pontine reticular tracts in the ventral column of white matter to affect alpha motor neurons (through interneurons) that innervate proximal/axial muscles?
Pontine Reticulospinal Pathway
What ventromedial pathway participates in all four of the brainstem motor control functions?
- It enhances extensor tone.
- It coordinates movement by influencing the trajectory of movement.
- Features control of balance with a strong influence on proximal and postural muscles
Lateral Vestibulospinal
What ventromedial pathway is for coordinating neck and head righting reactions for balance?
Medial Vestibulospinal
What dorsolateral pathway is for coordinating muscle tone in flexor muscles?
Ruprospinal
What projections control cranial nerve nuclei?
Corticobulbar (corticonuclear)
What are controlled by contralateral motor cortex?
Lower muscles of facial expression (CN VII)
What are the differences between a Cranial Nerve injury and a stroke?
Stroke - cortex is able to supply both sides (Right Facial UMN lesion); lower muscles of facial expression affected
Cranial Nerve - complete facial paralysis on side affected
What clinical test can be used to take a look at hypoglossal function within the corticobulbar function?
Evaluate genioglossus muscles. Part that is for genioglossus is crossed (CN XII – Hypoglossal)
What are the following clinical implications associated with:
Upper Motor Neuron Lesion (syndrome)
Lesion in the primary motor cortex, internal capsule or corticobulbar/corticospinal tract in the brainstem or spinal cord.
Primary motor cortex lesions have potential to produce all UMN signs and symptoms.
Upper Motor Neuron injury
What are the following signs and symptoms associated with:
- Weakness (paresis)
- Hyperreflexia and Hypertonia - spasticity (usually)
- No early atrophy (muscles may atrophy months later due to disuse)
- Abnormal synergy movements
- Abnormal reflex activity (Babinski reflex, clonus)
Upper Motor Neuron Disorders
The distribution of problems, when one has a lesion causing “UMN” signs and symptoms, is what (i.e. only in that segment or nerve)? Will be contralateral or ipsilateral depending on the lesion site.
Not segmental
