Homeostasis

Homeostasis is defined as the maintenance of constant internal conditions within organisms. The principle can be developed in a wide range of contexts, including the maintenance of balanced water levels in the blood, the regulation of body temperature in mammals, the regulation of blood glucose levels and the removal of excretory products, such as urea.

Osmoregulation: the regulation of water levels by the kidney

• Low water level in blood
  • water is reabsorbed from the kidney nephron into the blood
    • concentrated urine produced
• high water levels in the blood
  • less water is reabsorbed from filtrate in the kidney nephron
    • dilute urine produced

Excretion: is the removal of waste products of metabolic reactions made inside the body cells

The kidney

Purpose

1. removal of nitrogonous waste (urea)
2. production of urine
3. osmoregulation

Removal of Urea

• urea is made in liver
• amino acids -> ammonia -> urea -> blood transports it to the kidney

Production of Urine

kideny has filtration units called nephrons (they clean the blood)

Types

1. Ultrafiltration: small molecules are filtered through the nephrons, large molecules, such as red blood cells and proteins are not filtered.
2. Selective Reabsorbtion: useful molecules are returned to the blood. The rest is sent to the bladder as urine.

Humans are endothermic, warm blooded. Have body temperatre of 36.7 C.

Homeostasis: the maintencance if internal conditions within an organism

1. balance of water levels (osmosregulation)
2. regulation of body temperature
3. regulation of blood glucose level
4. removal of excretory prodcuts

Regulation of body temperature

• Sweating - sweat glands - letrs out a solution of urea, salt and water
• Vasodilation & Vasoconstriction
  • Hot Weater - Vasodilation
    • capillaries close the skin dilate
    • increased blood flow through skin
    • heat loss by radiation
    • skin fells warmer and looks redder
  • Cold Weater - Vasoconstriction
    • cappilliaries close to skin constrict
    • reduced blood supply to the skin
    • less heat lost throug skin
    • skin feels cold and looks pale

Regulation of Glucose levels

• Carbodydrate (stimulus): Pancreas (receptor) -> stimulated and secretes hormone insullin -> insulin decreases glucose levels to nromal
• Insulin causes body cells to absorb more glucose and change it into glycogen
  • Diabetes: when pancreas don;t create insulin. Diabetics take insulin shots.
    • It is not taken orally because it is a protein and woul be digested by protease

 

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