Corticospinal Tract: descending system Flashcards
Where does Corticospinal tract (CST)/ Pyramidal tract begin
Area 4 of the pre central gyrus ( in cortex).
2 neuron pathway:
Upper motor neuron: from cortex to ventral horn
Lower motor neuron: from ventral horn to the muscle
Where in the spinal cord does the CST synapse
Ventral (Anterior ) horn cells
Phrenic nucleus location
Cervical ventral horn ( C3 4, 5). C3, 4 5 keeps the diaphragm alive
spinal accessory nucleus location
located in the cervical ventral horn from C1-C6
cervical ventral horn
phrenic nucleus: C3, 4 and 5
Spinal accessory nucleus: C1-C6
Pathway of CST
starts at Area 4 (Betz cells)—> goes through corona radiata–>internal capsule–> cerebral peduncle(foot of the cerebrum)—>Pons–> pyramid (lower medulla)—> crosses the midline of the spinal cord–> enters grey matter and synapse in the ventral horn.
corona radiata
white matter (caused by axons) area in the cortex where the motor AXONS go through
substantia niagra
located close to the basal ganglia.
Destruction= Parkinson’s disease
Destruction of Anterior/Ventral horn cells?
Paralysis
same as cutting the motor nerves (ex femoral nerve)
Destruction of Upper Motor Neuron Pathway?
1) Positive Barbinski sign = Upper Motor Neuron Lesion
2) loss of voluntary movement: spasticity, rigidity, hemiplegia.
Polio
attacks anterior/ventral horn cells== Paralysis
Laterality of CST
Contralateral: crosses midline once it gets to the spinal cord
ALS
attacks pyramidal cells in brain==paralysis
attacks ventral horn cells of CST
Kills patients b/c eventually they lose ability to breathe
Upper Motor Neuron
neurons in CST that runs from the cortex to the ventral horn
Lower Motor Neuron
Neurons that arise from the anterior horn and innervates the muscle.
