Homeostasis in Humans

In response to Ms Aida..

...Homeostasis is one of the FAQ in examination.

Brief explanation:

..Firstly you must be clear about the meaning of homeostasis:

It is the process where the optimal physical and chemical conditions of the internal environment remain in a normal range..This is necessary to enable the body activities to function normally.

...and I'm sure you know what are the physical and chemical conditions involved...

The homeostasis process takes place to protect and correct a deviation by means of receptor and adjust changes back to normal range through negative feedback mechanism.

In negative feedback mechanism, there is a continuous cycle of events which finally enables the cells to function efficiently.

In SPM, there are 3 situations of homeostasis which possibly be asked:

1. Mechanism of Osmoregulation

2.The regulation of blood sugar level (SPM.....)

3.The regulation of body temperature (SPM 2003)

I will publish details about the 2 and 3 in my other post...and here I will elaborate more about the 1 .

• When you talk about osmoregulation...It is about the balancing of water in human body..


• The osmoregulation is controlled by two hormons: ADH and aldosterone


• and Osmoregulation controls and regulates the reabsorption of water from the

i. Distal Convulated Tubule

ii.Collecting Duct.

• The osmoregulation mechanism occurs when: the blood osmotic pressure increases OR decreases.


• and of course an organ involve is KIDNEY

...When talk about kidney, it plays two roles:
1. Urine formation: which involve processes of ULTRAFILTRATION, REABSORPTION and SECRETION.. (When explaining about urine formation, do not emphasise on hormones)

# ultrafiltration occurs at the glomerulus...filtered out substances ,passing through Bowman's capsule

#Reabsorption occurs along all the four tubules (ducts)

#Secretion occurs at Distal Convulated Tubule

2. As for OSMOREGULATION- homeostasis...You have to explain about the involvement of TWO hormones...

.. ADH and aldosterone affect Distal convulated tubules (DCT) and collecting ducts' s wall permeability!!...but not Proximal CT or Loop of Henle..

It depends on what is the situation given in the Qs...

Eg) What happens if the boy drinks too little water? Too much water?

..To make it easier for you to memorise, use schematic diagram and take note of the sequence of event..

Is it ok?