# Explain how the nervous system and the endocrine system are integrated to regulate body temperature when a person moves from a warm room into cold outdoor air.

> IB DP Biology Higher Level (2023 syllabus) — C3.1 Integration of body systems · Explain · 4 marks

## Mark scheme (4 marks)

1. Thermoreceptors in the skin detect the drop in external temperature and send nerve impulses to the hypothalamus.
2. The hypothalamus acts as the integrating centre and coordinates both nervous and hormonal responses.
3. Via the nervous system, the hypothalamus sends efferent nerve impulses causing vasoconstriction of skin arterioles and/or shivering of skeletal muscles.
4. Via the endocrine system, the hypothalamus stimulates the anterior pituitary to release TSH, which causes the thyroid gland to secrete thyroxine, increasing the basal metabolic rate to generate more heat.

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