Medula Espinal: Vias Eferentes, Descendentes ou Piramidais - Sistema Nervoso - VideoAula 093

Summary

This video lesson provides an in-depth explanation of efferent (motor) pathways in the spinal cord, focusing on their role in voluntary movement. The instructor explains the two main types of pathways: pyramidal (corticospinal) and extrapyramidal tracts. The corticospinal tracts, responsible for fine motor control, include the lateral and anterior tracts, with fibers crossing at different points in the medulla and spinal cord. Extrapyramidal tracts, originating in the brainstem, influence posture and involuntary movements. The lesson also touches on the importance of these pathways in conditions like ALS, which impacts the lateral corticospinal tract.

Takeaways

• 😀 Efferent pathways are also called descending or motor pathways, as they transmit motor signals from the brain to the muscles.
• 😀 These pathways originate in the CNS (central nervous system) and end in the PNS (peripheral nervous system).
• 😀 The corticospinal tracts (lateral and anterior) are the primary motor pathways, with the lateral tract being more prominent.
• 😀 The lateral corticospinal tract crosses at the medulla (decussation) and controls the opposite side of the body.
• 😀 The anterior corticospinal tract mostly stays on the same side but crosses within the spinal cord to control the opposite side.
• 😀 The pyramidal system consists of the corticospinal tracts, and it is responsible for voluntary movements.
• 😀 Extrapyramidal systems, which do not pass through the pyramids, include the rubrospinal, vestibulospinal, reticulospinal, and tectospinal tracts.
• 😀 Amyotrophic Lateral Sclerosis (ALS) affects the lateral corticospinal tract, leading to motor dysfunction.
• 😀 The decussation of the corticospinal tracts explains why damage to one side of the brain affects the opposite side of the body.
• 😀 Movement control involves two neurons: the upper motor neuron in the corticospinal tract and the lower motor neuron that innervates muscles.
• 😀 The term 'pyramidal system' refers to the passage of motor fibers through the medullary pyramids, which is crucial for voluntary motor control.

Q & A

What are the eferent pathways, and how are they also referred to?

Eferent pathways are responsible for sending signals from the central nervous system (CNS) to the peripheral nervous system (PNS), reaching the muscles. They are also known as descending pathways, motor pathways, or pyramidal pathways.

What is the origin of the eferent pathways?

The eferent pathways originate in the cerebral cortex or the brainstem. These pathways are motor pathways that carry impulses from the central nervous system to the peripheral nervous system.

What is the role of the eferent pathways in motor control?

The eferent pathways transmit motor signals from the brain to the muscles, allowing for voluntary movement. The signals travel down the spinal cord, making synapses with motor neurons, which then activate muscles.

What are the two major tracts involved in carrying motor information down the spinal cord?

The two major tracts involved are the lateral corticospinal tract and the anterior corticospinal tract. These tracts are responsible for transmitting motor information from the brain to the muscles.

What is the difference between the lateral and anterior corticospinal tracts?

The lateral corticospinal tract involves fibers that cross over at the pyramids of the medulla, while the anterior corticospinal tract involves fibers that do not cross over immediately but cross at the level of the spinal cord before reaching the motor neurons.

What is the significance of the term 'pyramidal system' in relation to the corticospinal tracts?

The term 'pyramidal system' refers to the corticospinal tracts because these tracts pass through the pyramids of the medulla. It is named after the pyramids due to the crossing of motor fibers that occurs at this location.

What happens during the decussation of the pyramids?

During the decussation of the pyramids, motor fibers crossing from one side of the brain to the opposite side of the body. This crossing is why damage to one hemisphere of the brain often affects the opposite side of the body.

What is the condition called when the corticospinal tract is damaged?

The condition is called amyotrophic lateral sclerosis (ALS), which is a degenerative disease that affects the motor neurons in the lateral corticospinal tract, leading to muscle weakness and paralysis.

How do the extrapyramidal pathways differ from the pyramidal pathways?

Extrapyramidal pathways, such as the vestibulospinal and reticulospinal tracts, do not pass through the pyramids of the medulla. These pathways originate in the brainstem and are responsible for controlling involuntary movements and muscle tone, unlike the pyramidal pathways which control voluntary movements.

Why does a stroke in the right cerebral cortex result in paralysis on the left side of the body?

A stroke in the right cerebral cortex affects the lateral corticospinal tract, which crosses over at the pyramids of the medulla. This means the right hemisphere controls the left side of the body, and damage to the right side of the brain causes left-side paralysis.