Final answer:
The biceps reflex checks the function of the C5 and C6 nerve roots, musculocutaneous nerve, and brachial plexus, and is tested by striking the biceps tendon with a reflex hammer, looking for muscle contraction and forearm flexion.
Step-by-step explanation:
The biceps reflex assesses the functioning of the C5 and C6 nerve roots, the musculocutaneous nerve, and the upper part of the brachial plexus. This reflex is tested by placing a thumb on the biceps tendon and striking the thumb with a reflex hammer. A normal response is the contraction of the biceps muscle and flexion of the forearm.
To conduct the test, the patient should be seated or lying down, with the arm relaxed and partially flexed at the elbow. The examiner locates the biceps tendon, places their thumb on it, and then strikes their thumb with the reflex hammer. An expected response is a visible or palpable contraction of the biceps muscle, causing the forearm to move towards the shoulder.
These reflexes are physiologically important for maintaining stability; if a muscle is stretched, it reflexively contracts to compensate for the change in length. In the clinical context, testing reflexes helps to confirm that the lower motor neurons (LMNs) and related neuronal circuits are functioning properly.