Somatic Motor I: Corticospinal Tracts

Front 1

How are the somatic pathways grouped together?

Back 1

they are grouped according to the location of the lower motor neuron

Front 2

What somatic motor column contains lower motor neurons innervating the limbs?

Back 2

Lateral Columns

Front 3

Where part of the spinal cord are the lateral columns located in?

Back 3

Cervical
Lumbo-sacral

Front 4

________ of voluntary movements of the extremities is the function of the lateral corticospinal tract.

Back 4

Mediating voluntary movements

Front 5

_______ and ________ are responsible for voluntary movement control of the extremities

Back 5

Lateral corticospinal
Rubrospinal

Front 6

Anteriomedial columns contain lower motor neurons innervating _______ and _________ musculature

Back 6

proximal and trunk

Front 7

What four tracts are found in the anteromedial cell column?

Back 7

anterior corticospinal
vestibulospinal
reticulospinal
tectospinal tracts

Front 8

Are the anteromedial column pathways primarily bilateral/contralateral/ipsilateral systems?

Back 8

Pathways are primarily bilateral

Front 9

Does the anteromedial column extend throughout the spinal cord?

Back 9

YES

Front 10

What does the term somatic indicate of the neurons/axons?

Back 10

somatic indicates innervation of striated muscle

Front 11

How many neurons are involved in the direct pathway of the corticospinal and corticobulbar pathways?

Back 11

ONLY TWO
Upper motor neuron
Lower motor neuron

Front 12

The upper motor neuron is in _______ and ________ cortex.

Back 12

primary and association motor and somatosensory cortex

Front 13

The LMNs of the _______ _______ tract are for innervation of limbs in lateral motor column of ventral horn.

Back 13

lateral corticospinal

Front 14

Where are the LMNs for the anterior corticospinal tract located?

Back 14

LMNs of anterior corticospinal tract for innervation of the trunk in medial motor column of ventral horn

Front 15

_______ motor neurons of the corticobulbar tract for innervation of the head in motor cranial nerve nuclei of brainstem

Back 15

Lower

Front 16

Based on appearance of the gray matter in the spinal cord, how would you know if you are in the thoracic vertebral region?

Back 16

know in the thoracic because the vental horn will be much smaller because there will be NO lateral motor nuclei present (Lamina IX is missing the lateral portion of it)

Front 17

all motor neurons are ________ ______ efferents

Back 17

general somatic efferents

Front 18

What is the basal ganglia input on the somatic motor system?

Back 18

primarily concerned with planning and initiation of movement

Front 19

________ primarily concerned with fine grained coordination of movement in which experience and sensory feedback plays an important role

Back 19

Cerebellum

Front 20

How many axons per side of the body are found in the corticospinal tracts?

Back 20

1 million axons per side from pyramidal neurons of cerebral cortex

Front 21

What is the division of the axons in the corticospinal tracts?

Back 21

-1/3 of axons in primary motor cortex, precentral gyrus, Brodmann's area 4
-1/3 of axons from premotor & supplementary motor cortex, B area 6
-1/3 from primary and association somatosensory cortex, B area 3,1,2,5,7

Front 22

What is the neurtransmitter present in the corticospinal tract from upper motor neuron to lower motor neuron?

Back 22

GLUTAMATE
-its excitatory

Front 23

True/False
in the corticospinal tracts the axons are heavily myelinated axons of the cortical pyramidal cells and can be up to 1 meter in length

Back 23

True

Front 24

Motor: _______

Back 24

Ventral

Front 25

Sensory: _________

Back 25

Dorsal

Front 26

Where do 50% of the upper motor neurons of the corticospinal tract synapse?

Back 26

50% end in cervical spinal cord

Front 27

Where do 20% of upper motor neurons of the corticospinal tract synapse?

Back 27

thoracic levels of spinal cord

Front 28

Where do 30% of upper motor neurons of the corticospinal tract synapse?

Back 28

lumbo-sacral levels of spinal cord

Front 29

The two distinct pathways of the corticospinal tracts are:

Back 29

Lateral corticospinal
anterior corticospinal

Front 30

What is the most clinically important tract in the nervous system?

Back 30

Lateral corticospinal tract

Front 31

______ % of corticospinal fibers are found in the lateral corticospinal tract

Back 31

85-90%

Front 32

What type of cells does the lateral corticospinal tract arise from?

Back 32

originates from pyramidal cells in both motor and somatosensory cortex

Front 33

describe the lateral corticospinal pathway as it descend from cortex to spinal cord:

Back 33

1. through lateral portions of PLIC
2. To basis pedunculi in midbrain
3. Axons broken up into smaller fascicles in pons by pontine nuclei and fibers
4. Axons coalesce in medulla to form pyramids
5. Axons decussate at cervicomedullary junction in the pyramidal decussation
6. Axons descend through lateral funiculus of spinal cord
7. motor fibers synapse in lateral motor column of ventral horn at cervical and lumbosacral levels

Front 34

Where does the UMN axons pass through the midbrain?

