Descending Pathways

Front 1

corticospinal tract

Back 1

primarily important for movements requiring a high degree of conscious, voluntary attention and for spontaneous acts of will

Front 2

pryamidal tract

Back 2

corticospinal tract;
60% originate from motor cortical areas anterior (in front) to the central sulcus and terminate in the ventral horn of the spinal cord. They also provide collateral innervation of the rubrospinal and reticulospinal tracts

Front 3

primary motor cortex

Back 3

Brodmann's area 4; corticospinal tract fibers from the frontal lobe originate here

Front 4

Premotor cortex

Back 4

Brodmann's area 6

Front 5

somatopically organized

Back 5

both the primary motor and premotor cortices. With the size of the regions controlling different body parts out of proprtion to their actual size

Front 6

Brodmanns area 3,1,2

Back 6

corticospinal tract fibers fro mthe parietal lobe originate from the primary somatosensory cortex

Front 7

topography

Back 7

corticospinal fibers maintain this with fibers destined for upper parts of the body running medially and those innervating lower body parts running laterally

Front 8

Corticobulbar pathways

Back 8

projections only to cranial nerves. travel in the anterior limb of the internal capsule and innervate cranial nerve nuclei controlling movements of the face, tongue, pharynx, and larynx

Front 9

corona radiata

Back 9

en route for the fibers leaving the cortex and entering the internal capsule where most travel in the posterior limb

Front 10

pyramids

Back 10

fibers split into longitudal bundles that course through the pontine gray matter before reuniting in the medulla to form the pyramids

Front 11

spinomedullary junction

Back 11

where most corticospinal fibers cross to the opposite side in the pyramidal decussation after medulla

Front 12

pyramidal tract lesion above decussation

Back 12

lead to contralateral motor deficits;
cause irreversible loss of independent finger movement and loss of the ability to oppose the thumb and fingers

Front 13

spinal cord lesion

Back 13

lead mainly to ipsilateral loss of motor control

Front 14

lateral column

Back 14

the crossed corticospinal tract travels through this and innervates neurons that control distal muscles

Front 15

ventral column

Back 15

most uncrossed fibers would travel in the ventral column and cross the midline near termination and innervate neurons controlling proximal and trunk muscles. still terminate in ventral horn

Front 16

A alpha and beta motor neurons

Back 16

are indirectly influenced via interneurons of most pyramidal tract fibers

Front 17

fractionated independent movement

Back 17

highly skilled motor acts which are controlled by the motor neurons of distal muscles of the hands that are innervated by the monosynaptic fibers from the primary motor cortex that trigger A alpha motor neurons

Front 18

parallel descending pathway

Back 18

provides an alternate route for voluntary motor control. Seen by corticoreticular fibers modifying reticulospinal projections

Front 19

red nucleus

Back 19

the caudal magnocellular division of this structure is the origin of the rubrospinal tract. Some cortical axons innervate the red nucleus. Therefore innervation from the motor cortex creates a corticorubrospinal pathway.
magnocellular cells of red nucleus is also innervated by the cerebellum (involved in a long loop feedback to help with on going movements)

Front 20

rubrospinal efferents

Back 20

cross the midline but do not travel in the pyramids. They travel in the lateral column and mainly control distal motor neurons

Front 21

decision of wanted movement

Back 21

prefrontal cortex. must be determined from the proprioceptive, vestibular, and visual, auditory signals

Front 22

planning and organizing

Back 22

premotor cortex.

Front 23

Initiation and executions

Back 23

motor cortex

Front 24

intracortical and thalamocortical circuitry

Back 24

helps with the intergration of sensory information into a motor plan

Front 25

intracortical inputs

Back 25

Area 4 by the primary somatosensory cortex.
Area 6 by the parietal association areas (5 and 7)
parietal-temporal-occipital association cortex

Front 26

area 5

Back 26

vestibular and proprioceptive info about the bodys position in space
to area 6

Front 27

area 7

Back 27

visual info from the dorsal stream (where pathway) about the position of objects in space
to area 6

Front 28

parietal-temporal-occipital association cortex

Back 28

relays integrated somatosensory, visual and auditory info to area 6

Front 29

thalamocortial circuits

Back 29

involve feedback from the basal ganglia and cerebellum that the cortex uses to assist planning

Front 30

5 evidences that motor planning occurs in PMC/SMA

Back 30

1.electrical stimulation
2. area 6 lesions to not produce paralysis but apraxia
3. mirror neurons that fire when complex movements
4. only fire when particular type of movement is executed
5. increased flood flow during complex movements

Front 31

4 evdiences that execution of movement occurs in the primary motor cortex

Back 31

1. increased blood flow in area 4 only when movement is performed
2. neurons begin to fire before contraction of muscle begins
3. frequency of neuronal firing codes for the amount of force executed
4.populations of neurons code for the direction of movment

Front 32

supraspinal pathway

Back 32

above spinal cord or vertebral column

Front 33

brain injury disruption to supraspinal pathway

Back 33

reveals a net effect that is inhibitory on motor neurons. The loss of the descending controls shifts the balance to local spinal inputs, leaving motor neurons slightly depolarized and closer to threshold for reflex activations.
Leads to rigidity and plasticity

Front 34

symptoms of supraspinal upper lesion

Back 34

-spastic weakness
-hyperactive/exaggerated stretch reflex
-hypertonia muscle tone
-loss of muscle tissue does not occur
-large groups of affected muscles

Front 35

symptoms of motor neutorn down lesions

Back 35

flaccid weakness/parayliss
-decreased or absent stretch reflex
-hypotonia muscle tone
-atrophy (loss of muscle tissue)
- single of small groups with a common nerve or root are the affected muscle

Front 36

if innervating arm muscle, is it coming down lateral or ventral?

Back 36

lateral column but terminates in the ventral horn