ch 9 hunger

Animals put on more fat

around fall intrinsically due to winter having less food

First half of digestion

In the mouth, enzymes in the saliva break down carbohydrates. Swallowed food travels down the esophagus to the stomach, where it mixes with hydrochloric acid and enzymes that digest proteins. The stomach stores food for a time, and then a ring-shaped sphincter muscle opens to release food to the small intestine.

Latter half of digestion

The small intestine has enzymes that digest proteins, fats, and carbohydrates. It absorbs digested materials into the blood, which carries them to cells that either use them or store them. The large intestine absorbs water and minerals and lubricates the remaining materials for excretion.

Vagus Nerve (Cranial Nerve X)

Signals between your brain, heart and digestive system. They're a key part of your parasympathetic nervous system.

Damaged vagus nerve

Disrupts signals between the brain and vital organs, causing issues with digestion, heart rate, and vocal cord function. Common symptoms include gastroparesis (delayed stomach emptying), chronic hoarseness, difficulty swallowing, acid reflux,

Glucose

one of the only sources of energy the brain uses. Other cells use other byproducts of proteins and diff types of sucrose.

Lactase

Lactose

ventromedial hypothalamus

These regions, particularly the ventromedial hypothalamus, respond to metabolic shifts to regulate hunger and blood sugar, while insulin crosses the blood-brain barrier to act as a satiety signal

Hindbrain (Dorsomedial Medulla)

Contains neurons that detect, and respond to, low blood glucose (glucoprivation).

The genetic ability to metabolize lactose in adulthood

is common in societies with a long history of domesticated cattle. Within Africa, the distribution of ability to digest lactose varies sharply from place to place.

Europeans with lactose

can digest lactose in adulthood all have variants of the same gene,

Type 1 diabetes,

sometimes called juvenile diabetes because it usually begins early in life, an autoimmune attack reduces or eliminates the ability of the pancreas to produce insulin.

Type 1 diabetes treatment

injections or a pump to provide the needed insulin. It also requires the person to maintain a careful diet, minimizing intake of sugars. Because the restricted diet is difficult, eating disorders are common, especially for adolescents

Type II diabetes

Usually begins in middle age or later, is the more common type. It occurs mostly in association with obesity and lack of exercise. In Type 2 diabetes, the pancreas produces enough insulin, but cells have become unresponsive to it.

Type 2 Diabetes Treatment

Restricted diet, increased exercise, and medications.

if untreated, the blood glucose level rises, sometimes to harmful levels, but not much glucose enters the cells. Because the cells are starving, hunger increases and eating increases, but the person continues losing weight.

Leptin

Hormone that tells our brain the long-term storage of energy. If levels go up, then it tells you you are full or need to eat less. If levels go down, indicates low levels of stored energy. Low levels of this hormone can delay puberty

Mutations in the leptin gene

does not make leptin, its brain reacts as if its body has no fat stores and must be starving. The mouse eats as much as possible, conserves its energy by not moving much, and fails to enter puberty.

tryptophan:

helps the brain produce melatonin, which aids sleepiness. Other than taking pills, the most reliable way to increase this in the brain is to eat a diet high in carbohydrates.

Fish and the brain:

Contain oils that support brain functioning. Mothers who eat much during pregnancy tend to have children who perform better on tests of cognitive ability

Mice on a severe diet:

Reduced their weight to 85 percent of normal. When energy levels get that low, the body reduces the fuel available to the brain.

Brain adjustments in hunger

Brings the resting potential of axons closer to their threshold for firing to continue generating action potentials without overburdening the sodium-potassium pump (which requires energy)

Sham-feeding:

a biological experimental procedure where food is ingested but not digested or absorbed, typically by exiting the body through an esophageal or gastric fistula

The importance of stomach distension:

explains why sham feeding does not satisfy hunger, and why eating satisfies your hunger before the nutrition reaches the cells that need it.

vagus nerve (cranial nerve X):

conveys information to the hypothalamus about the stretching of the stomach walls (Kim et al., 2020). However, people who have had their stomach surgically removed because of stomach cancer or other disease still report satiety, so stomach distension is not the only mechanisms of satiety.

The duodenum:

the part of the small intestine adjoining the stomach, is a major site for absorbing nutrients. Nerves inform the brain not only about distension, but also about the type and amount of nutrition.

Distension of the duodenum:

releases the hormone cholecystokinin (CCK), which produces satiety in two ways. First, CCK constricts the sphincter muscle between the stomach and the duodenum, causing the stomach to hold its contents and fill more quickly than usual. (CCK hastens stomach distension). Second, CCK stimulates the vagus nerve to send signals to the hypothalamus, causing cells there to release a neurotransmitter that is a shorter version of the CCK molecule itself.

cholecystokinin (CCK):

Hormone released from the duodenum promoting satiety

The CCK in the intestines:

cannot cross the blood–brain barrier, but it stimulates cells to release something almost like it.

Two pancreatic hormones:

insulin and glucagon

insulin and glucagon

regulate the flow of glucose into cells.

Insulin:

enables glucose to enter the cells.

The brain cells with glucose:

glucose can enter them without need for insulin.

Liver with glucose:

Converts it to glycogen and stores it.

Fat cells:

binds with glucose which convert it to fat and store it.

The net effect of insulin

: prevents blood glucose levels from rising too sharply.

As time passes after a meal:

the blood glucose level falls, insulin levels drop, glucose enters the cells more slowly, and hunger increases

The pancreas:

increases release of glucagon, stimulating the liver to convert some of its stored glycogen back to glucose.

Hibernation preparation:

Animals have constantly high insulin levels. They rapidly deposit much of each meal as fat and glycogen, quickly grow hungry again, and continue gaining weight