Sympathetic nervous system
- ICSE Class 10, Unit 3 Human Anatomy and Physiology
The sympathetic nervous system is the part of the autonomic nervous system that gets the body ready to face danger or stress.
The autonomic nervous system runs the organs you do not control by will, like the heart and gut. It has two parts that work against each other:
- Sympathetic: speeds things up for action. The heart beats faster, the pupils widen, the air tubes of the lungs open wider, and more adrenaline is released.
- Parasympathetic: calms the body back down. The heart slows and digestion picks up again.
A healthy body keeps moving between the two, as the day needs.
A small example
You wake up late and see the school bus pulling away. Your heart races and you breathe fast as you run. That is the sympathetic system at work. Once you are seated in class, the parasympathetic system slows you down again.
Where marks go
The 2025 ICSE Biology paper asked which part of the autonomic system raises adrenaline. The answer is the sympathetic nervous system. In CISCE's report on the 2025 Biology paper, examiners name two errors. One was writing "parasympathetic". The other was giving a broad name such as CNS, PNS or ANS.
The 2024 paper tested the same idea as an assertion and reason, where both statements were true. Learn the two systems as a pair of opposites. See assertion-reason questions.
Sources
Facts last checked against these sources on 30 September 2026.
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