lect 11- spinal cord, brainstem, cortex control of motor function 2 Flashcards
define pyramidal system
tracts that pass through the medullary pyramidals
where do the upper motor neurons of the pyramidal system originate
motor cortices
where do the majority of upper motor neurons in the pyramidal system decussate and what do they form
decussate in pyramids and form lateral corticospinal tracts
where do the neurons decussate in the pyramidal system that do not decussate in pyramids and what do they form
decussate near synapse with lower motor neurons and form anterior corticospinal tract
where do most upper motor neurons of the pyramidal system synapse
with association neurons in spinal cord central gray
what does the medial activation system of the pyramidal system innervate
innervates postural and girdle muscles
what is the lateral activation system of the pyramidal system associated with
associated with distally located muscles used for fine movements
what do nonspecific activating system of pyramidal system facilitate
facilitate local reflex arcs
what does the lateral corticospinal tract supply and what is it made up of
made up of corticospinal fibers that have crossed in medulla and supply all levels of spinal cord
what is the anterior corticospinal tract made up of and what does it supply
made up of uncrossed corticospinal fibers that cross near level of synapse with LMNs and supply neck and upper limbs
what are possible origins of tract for corticospinal tract
primary motor cortex, premotor cortex and somatosensory area
where are giant pyramidal (Betz) cells located
in motor cortex
what are the functions of the corticospinal tract
adds speed and agility to conscious movements (especially hand movements) and provides a high degree of motor control (i.e.: movement of individual fingers)
when does complete paralysis of corticospinal tract occur
if both pyramidal and extrapyramidal systems are involved
what does the corticobulbar tract innervate
the head
where do most fibers of the corticobulbar tract terminate
in reticular formation near cranial nerve nuclei
describe the association neurons of corticobulbar tract
leave reticular formation and synapse in cranial nerve nuclei. They synapse with lower motor neurons
were do fibers from the corticorubral pathway and branches from corticospinal tract synapse
in magnocellular portion of red nucleus
where does the rubrospinal tract decussate
in lower brain stem/midbrain
what does stimulation of red nucleus result in
stimulation of flexors; inhibition of extensors (antigravity muscles)
what does the extrapyramidal system include
pathways that contribute to motor control bot that are not part of corticospinal system (rubrospinal, vestibulospinal, and reticulospinal tracts)
where does the rubrospinal tract descend
lateral funiculus (columns)
what happens if there is a lesion in the rubrospinal tract
impairment of distal arm and hand movement and intention tremors
where does the vestibulospinal tract receive major input from
vestibular nerve
where does the vestibulospinal tract descend
anterior funiculus
where does the vestibulospinal tract synapse and what is it primarily involved with
synapses with LMNs to extensor muscles; primarily involved in maintenance of upright posture
where does the reticulospinal tract descend
anterior portion of lateral column
what is the reticulospinal tract thought to do
mediate larger movements of trunk and limbs that do not require balance or fine movement of upper limbs
what type of effects do pontine reticular nuclei have
stimulatory effect on both extensors and flexors, but especially extensors
what effect do medullary reticular nuclei have
inhibitory effect on both extensors and flexors, but especially extensors
define ampulla
enlargement of semicircular canal that contains hair cells
describe the macula of the utricle
located on a horizontal plane and plays role in determining orientation of head when head is upright
describe macula of saccule
located in a vertical plane and signals head orientation when person is lying down
how does the weight of the statoconia bend (of the macula)
bends cilia in the direction of gravitational pull
what does bending of stereociliar towards kinocilium cause
depolarization and excitation
what does bending of cilia in opposite direction of kinocilium cause
closure of channels and hyper polarization of receptor membrane
describe what happens to the 3 duds of the head of the semicircular canal
lateral are horizontal. anterior are in vertical planes projecting forward and posterior ducts are in vertical planes projecting backward
define the cupola of the ampulla
loose mass of gelatinous tissue on top of the crista
define the crystal ampullaris
small crest within each ampulla
