Hello everyone,how are you all? Hope you all are doing well.i did not posted anything in stemsocial from last 15 to 20 days.its a small gap that i  took.any way now we are going to learn about one important physiological mechanism that is happening in our body and you can see what it is in the title of this post.

# Why do we urinate less in summer?

The [NCBI](https://www.ncbi.nlm.nih.gov/books/NBK544365/)
has explained everything in detail in its article and you can read it here completely about it by clicking on its  that i shared

The article explains in molecular level.so lets learn in simple manner from it.

First we need to know what does normal plasma osmolality means.

"**It is number of solutes(proteins,ions,urea,sugar) per 1 kg solvent(water)**" as plasma constitutes solutes and water(solvent) so it is called plasma osmolality.


"**The Dorwart and Chalmers formula is widely used to estimate plasma osmolality. It utilizes the basic metabolic panel (BMP) to measure sodium, glucose, and blood urea nitrogen.**

**Serum Osmolality=1.86 (Na)+(Glucose)/18 +(BUN)/2.8+9**

**Normal serum osmolality ranges from 275 to 295 mmol/kg.[3][4]**"

[Source](https://www.ncbi.nlm.nih.gov/books/NBK544365/#:~:text=The%20Dorwart%20and%20Chalmers%20formula,.%5B3%5D%5B4%5D)
 for above highlighted statement

So we came to know that normal serum osmolality is **275 to 295 mol/kg** we have to remember this number for lifetime.

Now we have to remember these two golden points

1)If plasma osmolality is 300 mol/kg then it is said that there is increase in plasma osmolality.here it is due to increase in number of solutes or due to more loss of water.any thing among above two contribute to hyperosmolality.

2)If plasma looses more solutes or if there is increase in water content then these two will contribute to decrease in osmalality of plasma.it is called hypoosmolality.

So with this knowledge now lets learn what happens in summer?


I made a simple handmade diagram for easy understanding.


![Untitled89_20221005181630.png](https://files.peakd.com/file/peakd-hive/salomijale/AJmwEinZgZS6aLK13TtFmTq8FdEUF5J5R14w8PnEHVRsXTs7P6eMG2vWqh1cHKS.png)


You can see in the above diagram and please notice the labelling i did and i marked 1,2,3,4,5,6,7 and 8 and these are the steps and we are going to oearm in step wise manner how the physiological mechanism is going to happen in our body

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 1  

In summer,due to heat more water loss will be there through sweating mainly and perspiration etc. So here there is loss of water from the plasma.as we have discussed above the two golden points to remember plz read them again and try to understand.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 2

Here there is loss of water from plasma.so solutes remain same in the plasma but the solvent(water) is decreased.it leads to increase in osmolality(near to or above 295 mmol/kg)

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 3

The increase in plasma osmolality stimulates osmoreceptors in hypothalamus and so on(molecular level steps) and ultimately posterior pituitary gland is stimulated and it secretes ADH hormone.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 4

The ADH hormone(vasopressin) is then travelled through the blood and reaches to kidney.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 5

Nephron is the functional unit of kidney and it has collecting duct.there is a receptor called V2 receptor for ADH hormone in the collecting duct.ADH hormone acts on that receptor.

ADH(Anti diuretic hormone) action is to reabsorb water.so when it acts on the V2 receptor it reabsorb water from the lumen of collecting duct.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 6

You can see water is reabsorbed from collecting duct due to ADH hormone action.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)


Step 7

The reabsorbed water goes into the blood and compensate the water loss that happened due to sweating and perspiration etc in summer in the beginning and decreases plasma osmolality from 295 mmol/kg or above to  normal levels.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

Step 8

As some amount water is diverted from nephron(kidney) to blood.so the urine output will be less or urine output is decreased compared to normal.


So this is the physiological mechanism that happens in our body during summer.thats why we urinate less our body tends to reabsorb water to maintain plasma osmolality in normal range.

Thats why we are adviced to drink more water in summer.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)


# In winter

I don't need to explain much what is going to happen in winter if you understood what is happening in summer.
In winter the opposite will happen.

In winter, there is no water loss much comparatevily.sweating is not seen in winter.so if you drink more water the water will add upto plasma and osmolality will decrease because of increase in solvent(water).so ADH hormone is not stimulated much.so its action is decreased and there is less reabsorption of water compared to normal and the water remain in the collecting duct and passes out as urine.the urine output will be more than normal.

If he drink more and more water he tends to urinate more and more because of hypoosmolality of plasma and decrease in action of ADH.

Don't get afraid of thinking about diabetes if you urinate frequently.in winter it is common physiological condition to urinate frequently but don't forget to to check your blood glucose levels once to get rid of that fear.

![2N61tyyncFaFc5ntfuipfg8oUptKPSKgdk8JMWeKrePu2UkBZucwHAFWSEDe1GgcbUCGzEiDov2BQvXtq5MrgM4fhrsfrxnGQVriR6ZWWDFjytwMqeFxhxL6G1B6MTK9URF5Xa6bmA8n.png](https://files.peakd.com/file/peakd-hive/salomijale/EoGvX4fhcsCUhrW5hb5Y65CBq8a8L2ebU1F9yJtu5tsoWrrVNxb63AuiWPixtgqPJMu.png)

I tried to explain in a simple manner.if you have any queries you can ask me in comment section


*References* - 

 - https://www.ncbi.nlm.nih.gov/books/NBK544365/

Thanks for reading,
With regards

![26uUsAjKTsXCDw7zixZR182JbFKvgzJ9YwsFpTVcRaGCmsqhA1unTgprNwBZoigdjFeJnSjwy5R8qepJKAuivDWVbYrpLGqKmV2FjhYjpb8FrrLbdwM5GS2N467bMezxDAD4ApWvxtjiVbaNsneaEa4ZGuUPze1npVMr5U.png](https://files.peakd.com/file/peakd-hive/salomijale/23wBg3JPSSxFiquxb5E6zmbcU5kGtgMCqZSwFnU8TbcMMyRd4fmhn6dLimVZjxdAXyNC7.png)