Spinal Cord MAIN BIG STUFF

Question 1

Ascending spinal cord paths are 3 neuron pathways.

What is the location of the 3 neurons?

Answer 1

1st neuron: dorsal root ganglion (receptor to brainstem/spinal cord)

2nd neuron: brain stem or spinal cord (crosses to other side of NS) (to thalamus)

3rd neuron: thalamus (to cerebral cortex)

Question 2

Everything stops at the _____ before reaching the cortex.

Answer 2

Everything stops at THALAMUS before reaching the cortex.

Question 3

Posterior Column (Dorsal Column) Pathway

Modalities? Components?

Answer 3

• position sense
• vibration sense
• 2 point discrimination

Fasciculus gracilis (lower body).
Fasciculus cuneatus (upper body).

Question 4

Fasiculus Gracilis

Answer 4

Info from T6 and BELOW enters the spinal cord here and travels medially.

Question 5

Fasciculus Cuneatus

Answer 5

Info from T5 and ABOVE enters spinal cord here and travels laterally.

Question 6

Spinothalamic Pathway

Modalities?
Mechanism?

Answer 6

localization of pain and temperature

dorsal root ganglion central processes synapse ON sensory neurons (2nd order neurons) in dorsal horn of the cord

then those neurons cross to other side and head up to thalamus/cortex CONTRALATERALLY.

synapses in thalamus (2nd/3rd), then 3rd order neuron travels to cortex

Question 7

Posterior Column (Dorsal Column) Pathway

General mechanism?

Answer 7

dorsal root ganglion sensory neurons transmit signal through central processes up the column IPSILATERALLY.

@ brainstem/medulla, meet nuclei of same name (2nd order neurons) and THEN cross over to other side of NS. –> thalamus

@thalamus, synapse with 3rd order neuron taking signal to cerebral cortex

Question 8

describe neurons/axons of posterior column (dorsal column) Pathway

Answer 8

large neurons, heavily myelinated axons

Question 9

describe neurons/axons of spinothalamic pathway

Answer 9

small, poorly myelinated or non-myelinated axons

Question 10

corticospinal pathway (modalities)

Answer 10

voluntary fine movement of distal extremities

Question 11

corticospinal pathway (path of neurons)

Answer 11

Upper motor neuron (UMN) cell body in cerebral cortex (precentral gyrus).

Decussation in caudal medulla (85%) [other 15% decussate in anterior corticospinal pathway]

Lower motor neuron (LMN) cell body in ventral horn of spinal cord.

LMN axon heads to skeletal muscle.

Question 12

where do corticospinal tract fibers cross?

Answer 12

85% - caudal medulla - form lateral corticospinal pathway

15% - travel in anterior corticospinal pathway - cross at level of the LMN they will contact

Question 13

upper motor neuron lesion of corticospinal tract

Answer 13

1) hyperreflexia
2) spastic paralysis
3) increased muscle tone
4) clasp knife reflex
5) clonus
6) babinski sign present
7) large area of the body is affected (from level of lesion and below)

Question 14

lower motor neuron lesion of corticospinal tract

Answer 14

1) flaccid paralysis
2) loss of deep tendon reflexes
3) decreased muscle tone
4) atrophy
5) fasciculations
6) segmental distribution of deficit