Unit 9 – Food & Hunger

What is the difference between osmotic and hypovolemic thirst?

Osmotic thirst occurs when high salt levels pull water out of cells. Hypovolemic thirst occurs when the body loses blood or fluid volume.

How does the body detect osmotic and hypovolemic thirst?

Osmoreceptors detect changes in salt concentration. Baroreceptors detect changes in blood pressure caused by fluid loss.

How does the brain create the feeling of thirst?

Thirst signals reach the brain, including the insula and anterior cingulate cortex, which help create the feeling of thirst.

What are circumventricular organs, and how do they detect changes in the body?

Circumventricular organs (CVOs) have a weak or absent blood-brain barrier, allowing them to detect substances and changes in the blood.

What is the function of the area postrema?

The area postrema (AP) detects toxins in the blood and can trigger vomiting.

What is the function of the subfornical organ?

The subfornical organ (SFO) monitors fluid balance and salt concentration, helping trigger thirst.

What is the function of the organum vasculosum of the lamina terminalis?

The OVLT (organum vasculosum of the lamina terminalis) detects changes in salt concentration and helps regulate thirst and fever.

How does the renin-angiotensin system work?

The kidneys release renin, which converts angiotensinogen into angiotensin I. ACE converts it into angiotensin II, which helps restore blood pressure and fluid balance.

What are renin, ACE, and angiotensin II?

Renin (kidney enzyme) starts the pathway. ACE (angiotensin-converting enzyme) makes angiotensin II, which raises blood pressure and promotes thirst.

How does angiotensin II affect drinking behavior?

Angiotensin II activates thirst-related brain regions, including the SFO (subfornical organ), encouraging drinking.

How does angiotensin II help restore blood pressure?

It narrows blood vessels and triggers aldosterone and vasopressin release, increasing salt and water retention.

What do aldosterone and vasopressin do?

Aldosterone increases sodium and water retention. Vasopressin (ADH, antidiuretic hormone) helps the kidneys retain water.

What is the difference between hunger and satiety?

Hunger is the drive to eat. Satiety is the feeling of fullness that reduces eating.

What is ghrelin, where is it produced, and what does it do?

Ghrelin is an orexigenic hormone (increases hunger) produced mainly by the stomach. It activates NPY/AgRP hunger neurons.

What is leptin, where is it produced, and what does it do?

Leptin is an anorexigenic hormone (decreases hunger) released by fat cells. It activates POMC satiety neurons and helps regulate long-term energy balance.

What is insulin, where is it produced, and what does it do?

Insulin is an anorexigenic hormone (decreases hunger) produced by the pancreas. It lowers blood sugar and helps reduce hunger signaling.

What is GLP-1, and how does it affect hunger?

GLP-1 (glucagon-like peptide-1) is an anorexigenic gut hormone (decreases hunger). It increases insulin release, slows stomach emptying, and promotes fullness.

What is PYY, and how does it affect hunger?

PYY (peptide YY) is an anorexigenic hormone (decreases hunger) released by the intestines. It inhibits hunger signaling and reduces food intake.

What is CCK, and how does it affect hunger?

CCK (cholecystokinin) is an anorexigenic hormone (decreases hunger) released by the small intestine. It supports digestion and promotes fullness.

What area of the hypothalamus regulates hunger and satiety?

The arcuate nucleus of the hypothalamus receives hunger and fullness signals and contains neurons that control food intake.

What are NPY/AgRP neurons, and what do they do?

NPY (neuropeptide Y) and AgRP (agouti-related peptide) neurons are orexigenic, meaning they stimulate hunger and eating.

What are POMC neurons, and what do they do?

POMC (proopiomelanocortin) neurons are anorexigenic, meaning they promote satiety and reduce eating.

How do hunger and satiety hormones affect neurons in the arcuate nucleus?

Ghrelin: Activates NPY/AgRP neurons → increases hunger (orexigenic).

Leptin and insulin: Activate POMC neurons → decrease hunger (anorexigenic).

PYY: Reduces hunger signals → decreases hunger (anorexigenic).