11 - Motor Cortex and Motor Pathways

Question 1

what is the function of the lateral corticospinal tract pathway?

Answer 1

motor functions

Question 2

what is the function of the posterior column pathway?

Answer 2

sensory (vibration, joint position, fine touch)

Question 3

what is the function of the anterolateral pathway?

Answer 3

sensory (pain, temp, crude touch)

Question 4

major relay for sensory information ascending upwards?

Answer 4

thalamus

Question 5

what does the anterior view of the spinal cord look like?

Answer 5

butterfly shaped central gray matter surrounded by ascending and descending white matter columns

Question 6

in the spinal cord, which horn is used for sensory processing?

Answer 6

dorsal horn

Question 7

in the spinal cord, which horn is used for motor neurons?

Answer 7

ventral horn

Question 8

what does the intermediate horn of the spinal cord contain?

Answer 8

Intermediate zone contains interneurons & specialized nuclei

Question 9

what is Rexed’s Laminae?

Answer 9

numbering system from dorsal to anterior, becoming more nuclei

Question 10

where is the white matter the thickest?

Answer 10

cervical levels, most ascending fibers have already entered the cord, and most descending fibers have not yet terminated on their targets

Question 11

which cord is mostly gray matter?

Answer 11

the sacral cord

Question 12

where are the enlargements found along the spine?

Answer 12

cervical and lumbosacral areas and these give rise to the nerve plexi for the arms and legs

Question 13

what is the blood supply to the spinal cord?

Answer 13

vertebral arteries and spinal radicular arteries

Question 14

what do the anterior and posterior spinal arteries form?

Answer 14

spinal arterial plexus

Question 15

how much of the anterior spinal artery supplies the spine?

Answer 15

2/3 of the cord, including the anterior horns & anterior and lateral white mater columns; only one of these

Question 16

how much of the posterior spinal artery supplies the spine?

Answer 16

(either from the vertebral artery or from the posterior inferior cerebellar arteries) supply the posterior columns and part of the posterior horns; two of these

Question 17

how many segmental arterial branches arise from the aorta? how many of these reach the spinal cord and as what?

Answer 17

31; 6-10 of these reach the spinal cord as radicular arteries

Question 18

what is the major blood supply of the lumbar and sacral cord?

Answer 18

Great radicular artery of Adamkiewicz

Question 19

this is also known as the vulnerable zone of relatively decreased perfusion?

Answer 19

Mid-thorasic region (~ T4-T8)

Question 20

venous return from the spinal cord drain where?

Answer 20

Plexus of veins drain initially into the epidural space

Epidural veins “Batson’s plexus” do not contain valves: as a result ↑↑ intra-abdominal pressure can cause reflux of pelvic infections, or metastasis of tumor cells

Question 21

where do all motor signals originate from?

Answer 21

cerebral cortex

Question 22

T/F, Basal ganglia & cerebellum do not directly project to lower motor neurons? so which ones can?

Answer 22

T; Upper motor neurons project to lower motor neurons located in the spinal cord and brainstem

Question 23

what are the descending motor pathways?

Answer 23

Lateral motor systems

Medial motor systems

Question 24

where does the coritcospinal tract lie?

Answer 24

posterior limb

Question 25

what is the cerebral peduncles also known as?

Answer 25

feet of the brain

Question 26

in the lateral motor systems, more specifically the lateral corticospinal tract, what percent of pyramidal tract fibers decussate?

Answer 26

~ 85% of the pyramidal tract fibers

Question 27

what type of movement is carried out by the lateral corticospinal tract of the lateral motor systems?

Answer 27

movement of the contralateral limbs

Question 28

corticospinal tract fibers of the lateral motor systems form medullary pyramids called?

Answer 28

pyramidal tract

Question 29

rubrospinal tract of the lateral motor system is responsible for what movement?

Answer 29

movement of contralateral limbs

Question 30

anterior corticospinal tract of the medial motor systems is responsible for what movement?

Answer 30

Control of bilateral axial and girdle muscles

Question 31

Vestibulospinal Tract of the medial motor systems is responsible for what movement?

Answer 31

Positioning of head and neck

Question 32

Tectospinal Tract and Reticulospinal Tract of the medial motor systems responsible for what movement?

Answer 32

Tectospinal: coordination of head and eye movement

Reticulospinal: automatic posture and gait related

Question 33

what is a fasciculation?

Answer 33

abnormal muscle twitches due to spontaneous muscle activity

Question 34

what is spasticity?

Answer 34

hyperreflexia

Question 35

what is indicative of an upper motor lesion?

Answer 35

usually in the first year of infants life, if in adult you use babinski signs where toes go up and fanning of the toes

Question 36

what causes increased tone and hyperreflexia?

Answer 36

Damage to corticospinal tract: removes control over lower motor neurons

Damage to descending inhibitory pathways: increased excitability of motor neurons in the anterior horn