Chapter 4: Spinal Cord Flashcards
Conus medullaris
caudal end of the spinal cord ( in adults, ends at the L2 vertebrae)
Clarke’s nucleus vertebral levels.
T1-L2
Cauda equina
nerve roots of the lumbar, sacral and coccygeal spinal nerves
Filum terminale
slender pial extension that tethers the spinal cord to the bottom of the vertebral column
The dorsal horn carries what rexed laminae?
I - VI
Ventral horn contains which rexed laminae?
VIII-IX
The intermediate horn of gray matter contains which rexed laminnae?
lamina VII
Which sensory fibers carry proprioception sensation?
Ia, Ib fibers
Which sensory fibers carry touch?
II, A-beta fibers
Which sensory fibers carry sharp pain, cold?
III, A-delta fibers
Which sensory fibers carry dull pain, warmth?
IV, C fiber
Gamma motor neurons innervate what type of sk. muscle fibers?
intrafusal muscle fibers
Ia innervate what part of the body?
muscle spindle from muscle stretch receptors
Ib fibers innervate what structure?
Golgi tendon organ receptor; going to sense a increase in muscle force by contraction of sk muscle.
Roman numeral fibers typically innervate which structures?
sensory receptors in skeletal muscle
The fibers A beta A delta and C from skin typically innervate what structures?
cutaneous receptor in skin (meissner’s, pacinian)
Label the parts of the body innervated by parts of the ventral horn
inhibitory interneurons located in the ventral cord and through their localized connections with motor neurons and other interneurons help to ensure a balance between contraction of synergist and antagonist muscles
T/F UMNs have net inhibitory effect on muscle stretch reflexes.
True
60% of the fibers of the corticospinal tract arise from which areas of the brain?
from the primary motor cortex, located in the pre central gyrus of the frontal lobe and the premotor area, located immediately anterior to the primary motor cortex
40% of the fibers of the coritospinal tract are derived from what areas of brain?
primary and secondary somatosensory cortical areas located in the parietal lobe
What part of the spinal cord do the corticospinal cords pass?
in the lateral corticospinal tract
If lesions of the corticospinal tract occur above the pyramidal decussation then where is weakness seen?
in muscles on contralateral side
What is another name for deep tendon reflex?
myotatic reflex
The afferent limb of a muscle spindle is innervated by what fibers?
Ia sensory neuron
The efferent limb of deep tendon reflex is innervated by what fibers?
lower motor neuron
What are the spinal cord segments involved in the knee (patellar) reflex?
L2-L4 (femoral n)
What is the muscle tested in the knee (patellar) reflex?
quadriceps
What is the spinal cord segment involved in the ankle reflex?
S1 (tibial n.)
What is the muscle tested in the ankle reflex?
gastrocnemius
What is the cord segment involved in the elbow reflex?
C5-C6 (musculocutneous n)
What is the muscle tested in the elbow reflex? Also name corresponding segments involved.
C5-C6 (musculocutaneous n) - biceps
C7-C8 (radial n) - triceps
What is the spinal cord segment involved in the reflex for the forearm?
C5-C6 (radial n.)
What is the muscle involved in the reflex for the forearm?
brachioradialis
Does the inverse muscle stretch reflex utilize GTOs?
yes; utilizes golgi tendon organs
Purpose of firing of GTOs in the inverse muscle stretch reflex?
firing of Ib afferent neruons that innervate GTOs which in turn polysynaptically facilitate antagonists and inhibit agonist muscle
Inverse muscle stretch reflex causes activated muscle to contract or relax?
causes muscle to relax
How do gamma motor neurons act?
they cause intrafusal muscle fibers to contract which activates alpha motoneurons, causing an increase in muscle tone
Whats the flexion withdrawal reflex
protective reflex in which a stimulus (usually painful) causes withdrawal of the stimulated limb
Compare type of paralysis, reflex reaction, Babinski sign presentation, muscle tone, muscle characteristic, movement, different types of atrophy, and body area involved in UMN lesion with that of LMN lesions.
Refer to chart.
Which sensory systems use 3 neurons to convey sensory innervation?
DCML dorsal column medial lemniscal system
anterolateral (spinothalamic) system
clear card
Third order neuron for ventral sensory pathways is found where?
thalamus
Axon of the third neuron of general sensory pathways projects to which areas of the cortex?
primary somatosensory cortex
What is the function of the DCML?
to sense discriminative touch, conscious proprioception, vibration, pressure
What is the function of anterolateral system?
sensing pain and temperature
What is another name for the anterolateral system?
spinothalamic
The third order neuron in the DCML synapses in what part of the thalamus?
VPL
What does VPL stand for?
ventral posterolateral nucleus of the thalamus
From the VPL where do DCML fibers project ?
to the primary somesthetic (somatosensory) area of the postcentral gyrus, located in the most anterior portion of the parietal lobe
