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29 Cards in this Set

  • Front
  • Back
in the spinal cord, where is the PNS and CNS border?
about 1mm from posterior horn thus the CNS is on the peripheral nerve for a bit (note that the border is covered by astrocytes)
differentiate between gray and white matter.
gray matter has nerve cell bodies, dendrites, axon terminals, and synapses while the white matter contains ascending and descending axons
describe the central canal in the spinal cord.
it is lined with ependymal cells, but the lumen is no longer present in adults
where do lower motor neurons exit the CNS?
from the anterior horn
describe the embryologic structures of the gray matter of the spinal cord.
the alar plate becomes the posterior horn and the basal plate becomes the anterior horn and the sulcus limitans divides the two.
the white matter of the spinal cord is divided into what?
the posterior, anterior, and 2 lateral funiculi
1. posterolateral sulcus
2. posterior intermediate sulcus
3. posterior median sulcus
4. anterior median fissure
5. anterolateral sulcus
label the surface anatomy
what are patterns that help determine what spinal level when looking at cross sections?
wider gray commissure and more white matter at rostral levels, large anterior and posterior horns at cervical and lumbrosacral regions, lateral horns visible at thoracic levels bc of sympathetics, and posterior intermediate sulcus is visible above T6
what is the gray commissure?
it connects the left and right horns
how many posterior and anterior arteries are there?
two posterior and one anterior
the anterior spinal artery gives rise to what arteries that go into the body of the spinal cord, and what is special about these arteries?
the left and right succal arteries which alternate with each inferior and superior branch
what structures would be affected is the anterior spinal artery was occluded? succal? posterior spinal?
anterior spinal would affect both anterior horns, the succal artery would affect one anterior horn depending upon what side, and the one posterior horn would be affected depending upon what posterior artery is affected.
distinguish between radicular and medullary arteries.
radicular arteries supply spinal roots and ganglia at ecvery level while medullary arteries are specialized radicular arteries that supply eithere anterior or posterior spinal arteries
what are the segmental arteries which supply the radicular and medulary arteries?
vertebral, posterior intercostals, lumbar, and sacral arteries
what is the major medullary artery and where is it?
the artery of adamkiewiez found on the anterior left side usually around upper lumbar/lower thoracic
what peripheral axons are heavily mylenated
type I sensory fibers and type A motor fibers (GSE)
what peripheral axons have some myelin?
type II and III sensory fibers and type B motor fibers (preganglionic GVE's)
what peripheral axons are unmyelenated?
type IV sensory fibers and type C motor fibers (GVE postganglionics)
what spinal relflexes are very slow, slow, and fast?
visceral (autonomic), flexor withdrawal (skeletal), and muscle receptor (skeletal).
what is the difference in the interneurons of visceral and skeletal reflexes?
skeletal reflexes require two interneurons, an excitatory and inhibitory interneuron bc certain muscles must be inhibited in order for others to be contracted
describe the flexor withdrawal reflex and the cross extensor reflex.
type III or IV sensory fibers transmit pain message to interneuron and then to alpha motor neuron for a fast flex to move away. The sensory fiber also sends the message to the contralateral interneuron and then to that alpha motor neuron for extension so the body can correct itself (flex one leg and extend the other)
what type of lower motor neuron innervates the intrafusal muscle? extrafusal?
gamma for intrafusal and alpha for extrafusal
what is another name for the myotatic (stretch) reflex?
deep tendon reflex
describe the myotatic reflex (neural path and such)
a force stretches the intrafusal fibers which fires the 1A sensory fiber (fastest in body, has most myelin) which synapses with an alpha motor neuron in the spinal cord (note it skips the internueron) and then the extrafusal muscle contracts.
describe the golgi tendon reflex (neural path and such)
a load or force on activates the sensory Ib fibers to fire to the cord and then an inhibitory interneuron which fires an alpha motor neuron to relax the muscle which protects it by redistributing the load
the golgi tendon organ senses this while the muscle spindle senses this.
golgi senses overall muscle tension while the muscle spindle senses changes in length and stretch velocity of the muscle.
stimulation of the gamma motor neurons causes what sequence of events?
contraction of intrafusal muscle which causes stretch receptor to fire 1a fibers to an alpha motor neuron so the extrafusals contract
what are the 3 ways to stimulate the myotatic reflex?
stimulate gamma motor neuron, tap tendon or add load
how do upper motor neurons (from brain) cause mucle contraction?
via direct stimulation of alpha motor neurons or gamma motor neurons. They can also coactivate both. Note the final common pathway is the alpha motor neuron that causes contraction of extrafusal fibers