Biology A-Level Chapter 14

Summary:

Homeostasis is the regulation of internal conditions within an organism’s body to maintain a stable environment, which is crucial for optimal functioning. In mammals, various systems contribute to homeostasis, including the production of urea, kidney function, osmoregulation, and blood glucose control. Urea is produced in the liver as a byproduct of protein metabolism and is subsequently transported to the kidneys for excretion. The kidneys play a central role in homeostasis, filtering waste products from the bloodstream and regulating fluid balance. The nephron is the functional unit of the kidney, consisting of a renal corpuscle and a tubule. Blood filtration occurs in the renal corpuscle, where substances like glucose, amino acids, and ions are selectively reabsorbed in the tubule, while waste products are left behind to form urine. The formation of urine is a multistep process involving filtration, reabsorption, and secretion. Osmoregulation is another vital aspect of homeostasis that involves maintaining the right balance of water and solutes in the body. Hormones such as antidiuretic hormone and aldosterone help regulate water and electrolyte balance. The control of blood glucose is essential for energy supply and is maintained by the hormones insulin and glucagon.

Excerpt:

Biology A-Level Chapter 14

14.1 Homeostasis in Mammals

CONTENTS
14.1.1 Homeostasis
14.1.2 Production of Urea
14.1.3 Kidney Structure
14.1.4 Nephron Structure
14.1.5 Formation of Urine
14.1.6 Osmoregulation
14.1.7 The Control of Blood Glucose
14.1.8 Test Strips & Biosensors

14.1.1 HOMEOSTASIS

Homeostasis

• In order to function properly and efficiently, organisms have different control systems
  that ensure their internal conditions are kept relatively constant.
• The process of maintaining constant internal body conditions is known as homeostasis.
• Homeostasis is critically important for organisms as it ensures the maintenance of
  optimal conditions for enzyme action and cell function.
• Sensory cells can detect information about the conditions inside and outside of the body.
• Examples of physiological factors that are controlled by homeostasis in mammals include:
  • Core body temperature
  • Metabolic waste (e.g. carbon dioxide and urea)
  • Blood pH
  • Concentration of glucose in the blood
  • Water potential of the blood
  • Concentration of the respiratory gases (carbon dioxide and oxygen) in the blood