Regulation (Leaving Cert Biology): Revision Notes
📚 Revision Notes
Regulation
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Homeostasis: the maintenance of a constant internal environment.
Regulating Blood Glucose
- If blood glucose is too low, it can cause coma or death.
- If blood glucose is too high, it damages kidneys, nerves, and blood vessels.
- Insulin lowers blood glucose levels if they get too high.
- It is produced by the 'Islets of Langerhans' in the pancreas.
Regulating pH
- Blood pH must be maintained at 7.4.
- High CO₂ levels lower pH. To restore balance:
- Breathing rate increases to expel CO₂.
- Kidneys excrete H⁺ ions.
- The medulla oblongata in the brain detects increased CO₂ levels and signals an increase in the breathing rate, which expels CO₂.
Regulating Calcium Levels
- Calcium is needed for muscular contraction and healthy bones and teeth.
- If calcium levels are too low, the parathyroid glands release parathormone.
- Parathormone increases calcium levels in the blood.
Regulating Water and Salt Concentration
- The kidneys and brain work together to control water and salt levels in the body.
- In plants, stomata retain water when soil water levels are low.
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Exam Question - 2007 HL Q15 (c) (i)
What is homeostasis? Note one reason why it is important in the human body.
Answer
Homeostasis: The maintenance of a constant internal environment.
Reason:
- Allows normal metabolic activities.
- Keeps temperature suitable for enzyme reactions.
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Exam Question - 2011 HL Q4 (a)
(i) What is an endotherm?
(ii) What word is used to describe animals which are not endotherms?
(iii) Suggest an advantage of being an endotherm.
Answer
(i) An endotherm is an animal that can maintain a constant internal body temperature, despite changes in external temperature (e.g., mammals, birds).
(ii) Ectotherms
(iii) Advantage of being an endotherm: Body temperature is always suitable for efficient enzyme activity, allowing consistent activity regardless of environmental temperature.