7.2 - Adrenalin and fight or flight
Explain how adrenalin coordinates the body’s response to a sudden threat. This Higher lesson links changes in circulation and blood glucose to the needs of active muscles.
7.2 - Higher: adrenalin and fight or flight
Higher only (7.2). In a threatening or stressful situation, the adrenal glands release adrenalin into the blood. Its target organs respond together, rapidly preparing the body for fight or flight.
| Effect of adrenalin | How this prepares the body |
|---|---|
| Heart rate increases | The heart pumps blood around the body more rapidly, increasing the rate at which oxygen and glucose can reach muscles. |
| Blood pressure increases | A greater pressure helps drive blood rapidly through the circulation. |
| Blood flow to muscles increases | More oxygen and glucose are delivered to muscle cells for increased respiration and contraction. |
| The liver changes glycogen into glucose | Glucose enters the blood, so blood glucose concentration rises and more respiratory substrate is available to muscle cells. |
Adrenalin does not create energy. It makes fuel and oxygen more available to active muscles; respiration then releases energy for muscle contraction. Also keep the storage molecule and the soluble fuel in the correct direction: glycogen is changed into glucose, not glucose into glycogen, during fight or flight.
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