Lecture 21: Nutrients and digestion

what do the OVLT and lateral preoptic nucleus detect?

thirst and dehydration levels in the hypothalamus

how does osmotic thirst work?

they hypothalamus regions detect intracellular dehydration (water deficit), when other methods fail to restore osmotic balance

What is hypovolemia?

low blood volume

what happens if the baroreceptors detect low blood pressure?

the kidney releases renin

what is the hormone renin's target?

angiotensin in the blood

What does angiotensin do?

goes to subfornical constriction of vessels, raises BP, stimulates the release of aldosterone from the adrenal cortex.

once angiotensin activates the hypothalamus, what is released?

the pituitary gland releases vasopressin

what 3 tasks does vasopressin complete?

1. constricts blood vessels to increase pressure

2. tells kidneys to release less water in urine

3. causes animals to drink water

what are the 2 types of thirst?

osmotic thirst; hypovolemic thirst

why is it important for the regions of thirst (hypothalamus) to be close to the bottom of the brain structure?

in this function, they are close to the blood-brain barrier to monitor hormone and water levels, and can easily activate the brainstem for motor movements

what are the steps of digestion?

mouth (chewing).. esophagus.. sphincter.. stomach.. duodenum.. small intestine.. large intestine

What is the role of the small intestine?

Finalize digestion and absorption of nutrients, transports nutrients to blood then to interstitial space then into cells

what is the role of the stomach?

Temporary storage tank where chemical breakdown of proteins begins with adding hydrochloric acid and other enzymes

what is the role of the large intestine?

absorbs water, recycles salt and nutrients, collects waste

why did ballooning or stretching the mice's stomachs in the stretch experiment cause them to eat less?

the vagus and splanchnic nerves detected the stretch which equates to fullness or satiety, and when they were cut the mice ate too much

what are signs of satiety?

unpalatable food is eaten less

when adipose tissue (fat) releases more leptin, what does this mean?

the higher the fat content of the body

how do grhelin and leptin differ?

ghrelin- stomach, produced between meals to signal hunger

leptin- adipose tissue, produced when more fat is stored (long term satiety signal)

What do ob/ob mice not produce?

leptin, they lack leptin receptors so they became morbidly obese bc they had no info on fat storage

what do Prader-Willi syndrome lack?

peaks and valleys of ghrelin, they are constantly producing ghrelin as a hunger cue

what happened when they cut the lateral hypothalamus?

produces skinny rats, can't move nor thermoregulate

what happened when they cut the ventromedial hypothalamus ?

produces fat rats, could not secrete insulin and had problems moving and thermoregulating due to the medial forebrain tract being severed

What are the 3 satiety signals?

leptin (long term)

insulin (intermediate)

CCK (short term, sent by stretch signals of the duodenum in small intestine)

what are the 2 hunger signals?

taste input (is it delicious?)

ghrelin, secreted by stomach between meals

where is the duodenum?

first part of the small intestine

what is the role of renin?

it is a hormone secreted by the kidney, targets angiotensin, and increases blood pressure by the pituitary gland's vasopressin

When animals preferentially eat foods containing specific nutrients, they are said to be exhibiting specific hunger.

true