¡Vía CORTICOESPINAL y Síndromes de Motoneurona! PARA ESTUDIANTES

Summary

This script delves into the corticospinal pathway, also known as the pyramidal tract, which is crucial for voluntary muscle movements. It explains the pathway's composition of two neurons: the upper motor neuron in the cerebral cortex and the lower motor neuron in the spinal cord. The script discusses the implications of lesions at different levels, resulting in either upper or lower motor neuron symptoms, and touches upon the Jacksonian principle of dissolution, highlighting the inhibition of older structures by newer ones. It also covers the physical examination signs such as spasticity, hyperreflexia, and the Babinski sign, providing insight into various neurological conditions like poliomyelitis and Guillain-Barré syndrome.

Takeaways

• 🧠 The corticospinal tract, also known as the pyramidal tract, is a major pathway in the brain that controls voluntary movements.
• 🏃‍♂️ Voluntary movements involve the somatic or striated muscles, which are under conscious control, unlike the smooth muscles of the viscera like the intestines or heart.
• 🚶‍♀️ The corticospinal tract originates from the motor cortex in the frontal lobe and extends down to the spinal cord, involving both upper and lower motor neurons.
• 🔁 The upper motor neuron is located in the brain's cortex, while the lower motor neuron is in the spinal cord, and both are crucial for skeletal muscle control.
• 🔑 The principle of Jackson's hierarchy states that more evolutionarily advanced structures (like the upper motor neuron) typically inhibit the activity of more primitive structures (like the lower motor neuron).
• 🤕 Lesions in different parts of the corticospinal tract can lead to distinct symptoms, categorized as either upper motor neuron symptoms (spasticity, increased muscle tone) or lower motor neuron symptoms (flaccid paralysis, muscle atrophy).
• 📍 The location of a lesion in the corticospinal tract can be identified through imaging techniques such as MRI or CT scans, which can show damage to the brain or spinal cord.
• 🔍 Signs of upper motor neuron damage include increased muscle tone (spasticity), hyperreflexia, and the presence of Babinski's sign, indicating a disruption in the normal inhibitory control.
• 💉 In contrast, lower motor neuron damage results in decreased muscle tone (flaccidity), muscle weakness, fasciculations, and the absence of reflexes, as seen in conditions like poliomyelitis or Guillain-Barré syndrome.
• 🔄 The corticospinal tract travels through the white matter of the spinal cord, which is composed of axons, and is part of the motor pathways that control muscle movement.
• 📚 Understanding the corticospinal tract and its functions is essential for diagnosing and managing neurological conditions that affect motor control.

Q & A

What is the corticospinal tract also known as?

The corticospinal tract is also known as the pyramidal tract due to its origin from the internal pyramidal layer of the cerebral cortex.

What is the primary function of the corticospinal tract?

The primary function of the corticospinal tract is to control voluntary movements, which involves innervation of the skeletal muscles.

How does the corticospinal tract differ from the extrapyramidal motor pathways?

The corticospinal tract is specifically responsible for voluntary movements of skeletal muscles, whereas extrapyramidal pathways are involved in other motor functions not related to voluntary control.

What are the two types of neurons that make up the corticospinal tract?

The corticospinal tract is composed of two types of neurons: the upper motor neuron, located in the cerebral cortex, and the lower motor neuron, located in the spinal cord.

What is the significance of the principle of Jackson in the context of the corticospinal tract?

The principle of Jackson, also known as the principle of dissolution, states that more recently evolved structures (like the upper motor neuron) will inhibit the activity of older structures (like the lower motor neuron) unless they decide otherwise.

How does a lesion in the upper motor neuron affect the activity of the lower motor neuron?

If the upper motor neuron is lesioned, the inhibitory effect on the lower motor neuron is lost, leading to an increase in the activity of the lower motor neuron and its associated structures.

What are the symptoms associated with a lesion in the upper motor neuron?

Symptoms of a lesion in the upper motor neuron include increased muscle tone (spasticity), hyperreflexia, and the presence of pathological reflexes such as the Babinski sign.

What is the difference between the symptoms of a lesion in the upper motor neuron and the lower motor neuron?

A lesion in the upper motor neuron typically results in spastic paralysis, increased muscle tone, and hyperreflexia, while a lesion in the lower motor neuron leads to flaccid paralysis, muscle atrophy, and loss of reflexes.

How can the location of a lesion in the corticospinal tract be identified through imaging techniques?

Imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT) can help identify the location of a lesion in the corticospinal tract by examining different sections of the brain and spinal cord.

What is the role of the corticospinal tract in the context of the autonomic nervous system?

While the corticospinal tract is primarily involved in voluntary movements, the autonomic nervous system controls involuntary functions such as the heart rate and digestion, and is not directly influenced by the corticospinal tract.