lect 11- spinal cord, brainstem, cortex control of motor function 2

Question 1

define pyramidal system

Answer 1

tracts that pass through the medullary pyramidals

Question 2

where do the upper motor neurons of the pyramidal system originate

Answer 2

motor cortices

Question 3

where do the majority of upper motor neurons in the pyramidal system decussate and what do they form

Answer 3

decussate in pyramids and form lateral corticospinal tracts

Question 4

where do the neurons decussate in the pyramidal system that do not decussate in pyramids and what do they form

Answer 4

decussate near synapse with lower motor neurons and form anterior corticospinal tract

Question 5

where do most upper motor neurons of the pyramidal system synapse

Answer 5

with association neurons in spinal cord central gray

Question 6

what does the medial activation system of the pyramidal system innervate

Answer 6

innervates postural and girdle muscles

Question 7

what is the lateral activation system of the pyramidal system associated with

Answer 7

associated with distally located muscles used for fine movements

Question 8

what do nonspecific activating system of pyramidal system facilitate

Answer 8

facilitate local reflex arcs

Question 9

what does the lateral corticospinal tract supply and what is it made up of

Answer 9

made up of corticospinal fibers that have crossed in medulla and supply all levels of spinal cord

Question 10

what is the anterior corticospinal tract made up of and what does it supply

Answer 10

made up of uncrossed corticospinal fibers that cross near level of synapse with LMNs and supply neck and upper limbs

Question 11

what are possible origins of tract for corticospinal tract

Answer 11

primary motor cortex, premotor cortex and somatosensory area

Question 12

where are giant pyramidal (Betz) cells located

Answer 12

in motor cortex

Question 13

what are the functions of the corticospinal tract

Answer 13

adds speed and agility to conscious movements (especially hand movements) and provides a high degree of motor control (i.e.: movement of individual fingers)

Question 14

when does complete paralysis of corticospinal tract occur

Answer 14

if both pyramidal and extrapyramidal systems are involved

Question 15

what does the corticobulbar tract innervate

Answer 15

the head

Question 16

where do most fibers of the corticobulbar tract terminate

Answer 16

in reticular formation near cranial nerve nuclei

Question 17

describe the association neurons of corticobulbar tract

Answer 17

leave reticular formation and synapse in cranial nerve nuclei. They synapse with lower motor neurons

Question 18

were do fibers from the corticorubral pathway and branches from corticospinal tract synapse

Answer 18

in magnocellular portion of red nucleus

Question 19

where does the rubrospinal tract decussate

Answer 19

in lower brain stem/midbrain

Question 20

what does stimulation of red nucleus result in

Answer 20

stimulation of flexors; inhibition of extensors (antigravity muscles)

Question 21

what does the extrapyramidal system include

Answer 21

pathways that contribute to motor control bot that are not part of corticospinal system (rubrospinal, vestibulospinal, and reticulospinal tracts)

Question 22

where does the rubrospinal tract descend

Answer 22

lateral funiculus (columns)

Question 23

what happens if there is a lesion in the rubrospinal tract

Answer 23

impairment of distal arm and hand movement and intention tremors

Question 24

where does the vestibulospinal tract receive major input from

Answer 24

vestibular nerve

Question 25

where does the vestibulospinal tract descend

Answer 25

anterior funiculus

Question 26

where does the vestibulospinal tract synapse and what is it primarily involved with

Answer 26

synapses with LMNs to extensor muscles; primarily involved in maintenance of upright posture

Question 27

where does the reticulospinal tract descend

Answer 27

anterior portion of lateral column

Question 28

what is the reticulospinal tract thought to do

Answer 28

mediate larger movements of trunk and limbs that do not require balance or fine movement of upper limbs

Question 29

what type of effects do pontine reticular nuclei have

Answer 29

stimulatory effect on both extensors and flexors, but especially extensors

Question 30

what effect do medullary reticular nuclei have

Answer 30

inhibitory effect on both extensors and flexors, but especially extensors

Question 31

define ampulla

Answer 31

enlargement of semicircular canal that contains hair cells

Question 32

describe the macula of the utricle

Answer 32

located on a horizontal plane and plays role in determining orientation of head when head is upright

Question 33

describe macula of saccule

Answer 33

located in a vertical plane and signals head orientation when person is lying down

Question 34

how does the weight of the statoconia bend (of the macula)

Answer 34

bends cilia in the direction of gravitational pull

Question 35

what does bending of stereociliar towards kinocilium cause

Answer 35

depolarization and excitation

Question 36

what does bending of cilia in opposite direction of kinocilium cause

Answer 36

closure of channels and hyper polarization of receptor membrane

Question 37

describe what happens to the 3 duds of the head of the semicircular canal

Answer 37

lateral are horizontal. anterior are in vertical planes projecting forward and posterior ducts are in vertical planes projecting backward

Question 38

define the cupola of the ampulla

Answer 38

loose mass of gelatinous tissue on top of the crista

Question 39

define the crystal ampullaris

Answer 39

small crest within each ampulla