Essay Questions
2. Discuss the mechanisms which mediate thirst and drinking.
Key Points:
- Acknowledge that the human body can survive without food for very much longer than it can survive without water.
- Identify the two main compartments containing body water (intracellular and extracellular), where they are situated, and what they do.
- Consider what happens to our bodies and water compartments when we are deprived of water, e.g. both the intracellular and extracellular fluid compartments are significantly depleted, we eat foods rich in salt etc.
- Identify where cellular dehydration is sensed (centrally in the brain, rather than peripherally in the body).
- The part of the brain that senses cellular dehydration appears to be near or in a region extending from the preoptic area through the hypothalamus, via shrinkage of the neurons.
- Discuss the two main thirst-inducing systems (one mediated by the kidneys and another implemented by receptors in the heart) and how they work, and point that that they are activated by hypovolaemia.
- Understand that we usually drink fluids, even when our bodies are not deprived of water.
