Spinal Cord Motor Pathways

Question 1

Which tracts convey impulses to control the skeletal muscles of the limbs and trunk? Which tracts does it include?

Answer 1

pyramidal tracts

lateral and anterior corticospinal tracts

(Inside the pyramid, they Love Courtney and Vent to Courtney)

Question 2

Which tracts conducts signals that regulate those body movements that are subconscious or postural in nature? Which tracts does it include?

Answer 2

extrapyramidal

rubrospinal, tectospinal, vestibulospinal, rectilospinal

(outside of the pyramid, Ross and Rachel on T.V)

Question 3

How many sets of neurons do both pyramidal and extrapyramidal tracts consist of ?

Answer 3

2 sets of neurons

Question 4

Where do the upper motor neurons of the pyramidal tracts reside?

Answer 4

cerebral hemispheres’ motor cortex

Question 5

Where do the upper motor neurons of the extrapyramidal tracts begin and terminate?

Answer 5

cortex

brainstem or spinal cord

Question 6

Where do the lower motor neurons of both pyramidal and extrapyramidal tracts located?

Answer 6

ant. horn of spinal cord

(begin in brainstem or spinal cord)

Question 7

What do the axons of the LMNs exit the spinal cord as? What do they target?

Answer 7

ventral root, skeletal muscles

Question 8

Where are the lower motor neurons of CRANIAL nerves? And SPINAL nerves?

Answer 8

cranial = cell body in the motor nuclei of the cranial nerves in the brainstem (exit with cranial nerve)

spinal = cell body in the VENTRAL HORN of the spinal cord that form the motor root of the spinal nerve (exit with spinal nerve)

Question 9

Corticospinal tract pathway:

Answer 9

Pathway:
Neuron 1: Upper Motor neuron “UMN”
Originates in primary motor cortex of frontal lobe (pre-central gyrus)
Descends via large white matter tract within diencephalon
Tract decussates at medulla oblongata
Travels in antero-lateral white columns of spinal cord
Synapses in anterior grey horn of spinal cord

Neuron 2: Lower Motor neuron “LMN”
Cell body originates in anterior grey horn of spinal cord
Exits cord via ventral root of spinal nerve
Travels via peripheral spinal nerve to reach target (skeletal muscle)

Question 10

What does the corticospinal tract transmit?

Answer 10

VOLUNTARY motor/ CONSCIOUS control of ALL skeletal muscles

(While in the pyramid, Courtney VOLUNTEERS to move)

Question 11

What are the pyramids of the medulla made of?

Answer 11

Decussating neurons, specifically the upper motor neuron coming from the corticospinal pathway

Question 12

The descending fibers of the CST pass through which anatomical structures? (4)

Answer 12

internal capsule, crus cerebri of the midbrain, basilar portion of the pons, pyramids of the medulla

Question 13

1.) The crossed fibers of the CST form what?
2.) And descend in what?

3.) The fibers that don’t cross at the decussation of the pyramids descend in what?

Answer 13

1.) lateral coricospinal tract
2.) descend in the lateral column of the spinal cord
3.) In the ventral column of the spinal cord as the ventral corticospinal tract

Question 14

Where do the fibers of the ventral corticospinal tract synapse, after crossing the SC?

Answer 14

anterior horn

Question 15

What are the 2 major categorizations of injury to the CST? What are the symptoms?

Answer 15

CONTROL LOWER upper motor neuron lesions (UMNL): corticospinal tract (contralateral signs) & spastic muscles (no inhibitory influences & exaggerated/path. reflexes (ex. babinski sign) & paresis (weakness) or paralysis when voluntary movement attempted HYPER (UPtight) NO FASCICULATIONS (all muscles are on) Slow progression of atrophy

GO or NO GO*lower motor neuron lesions (LMNL): motor root of spinal nerves (ipsilateral signs) Flaccid muscles and atrophy (decreased muscle tone- no reflex input) & loss of reflexes & paresis or paralysis when voluntary movement attempted FLACID. FASCICULATIONS ( muscle twitching) partially getting through) rapid atrophy

Question 16

Where is the most common site of injury for the UMN? LMN?

Answer 16

UMN: CNS= motor cortex, medulla, anterolateral WHITE columns of SC

LMN: PNS= anterior GREY horn, ventral root, spinal/peripheral nerve

Question 17

1.) Where does the lateral CST cross?

2.) Where does the anterior CST cross?

Answer 17

1.) pyramids of medulla, then descends
2.) descends, then crosses and level of innervation

Question 18

Where does the rubrospinal tract originate? Where does it cross? Where does it terminate?

