Flashcards in 11. spinal cord, brainstem, cortex control of motor function II Deck (25):
What are the components of the pyramidal system?
1. corticospinal tract
2. corticobulbar tract
* tracts pass through the medullary pyramidals
What are the characteristics of pyramidal systems within the upper motor neurons?
1. originate in motor cortices
2. 75-85% decussate in pyramids and form the lateral corticospinal tracts
3. others decussate in the lower motor neurons
What are the different classifications of upper motor neurons of the pyramidal system?
1. medial activation system: innervate postural and girdle muscles
2. lateral activation system: associate with distally located muscles used for fine movements
3. nonspecific activating system: facilitate local reflex arcs
What are the lateral cortical tract used for?
1. made of corticospinal fibers that cross in medulla
2. supply all levels of spinal cord
What makes up the anterior corticospinal tract?
1. uncrossed corticospinal fibers that cross near the level of synapse with the lower motor neurons
2. supply to the neck and upper limbs
Where does the corticospinal tract originate?
primary motor cortex, premotor cortex, somatosensory area
Where are the giant pyramidal cells located?
1. in corticospinal tract (motor cortex)
2. send collaterals back to cortex quickly.
3. large cells/fibers
Fibers of the corticospinal tract run from the cortex into what different regions of the brain?
1. into caudate nucleus and putamen
2. to red nucleus
3. to reticular substance and vestibular nuclei
4. to pontine nuclei
What are the functions of the corticospinal tract?
1. add speed and agility to conscious movements
2. provide high level of motor control
What happens if a lesion arises in the corticospinal tract?
1. loss of muscle tone
4. paralysis will only occur if the pyramidal and extrapyramidal systems are damaged
Where do the majority of fibers terminate from the corticobulbar tract?
1. reticular formation near cranial nerve nuclei
2. this tract innervates the head
What does red nucleus stimulus results in?
1. stimulation of flexors
2. inhibition of extensors
What forms the red nucleus?
1. formed by fibers from primary motor cortex and corticospinal tract that synapse in magnocellular portion
Where is a somatotopic representation of the muscles of teh body located?
1. magnocellular region of the red nucleus
What forms the extrapyramidal system?
1. rubrospinal tract
2. vestibulospinal tract
3. reticulospinal tract
What are characteristics of the rubrospinal tract?
1. originate in red nucleus
2. decussate in midbrain
3. descends lateral funiculus
What happens if a lesion arises in the rubrospinal tract?
1. impair distal arm and hand movement
2. intention tremors appear
Where does the vestibulospinal tract originate, descend, and synapse?
1. originate: receives major input from vestibular nerve (CN 8)
2. descends anterior funiculus
3. synapse with lower motor neurons, involved with maintaining upright posture
What are the acharacteristics of the reticulospinal tract?
1. originates in regions of reticular formation
2. descends anterior portion of lateral funiculus
3. mediates larger movements of trunk and limbs
The reticular nuclei contains the pontine reticular nuclei and has what function?
1. fibers form the pontine reticulospinal tract
2. stimulatory effect on extensors, and minor effect on flexors
The reticular nuclei contains the medullary reticular nuclei and has what function?
1. the fibers form the medullary reticulospinal tract
2. have major inhibitory effect on extensors, and minor inhibition on flexors
What are the components of the vestibular componentts?
1. utricle: located on horizontal plane that determines the orientation of the head when upright
2. saccule: located in vertical plane, that signals the head orientation while laying down
3. semicircular canals
What is the function of the hair cell in the macula?
1. bends the sterocilia towards kinocilium causes depolarization
2. bending of sterocilia away from kinocilium causes hyperpolarization
How do the semicircular canals align when the head is bent forward 30 degrees?
1. lateral ducts are horizontal
2. anterior ducts are in vertical planes and project forward and outward 45 degrees
3. posterior ducts are in vertical planes and project backwards and 45 degrees outward