Descending motor pathways

Question 1

Where does the corticotectal tract originate?

Answer 1

Originates in the visual association cortex of the occipital lobe.

Question 2

Which two nuclei does the corticotectal tract send its nerves to?

Answer 2

Oculomotor acessory nuclei for extraocullar muscles.
and
Superior colliculus for the tectospinal tract to the upper thoracic and cervical muscles.

Question 3

What function does the tectospinal tract have?

Answer 3

Within the superior colliculi acts to innervate the neck and upper thoracic spinal cord levels to turn the head towards a stimulus.

Question 4

What function does the occulomotor acessor nuclei have?

Answer 4

Controlls the ocular muscles to make them regard the incoming stimulus.

Question 5

Which cortex gives rise to the corticorubral tract?

Answer 5

These come from the sensorimotor cortex.

Question 6

Where does the rubrospinal tract come from?

Answer 6

The corticorubral tract terminates in the red nucleus of the mid brain where it then gives rise to the rubrospinal tract.
This tract crosses the midbrain and descends to the upper spinal cord.

Question 7

What function does the rubrospinal tract have

Answer 7

Controls the movement of the hand and digits by facillitating upper limb distal flexor muscles and inhibiting distal extensor muscles.

Question 8

The rubrospinal tract supplements what other tract to the distal flexors?

Answer 8

Supplements the fine actions of the corticospinal tract but is relatively useless in humans.

Question 9

A lesion in the rubrospinal tract will present in what way?

Answer 9

The rubrospinal tract is an upper motor neuron and it will present with UMN signs.

Question 10

The corticoreticular fibers from the motor cortex descends with what two other fibers?

Answer 10

Corticonuclear and the corticospinal tracts!

Question 11

Where does the corticoreticular tract travel?

Answer 11

The corticoreticular tract travels to the reticular formation.
From here nerves can either head to the medulla or the pons for two different tract destinations.

Question 12

What does the medial (pontine) reticulospinal tract descend with?

Answer 12

Descends ipsilaterally in the anterior funiculus terminating at all spinal cord levels finally synapsing with interneurons and gamma motor neurons in the gray matter.

Question 13

What effect does the medial (pontine) reticulospinal tract have?

Answer 13

Excitatory influence on motor neurons that innervate paravertebral and limb extensors.

Also inhibits the flexors.

Question 14

The lateral (medullary) reticulospinal tract descends within what structure in the spinal cord?

Answer 14

Descends within the lateral funiculus synapsing onto interneurons within the gray matter.

Question 15

What effect does the lateral (medullary) reticulospinal tract have?

Answer 15

These are inhibitory on motor neurons that innervate paravertebral and limb extensors.

Also excitatory to the flexors.

Question 16

Corticoreticular fibers control which two tracts?

Answer 16

Medial and lateral reticulospinal tracts.
Its important to remember that both of these tracts terminate at all spinal cord levels on interneurons that synapse with alpha and gamma motor neurons.

Question 17

What is the overall role of the medial and lateral reticulospinal tracts from the corticoreticular fibers?

Answer 17

These play a role in muscle tonality and posture maitenance that arise from the basal ganglia and the cerebellum.

Question 18

What is the terminating point for the medial vestibulospinal tracts coming from the medial vestibular nucleus?

Answer 18

Terminate bilaterally at cervical and upper thoracic spinal cord levels with interneurons synapsing onto alpha and gamma motorneurons.

Question 19

What is the function of the medial vestibularspinal tracts?

Answer 19

Act to maintain balance in response to vistibular input

Act to control head movement to keep image on retina.

Question 20

Where does the lateral vestibular nucleus receive its input from?

Answer 20

Receives input from the vestibular apparatus.

Question 21

Where does the lateral vestibulospinal tract terminate?

Answer 21

Travells ipsilaterally to all spinal cord levels using interneurons and alpha motor neurons.

NO GAMMA NUERONS HERE

Question 22

What function does the lateral vestibulospinal tract have?

Answer 22

Excites the antigravity muscles while inhibiting the LMN that innervate the limb flexor muscles.

Maintains posture and balance.

Question 23

What tracts makes up the ventromedial Group of descending motor pathways?

Answer 23

“VART”
Tectospinal tract
Anterior corticospinal tract
Medial and lateral reticulospinal tracts
medial and lateral vestibulospinal tracts
These bilaterally influence axial, proximal limb muscles to maintain balance and posture.

Question 24

What makes up the Lateral group of descending motor pathways?

Answer 24

Lateral corticospinal tract
and
Rubrospinal tract (Rudimentary)

These tracts mostly control the digits.

Question 25

What makes up the cortical group of descending motor pathways?

Answer 25

Only the lateral corticospinal tract which terminate on lowermotor neurons innervating the distal muscles of the limbs and hand.

Question 26

What is the order of cell bodies in the ventral horn from medial to lateral in a cross section?

Answer 26

T = Trunk
S = Shoulder
A = Arm
F = Forearm
H = Hand