The first reflex response to appear as spinal shock wears off in humans is:
**Core Concept**
Spinal shock is a condition that occurs after a spinal cord injury, characterized by a temporary loss of spinal cord function below the level of the injury. As the shock wears off, reflex responses gradually return, indicating recovery of spinal cord function.
**Why the Correct Answer is Right**
The first reflex response to appear as spinal shock wears off is the **Babinski reflex**. This reflex is mediated by the corticospinal tract, which is responsible for controlling voluntary motor functions. The Babinski reflex involves stroking the plantar surface of the foot, causing the great toe to extend and the other toes to fan out. This reflex is a sign of upper motor neuron function, indicating that the corticospinal tract is recovering. The return of the Babinski reflex is an important indicator of the resolution of spinal shock.
**Why Each Wrong Option is Incorrect**
* **Option A:** The return of the cremasteric reflex is not typically the first sign of recovery from spinal shock. The cremasteric reflex is mediated by the T7-T12 spinal segments and is not as sensitive an indicator of upper motor neuron function as the Babinski reflex.
* **Option B:** The plantar grasp reflex is a primitive reflex that is typically seen in infants and is not a reliable indicator of recovery from spinal shock.
* **Option C:** The ankle jerk reflex is a lower motor neuron reflex that is not affected by spinal shock and is therefore not a useful indicator of recovery.
**Clinical Pearl / High-Yield Fact**
The Babinski reflex is a key indicator of upper motor neuron function and is often used as a clinical sign of recovery from spinal shock. However, it is essential to note that the Babinski reflex can be present in normal individuals, particularly in children and after certain types of neurological injury.
**Correct Answer: B. Babinski reflex**