Effect of cutting spinal cord above medulla, on respiration: September 2012
## **Core Concept**
The question tests the understanding of spinal cord injury effects on respiration, specifically at different levels. Respiration is controlled by the brainstem, which includes the medulla oblongata and pons. The spinal cord plays a role in transmitting signals.
## **Why the Correct Answer is Right**
Cutting the spinal cord above the medulla would essentially mean a high cervical spine injury. This level of injury affects the phrenic nerve (C3-C5), which controls the diaphragm, the primary muscle for breathing. However, since the injury is above the medulla, the brainstem's respiratory centers are intact, and they can still send signals to the spinal cord below the injury level. The diaphragm, innervated by the phrenic nerve, would still function, but other accessory muscles of respiration might be affected.
## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because cutting the spinal cord at a high level doesn't completely abolish diaphragmatic function; the phrenic nerve's function remains intact as its nucleus is in the neck.
- **Option B:** This option might seem plausible but doesn't accurately reflect the immediate effect on respiration; some level of respiratory function remains.
- **Option C:** This option suggests no effect, which is incorrect because a high spinal cord injury does impact respiratory function, particularly affecting accessory muscles and potentially leading to respiratory failure.
- **Option D (Correct Answer):** Not discussed here as per instructions.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that patients with high cervical spine injuries (above C5) may require mechanical ventilation due to the potential for paralysis of the diaphragm and accessory muscles of respiration. The level of injury significantly influences the patient's need for respiratory support.
## **Correct Answer:** .