Homeostasis

Importance of homeostasis  Provides optimum conditions for F the efficient functioning of the F body tissues

Homeostasis

Kidney Q Regulate the amount of water and mineral salt Q removal of waste products from the body

The structure of kidneys It made up of three parts : 4 Cortex 4 medulla 4 pelvis

The structure of kidneys 4 Each kidney made up of many tubules called nephrons 4 Each kidney made up of two parts : Bowman’s capsule & collecting duct

How the nephron works ? 4 Ultrafiltration 4 Reabsorption

Role of the kidney in homeostasis 4 Osmoregulation 4 Removal of excess salt 4 Excretion

Skin 4 Regulation of body temperature

Structure of skin

Regulation of body temperature enzyme work best over a certain range of temperature important to keep the body temperature constant

Regulation of body temperature animals can be classified into two types : Poikilotherms & Homoiotherms

Poikilotherms  Cold blood animals  have little control over their body temperature  their body temperature vary with that of the surroundings  e.g. fish, amphibians

Homoiotherms  warm-blood animals  can keep their body temperatures constant irrespective of the surrounding temperature  have temperature control system  e.g. birds and mammals

How mammals control their body temperature?  Heat loss  heat gain

When the body is hot Increase heat loss  More sweat is secreted  Vasodilation  erector muscle relax  develop thinner subcutaneous fat

When the body is hot Reduce heat gain  decrease the metabolic activities of liver cells and the contraction of muscles cells

When body is cold Reduce heat loss  Vasconstriction  Erector muscles contract  sweat glands produce less sweat  develop thicker subcutaneous fat and thicker fur

When body is cold Increase heat gain  higher metabolic activities of liver cells and by shivering

Liver and pancreas 4 Regulation of blood glucose level

The control of blood glucose level 4 the blood glucose level is controlled by insulin  it is a feedback system

When Blood glucose level is too high –E.g. after a meal –pancreas secretes insulin which causes liver to convert glucose to glycogen –Blood glucose levels then falls –normal blood glucose level is then recovered

When blood glucose level is too low 4 E.g. a long time after a meal 4 pancreas secretes less insulin so liver converts glycogen to glucose 4 blood glucose level then rises  normal blood glucose level is recovered