OCR GCSE Biology 2025 – 400 Free Practice Questions to Pass the Exam

The correct choice highlights the response of the muscle in moving the arm away from the stimulus of a bee sting. When a bee sting occurs, pain receptors in the skin are activated, sending signals through sensory neurons to the spinal cord. The spinal cord processes this information and, in a reflex arc, sends a signal back out through motor neurons to the muscles in the arm, prompting them to contract. This rapid, automatic response allows for quick withdrawal away from the painful stimulus, which is crucial for protecting the body from harm.

In the context of the other options:

- The brain deciding to move the arm indicates a conscious action, which is part of a more complex process involving the brain rather than a simple reflex.

- The release of a chemical in the brain pertains to higher-level processing and does not directly contribute to the immediate withdrawal response occurring within the reflex arc.

- Deactivating the pain receptor is not part of the reflex response; instead, it might be a later reaction once the threat has been addressed, but it does not play a role in the initial withdrawal from the sting.

Thus, the muscle contraction is the crucial element of the high-speed response that characterizes the reflex action in reaction to a bee sting.