Motor Paralysis occurs when there is an interruption in the motor tracts of the spinal cord. A careful examination of involved muscles can help locate the lesion but actual paralyses are not sharply defined as hysterical ones. Poliomyelitis, progressive muscular atrophy, and amyotrophic lateral sclerosis interrupt these tracts causing paralysis. Myelitis produces paresis due to diffuse nodules.
Decussation of Descending Tracts: The lateral motor tracts decussate in the medulla supplying opposite sides of the body while anterior motor tracts continue directly down the same side but eventually cross at various levels. Injury above decussation causes crossed paralysis, injury below produces ipsilateral paralysis. Direct motor tract injuries cause bilateral paralysis often associated with sensory tract involvement leading to ataxia.
The Cord as a Center: The spinal cord functions primarily by producing true reflexes through its segments acting as arcs for reflexes produced by sensory nerves. Reflex overflow occurs when the stimulus is vigorous, causing motion in unnecessary muscle groups. Special reflexes are listed in a table (not provided here).
Absence or exaggeration of knee-jerk indicates issues with spinal tracts and neurons. Central myelitis shows exaggerated reflex due to upper neuron involvement while diffuse myelitis affects lower neurons leading to diminished reflexes.
Tonic Functions: The cord continually sends out nerve energy maintaining muscle tone, modified by the brain's inhibitory influence. Spastic paralysis and exaggerated reflex indicate injury to upper neuron or brain; flaccid paralysis and absent reflex point to lower neuron injury.
The Medulla Oblongata performs dual roles as a conducting medium and center for certain functions like respiration, vaso-motor control, deglutition, vomiting, heat regulation. Injury disrupts these vital centers causing severe complications including death.
Key Takeaways
- Motor paralysis results from interruptions in spinal motor tracts.
- Reflex testing can indicate the location and nature of neurological lesions.
- The medulla oblongata controls vital functions like respiration and blood pressure.
Practical Tips
- Use reflex tests to assess spinal cord integrity during triage.
- Understand the difference between spastic and flaccid paralysis for better diagnosis.
Warnings & Risks
- Injury to the medulla oblongata can lead to immediate respiratory failure or death.
- Misinterpreting reflexes can delay proper treatment of neurological conditions.
Modern Application
While this chapter's diagnostic methods are outdated, understanding spinal cord function and reflex testing remains crucial for modern triage. Reflex tests still help identify neural injuries quickly in emergency settings, though imaging technology now provides more precise diagnoses.
Frequently Asked Questions
Q: What does an exaggerated knee-jerk reflex indicate?
An exaggerated knee-jerk reflex indicates an interruption in one or more of the descending spinal tracts between the third lumbar segment and the brain, cutting off inhibitory influence from the brain.
Q: How can you differentiate spastic paralysis from flaccid paralysis?
Spastic paralysis is characterized by muscle stiffness and exaggerated reflexes due to injury to upper neurons or brain. Flaccid paralysis shows a lack of muscle tone and diminished reflexes, indicating lower neuron injury.
Q: What role does the medulla oblongata play in bodily functions?
The medulla oblongata controls vital functions such as respiration through neurons that terminate at various levels of the spinal cord, vaso-motor control by regulating blood pressure via constriction and dilation of vessels.