spinal cord part 2 Flashcards
how many circuits are in the spinal cord?
2
- contained all within one segment
- come in and go out the same segment
myotactic reflexes
circuits that cross into or through many different spinal cord segments
intersegmental or multisegmental
- responsible for coordination events
- central pattern generator
- breathing, walking
- rhythmic activity
ascending multisegmental circuits
- wiring that connects the different segments of the CNS
- they bring sensory info to the conscious
- three separate ascending pathways into brain
multisegmental circuits
- afferent but getting sensory info from muscles
- uses clarkes columns and external cuneate nusclei in spinal cord
- part of spinocerebellar pathways
proprioception
- conscious experience
- dorsal column nuclei shuttles the info
- dorsal column nuclei give rise to the dorsal columns at the base of the brain which is also called the lemniscus system
touch pressure
- clarkes columns
- external cuneate nucleus
- spinocerebular
- ipsi
proprioception
- dorsal column
- cross at base/brain stem
- contra
- VPLN
touch pressure
- sub gelatinous
- nucleus proprius
- cross spinal cord
- VPLN
- contra
pain/temp
- conscious experience
- info carried by spinothalamic tract
- uses the subtantia gelatinous and the nucleus proprius at the spinal cord
pain and temperature
- most go down through clarke’s column and the external cuneate nucleus
descending multisegmental tracts
- largest tract in primates
- 2/3 of neurons start at motor cortex
- mediates voluntary movement
- starts as large cells in all parts of the cortex, mostly broddmans 4
corticospinal tract
what is the corticospinal tract also called
pyramid tract
what are the two divisions of the pyramid tract (corticospinal tract)?
lateral corticospinal and anterior corticospinal tracts
- motor commend for muscle control
- 90% of fibers
- cross at medulla (decussation)
- cell bodies in motor cortex ( layer V )
- limb muscles
lateral corticospinal tract
- 10% of fibers
- cell bodies in the motor cortex (layer V)
- runs ipsi and then branch at the spinal segment
- proximal trunk muscles
anterior corticospinal tract
why do a lot of neurons go to sensory areas as well as motor areas when they descend?
to modulate the ascending input
what is a common pattern of all sensory systems?
rostral sites of projection in the sensory systems always send descending feedback
what kind of feedback does the rostral site send?
inhibitory
why is it important for the brain to comodulate?
the brain coordinates the type of input it gets
- cell body in cortex
- dont go out of periphery
- not a “motor” neuron because it does not innervate a muscle
- part of corticospinal and corticobulbar
UMN (upper motor neuron)
- cell body in spinal cord or cranial nerve cell body in brainstem
- axons innervate muscles in periphery
LMN (lower motor neuron)
damage to the pyramidal tract causes….
- hyperflexion and problems with fine motor control
what does damage to the pyramidal tract cause hyperflexion?
the inhibitory effects of a normal working descending corticospinal tract are used to tone down reflexes
what is a sign that damage to the pyramidal tract has caused oversensitivity of the reflexes?
babinski sign
how does damage to the corticospinal tract cause CP (cerebral palsy)
the cortex is damaged, but still in tact and working, but you dont see the inhibition from the corticospinals and therefore you get hyperflexion
what are disorders of UMN
- increased tone
- spacticy
- over reactive tendon reflex (babinski)
- can not quickly contract muscles
- affects groups of muscles
disorders of LMN
- results in muscle atrophy
- fibrillation
- loss of reflex
- decreased tone
- affects single muscles
- starts in the red nucleus
- cross at midline in the midbrain and then runs down the length of the spinal cord next to the corticospinal tract
- it terminated at both sensory and motor fibers about 1/2 and 1/2
rubrospinal tract
- receives input from the cerebellum and the cortex
- in midbrain
- could be apart of reticular formation
red nucleus
this tract
- is involved in the excitation of the flexors and inhibition of the extensors
- the flexors and extensors are innervated by different neurons
- if there werent different neurons there wouldnt be movement
rubrospinal tract
- begins at the level of the reticular formation (pons, medulla, parts of midbrain)
- its a sampling mechanism
- receives info from the cerebrum and the cerebellum
- allows the reticular formation to influence muscles
- both excitatory and inhibitory
reticulospinal tract
what is a sampling mechanism
samples info going up and down the brain stem and prioritizes
- slows vestibular input to be translated back down to the motor neurons
- allows muscles in trunk, limbs, and head to adjust to balance info
- starts at vestibular nuclei in medulla
- ipsi only system
- no sensory connections, requires no feedback
vestibulospinal tract
where does the vestibular nuclei get the info from?
cranial nerve VIII and cerebellum
- starts at superior colliculus
- sends input to the cervical region of spinal cord from lower brain stem
- its purpose is to work in head tuns to visual stimuli and tracking behaviors
tectospinal tract
- located midline in the brain stem
- inhibitory to the spinal cord and to sensory areas
- part of the reticular formation
- its main function is in pain control
raphe nucleus