Back 34

basis pedunculi

Front 35

Axons are broken up into smaller fascicles in this portion of the brainstem.

Back 35

Axons are broken up into smaller fascicles in pons by pontine nuclei and fibers

Front 36

Where do the UMN fascicles coalesce to form pyramids on the descent down from the cortex?

Back 36

Axons coalesce in the medulla to form the pyramids

Front 37

Where is the decussation of the lateral corticospinal tract located?

Back 37

Axons decussate at the cervicomedullary junction in the pyramidal decussation

Front 38

Axons of the lateral corticospinal tract descend in the _________ funiculus of the spinal cord

Back 38

lateral funiculus

Front 39

What lamina does the lateral corticospinal upper motor neuron synapse on its lower motor neuron in the spinal cord?

Back 39

Motor fibers synapse in the lateral motor column of ventral horn/Rexed's lamina IX at cervical and lumbosacral levels

Front 40

________ % of corticospinal tract is the anterior corticospinal tract

Back 40

10-15%

Front 41

what regions of the cortex does the anterior corticospinal tract originate from?

Back 41

area 4 & 6 representing the trunk

Front 42

True or False
There are somatosensory fibers present in the anterior corticospinal tract

Back 42

False
No somatosensory is present in the anterior corticospinal tract

Front 43

Describe the path of the anterior corticospinal tract

Back 43

1. through lateral portions of PLIC
2. to basis pedunculi of midbrain
3. axons broken up into smaller fascicles in pons by pontine nuclei and fibers
4. Axons coalesce in medulla to form the pyramids
5. descends ipsilaterally in ventral funiculus of spinal cord to cervical and upper thoracic levels
6. axons of anterior corticospinal tract synapse on medial intermediate zone and on LMNs in medial motor column (lamina IX) of ventral horn bilaterally

Front 44

Where do the axons of the anterior corticospinal tract cross to synapse bilaterally in the cervical and upper thoracic spinal cord?

Back 44

anterior white commissure

Front 45

Primary motor cortex controls ______ body and face via corticospinal and corticobulbar tracts.

Back 45

contralateral

Front 46

in the primary motor cortex the lower extremity upper motor neuron is supplied by what artery?

Back 46

ACA (medial)

Front 47

What part of the body according to the homunculus does the MCA supply blood to the corticospinal tract for?

Back 47

Upper extremity & head that is located laterally on the homunculus

Front 48

________ __________ cortex on medial-dorsal surface in Area 6 receives projection from basal ganglia via ventral anterior nucleus of thalamus

Back 48

Supplementary motor nucleus

Front 49

Where does the premotor cortex located in ara 6 receive input from?

Back 49

Cerebellum via ventral lateral nucleus of thalamus

Front 50

As the corticospinal tract descends through the PLIC what arteries are responsible for the blood supply?

Back 50

lenticulostriate/anterior choridal arteries

Front 51

Somatotophy of the internal capsule with respect to the corticospinal tracts

Back 51

Face at genu
Moving posterolaterally: arm, trunk, leg
Corticopontine fibers are located in the anterior limb of the internal capsule

Front 52

________ is supplied by the PCA.

Back 52

Basis pedunculi

Front 53

Somatotophy of the basis pedunculi with respect to the corticospinal tract.

Back 53

Face medial to leg lateral
Bounded on either side by the corticopontine fibers

Front 54

True/False
both the corticospinal tracts and the ventral horn are supplied by the anterior spinal artery

Back 54

true

Front 55

True or False
The medial motor cell columns are continuous throughout the spinal cord whereas the lateral column neurons are only present in cervical and lumbo-sacral enlargements

Back 55

true

Front 56

What are the multiple inputs that converge on the LMNs in the ventral horn?

Back 56

1. upper motor neurons of cortex & brainstem
2. proprioceptive sensory afferents from muscle spindles & golgi tendon organs
3. interneurons relaying information descending pathways and sensory receptors

Front 57

What is important for reflexes and coordination of flexors and extensors?

Back 57

segmental interneurons having a short axon that contacts the motor neurons in a single spinal cord segment

Front 58

What is important for posture and coordination with respect to lower motor neurons?

Back 58

propriospinal interneurons have long axons that distribute to multiple spinal segments

Front 59

Myotatic reflexes are mediated by:

Back 59

monosynaptic input from primary muscle spindle receptor afferents
-the muscle spindles also synapse on interneurons that inhibit antagonist muscles

Front 60

_______ ________ is mediated by interneurons receiving nociceptive afferents making the limb withdraw before all the somatosensory information gets to the cortex

Back 60

Flexor reflex

Front 61

What is the crossed extensor reflex?

