Flashcards in functional organization of spinal cord Deck (18):
Across which vertebrae does the spinal cord spine?
C1 to L1-L2
Where is the safest place to do a lumbar puncture? Why?
L3-L4, reduced risk of damaging neural tissue
What is the terminal point of the spinal cord called?
What is the filum terminale?
connective tissue sheath extending posteriorly from the conus medullaris. it is continuous with the pia mater.
1. internum - upper 3/4
2. externum - lower 1/4, attaches to dorsal coccyx
What are distinguishing features of each spinal cord segment on CT scan?
In cross section spinal cord:
-Cervical: oval shaped, lots of white matter
-Thoracic: has characteristic Clark's nucleus and Interomediolateral cell columns
-Lumbar: large ratio of gray matter to white matter
-Sacral Spine cord has only small rim of white matter
What do the white matter portions of the spinal cord contain?
Ascending sensory tracts and descending motor tracts
what do propriospinal tracts do?
Stay within the spinal cord, linking segments of the spinal cord together
Distal muscles are innervated by motor nuclei that are most lateral or medial in the spinal cord?
Proximal muscles have root nuclei in the medial part.
What is motor pool?
All the particular motor neurons in the spinal cord that innervate a particular muscle
Why antagonistic grouping of muscle pairs?
Muscles can only be stimulated to contract, thus need opposing muscle that can counter a movement, provide balance=pulling/pushing pairs.
What is mechanoreception?
rapidly reported sensory information RE: length of muscle and extent of force
what role does the muscle spindle play in relaying proprioceptive info?
contains fastest conducting fibres. detects muscle stretch and induces the muscle to relay information RE stretch and position
What information do GTO (golgi tendon organ) relay about skeletal muscles
The Golgi Tendon organ lies in series with muscle fibre bundles, thus relay info re extent of force being applied through the tendon.
What is the purpose of the Ib afferent neuron in the GTO
when the muscle generates force the sensory terminals of Ib afferent neuron are stretched, opens stretch sensitive ion channels causing depolarization --> sending signal to interneurons in spinal cord that project to cerebellum and motor cortex.
Sensory feedback from Ib produces spinal reflexes. (deep tendon reflexes)
How is a deep tendon reflex generated?
1. tap the patellar tendon-->small stretch to the extensor muscle
2. Burst of neural activity-->spindle afferents go to spinal cord
3. Afferent excitatory fibre will stimulate extensor motor neuron and inhibit flexor motor neuron via inhibitory motor neuron
4. Efferent fibres from motor neuron pool excites muscle to extend
**Spindles are the only sensory organ that feeds directly. mono-synaptically, to motor neurons.****
how does the bilateral (cross-extensor) reflex work?
withdrawing one limb in response to threatening/noxious stimulus increases stimulation to the other supporting lumb
what are complex multisegmental reflex actions?
When a noxious stimuli causes all the flexors in the limb to contract ( touch something hot and your whole arm jolts back)