Extrapyramidal and Pyramidal Tracts - Descending Tracts of the Spinal Cord | (Includes Lesions)

Summary

This transcript explores the descending motor pathways of the nervous system, detailing the pyramidal and extrapyramidal tracts. It explains the origin, function, and anatomical features of each tract, emphasizing the pyramidal tracts' role in voluntary muscle control and the extrapyramidal tracts' involvement in involuntary muscle modulation. The impact of lesions in these pathways is also discussed, highlighting clinical signs such as hypertonicity, hyperreflexia, and specific reflex responses. This comprehensive overview enhances understanding of motor function and its clinical implications.

Takeaways

• 🧠 The descending pathways in the spinal cord are divided into pyramidal and extrapyramidal tracts, which carry motor signals.
• 🔺 Pyramidal tracts are responsible for voluntary muscle control and consist of corticospinal and cortical bulbar tracts.
• 🧍 The corticospinal tract controls body muscles, with 75% of fibers decussating and synapsing on the opposite side of the spinal cord.
• 👶 The anterior corticospinal tract contains 25% of fibers that remain ipsilateral until higher cervical levels, where they decussate.
• 👤 The cortical bulbar tract controls head and facial muscles, with most neurons innervating bilaterally, except for specific facial muscle innervations.
• ⚖️ Extrapyramidal tracts are involved in involuntary muscle control, affecting muscle tone and balance, and originate in the brainstem.
• 🎯 The rubrospinal tract is responsible for fine motor control of upper limbs and has contralateral innervation.
• 💪 The reticulospinal tracts consist of two components: the medial tract facilitates muscle movement while the lateral tract inhibits it.
• 🚶‍♂️ The vestibulospinal tract maintains balance and posture with primarily ipsilateral innervation.
• 💡 Lesions in the pyramidal tracts can lead to contralateral deficits, hypertonicity, hyperreflexia, and abnormal reflex signs like Babinski's and Hoffmann's.

Q & A

What are the two main types of descending pathways in the nervous system?

The two main types of descending pathways are pyramidal tracts and extrapyramidal tracts.

What is the primary function of pyramidal tracts?

Pyramidal tracts are responsible for the voluntary control of muscles in the body and face.

Where do the corticospinal tracts originate, and what is their primary role?

Corticospinal tracts originate in the cerebral cortex and control body movements.

What happens to approximately 75% of fibers in the corticospinal tract at the level of the medulla oblongata?

About 75% of the fibers decussate (cross to the opposite side) at the level of the medulla oblongata.

How do corticobulbar tracts differ from corticospinal tracts?

Corticobulbar tracts control voluntary movements of the head, face, and neck and synapse with lower motor neurons in the brainstem rather than descending into the spinal cord.

What is the significance of the bilaterality in the cortical bulbar tract?

Most neurons in the cortical bulbar tract innervate bilaterally, allowing motor function for both sides of the face; exceptions include specific cranial nerves, such as cranial nerve VII.

What are extrapyramidal tracts responsible for?

Extrapyramidal tracts are involved in the involuntary control and modulation of muscles, including muscle tone and balance.

What role does the rubrospinal tract play in motor control?

The rubrospinal tract, originating from the red nucleus, is involved in fine motor control, primarily affecting the upper limbs.

How do lesions in the pyramidal tracts affect the body?

Lesions in the pyramidal tracts can lead to upper motor neuron signs, such as hypertonicity, hyperreflexia, weakness, and abnormal reflexes like Babinski's sign.

What symptoms are associated with damage to extrapyramidal tracts?

Damage to extrapyramidal tracts can lead to symptoms such as rigidity, bradykinesia, tremors, and postural deficits, characteristic of conditions like Parkinsonism.