Lecture 18 (4/9)

Question 1

Spinothalamic Tract

Answer 1

Transmits info on pain, temperature, and crude touch

Has 3 Order Neuron pathway

Question 2

Spinothalamic Tract - 3 Order neuron pathway (General)

Answer 2

First Order: begins in the dorsal root ganglion (receptors in the skin, muscles, and organs send their info to the dorsal root ganglion)

Then it goes to the dorsal horn of the spinal column

Then to do medulla

Then to the thalamus

Then to the somatosensory cortex

Question 3

Spinothalamic Tract - 3 Order neuron pathway (Specific)

Answer 3

First Order:

Dorsal root ganglion
Enters the spinal cord through the dorsal root and goes into the dorsal horn
-then the cells synapse in the dorsal horn on a group of cells called substantial gelationsa and nucleus proprius

Second Order:

Then the axons of the second order neurons cross the midline and ascend contra laterally through the medulla, the pons, the midbrain, and then synapse in the thalamus on third order neurons.

Third Order:

Then the axons of the third order neurons take over and go through the internal capsule, the corona radiate, and then finally in the somatosensory cortex

Question 4

Anterior Spinothalamic Tract

Answer 4

Carries information on crude touch

Question 5

Spinocerebellar Tract

Answer 5

Carries information on unconscious proprioception

Conveyed from muscle spindles, tendon organs, and joint receptors

Question 6

Spinocerebellar Tract (Pathway Overview)

Answer 6

Exception to the rule: Has a 2 order pathway and goes to the cerebellum instead of the cerebrum

There are 3 types of Spinocerebellar tracts:
Ventral Spinocerebellar Tract
Dorsal Spinocerebellar Tract
Cuneocerebellar Tract

Question 7

Ventral Spinocerebellar Tract

Answer 7

One of 3 types of spinocerebellar tracts

Carries info from the lower limbs to the cerebellum

Pathway:
Begins in the dorsal root ganglion

First Order: Enters the cord and synapses on cells in the dorsal horn

Second Order: The axons of the second order neurons cross the midline and ascend contra laterally through the rest of the cord, goes through the medulla, midbrain, pons, and through the superior cerebellar peduncle, and eventually goes into the cerebellum.

Question 8

Dorsal Spinocerebellar Tract

Answer 8

Carries information from the trunk and lower limbs

Pathway:

First Order:
Originate from the dorsal root ganglion

Enter the spinal cord and synapse on cells in the dorsal horn called Nucleus dorsalis of Clark

Second Order:

Unlike the ventral tract, the cells from the nucleus dorsal is of Clark ascend ipsilaterally up through the medulla, midbrain, pons, through the inferior cerebellar peduncle and then into the cerebellum

Question 9

Cuneocerebellar Tract

Answer 9

Carries information from the upper limbs and neck

Pathway:

First Order:
Originate from the dorsal root ganglion
Enters the spinal cord and ascends ipsilaterally WITHOUT synapsing
When they reach the medulla they synapse on cells called external cuneate nuclei

Second Order:
From the medulla the second order neurons ascend ipsilaterally through the midbrain, pons, and inferior cerebellar peduncle into the cerebellum

Question 10

Corticospinal Tract (Overview)

Answer 10

The cells in the corticospinal tract originate from the premotor cortex, supplementary motor cortex, and motor cortex

Information is descending

Question 11

Corticospinal Tract (Pathway)

Answer 11

Diencephalon -> Midbrain -> Pons -> Medulla (Decussates in the pyramid then synapses on alpha and gamma motor neurons) -> Spinal cord

About 10% of neurons don’t decussate in the medulla, they continue on through the medulla and decussate in the spinal ore instead and synapse on the alpha and gamma motor neurons

Once leaving the corticospinal tract the alpha and gamma motor neurons send info to the muscles

Question 12

Damage to the Corticospinal Tract

Answer 12

If severed in the pons (before the decussation) the damage will occur CONTRALATERALLY

If severed below the medulla (after the decussation) the damage will occur IPSILATERALLY