Lecture 27: Major Neuroanatomical Pathways I Flashcards
Central pathways definition
Axon tracts to and from brain that carry motor commands or sensory info
Sensory tracts definition
Carry info on stimuli by ascending the spinal cord to brainstem and cortex
motor tracts definition
Leave cortex and descend through spinal cord carrying motor commands
What kind of info do spinal nerves carry (4)
Somatic motor
Somatic sensory
Visceral sensory
Visceral motor/autonomic
2 primary motor tracts
Pyramidal
Extrapyramidal
Pyramidal motor tracts: type of movement, originating location
Finely adjusted movements
Originate in cortex
Aka corticospinal tract
Extrapyramidal system/motor tracts: type of movement, originating location
Coarser/larger movements
Originates in brainstem
Aka rubrospinal tract
Motor tracts are made of what kind of neurons
Upper motor neurons
Upper motor neurons definition
Delivery motor impulses from brain through spinal cord
Where do upper motor neurons synapse
On lower motor neurons
Lower motor neurons
Cell bodies in ventral horn of spinal gray matter
Innervate muscle tissue
Do upper or motor neurons contribute to reflexes
Lower
Collections of axons are called
Tracts
Where do pyramidal tracts begin and decussate/cross (what brain regions)
Motor cortex
Medulla
within the spinal cord: Tracts will innervate lower motor neurons on (same OR opposite?) side
Same
Somatic motor pathways are _______ projecting pathways
Caudally
Upper motor neuron damage: definition
No longer synapse on Lowe motor neuron cell bodies
No initial damage to lower motor neurons (can still function for a little while)
Lower motor neuron damage: definition
Lower motors neurons don’t synapse on motor endplates of muscles
Upper motor neurons not damaged
Upper motor neuron damage: clinical signs (3)
Spastic paralysis – muscles may be excessively and uncontrollable contracted
Hyperreflexia – exaggerated muscle reflexes
Clonus - rapid uncontrollable rhythmic muscle contractions
Lower motor neuron damage: clinical signs (3)
Flaccid paralysis – muscles soft
Hyporeflexia – lacks reflex signs
Atrophy of muscle after weeks or month
If Large groups of muscles may be affected, such as entire limbs or an entire side of the body —> is this Lower or upper motor neuron damage?
Upper
If peripheral nerve lesions are localized, is this upper or lower motor neuron damage
Lower
