Upper And Lower Motor Neurons Flashcards
Where is the origin of the cell bodies of the upper motor neuron?
Primary motor cortex
Where is the termination of the cell bodies of the upper motor neuron?
Brainstem or spinal cord
Where is the origin of the cell bodies of the lower motor neuron?
Ventral horn of spinal cord or nuclei of brainstem
Where is the termination of the cell bodies of the lower motor neuron?
Somatic effectors
What are the types of lower motor neurons?
Alpha and gamma
What is an alpha lower motor neuron?
Large size and innervates extrafusal fibers
What is an gamma lower motor neuron?
Medium sized and innervates intrafusal fibers in muscle spindle
What is a motor unit?
One alpha neuron and all the muscle fibers it innervates
What is muscle tone?
Resistance to passive stretch (not voluntary)
Why is hypotonia an effect that occurs directly after a UMN lesion?
Because the muscles are in shock but later on it shifts to hypertonia
What is atrophy due to in an UMN lesion?
Disuse
What is atrophy due to in a LMN lesion?
Neurogenic
What is spasticity?
Velocity dependent resistance to passive stretch
What happens in spasticity?
Intermittent or sustained involuntary activation of muscles (caused by UMN lesion)
What is rigidity?
Velocity independent resistance to passive stretch (not caused by UMN lesion)
