Neuro L6 Flashcards
(47 cards)
Importance of Lower motor neuron
Only way movement can be initiated
“Last neuron in chain of neurons”
Alpha motor neurons project to
extrafusal muscle fibers
Gamma motor neurons project to
intrafusal muscle fibers
Lower motor neuron lesion can cause (5)
Atonia: loss of muscle tone (floppy) Areflexia: loss of knee jerk reflex Flaccid paralysis Fasciculations: spont. muscle contractions Atrophy: loss of muscle tissue
Upper motor neuron lesion causes
Spastic paralysis (paresis)
-hypertonia (increased resting tension in arm flexors and leg extensons
-hyperreflexia
Babinski sign
Babinksi sign
Big toe dorsoflexion
fanning of other toes when heal is stoked
LMN vs UMN Strength Muscle tone Stretch relfex Atrophy Other
decrease decrease decrease increase decrease increase severe mild fasciculation and fibrillations vs clonus pathologic reflexes (babinski)
Arrangement of motor neurons
Axial
Flexors
Extensors
(All still in anterior horn)
Axial muscles are more medial
Flexors are posterior
Extensors are anterior
Motor unit
1 motor neurons plus all myofibers it innervates
Large antigravity muscles vs extraocular muscles
Myofibers/motor unit
Extraocular: 10 (10 myofibers/1neuron)
Antigravity: 100s (100s of myofibers/1 neuron)
True or false: One motor unit my contain several different muscle fiber types
False: there is no mixing
Type 1 muscle
One Slow Fat (lipids) Red Ox (mitochondira)
Type 2 muscle
Fast Little lipid High glycogen Little mitochondria White
Damage to basal ganglia, cerebellum or cerebral cortex will cause
DOES NOT cause weakness DOES CAUSE Involuntary movements Incoordination Difficulty initiating movements
Basal ganglia, cerebellum, and cortex role in movement
design, choice and monitoring of movement
BUT NO direct effect on LMN
Outputs go to motor and premotor cortex NOT spinal cord
Hierarchical order of motor control
Premotor cortex plans
Motor cortex
LMN
Parallel arrangement of motor control
Premotor cortex can talk directly to LMN
Most descending motor pathways synapse where
What are the exceptions
interneurons in spinal cord
some directly with primary motor neuron (hand and CST)
Main descending motor pathways
Corticospinal: cortex to spinal cord
Corticobulbar: cortex to brainstem
Corticopontine: cortex to basilar pons
Primary motor area
Area number
Function
Area 4 precentral gyrus
Contralateral voluntary movements
Control fine digital movements
Somatic sensory area
Post central gyrus (brachmanns 312)
Supplementary motor
Area number and location
Function
Area 6 medial surface of cerebrum Plans movements while thinking Learns no sequences Assembles previously learned sequences Imagines movements
Premotor area
area number and location
function
area 6: lateral surface of cerebrum
Plans movements in response to external cues
Corticospinal tract areas
Primary motor Somatic sensory Premotor Supplementary motor Superior parietal lobule
