What are the differences between upper motor neurons and lower motor neurons?

Question

Accepted Answer

Basis of differentiation

Upper motor neurons
Lower motor neurons

Definition

Are motor neurons whose cell body originates from the motor region of the cerebral cortex or from the brainstem
Are motor neurons that transmit nerve impulses from the upper motor neurons to the effector muscles to perform a movement

Location

Located in the central nervous system
Located near muscles

Area of containment

Contained entirely within the central nervous system
May be contained either in the grey matter of the spinal cord or the cranial nerve nuclei in the brain stem

Size of cell bodies

Larger than lower motor neuron
Smaller than upper motor neurons

Basis of classification

Pathway that the neurons are participating in  
Type of muscle fiber that the neurons innervate

Synapses Formation

Form synapses with lower motor neurons 
Form synapses with muscles

Transmission

Transmits nerve impulses from the brain to the synapses of lower motor neurons 
Gathers transmitted nerve impulses from upper motor neurons and transmits them to muscles in the body

Result of lesions

Results in muscle weakness and spastic hyperreflexia
Results in flaccid muscle weakness, muscular atrophy, hyporeflexia, and fasciculation

Basis of differentiation	Upper motor neurons	Lower motor neurons
Definition	Are motor neurons whose cell body originates from the motor region of the cerebral cortex or from the brainstem	Are motor neurons that transmit nerve impulses from the upper motor neurons to the effector muscles to perform a movement
Location	Located in the central nervous system	Located near muscles
Area of containment	Contained entirely within the central nervous system	May be contained either in the grey matter of the spinal cord or the cranial nerve nuclei in the brain stem
Size of cell bodies	Larger than lower motor neuron	Smaller than upper motor neurons
Basis of classification	Pathway that the neurons are participating in	Type of muscle fiber that the neurons innervate
Synapses Formation	Form synapses with lower motor neurons	Form synapses with muscles
Transmission	Transmits nerve impulses from the brain to the synapses of lower motor neurons	Gathers transmitted nerve impulses from upper motor neurons and transmits them to muscles in the body
Result of lesions	Results in muscle weakness and spastic hyperreflexia	Results in flaccid muscle weakness, muscular atrophy, hyporeflexia, and fasciculation

What are the differences between upper motor neurons and lower motor neurons?

Posted January 10, 2024