# Explain why inorganic ions are essential for the transmission of nerve impulses and for the production of thyroid hormones in the human body.

> AQA A-Level Biology (7402) — 3.1.8 Inorganic Ions · Explain · 5 marks

## Mark scheme (5 marks)

1. Sodium ions (Na⁺) are involved in nerve impulse transmission
2. Sodium ions move into the neurone / axon causing depolarisation / a change in membrane potential / generating an action potential
3. Potassium ions (K⁺) also contribute to nerve impulse transmission / repolarisation of the membrane
4. Iodine ions / iodide ions are needed to produce thyroid hormones
5. Thyroid hormones regulate / control metabolic rate

## Key terms

- [inorganic ions](https://www.gradenine.co.uk/glossary/inorganic-ions)
- [nerve impulse](https://www.gradenine.co.uk/glossary/nerve-impulse)
- [thyroid hormones](https://www.gradenine.co.uk/glossary/thyroid-hormones)

## Related

- [Revision notes for AQA A-Level Biology (7402)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-inorganic-ions-are-essential-a51e19ea) · Published by Druglandscape Ltd.