Adrenaline causes blood supply to the digestive system and skin to decrease while blood supply to skeletal mu…

Question

Adrenaline causes blood supply to the digestive system and skin to decrease while blood supply to skeletal muscles increases. Explain the physiological mechanism behind this shift and why it is useful during an emergency.

Accepted Answer

## Model Answer Adrenaline is secreted by the **adrenal glands** directly into the blood during an emergency (fight-or-flight situation). It acts on small arteries supplying the digestive system and skin, causing the **muscles around these arteries to contract**, which reduces blood flow to these organs. This diverts extra blood to the **skeletal muscles**. Simultaneously, the heart beats faster, increasing oxygen supply to muscles, and breathing rate increases. This shift is useful because during an emergency, digestion is non-essential, while skeletal muscles need maximum oxygen and glucose to fight or flee quickly. *Source: Chapter 6, Section 6.3 — Hormones in Animals* --- ## Explanation - The key mechanism is **contraction of muscles around small arteries** — examiners specifically look for this phrase. - Link the redistribution of blood to the **purpose** (fight-or-flight) for full marks. - Three points to cover: (1) adrenaline source, (2) mechanism of blood shift, (3) why it is…

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