Part 2. Internal Regulation (Hunger and Thirst)

What percent of the mammalian body does water constitute?

70%

Vasopressin/anti-diuretic hormone

Raises blood pressure by constricting blood vessels

Helps to compensate for decreased water volume

Enables the kidneys to reabsorb water and excrete highly concentrated urine

What is vasopressin also known as?

Anti-diuretic hormone

Diuretic

Increasing the passing of urine

Osmotic thirst

Caused by eating salty foods

Hypovolemic thirst

A thirst resulting from loss of fluids due to bleeding or sweating

Why do salty foods makes one thirsty?

Because salty foods increase solute concentration outside the cell, so water leaves the cell to balance it out

What is the set-point of solutes in mammals?

0.15 M (molar)

What receptors around the third ventricle detect osmotic pressure?

OVLT (organum vasculosum laminae terminalis)

Subfornical organ (SFO)

NOTE: Peripheral receptors, such as in the stomach and digestive track also exist. 

What three areas of the hypothalamus do the OVLT, SFO, stomach and like organs send signals too?

Supraoptic nucleus

Paraventricular nucleus

Lateral preoptic area 

What do the supraoptic and paraventricular nuclei control?

The release of vasopressin 

What does the lateral preoptic area control?

Drinking

What happens when blood volume is low?

Cause, reliever, and receptor location of osmotic thirst

Cause, reliever, and receptor location for hypovolemic thirst

Animals with hypovolemic thirst prefer slightly salty fluids, like Gatorade, as such fluids compensate for sodium, potassium, and carbohydrates lost in the blood

What amino acid is Turkey supposed to release that makes you sleepy?

Tryptophan

What smaller molecule is food broken down into for cells to use?

Glucose 

Three key facts about glucose 

Main product of digestion

Important source of energy for the body

Nearly the only fuel used by the brain

Where does excess glucose go?

The liver and fat cells

Insulin

Causes the body to store glucose

Glucagon

Stimulates the liver to convert some of its stored glycogen to glucose

What organ releases insulin and glucagon?

The pancreas

Two main body parts that tell us we’re full

The vagus nerve

The duodenum 

The vagus nerve

Conveys information about the stretching of the stomach walls to the brain

Duodenum 

Distention of the duodenum can produce feelings of satiety, and it also releases CCK, a satiety hormone 

Leptin 

A hormone released by fat cells in proportion to their volume which signals your brain about your fat reserves

What happens when your fat reserves decrease?

Leptin levels decrease, causing your appetite to increase

Does increase leptin automatically increase hunger?

Not necessarily, as obese people are often less sensitive to leptin

Hypothalamic transmitters of feeding

See paper flashcards

Three hypothalamic feeding areas (in order)

Arcuate nuclei — paraventricular nucleus — lateral nuclei