Neurology | Spinal Cord: White Matter Structure & Function

Summary

This educational video offers an in-depth exploration of the spinal cord's white matter, focusing on its structure and function. It explains the concept of white matter as myelinated axons and introduces the term 'tract' as bundles of axons in the central nervous system. The video outlines the anatomy of the white matter in the spinal cord, including dorsal, lateral, and ventral columns, and discusses the ascending and descending tracks that carry sensory and motor information. It provides a detailed overview of specific tracts like the tract of Lissauer, corticospinal, reticulospinal, and spinothalamic tracts, emphasizing their roles in pain, temperature, touch, and motor control. The script also highlights the somatotopic organization of these tracts, crucial for understanding the implications of spinal cord injuries.

Takeaways

• 🧠 The white matter of the spinal cord is primarily composed of myelinated axons, which give it a whitish appearance.
• 🌐 Myelin sheaths are lipid-protein layers that insulate axons and facilitate the rapid transmission of action potentials.
• 🔄 A tract, or fasciculus, is a bundle of axons in the central nervous system that transmits information either ascending (sensory) or descending (motor).
• 🌱 The white matter is anatomically divided into dorsal (posterior), lateral, and ventral (anterior) columns relative to the gray matter of the spinal cord.
• ➡️ Ascending tracts carry sensory information up the spinal cord, such as the spinothalamic tracts responsible for pain and temperature sensations.
• 🔽 Descending tracts, like the corticospinal tracts, carry motor information down the spinal cord to stimulate voluntary muscle control.
• 🔄 The tract of Lissauer is involved in the pain and temperature pathway, with fibers ascending or descending one or two segments before synapsing in the posterior gray horn.
• 🏃‍♂️ The lateral corticospinal tract is the most significant descending motor tract, responsible for voluntary control of skeletal muscles.
• 🦾 The somatotopic arrangement of the lateral corticospinal and spinothalamic tracts places the sacral region laterally, followed by lumbar, thoracic, and cervical.
• 👣 The dorsal column contains only ascending tracts, specifically the fasciculus gracilis and fasciculus cuneatus, which transmit fine touch, vibration, and proprioceptive sensations.
• 🧍 The anterior spinothalamic tract in the ventral column carries crude touch and pressure sensations.

Q & A

What is white matter in the context of the spinal cord?

White matter in the spinal cord refers to the myelinated axons, which give the tissue its whitish appearance due to the myelin sheaths that insulate the axons and facilitate quick transmission of action potentials.

What is the function of the myelin sheath in neurons?

The myelin sheath serves as an insulating layer around the axon of a neuron, allowing for faster transmission of action potentials along the axon.

What is a tract in the context of the central nervous system?

A tract is a bundle of axons within the central nervous system that facilitates the transmission of information either ascending (upwards) or descending (downwards).

What are the different columns of white matter in the spinal cord?

The different columns of white matter in the spinal cord are the dorsal white column (posterior to the gray matter), the lateral white column (on the sides), and the ventral white column (anterior to the gray matter).

What is the anterior white commissure and its significance?

The anterior white commissure is a structure in the spinal cord where crossing of fibers occurs, allowing for the transmission of information across different sides of the spinal cord.

What is the function of the tract of Lissauer and how does it relate to pain and temperature sensations?

The tract of Lissauer is involved in the pain and temperature pathway. It allows these sensory fibers to ascend or descend one or two spinal cord segments before synapsing on the cell bodies in the posterior gray horn, which is important for understanding the levels affected by a lesion in the spinal cord.

What is the primary descending motor tract in the lateral white column of the spinal cord?

The primary descending motor tract in the lateral white column is the lateral corticospinal tract, which is crucial for voluntary control of skeletal muscles.

What are the two main ascending tracts in the dorsal white column of the spinal cord?

The two main ascending tracts in the dorsal white column are the fasciculus gracilis and the fasciculus cuneatus, which are responsible for carrying fine touch, vibration, and proprioceptive sensations.

What is the somatotopic arrangement of the lateral corticospinal tract and its significance?

The somatotopic arrangement of the lateral corticospinal tract places the legs laterally, with sacral motor supply being the farthest lateral, followed by lumbar, thoracic, and cervical. This arrangement is significant for understanding the impact of lesions on specific body regions.

What types of sensations are carried by the dorsal spinocerebellar and ventral spinocerebellar tracts?

The dorsal and ventral spinocerebellar tracts primarily carry proprioceptive sensations, which provide information about the position and movement of the body in space.