Physiology Of Thirst and salt Appetite

1. Thirst and Salt appetite

2. Thirst
• A sensation of dryness in the mouth and throat associated with a
desire for liquids

4. Plasma osmolality
• It is the ratio of solutes to water in blood plasma.
• A person’s plasma osmolality value reflects his or her state of
hydration.
• A healthy body maintains plasma osmolality within a narrow
range.

6. kinds of Dehydration
Intracellular:
• Intracellular dehydration refers to the loss of water from inside cells.
• Caused by an increase in blood osmolality, which draws water out of
cells by osmosis and causes them to shrink.
• Intracellular dehydration can be corrected by drinking water alone.
Extracellular:
• Extracellular dehydration refers to a decrease in the total blood
volume, such as occurs during bleeding.
• Extracellular dehydration requires consumption of both water and salt
in order to regenerate the blood at its correct osmolality.
• For this reason extracellular dehydration triggers not only thirst but
also salt appetite.

8. Barroreceptors:
• Blood pressure is also monitored by stretch-sensitive
mechanoreceptor neurons called baroreceptors
• Baroreceptors respond to decreases or increases in blood
pressure by inducing or inhibiting thirst.

9. SaltAppetite:
• Thirst is not the only urge associated with fluid balance.
• Salt appetite is a craving for salty foods that occurs when
plasma Na+ concentrations drop.
• In humans, salt appetite is linked to aldosterone and
angiotensin, hormones that regulate Na+ balance.
• The centers for salt appetite are in the hypothalamus close to the
center for thirst.

11. Sweating/Perspiration:
• Perspiration, also known as sweating, is the production of
fluids secreted by the sweat glands in the skin of mammals.
• In humans, sweating is primarily a means of thermoregulation,
which is achieved by the water-rich secretion of the eccrine
glands.
• Evaporation of sweat from the skin surface has a cooling effect
due to evaporative cooling.
• Sweating is directly related to thirst, when water loss takes
place from skin, the blood volume and osmotic pressure decrease
as a result the barroreceptors detect change and send message to
brain for drinking water.

13. Thank You…!