Summary of Jaras/Traktus/Sistem Saraf Motorik (Part 1) - Traktus Kortikospinal

Summary of "Jaras/Traktus/Sistem Saraf Motorik (Part 1) - Traktus Kortikospinal"

This video provides an in-depth explanation of the motor pathways in the human nervous system, focusing primarily on the Pyramidal tract (specifically the Corticospinal tract) and briefly contrasting it with the Extrapyramidal tract. The content is aimed at helping learners understand the anatomy, function, and clinical relevance of these motor pathways.

Main Ideas and Concepts

Human Body as Input-Output System
The body is compared to a computer system with inputs (sensory pathways) and outputs (motor pathways).
- Sensory pathways: Input from receptors to brain
- Motor pathways: Output from brain to muscles
Motor Pathways (Descending Tracts)
These carry impulses from the brain down to muscles and are divided into:
- Pyramidal tract (passes through the Medulla oblongata pyramid)
- Extrapyramidal tract (does not pass through the pyramid)
Pyramidal tract
- Named because it passes through the "pyramid" structure in the Medulla oblongata
- Controls voluntary movements of skeletal muscles
- Analogized as an intercity bus delivering impulses over long distances from brain to skeletal muscles
- Divided into three main tracts:
  1. Corticobulbar tract: Cortex to cranial nerve nuclei in brainstem (Medulla oblongata)
  2. Corticospinal tract: Cortex to spinal cord (innervates all skeletal muscles except facial muscles)
  3. Corticomesencephalic tract (briefly mentioned): Cortex to midbrain (mesencephalon)
Extrapyramidal tract
- Does not pass through the medullary pyramid
- Regulates motor feedback circuits between spinal cord, brainstem, cerebellum, and cerebral cortex
- Analogized as city transportation for short-distance communication within brain structures
Focus on Corticospinal tract
- Important clinically, especially in stroke
- Innervates all skeletal muscles except facial muscles (which are innervated by Corticobulbar tract)
- Pathway journey:
  1. Originates from Motor cortex
  2. Passes through internal capsule (between caudate nucleus, thalamus, lentiform nucleus)
  3. Descends through midbrain (mesencephalon), pons, and Medulla oblongata
  4. At medulla, about 90% of fibers decussate (cross over) at the pyramids → form lateral Corticospinal tract (contralateral control)
  5. About 8% do not cross here, descend as ventral (anterior) Corticospinal tract and cross later at spinal cord level
  6. About 2% remain ipsilateral (do not cross) and innervate muscles on the same side
Decussation (Crossing)
- 90% lateral Corticospinal tract crosses at the medullary pyramids (contralateral control)
- 8% ventral Corticospinal tract crosses at spinal cord level (contralateral)
- 2% lateral Corticospinal tract remains ipsilateral (no crossing)
Synapse and Innervation
- Corticospinal fibers synapse in the anterior horn of spinal cord gray matter
- Then continue via peripheral nerves to skeletal muscles

Detailed Bullet Points: Corticospinal tract Pathway and Characteristics

Origin: Motor cortex (cerebral cortex)
Path:
- Passes through internal capsule (between caudate nucleus, thalamus, lentiform nucleus)
- Descends through midbrain (mesencephalon), pons, Medulla oblongata
Decussation:
- 90% cross at medullary pyramids → lateral Corticospinal tract (contralateral control)
- 8% descend uncrossed as ventral Corticospinal tract, cross at spinal cord level
- 2% remain ipsilateral, do not cross
Synapse: Anterior horn of spinal cord gray matter
Function: Controls voluntary movement of skeletal muscles (except facial muscles)
Clinical relevance: Important in stroke and motor disorders

Comparison: Pyramidal vs Extrapyramidal Tracts

Feature	Pyramidal tract	Extrapyramidal tract
Anatomical pathway	Passes through the medullary pyramid	Does not pass through the medullary pyramid

Notable Quotes

— 03:11 — « To make it easier to imagine, we analogize it like a pyramidal attraction like an intercity interprovincial bus. Its function is to deliver passengers, in this case, electrical impulses or commands from the brain through a long journey to the intended skeletal muscle. »

— 03:36 — « For example, the extrapyramidal tract we imagine as public transportation or city transportation whose job is to deliver passengers or electrical impulses to adjacent areas only, so that is the area that is anatomically close. »

— 12:08 — « It's really confusing to learn this but nothing can't be learned if there is intention. »

— 12:29 — « If we analogize it as a public transportation, this purpose is for short distances only on the route; the route is close, so with the spinal cord, brainstem, and cerebral cortex this tract is located close to the location. »