Answer 18

1.) red nucleus of midbrain (red=ruby)
2.) crosses midline, exits nuclei in caudal midbrain
3.) terminate on LMN of grey matter of ant. grey horn

Question 19

What is the rubrospinal tract responsible for?
*** fun fact

Answer 19

MUSCLE TONE, posture and skeletal muscle control, regulation of flexor-extensor TONE

*** older than CST. Crawling before walking

Question 20

Where does the rubrospinal tract receive input from?

Answer 20

cerebellum: cerebellar cortex, and CSTs

Question 21

Rubrospinal Tract Pathway:

Answer 21

Originates from the red nucleus of the midbrain
Crosses the midline as it exits from nuclei in the caudal midbrain and descends through brainstem
Travels in the ventrolateral white column of the spinal cord.
Fibers terminate by synapsing in on lower motor neurons within grey matter of anterior grey horn

Involved in mediation of involuntary movement

Question 22

Tectospinal tract pathway:

Answer 22

1.) This tract begins at the tectum of the midbrain. Note that this is where sensory fibers carried by the spinotectal tract terminated.
2.) The fibers cross soon after their origin and descend through the brainstem to the anterior column of the spinal cord
3.) Terminate in the upper cervical segments of the spinal cord.
4.) The tract functions to control movements of the head in response to visual stimuli (similar tract receives info from cochlear (hearing) nuclei and then starts from the inferior colliculi and terminates in the upper cervical segments of the spinal cord for auditory reflexes)

Question 23

Where does the tectospinal tract:
Originate?
Decussate?
Terminate?
Function?

Answer 23

Superior colliculus of midbrain
midbrain
ant. grey horn of spinal cord cervical region only
POSTURAL movements of head in RESPONSE to visual and auditory stimuli

Question 24

Lateral vestibulospinal tract pathway:

Answer 24

1.) This tract begins at the lateral vestibular nucleus (in the medulla; CN VIII)
2.) The fibres do not cross and descend to the anterior column of the spinal cord.

The function of this tract is to regulate muscle tone in response to movements of the head, and hence it plays a role in: balance and equilibrium.

The tract receives input from: the inner ear via the vestibulocochlear nerve, and also the cerebellum.

Question 25

Where does the lateral vestibulospinal tract:
Originate?
Decussate?
Terminate?
Function?

Answer 25

lateral vestibular nucleus of medulla
remains ipsilateral (DOES NOT CROSS)
ant. grey horn of spinal cord
postural stabilization

When you turn head you don’t get dizzy

Question 26

The vestibulospinal tract balancing activity depends upon the position of the head and neck, and is indirectly aided by what other 2 regions?

Answer 26

balance receptors in the inner ear (VIII)
cerebellum

Question 27

What are the 2 vesticulospinal tracts?

Answer 27

lateral
medial

Question 28

What is the tone called that vestibulospinal tracts are responsible for, in responding to the head being tilted to one side?

Answer 28

antigravity muscle tone

Question 29

Reticulospinal tract pathway:

Answer 29

1.) The pontine reticulospinal tract begins from the reticular formation of the pons
2.) The medullary reticulospinal tract begins from the reticular formation of the medulla
3.) The pontine tract tends to remain uncrossed, while the medullary tract has both crossed and uncrossed fibers
4.) The pontine tract descends in the anterior column of the spinal cord, while the medullary tract descends in lateral column
5.) Both tracts influence reflexes and voluntary movements (allow for inhibition of antagonist muscle when agonist is contracted), and carry autonomic information from hypothalamus to lateral horn of T1 to L2 and S2,S3,S4 segments of the spinal cord (Sources of sympathetic and parasympathetic N.S respectively)
6.) Input for these tracts comes from the cerebral cortex and cerebellum, but as the tracts also carry autonomic fibers, they also receive input from the hypothalamus.

Question 30

What are the 2 reticulospinal tracts? What do they do?

Answer 30

Pontine RST (PONS): controlling axial and extensor motor neurons, e.g enabling EXTENSION of the legs to maintain postural support

Medullary RST (MEDULLA): Inhibits extensor motor neurons to enable modulation of the STRETCH REFLEX (turning on and off)

ALSO RECEIVE AUTONOMIC INFO FROM HYPOTHALAMUS to LATERAL HORN (T1-L2) and (S2, S3, S4) —-> smooth and cardiac muscle

Question 31

Where does the reticulospinal tract:
Originate?
Decussate?
Terminate?
Function?

Answer 31

origin- reticular formation of pons and medulla
Cross
Pontine = ipsilateral
medullary = both crossed and ipsilateral
termination- ant. grey horn of SC
function- muscle tone, balance, postural changes

Question 32

Which one of the corticospinal tracts decussates at the pyramids? Which one travels through white horn and decussates down the spinal cord in gray horn?

(Double check)

Answer 32

Lateral

Anterior