Dr. Najeed- Ascending Tracts 1

Question 1

Which structures form the dorsal column system?

Answer 1

Central processes of first order neurons.

Question 2

Where can we find ascending tracts within the spinal cord?

Answer 2

Either in the dorsal root system (contains only ascending/sensory tracts) or in the anterolateral column system (contain ascending and descending/ sensory and motor tracts)

Question 3

Regarding the dorsal system and the anterolateral systems- which one is more primitive and which one is more evolutionary ’modern’?

Answer 3

Dorsal= modern
Anterolateral= primitive

Question 4

The sensation of pain

Belongs to which column system?

Answer 4

Anterolateral

Question 5

The sensation of temperature

Belongs to which column system?

Answer 5

Anterolateral

Question 6

The sensation of itching

Belongs to which column system?

Answer 6

Anterolateral

Question 7

Sexual sensations

Belongs to which column system?

Answer 7

Anterolateral

Question 8

The sensation of proprioception

Belongs to which column system?

Answer 8

Dorsal

Question 9

The sensation of gentle touch

Belongs to which column system?

Answer 9

Dorsal

Question 10

Sense of position

Belongs to which column system?

Answer 10

Dorsal

Question 11

What are the 2 levels of the sense of position?

Answer 11

• aware (of the sensory position/ proprioception)

- not aware

Question 12

The sensation of vibration

Belongs to which column system?

Answer 12

Dorsal

Question 13

The sensation of 2 points discrimination

Belongs to which column system?

Answer 13

Dorsal

Question 14

What are the main characteristics of the dorsal column system tracts?

Answer 14

• more modern
• only ascending/ sensory tracts
• less variety of sensations
• heavily myelinated
• high velocity of conduction + very accurately delivery to CNS
• convey sensations that are more modern, and require fast and accurate delivery to the the CNS
• dorsal column sensations are moving ipsilaterally, and uncrossed.
• follow the “line and lane” principle (spatial orientation, topographic organization of fibers; sensations are added; more medial in dorsal column = sensations from lower part of the body, more lateral in the dorsal column = sensations from upper part of the body)

Question 15

What are the main characteristics of the anterolateral column system(s) tracts?

Answer 15

• more primitive
• mixed- ascending (sensory) & descending (motor) tracts
• higher variety of sensations
• lightly myelinated
• slow velocity of conduction + not very accurate
• convey sensations that are more primitive or crude, and don’t require high speed and accurate conduction to the CNS
• doesn’t follow the “line and lane” principle.

Question 16

The sensation of crude touch

Belongs to which column system?

Answer 16

Anterolateral

Question 17

The sensation of tickling

Belongs to which column system?

Answer 17

Anterolateral

Question 18

What are first order neurons?

Where can they be found?

Answer 18

First in the chain of sensory system

Dorsal root ganglia

Question 19

What is the name of the more medial fasiculus within he dorsal column system?
It conveys sensations from which part of the body?

Answer 19

Fasiculus gracilis

Lower part

Question 20

What is the name of the more lateral fasiculus within he dorsal column system?
It conveys sensations from which part of the body?

Answer 20

Fasiculus cuneus

Upper part

Question 21

What types of processes can we find on first order neurons (within dorsal root ganglia)?
What’s their course?

Answer 21

1. Peripheral process: from receptors to cell body/ dorsal root ganglia
2. Central processes
   • > medial division (D.C.S- ascending, sensory tracts)
   • > lateral division (/root)

Question 22

If we make 2 cross sections of the spinal cord, one at a (very) low level and one at a higher level- which dorsal column fasiculi can be seen on each?

Answer 22

Lower level = only fasiculus gracilis

Higher level = both fasiculus gracilis and fasiculus cuniatus

Why? Bc sensations are added- fibers from lower level are more medial, and as they ascend through the dorsal column, more and more fibers join laterally (as we move up, fibers innervating higher regions will also be positioned more laterally)

Question 23

What is the name and course of the processes belonging to first order neurons, that continue to form the dorsal column system?

Answer 23

Central processes of first order neurons
|
Medial division
|