Why your body reacts before your brain even thinks about it
In short: Ever wondered how you pull your hand away from a hot stove instantly? This video breaks down the reflex arc, the biological shortcut that prioritizes survival over conscious thought.
The nervous system coordinates responses to internal and external environments through specialized nerve cells called neurones. These cells are adapted with long, thin, branched connections to transmit electrical impulses efficiently across the body. A reflex arc is a specific pathway for rapid, automatic, and unconscious responses designed to protect the organism from harm. Instead of waiting for the brain to process information, a stimulus travels from a receptor through a sensory neurone to a relay neurone in the Central Nervous System (CNS). From there, a motor neurone carries instructions to an effector—such as a muscle or gland—to produce an immediate response.
The video illustrates this mechanism using the example of touching a pin, mapping out the precise sequence: Stimulus $\rightarrow$ Receptor $\rightarrow$ Sensory Neurone $\rightarrow$ Relay Neurone $\rightarrow$ Motor Neurone $\rightarrow$ Effector $\rightarrow$ Response.
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Sources
- Summary by Intellect · source: GCSE Biology - The Nervous System | Reflex Arcs Explained (2027/28 exams)
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