3.19 Spinal Region Flashcards
rootlets
small groups of axons sending information to the periphery
ventral root
combo of ventral rootlets
dorsal root
- contains sensory axons bring info to the spinal cord
- enters posterolateral SC via rootlets
How is the SC organized?
segmentally
How is each segment of SC connected to a specific region of the body?
by axons traveling through a pair of spinal nerves
What indicates segments?
connections of nerve rootlets to exterior of the cord
What do spinal nerves carry?
all motor and sensory axons of a single spinal segment
Where are the spinal nerves in the c-spine?
above corresponding vertebrae (except 8th)
Where do the spinal nerves run in thoracic and lumbar spine?
below corresponding vertebrae
dorsal horn processes:
sensory info
lateral horn processes:
autonomic info
ventral horn processes:
motor info
most gray matter in SC composed of
interneurons
interneuron locations
- cells entirely in gray matter AND
- cells with axons that travel to different levels of the cord
meninges
- layers of connective tissue that surround the cord
- continuous with meninges that surround the brain
arachnoid mater separated from pia by
CSF in the subarachnoid space
What causes stretching of the lumbosacral roots?
hip flexion: produces anterior mvt of cauda equina
effect of extension/lateral flexion on c-spine
increased intervertebral foramen pressure at all cervical levels
effect of physiologic motions on vertebral canal
don’t significantly change size in people with normal vertebral canals
What neck movement increases cervical nerve root s/s?
extension
afferent and descending info converge on
the same spinal interneurons
What acts together to produce goal-oriented movements?
- reflexes
- voluntary control
What do reflexes depend on?
- environmental context
- task
not hardwired
What does spinal circuitry provide by integrating volleys of peripheral, ascending, and descending inputs?
- modulation of sensory information
- coordination of movement patterns
- autonomic regulation
These circuits integrate activity from all sources and adjust output of LMN
interneuronal circuits
What do interneurons coordinate when a limb moves?
activity in all the muscles
What determines whether a single alpha motor neuron will fire?
Summation of activity at 20,000 to 50,000 synapses determines whether an alpha motor neuron will fire.
What is a stepping pattern generator?
adaptable neural networks that produce rhythmic output
How does a stepping pattern generator contribute to stepping?
activating LMNs, causing alternating flexion and extension at the hips and knees
Normal activation of stepping pattern generators occurs when
the person voluntarily sends signals from the brain to the stepping pattern generators (SPGs) in the spinal cord to initiate walking.
When walking, __________ produces different responses, depending on the phase of the gait cycle
electrical stimulation to a single point on the foot
stepping pattern generation
If stimulus occurs at the onset of swing phase, this activity increases
tibialis anterior activity
stepping pattern generation
If stimulus occurs at the end of the swing phase, this happens
- tibialis anterior activity decreases
- antagonist muscle activity increases
