Homeostasis and Heat Loss Mechanisms

Homeostasis Examples

• Glucose Levels: Maintaining stable blood sugar levels is crucial for energy production and overall body function.
• Water Levels: Keeping a balanced water content is essential for all bodily processes, as most reactions occur in water.
• Temperature: Maintaining a constant internal body temperature (around 37°C or 98.6°F) is vital for various biochemical reactions.
• pH levels: Maintaining a stable pH balance, typically within a narrow range, is essential for the optimal function of enzymes and other biological processes.

Heat Loss

• Conduction: Transfer of heat through direct contact with a cooler object or surface. Imagine holding a cold ice cube.
• Convection: Heat transfer through movement of fluids (air or water). Think of wind carrying away heat from your skin.

Skin and Temperature Regulation

• Vasodilation: Widening of blood vessels near the skin surface, increasing heat loss through radiation and convection.
• Vasoconstriction: Narrowing of blood vessels near the skin surface, reducing heat loss.

Temperature Control Center

• Hypothalamus: The hypothalamus is a region in the brain responsible for sensing and controlling body temperature.

Effectors for Reducing Core Temperature

• Sweat Glands: Release sweat, which evaporates and cools the skin.
• Capillaries Open: Widening of blood vessels, increasing heat loss.

Effectors for Raising Core Temperature

• Capillaries Close: Narrowing of blood vessels, reducing heat loss.
• Shivering: Involuntary muscle contractions that generate heat.

Glucose Homeostasis

• Importance: Maintaining constant glucose levels is crucial because cells need glucose for respiration (energy production).

Pancreas

• Role: Secreted hormones like insulin and glucagon regulate blood glucose levels.
• Islet Cells Alpha: Release glucagon, which increases blood glucose.
• Islet Cells Beta: Produce insulin, which reduces blood glucose.
• Glucagon: Acts as a glucose-mobilizing hormone, increasing blood glucose levels.
• Insulin: Decreases blood glucose levels.

Liver

• Role: Major organ for glucose storage, controls glucose metabolism.

Fluid balance

• Importance: Maintaining a balanced water content is vital for bodily processes.
• Intake: From liquids and foods we eat and drink
• Output: Through urine, faeces, sweating, expired air and occasionally tears and vomiting.

Renal System

• Role: Responsible for maintaining the composition and volume of body fluids.
• Kidneys: Filter waste products (urea, enzymes, hormones, drugs) from the blood.

Nephrons

• Role: Tiny filtering units in the kidneys, each kidney has about 1 million.
• Glomerulus: A specialized blood vessel within a nephron, acts like a strainer, filtering out waste products.

Dehydration

• Causes: Environmental conditions, fever, excessive vomiting, urine production, food poisoning, diabetes.
• Symptoms: Dry mouth, weight loss, low urine output, dark urine, poor skin turgor, delayed capillary refill, dizziness, confusion, lack of tears and sweat, falls, difficulty walking, low blood pressure, rapid heart rate, lethargy, sunken eyes.

Hormone Roles

• Insulin and Glucagon: Work in opposite ways to maintain blood glucose levels.
• Alpha Cells: Secrete glucagon when blood glucose falls, converting stored glucose to useable form.
• Beta Cells: Produce insulin to reduce blood glucose after carbs are eaten.
• Delta Cells: Secrete somatostatin, which inhibits the secretion of glucagon and insulin, acting as a "brake" on hormonal activity.