6 Descending Motor Systems Flashcards
(23 cards)
Innervates striated muscle, directly signals muscle to contract, only way to initiate movement.
Lower Motor Neuron
Lower Motor Neuron Types:
Alpha Motor Neuron- Extrafusal muscle fibers (actually contract)
Gamma Motor Neuron- intrafusal muscle fibers (regulate contraction)
Loss of muscle tone (lower motor neuron lesion)
Atonia
Loss of myotatic (knee jerk) reflex (lower motor neuron lesion)
Areflexia
Spontaneous muscle contractions (lower motor neuron lesion)
Fasciculations
Loss of muscle tissue (lower motor neuron lesion)
Atrophy
Upper motor neuron lesions cause _____ paralysis including:
Spastic
- Hypertonia (increased resting tension)
- Hyperreflexia
- Pathological reflexes (Babinski sign)
- Big toe dorsoflexion
In the ventral horn: Neurons controlling axial muscles are ____ to those controlling distal muscles. Neurons controlling flexors are located _____ to the extensor group.
Medial
Posterior
1 motor neuron plus all myofibers it innervates.
Motor Unit
______, ______, and association cortex are vital in design, choice, and monitoring of movement, but have no direct effect on the lower motor neuron. Damage to these areas may cause involuntary movements, incoordination, and difficulty initiating movement.
Basal ganglia
Cerebellum
The _____ has hierarchical motor control (by controlling motor cortex which controls the LMN) and parallel motor control (by directly controlling LMN)
Premotor cortex
Corticospinal tract origins:
- Primary Motor Area
- Somatosensory area
- Premotor Area
- Supplementary motor area
- Superior parietal lobule
Area of brain that controls execution of contralateral voluntary movements and fine digital movements.
Primary Motor Area
Area of brain that plans movements in response to external cues, controls proximal and axial musculature, may assemble empathetic facial movements.
Premotor Area
Area of brain that plans movements while thinking (assembles/learns new sequence [music], imagines movements).
Supplementary Motor Area
Areas of brain that direct motor patterns in response to sensory input and modulate sensory signals.
Somatic Sensory Area
Superior Parietal Lobule
The corticospinal tract originates in the _____ and _____ areas. It descends thru ______, ______, ______, and decussates at ________.
Cerebral Cortex
Precentral Gyrus
Cerebral Peduncle
Basis Points
Medullary Pyramid
Spinomedullary Junction
Desc pathway. Controls shoulder and proximal arm musculature
Rubrospinal Tract
Desc pathway. Controls axial musculature (walking)
Reticulospinal tract
Desc pathway. Controls axial musculature (balance)
Vestibulospinal tract
Desc pathway. Believed to be important in head turning reflexes in response to visual stimuli, unclear human function.
Tectospinal tract
The _____ is the exception to the typical Corticobulbar Pathway pattern because the lower face is contralaterally innervated while the upper face is bilaterally innervated.
Facial Motor Nucleus
The corticobulbar pathway originates in the face/mouth portion of the motor cortex area and descends with CST to level of target nucleus, but splits off and does not _____. It gives bilateral input to V, VII, XII, nucleus ambiguus, and XI.
Decussate
