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Spinal Cord and Pathways

Terms in this set (33)

- 2 Enlargements
-Cervical
-Lumbosacral
What are the enlargements of the spinal cord?
horns
part of gray matter - cell bodies are here - relay info from one area of the CNS to another
- posterior (dorsal)
- anterior (ventral)
- lateral
funiculi
white matter -axonal processes of neurons here - travel together in groups called tracts
- dorsal
- ventral
- lateral
white matter in funiculi
-Axonal processes in white matter travel together in groups to form a tract
-Sensory tracts ascend the cord (to the brain)
-Motor tracts descend the cord (from the brain to the effector)
form a tract
Axonal processes in white matter travel together in groups to _____ ______ _________
sensory tracts
ascend the cord (to the brain)
motor tracts
descend the cord (from the brain to the effector)
dorsal funiculis
- bound on either side by the entering sensory rootlets (where conscious info goes)
-contains the
-Fasciculus gracilis
- Fasiculus cuneatus
Fasciculus gracilis
-dorsal funiculis
- at all cord levels; carries
information (touch) from
the legs and lower trunk
Fasiculus cuneatus
-dorsal funiculis
- present only above T6; carries information (touch) from arms and hands (upper trunk)
lateral funiculus
bound dorsally by the entering sensory rootlets and ventrally by the exiting motor rootlets. It contains both motor and sensory tracts
lateral spinothalmic tract
What tract carries pain, temperature, itching, tickling?
lateral corticospinal
What tract is the main motor tract; terminates on the alpha
motor neurons in the ventral horn?
pain receptors
- Naked nerve endings
- Not surrounded by
myelin (insulating
material)
- found all throughout the whole body except for the brain, lungs, and liver
Spinothalamic pathway
- main pathway for pain
- a 3 neuron pathway
-Neurons are called
-First order, second order,
and third order neurons
Pain/Temperature
What is the modality of the spinothalamic pathway?
First order neuron - cell body in DRG

Second order neuron- cell body in dorsal horn of spinal cord - crosses the midline and forms Spinothalamic tract**(once it goes into white matter it is a tract)

Third order neuron cell body in thalamus and travels to postcentral (primary sensory) gyrus in the cortex for last synapse Remember the Thalamus is the relay center for sensory information
Explain the Spinothalamic Pathway
Trigeminal nerve serves the same function for the face (Remember CNV comes out of the Pons)

1st order cell body in trigeminal ganglion

Receptors are free nerve endings (microscopic sensory nerve endings in the skin that are not connected to any specific sensory receptor)

- These axons will descend into medulla on same side and upper spinal cord before synapse on second order neuron (spinal nucleus of V - located in the medulla)

Second order neuron crosses and sends pain on to third neuron in thalamus and ends in postcentral gyrus
Explain the Pain & Temperature from Head (toothache etc.)
brain freeze
-Rapid cooling of the
palate by eating
very cold substances
quickly causes a cycle of blood vessel constriction and dilation that activates pain endings around them. This causes the stabbing pain typical of ___________. It is a type of referred pain.
referred pain
the pain is in a different area than it is thought to be...
- enters the brain stem with the Trigeminal (Vth) nerve in the pons (Trigeminal Gang.)
-These axons will descend into medulla on same side and upper spinal cord before synapse on second order neuron (spinal nucleus of V - located in the medulla)
Second order neuron crosses and sends pain on to third neuron in thalamus and ends in postcentral gyrus
Describe the pathway for face pain
touch and vibration
- Also a 3 neuron pathway

- Receptors are located mainly on the skin
First order neuron cell body in DRG

Depending on where receptors are

Axons from legs/lower trunk enter the FASCICULUS GRACILIS

Axons from upper trunk/arms enter the FASCICULUS CUNEATUS

Second order neuron cell body in medulla on same side, axon crosses midline (DECUSSATION)

Third order neuron cell body in thalamus and travels to postcentral gyrus for last synapse
Explain the touch and vibration pathway - body
First order neuron cell body in trigeminal ganglion, axon enters into pons with Trigeminal Nerve (Vth) nerve

Second order neuron cell body also in pons (same side), axon crosses midline (decussation)

Third order neuron cell body in thalamus travels to postcentral gyrus for last synapse
Explain the touch and vibration pathway - face
trigeminal motor nucleus
contains motor neurons that innervate muscles of the first branchial arch, namely the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid, and anterior belly of the digastric. This nucleus is located in the mid-pons (i.e. in the middle of the pons going inferior to superior).
motor pathway
Lateral Corticospinal pathway
- From the Brain (Cortex) to the Spinal cord
What type of pathway?
Upper motor neuron (UMN)
Found in precentral gyrus (motor cortex)
Lower motor neuron (LMN)
- Anterior horn of the
spinal cord
- "Alpha Motor
Neuron"
Lateral Corticospinal pathway
- Main motor pathway to body (arms, legs, trunk)
- Two neuron pathway
- Upper motor neuron
(UMN)
- Lower motor neuron
(LMN)
Two neurons

UMN originates in cortex - brain (precentral gyrus), descends without synapse, crosses at pyramidal decussation and becomes lateral corticospinal tract (in the spinal cord)

UMN synapses on LMN (alpha motor neuron) in the anterior horn of the spinal cord

Out to the ventral root (motor) then to the muscle
Explain the Motor Pathway - Lateral Corticospinal pathway
UMN in precentral gyrus

UMN innervates hypoglossal neurons (in medulla) to the genioglossus muscle on the opposite side

Hypoglossal nucleus has axons in XII nerve that innervate genioglossus (motor function)
motor pathway face (stick out tongue)
- UMN in precentral gyrus

- UMN innervates hypoglossal neurons (in medulla) to the genioglossus muscle on the opposite side

- Hypoglossal nucleus has axons in XII nerve that innervate genioglossus (motor function)
Explain the motor pathway face (stick out tongue)- UMN in precentral gyrus
- UMN in precentral gyrus

- UMN innervates motor neurons of V in the pons

- Motor nucleus of V has lower motor neurons that exit with the Vth nerve
Explain the motor pathway face (open mouth)
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