Dr. Najeed- Ascending Tracts 1 Flashcards
Which structures form the dorsal column system?
Central processes of first order neurons.
Where can we find ascending tracts within the spinal cord?
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)
Regarding the dorsal system and the anterolateral systems- which one is more primitive and which one is more evolutionary ’modern’?
Dorsal= modern Anterolateral= primitive
The sensation of pain
Belongs to which column system?
Anterolateral
The sensation of temperature
Belongs to which column system?
Anterolateral
The sensation of itching
Belongs to which column system?
Anterolateral
Sexual sensations
Belongs to which column system?
Anterolateral
The sensation of proprioception
Belongs to which column system?
Dorsal
The sensation of gentle touch
Belongs to which column system?
Dorsal
Sense of position
Belongs to which column system?
Dorsal
What are the 2 levels of the sense of position?
- aware (of the sensory position/ proprioception)
- not aware
The sensation of vibration
Belongs to which column system?
Dorsal
The sensation of 2 points discrimination
Belongs to which column system?
Dorsal
What are the main characteristics of the dorsal column system tracts?
- 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)
What are the main characteristics of the anterolateral column system(s) tracts?
- 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.
The sensation of crude touch
Belongs to which column system?
Anterolateral
The sensation of tickling
Belongs to which column system?
Anterolateral
What are first order neurons?
Where can they be found?
First in the chain of sensory system
Dorsal root ganglia
What is the name of the more medial fasiculus within he dorsal column system?
It conveys sensations from which part of the body?
Fasiculus gracilis
Lower part
What is the name of the more lateral fasiculus within he dorsal column system?
It conveys sensations from which part of the body?
Fasiculus cuneus
Upper part
What types of processes can we find on first order neurons (within dorsal root ganglia)?
What’s their course?
- Peripheral process: from receptors to cell body/ dorsal root ganglia
- Central processes
- > medial division (D.C.S- ascending, sensory tracts)
- > lateral division (/root)
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?
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)
What is the name and course of the processes belonging to first order neurons, that continue to form the dorsal column system?
Central processes of first order neurons
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Medial division
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