Regulation Of Water In Body

Journal#1 (OBS) 

During OBS, our class experienced a sea and land expedition. Before these 2 expeditions, our instructors were really strict with us about the amount of  water we needed to bring with us for these expeditions. They specifically told us to bring 4L of water as this is the amount of water needed to replenish while exercising. 

However, I did not drink enough water (only about 1 1/2L) despite sweating a lot under the heat. Hence, my body will try to balance the amount of water lost and gained in my blood. 

Homeostasis is the ability of an organism or cell to regulate its internal conditions or to maintain a constant internal environment. These conditions include:
1. Body's water content
2. Body temperature
3. Body's blood sugar level
4. Carbon dioxide level
Homeostasis is maintained by our hormones and nervous system. Hormones are chemicals secreted by glands to travel through bloodstream to targeted organs. These hormones regulate functions of many organs and cells. For instance, the amount of water in our kidneys.


Body's Water Content
It needs to be controlled so as to prevent cells in our body from damaging due to too much water from entering or leaving the cells caused by osmosis. On a daily basis, we gain water by drinking water or consuming food and the production of water through cellular respiration. We lose water through sweating from skin, urination/faeces and evaporation of water vapour we exhale from lungs. However, we need a balance for gain or loss of water in our body.

This balance is achieved by the hormones anti-diuretic hormone (ADH). ADH aids in negative feedback mechanism, a process which maintains the level of water in our blood. As the level of water falls in our blood, the negative feedback will ensure the amount of ADH rises and as the level of water rises in our blood, the negative feedback will release less amount of ADH.

(If We Had Too Little Water)
Caused by: (heat) sweating a lot, not drinking enough water
-Part of brain, hypothalamus, detects too little water in blood
-Sends a signal to pituitary gland to release more ADH
-More ADH travels in blood to kidneys
-Kidneys remove less water from blood (renal tubule reabsorbs more water into blood)
-Less water is to dilute the urine, hence urine is smaller volume and more concentrated
-Person will become thirsty and hence drink more water
-Water level in blood returned to normal

(If We Had Too Much Water)
Caused by: weather is cold and body not losing water through sweat, drinking enough water
-Part of brain, hypothalamus, detects too much water in blood
-Sends a signal to pituitary gland to release less ADH
-Less ADH travels in blood to kidneys
-Kidneys remove more water from blood (renal tubule reabsorbs less water into blood)
-More water is to dilute the urine, hence urine is greater in volume and more dilute
-Water level in blood returned to normal

Factors affecting amount of ADH produced: alcohol (decrease amount of ADH--> greater in volume of dilute urine--> leads to dehydration), ecstasy (reduce amount of ADH--> smaller volume of concentrated urine--> reduce amount of urine produced)


Links:
http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/ourselves/5_staying_in_balance1.shtml
http://www.abpischools.org.uk/page/modules/homeostasis_kidneys/kidneys6.cfm