Lateral Descending

Question 1

Lateral descending pathways are for?

Answer 1

Fine motor
Controls all muscles, especially important in control of the distal limbs
Limb movement

Question 2

The three tracts of the lateral activation system?

Answer 2

Rubrospinal tract
Lateral reticulospinal tract
Lateral corticospinal tract

Question 3

What is the ability to activate individual muscles independently of other muscles?

Answer 3

Fractionation

• Very important function of the lateral corticospinal tract that allows for fine dexterity
• -Moves joints separately from one another
• -If we loose the lateral corticospinal tract or corticospinal tract is damaged in brain or brainstem we loose fractionation.

Question 4

What is the rubrospinal tract?

Answer 4

Originates in the red nucleus of the midbrain

• Crosses in the midbrain
• May enable initiation of distal limb movement but does not allow for fractionation of the hand
• Receives input from the cerebral cortex and cerebellum

Question 5

Where is the lateral reticulospinal tract?

Answer 5

Originates in the reticular formation in the medulla

-Next to the lateral corticospinal tract in the spinal cord

Question 6

The lateral reticulospinal tract receives input from many areas is likely a major contributor to functional?

Answer 6

recovery following a stroke.

Does not allow for fractionation of the digits

Question 7

The lateral reticulospinal tract does what?

Answer 7

Inhibits phasic and tonic stretch reflexes
-Likely involved in the development of hyperreflexia with spinal cord injuries rather than the lateral corticospinal tract

Question 8

What is the lateral corticospinal tract and pathway?

Answer 8

Upper motor neuron within has soma in the cerebral cortex and ends in the spinal cord.
Function= voluntary movement
-Fractionation
-Injury is associated with a positive Babinski sign

Question 9

The lateral corticospinal tract and pathway is important for control of?

Answer 9

Hand muscles

Question 10

The lateral corticospinal tract and pathway is not necessary for?

Answer 10

Walking, except control of foot/ankle

Question 11

What is important for creating the gait pattern at the trunk, hips and knees?

Answer 11

Medial reticulospinal tract and central pattern generators

Question 12

Where is the upper motor neuron soma for lateral corticospinal tract and pathway located in?

Answer 12

The primary motor cortex on precentral gyrus (trunk and UE)

or

Anterior paracentral gyrus (LE) of the frontal lobe

Question 13

What is the primary motor cortex?

Answer 13

Motor homunculus
Anterior to the central sulcus
-On the surface of the precentral gyrus (Trunk, UE, Face)

• On the surface of the anterior paracentral gyrus (LE)
• Somatotopic organization

Question 14

What are the two tracts in the lateral corticospinal tract and pathway?

Answer 14

Corticospinal tract in cerebrum and brainstem

Lateral corticospinal tract in the spinal cord

Question 15

The corticospinal neurons pass where?

Answer 15

Lateral to the thalamus and down through the ventral brainstem

• Travels through the cerebral peduncle of the midbrain
• Form the medullary pyramids

Question 16

What kinds of neurons does the lateral corticospinal tract and pathway contain?

Answer 16

Anterior corticospinal and lateral corticospinal

Question 17

For the lateral corticospinal tract and pathway once at the base of the caudal medulla the two sets of neurons separate and run?

Answer 17

In separate spinal cord tracts

Question 18

The lateral corticospinal tract and pathway neurons cross in?

Answer 18

The pyramidal decussations at the base of the medulla oblongata, then run down the spinal cord in the lateral corticospinal tract to the level they need.

Question 19

Once the lateral corticospinal tract and pathway is at the target level, the upper motor neuron axons enter the?

Answer 19

Gray matter and synapses with an interneuron or a lower motor neuron (alpha motor neuron) in the ventral horn.

The only upper motor neurons with direct synapses on the lower motor neuron