Somatic and Autonomic Nervous Systems

Question 1

Laminae of the spinal cord

Answer 1

• grey matter of the spinal cord divided up into 10 laminae
  
  • I-VI, dorsal gray matter = somatic sensory fibers
  • VII-IX, ventral gray matter = somatic motor fibers.

Question 2

Laminae X

Answer 2

• Surrounds central canal and contains neuroglial cells.
• Does not play a significant role in relay of information

Question 3

Sensory/Afferent tracts

Answer 3

1. Dorsal column
2. Lateral spinothalamic
3. Ventral spinothalamic tract
4. Tract Lissauer

Question 4

Motor/Efferent tracts

Answer 4

• Lateral corticospinal tract
• Ventral corticospinal tract

Question 5

Dorsal Column-Medial Lemniscal pathway

Answer 5

• Sensory pathway
• fine touch, proprioception, vibration
• large myelinated, fast conducting
  
  • A alpha
• 1st order neuron: enters spinal cord via dorsal root ganglion, relays to medulla.
  
  • ascends spinal cord on ipsilateral side
• ​2nd order neuron: dessucates in medulla and ascends to thalamus via medial lemniscus. Synapses in thalamus
• 3nd order neuron: thalamus to cortex

Question 6

Anteriolateral Spinothalamic tract

Answer 6

• Pain, temp, crude touch and pressure
• smaller; myelinated: slow
• poor discrimination
• 1st order neuron: enters spinal cord (may go up or down a bit on Lissauer tract). Synapses in dorsal laminae
• 2nd order neuron: crosses to other side, ascends to brain via anterior or lateral spinothalamic tracts, synapses in thalamus
• 3rd order neuron: thalamus to somatosensory cortex

Question 7

In what laminae does the anteriolateral spinothalamic tract synapse?

Answer 7

• I, IV, V, VI
• pain in II and III

Question 8

Corticospinal path

aka pyramidal tract

(pyramids are formed by corticospinal neurons as they run through the medula)

Answer 8

• motor neurons exit precentral gyrus of frontal lobe and travel through the pyramids of the medulla
• lateral corticospinal tract: dessucates in medulla and descends the spinal cord via lateral corticospinal tract
  
  • innervates the limbs
• Ventral: remain on same side and descend. Most dessucate in cervical/thoracic area
  
  • innervates axial muscles

Question 9

Which part of the corticospinal tract innervates the limbs?

Answer 9

lateral corticospinal tract

Question 10

Which part of the corticospinal tract innervates the axial muscles?

Answer 10

Ventral corticospinal tract

Question 11

Where does the upper motor neuron of the corticospinal tract go?

What happend to an injury below level of dessucation?

above?

Answer 11

cerebral cortex to ventral horn of spinal cord

Injury below dessucation results in paralysis on same side of body

Injury above dessucation results in paralysis on opposite side of body

Question 12

What causes spastic paralysis and positive babinski sign?

Answer 12

There are some neurons in the corticospinal tract that inhibit lower motor neurons, preventing them from firing too much. Injury to upper motor neurons (above where it dessucates in the medulla) makes the inhibitory neurons not work, causing spasms

Question 13

What causes flaccid paralysis?

Answer 13

When injury is below dessucation in corticospinal tract, paralysis is on the same side. Motor is no longer functioning, but the neurons above that inhibit the lower neurons are still functioning, causing flaccid paralysis

Question 14

Where is motor/sensory input found on the humonculus in relation to where it is coming from/going to?

Answer 14

input/output coming from the center of the body is on the outside of the humonculus and vice versa

Question 15

Where are the cell bodies ofpresynaptic neurons of the sympathetic system located?

Answer 15

in the Intermediolateral cell columns in the gray matter of the spinal cord

1st thoracic to 2nd lumbar of spinal cord

Question 16

Where are the cell bodies of the postsynaptic neurons of the sympathetic nervous system located?

Answer 16

either in the paravertebral or prevertebral ganglia

Question 17

Where are the prevertebral ganglia located?

Answer 17

in the plexuses that surroundthe main branches of the abdominal aorta