Biology
Form III
BIO-F3-03
✓ Verified TIE Syllabus
Regulation in the Human Body (Homeostasis)
Physiological mechanisms of internal constancy: principles of negative feedback loops, thermoregulation (skin responses), blood glucose homeostasis (insulin and glucagon), and osmoregulation (ADH).
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🎯 Syllabus Competencies & Learning Objectives
Key Competencies
- Main: 1.0 Demonstrate mastery of the concepts, principles and processes of Biology
- Specific: 1.1 Describe the physiological, anatomical and ecological processes of living organisms
Specific Learning Objectives
- Define homeostasis and explain the principle of negative feedback.
- Describe the role of the skin and hypothalamus in thermoregulation.
- Explain the hormonal regulation of blood sugar by insulin and glucagon in the pancreas and liver.
- Explain the control of water and solute potential (osmoregulation) by ADH.
- Discuss health consequences of homeostatic failure (hypothermia, heat stroke, diabetes).
📖 Comprehensive Study Notes Summary
### Principles of Homeostasis
Homeostasis is the maintenance of a relatively stable internal environment despite external fluctuations.
#### 1. Thermoregulation (Normal Body Temp: 37 C)
- **When Body Temperature Rises**:
- Vasodilation: Arterioles in skin dilate, increasing blood flow to surface capillaries -> heat loss via radiation.
- Sweating: Sweat glands secrete sweat -> latent heat of vaporization cools skin.
- Erector pili muscles relax: Hair lies flat, preventing trapped insulating air layer.
- **When Body Temperature Drops**:
- Vasoconstriction: Surface blood flow reduced.
- Shivering: Rapid skeletal muscle contraction generates metabolic heat.
#### 2. Blood Glucose Regulation
- High glucose: Beta cells of Islets of Langerhans secrete Insulin -> stimulates liver/muscles to convert glucose to glycogen (glycogenesis).
- Low glucose: Alpha cells secrete Glucagon -> stimulates liver to convert glycogen to glucose (glycogenolysis).
#### 3. Osmoregulation
- Dehydration -> Hypothalamus stimulates posterior pituitary to release ADH (antidiuretic hormone) -> collecting duct becomes more permeable -> concentrated urine excreted.
Homeostasis is the maintenance of a relatively stable internal environment despite external fluctuations.
#### 1. Thermoregulation (Normal Body Temp: 37 C)
- **When Body Temperature Rises**:
- Vasodilation: Arterioles in skin dilate, increasing blood flow to surface capillaries -> heat loss via radiation.
- Sweating: Sweat glands secrete sweat -> latent heat of vaporization cools skin.
- Erector pili muscles relax: Hair lies flat, preventing trapped insulating air layer.
- **When Body Temperature Drops**:
- Vasoconstriction: Surface blood flow reduced.
- Shivering: Rapid skeletal muscle contraction generates metabolic heat.
#### 2. Blood Glucose Regulation
- High glucose: Beta cells of Islets of Langerhans secrete Insulin -> stimulates liver/muscles to convert glucose to glycogen (glycogenesis).
- Low glucose: Alpha cells secrete Glucagon -> stimulates liver to convert glycogen to glucose (glycogenolysis).
#### 3. Osmoregulation
- Dehydration -> Hypothalamus stimulates posterior pituitary to release ADH (antidiuretic hormone) -> collecting duct becomes more permeable -> concentrated urine excreted.