4.2 - Descending Tracts and UMNs Flashcards Preview

ESA 5 - Nervous System > 4.2 - Descending Tracts and UMNs > Flashcards

Flashcards in 4.2 - Descending Tracts and UMNs Deck (23)
Loading flashcards...

In what part of th ebrain do most muscle movements originate?

pre central gyrus


What parts of the spinal cord are considered parasympathetic and sympathetic?

parasympathetic - craniosacral

Sympathetic - Thoracolumbar


Explain the distinction between pyramidal and extra-pyramidal UMN. What tracts does each contain?

Pyramidal - consists of corticospinal (begins in cerebral cortex and terminates in spine) and corticobulbar tracts which are both responsible for voluntary movement of body and fascial muscles respectively. Directly innervates motor neurons

Extra-pyramidal - Modulate motor activity without directly innervating motor neurons. Involved in reflexes, locomotion, complex movement and postural control. Consists of vestibulospinal, reticulospinal, rubrospinal, and tectospinal tracts.


Which side of the brain controls skeletal muscle movement son the left side of the body and vice versa?

right side and vice versa



What does the corticospinal tract convey?

Axial and limb motor control 


Where does the corticospinal tract begin?

pre central gyrus


Which neurons innervate the axial muscles and the limb muscles


Describe the pathway of the 1st order neurons of the corticospinal tract

Leaves nuclei and cortex by descending through internal capsule and into medulla through brainstem where:

  • 75-90% decussate AKA decussation of pyramids and runs through the lateral corticospinal tract (goes on to innervate limbs) and once they reach their intended spinal level they synapse with a neuron on the anterior horn of grey matter
  • 10-25% dont decussate and run through the anterior corticospinal tract (innervate axial muscles). However, once the anterior corticospinal tract nerves reach their intended spinal level they decussate through the anterior white commissure and synapse with neuron in anterior horn of grey matter


What is a UMN lesion of corticospinal tract?

A lesion in the 1st order neurons of the corticospinal tract


What is the pathway of the 2nd order neurones of the corticospinal tract? What can these neurones be described as?

Project from anterior horn nuclei to the limb and axial muscles AKA LMN


Describe the pathway of the corticobulbar tract

Starts in cerebral cortex and descrends through internal capsule to brainstem where they decussate. terminate on contralateral cranial nerve motor nuclei in midbrain, pons, and medulla


What muscles does the corticobulbar tract control?

facial expression, extra-ocular muscles


What is the function of the vestibulospinal tract? Where does it arise from? Does it decussate?

Balance and posture

Does not decussate

Arises from vestibular nucleus


What is the function of the reticulospinal tract?

Helps with extensor spinal reflexes


What is the function of the rubrospinal tract? Does it decussate? Describe its pathway

Arises from red nucleus and decussates in midbrain and descends the spinal cord

Function is to facilitate flexor motoneurones and inhibit extensor motoneurones


What is the function and pathway of the tectospinal tract?

Function - aids in directing head movements 

Neurons arise from tectum of brainstem and decussate within brainstem. Terminate in the upper cervical segments


What tract inhibits the reticulospinal tract and what would occur if inhibition was released?

corticospinal tract inhibits

Release from inhibition would result in upposed extension of head and limbs


What would occur if the vestibulospinal tract was damaged?

loss of righting reflex, ataxia of gait, postural instability


Give the strict definition of a reflex

An automatic, unlearned, repeatable response to a specific stimulus that does not require the brain to be intact


Why is it important to distinguish between a voluntary and a reflex movement?

Both use different and separate neural circuits. Reflex movements can be achieved with a brain that is not intact and thus does not tell us much about the functionality of the brain


What is a monosynaptic stretch reflex and a muscle stretch reflex?

Muscle stretch reflex is an umbrella term that covers all the versions of the reflex circuits

The monosynaptic stretch reflex is the simplest muscle stretch reflex, containing only one synapse between afferent and efferent neurone


Explain how some relaxed healthy individuals are found to be areflexic

Severity of constant descending inhibition is variable in time.