Back 61

flexion of one leg activates extensors of the other leg to maintain balance (walking)

Front 62

Why does loss of upper motor neuron input remove reflexes from descending control resulting in hyperreflexia?

Back 62

Reflex circuits are under voluntary control
the upper motor neurons excite lower motor neurons directly to contract muscle and interneurons that inhibit the antagonist muscle

Front 63

True of False
Muscle Tone is the resting level of tension in a muscle this is referred to as sympathetic tone

Back 63

True

Front 64

Hypertonia results from loss of inhibitory control from higher cortical levels. Why?

Back 64

the lower motor neuron and interneurons have nothing controlling how much tone is introduced into the muscle (there is no inhibition of the LMN from the cortex)

Front 65

Why is hypotonia the result of damage to lower motor neurons or sensory afferents?

Back 65

There are no signals being sent to the muscle from the lower motor neuron so there is no state of readiness to resist stretch, maintenance of posture (no basal level of activity)

Front 66

What are signs of an upper motor neuron lesion?

Back 66

weakness, increased reflexes, increased tone

Front 67

what are signs of lower motor neuron lesion?

Back 67

weakness, atrophy, fasciciulations, decreased reflexes, and decreased tone

Front 68

If there is a lesion of the upper motor neuron in the cortex where will symptoms be seen?

Back 68

1. deficit in the contralateral side of the lesion
2. increased reflexes & tone: spasticity
3. abnormal reflexes: Babinski sign
4. causes: infarct, MS, ALS

Front 69

Where is the decussation of the lateral corticospinal tract?

Back 69

cervicomedullary junction this is still location of upper motor neuron

Front 70

Where are the lower motor neurons of the corticospinal tract located?

Back 70

anterior horn of spinal cord

Front 71

What would symptoms be appearing if there were a Lower motor neuron lesion of the corticospinal tract?

Back 71

1. deficit would be ipsilateral to lesion
2. muscle atrophy & fasaciculations
3. reflexes and tone decreased because of no basal input & no reflex arc
4. caused by polio, cauda-equina syndrome, Guillain-Barr Syndrome, ALS

Front 72

Weakness due to partial paralysis

Back 72

Paresis

Front 73

lack of movement

Back 73

plegia and paralysis

Front 74

can indicate weakness or paralysis

Back 74

palsy

Front 75

hemi

Back 75

one side

Front 76

para

Back 76

both legs

Front 77

mono

Back 77

one limb

Front 78

di

Back 78

affects both sides equally

Front 79

quadri

Back 79

four limbs

Front 80

In a transection of the spinal cord what would be lost?

Back 80

complete motor and sensory loss below the lesion

Front 81

What are symptoms of Brown-Sequard syndrome (hemicord)

Back 81

1. Corticospinal: ipsilateral motor loss
2. ALS: contralateral loss of pain and temperature
3. PCML: loss of two point discrimination and proprioception

Front 82

Bilateral motor loss, bilateral los of pain and temperature, and intact two point discrimination and proprioception are symptoms of what type of spinal cord lesion?

Back 82

Anterior spinal cord lesion:
corticospinal: bilateral motor loss
ALS: bilateral loss of pain and temperature

Front 83

Demyelination in CNS and motor deficits of upper motor neuron type, relapsing-remitting, multiple deficits over time and over space, an oligoclonal bands on CSF electrophoresis, and bright white areas in white matter on T@ weighted MRI are indicative of what disease

Back 83

Multiple Sclerosis

Front 84

In a T2 weighted MRI what is the appearance of white matter look like?

Back 84

white matter/axons should be myelinated and in a normal T2 weighted MRI the white matter is dark

Front 85

What occurs in ALS?

Back 85

1. degeneration of upper & lower motor neurons: weakness, upper & lower motor neuron signs, affects the brainstem excluding those controlling the eye movements
2. sensation & cognition are normal
3. rapidly progressing, survival 2-5 years
4. Excitotoxic: blocking glutamate release prolongs survival

Front 86

apraxia

Back 86

a condition characterized by a deficit in higher order motor planning and execution despite normal strength

Front 87

fasciculaitons

Back 87

abnormal muscle twitches caused by spontaneous activity in groups of muscle cells

Front 88

ataxia

Back 88

wobbliness, incoordination, unsteadiness due to the brains failure to regulate the bodies posture & regulate the strength & direction of limb movement

Front 89

dysarthria

Back 89

motor speech disorder resulting from neurological injury characterized by poor articulation

Front 90

facial diplegia

Back 90

bilateral facial weakness

Front 91

optic neuritis

Back 91

inflammation of the optic nerve that may cause partial or complete loss of vision

Front 92

transverse myelitis

Back 92

neurological syndrome caused by inflammation of the spinal cord