OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

How does the central nervous system respond to a stimulus?

1. By sending motor impulses to glands

2. By engaging all muscles in the body

3. By sending electrical impulses to muscles or glands

4. By interpreting sensory information only

The correct answer is: By sending electrical impulses to muscles or glands

The central nervous system (CNS) responds to a stimulus by sending electrical impulses to muscles or glands. This process begins when sensory receptors detect a stimulus and transmit this information to the CNS, specifically the brain and spinal cord. The CNS then processes the information, decides on an appropriate response, and generates electrical impulses, or action potentials, to convey signals to the relevant muscles or glands, prompting a reaction. This response is crucial for a wide range of bodily functions, including movement, reflex actions, and the regulation of metabolic activities. While option A mentions sending impulses to glands, which is part of the response, it does not fully encompass the interaction with muscles, which is an essential component of how the CNS coordinates bodily reactions to stimuli. The other options do not accurately capture the comprehensive response of the CNS, especially in failing to include the essential role of electrical impulses in relaying information and orchestrating responses throughout the body.