Influence on Tone
What is postural tone?
activity in muscles that counteract the force of gravity in upright position, to maintain normal function tone must be high enough to allow the body to move in relationship to gravity
Describe paired vs. unpaired
unpaired - 1, straight column down the middle
paired - 1 on each side
What are extrapyramidal tracts important for?
tone, reflexes, balance, flexion and extension
How does a muscle spindle influence muscle tone?
1. keeps the spindle length in sync with extrafusal contraction
2. keeps the muscle ready to contract
3. activate AMN through the "back door"
Where does the tectosp. tract start and end?
superior colliculus in the midbrain --> cervical SC
RF function
motor activity, somatic and visceral sensation, endocrine function, biological rhythm, level of consciousness
Describe flower spray
at the myotome region of nuclear chain, gives off 2A fibers, aids in facilitations of flexion and inhibition of extension, slow adapting, monitors how long the muscle has changed its length
Rubrospinal tract function
error control, refinement of movement/coordination
How is muscle tone maintained?
alpha-gamma co-activation principle
Lateral vestibulsp. tract and its influence on tone
activates motor neurons innervating extensor muscles of the trunk and IL limb to maintain upright posture and balance
Describe the lateral, medial, and central column
lateral = sensory
medial = motor
central = RAS/autonomic
Describe the annulospiral ending
it is afferent, detects a change of length and velocity, fast adapting, lives in nuclear chain and bag
Vestibulospinal tract
righting and equilibrium response, static, anticipatory, and reactionary
What causes spinal shock
any acute issues within the brain
Medial Zone Center - extensor facilitatory vs. extensor inhibitory
EI - medullary reticular nucleus, lateral reticulosp. tract, facilitates flex
corticoreticulosp. system and cerebellum
Explain the pathway of type 1A fibers
muscle spindle -> DRG -> posterior horn -> AMN -> stimulat extrafusal
Tectospinal Tracts
links eye and head motion to body motion, eye-hand and eye-leg coordination
What would happen if there is a lesion above and below the RN?
above - pyramidal tract is gone, extrapyramidal takes over, rubrosp. (flex) and vestibulosp. (ext) --> decorticate posture
below - pyramidal and EP are effects, ext. bias (decerebrate)
Medial vestibulosp. tract influence on tone and PC
adjusts position of the head in response to changes in posture (keeps head stable when walking)
Unpaired median zone function
transmission of pain, communication with serotonin
Explain the pathway of type II fibers
flower spray -> DRG -> posterior horn -> AMN
Reticulospinal tract function
sets readiness to contract, regulates antigravity tone
What happens if there is damage to the rubrosp. tract?
cortex information is wrong and not modulated, there is an increase in flexion because the RS tract is dominating