Spinal Cord Organization Flashcards
what are segmental pattern generators?
eg. gait/walking reflex, complex patterns generated in only spinal cord
spinal nerve at L5 longer or shorter than at T7?
Longer
Where do to a lumbar puncture?
L3-4
more or less white matter as you go caudally? rostrally?
caudally: less white matter
rostrally: more white matter for more tracts joining up
nociceptors travel up which system on which side?
contralateral side
anterolateral system
mechanoreceptors travel up which columns?
dorsal or posterior columns
more ascending or descending tracts?
more descending
lateral descending tract is for what?
motor
communication within spinal cord?
yes, a lot of interneurons talk to each other
as you move more later in ventral roots, what is innervated?
more distal muscles
medial ventral horn innervated what?
proximal muscles
what is a motor unit
a motor neuron connected to a collection of muscle fibers: varied in numbers
what is an intrafusal muscle fiber?
sensory fiber embedded within muscle spindle to detect amount of muscle stretch
can an intrafusal muscle fiber contract?
yes to adjust their position with surrounding muscles via gamma motor neurons (not alpha like the normal ones)
What is the only exception where a muscle as no intrafusal muscle fiber?
extraoccular eye muscles
What do golgi tendon organs do?
respond to force
placed in series
How are intrafusal muscle fibers placed in spindle?
in parallel
what is the ‘most important sign in neurology’?
monosynaptic stretch reflex
When the spindle afferent sends signal after stretch reflex, where does it go what does it do?
Goes to dorsal horn splits:
activates agonist
interneuron to antagonist: inhibites antagonist
is golgi organ afferent signalling monosynaptic?
Nope.
what is intersegmental cross-extensor reflex?
usually in cats/dogs, withdraw one limb, extend other 3 to maintain stability
are all interneurons short?
Nope, some really long can span multiple segments for complex reflexes
do lateral of medial have short or long interneurons?
medial: longer interneurons
lateral: shorter interneurons
spinal cord is in a usual state of?
inhibition until it’s lifted to allow excitation
what is an upper motor neuron problem?
any neuron that affects excitability of lower motor neuron
what is lower motor neuron?
ventral horn of spinal cord out to periphery
most interneurons are excitatory or inhibitory?
inhibitory
if you have a lesion in a descending upper motor neuron, what happens down stream?
increased tone/clonus cause lost inhibition
if you have a lesion in a lower motor neuron what happens downstream?
flaccid
What happens to muscles affected by stroke?
increased tone, exaggerated contractions where there is little inhibition
