CAPF AC 2020 Q16: Science & Technology – Biology
In human body, the hormone which is secreted into blood and which controls the rate of heart beat is
- (a) Adrenaline
- (b) Thyroxine
- (c) Insulin
- (d) Testosterone
Answer: (a) Adrenaline
Explanation
Adrenaline and the heart beat
How to think: the question wants a hormone that acts fast on the heart.
Only the emergency hormone does that.
Adrenaline is made by the adrenal glands, which sit on top of the kidneys.
It is released directly into the blood.
It makes the heart beat faster, so the muscles get more oxygen.
This is the fight or flight response.
| Hormone | Gland | Main job |
|---|---|---|
| Adrenaline | Adrenal | Raises heart beat and breathing rate in an emergency |
| Thyroxine | Thyroid | Controls metabolism; needs iodine |
| Insulin | Pancreas | Lowers blood sugar |
| Testosterone | Testes | Changes in boys at puberty |
Answer: (a) Adrenaline.
Why each option is right or wrong
- (a) CORRECT. Adrenaline is secreted into the blood and makes the heart beat faster.
- (b) Incorrect. Thyroxine regulates the metabolism of carbohydrates, proteins and fats.
- (c) Incorrect. Insulin controls the level of sugar in the blood, not the heart beat.
- (d) Incorrect. Testosterone is the male sex hormone that brings changes at puberty.
Key point
Adrenaline (adrenal gland): emergency hormone; faster heart beat and breathing. Thyroxine: metabolism. Insulin: blood sugar. Testosterone: puberty in boys.
Remember
Adrenaline = fight or flight hormone; speeds up the heart.
Common mistakes
- Choosing thyroxine because it controls the general rate of metabolism.
- Thinking the adrenal glands are in the brain; they sit on top of the kidneys.
- Mixing up insulin (lowers blood sugar) with adrenaline (raises heart beat).
Exam tip
Think of fear: your heart pounds within seconds. That fast action is adrenaline.
Sources
- NCERT Class X Science — Control and Coordination (hormones in animals)
- NCERT Class XI Biology — Chemical Coordination and Integration