PSYC 220 Exam 3 Chapter 9 Internal Regulation

When/Why do we have fevers?

A fever represents an increased set point for body temperature. It is something the hypothalamus directs the body to produce. Certain types of bacteria grow less vigorously at high temperatures, and the immune system works more vigorously at an increased temperature. (We have fevers when we get sick.)

What are the differences between the two major types of eating disorders we discussed in class?

A prominent symptom of anorexia nervosa is fear of getting fat while a prominent symptom of bulimia nerviosa is a sense of lack of control.

Glucagon

After a time passes after a meal, blood glucose levels fall and insulin levels drop, and glucose enters the cells more slowly as hunger increases. The pancreas increases the release of glucagon to stimulate the liver to convert it's stored glycogen back to glucose.

What is the series of events for volumetric thirst?

After an event which causes the body to lose water volume, the kidneys release renin, which turns into aniotensinogen, which other enzymes in the blood convert to angiotensin II. Angiotensin II triggers thirst based on water volume and salts and also constricts blood vessels. The animal increases it's preference for salty water because it needs to restore salts, so it needs sodium-specific hunger. Low blood volume-kidneys release renin into the blood, proteins in the blood form angiotensin I, angiotensin I is converted to angiotensin II, angiotensin II constricts blood vessels and stimulates cells in subfornical organ to increase drinking.

Melanocortins

Axons from satiety-sensitive cells of the arcuate nucleus deliver an excitatory message to the paraventricular nucleus which releases this. These receptors in the paraventricular nucleus are important for limiting food intake, and anything that damages these receptors leads to overeating.

Lateral Hypothalamus (LH)

Controls insulin secretion, alters taste responsiveness, and facilitates feeding in other ways. (Output from the paraventricular nucleus acts on this.) When it is destroyed, an animal refuses food and water, averting its head as if the food were distasteful. The animal may starve to death unless it is force fed. Stimulation of this area increases the drive to eat.

Glucose

Digestion converts much of a meal into glucose, an important source of energy throughout the body and nearly the only fuel of the brain.

What evidence do we have the environmental factors play a role in obesity?

Example: Native American Pima of Arizona and Mexico; obesity was uncommon in the early 1900's, however, with a more typical U.S. diet and their habits of eating all they could when it was available have become maladaptive.

Glycogen

Excess glucose produced by a meal. It enters the liver and is stored to glycogen, and some enter fat cells, which convert it to fat and store it. (This prevents blood glucose levels from rising too sharply.)

What happens to increase or decrease body temperature?

Increase: shivering, increased heart rate, decreased blood flow to the skin, and increased metabolism by brown adipose tissue. Decrease: Sweating, panting.

Diabetes (Type I)

Insulin levels remain constantly low, and blood glucose levels may be three or more times than normal level, but little of it actually enters the cell. But because glucose does not enter cells, it leaves in urine and feces instead and hunger remains high. Blood glucose levels stay high but cells are starving.

What factors in the modern diet may be contributing to the rise in obesity?

Intake of high-fructose corn syrup is bad because it cannot be used to have any affect on leptin or insulin, but has all the calories of regular sugar. (You gain calories without feeling satiety.) Fat or sugar substitutes also cause a person to overeat in fat or sugar when those things are available to them.

Leptin

Limited to vertebrates, it signals the brain about fat reserves and provides a long-term indicator of whether an individual has been overeating or under eating. (Provides for long-term satiety signals.)

CCK, Cholecystokinin

Limits meal size by constricting the spincter muscle between the stomach and the duodenum, and stimulates the vagus nerve to send signals to the hypothalamus causing cells to release a neurotransmitter like CCK to stop eating.

Homeothermic

Mammals and Birds are homeothermic, meaning that they are capable of generating their own body heat internally and use physiological mechanisms to maintain a nearly constant core temperature despite changes in the temperature of the environment. (Synonym: endothermic)

What factors are infrequently involved with obesity?

Mood has a weak relationship with weight gain, as well as single-gene mutations. (Which only account for syndromal obesity, which accounts for less than 5% of all cases of severe obesity.) As well as prenatal environment. (Mom rats that consume a high-fat diet during pregnancy and her babies develop a larger than average lateral hypothalamus.)

Where are temperature receptors located?

Most are found in the skin, and can also be found in the internal organs.

What factor is most likely involved with obesity?

Most cases relate to the combined influences of genes and environment. (Overeating and inactivity or sedentary lifestyle.)

What are the different parts involved with digestion and what do these parts do?

Mouth- enzymes in saliva break down carbohydrates. Esophagus- transfers food from mouth to stomach. Stomach-Food mixes with hydrocholoric acid and enzymes that digest proteins. Stomach stores food for a time, and then a round sphicnter muscle opens at the end of the stomach to go into the Small intestine-has enzymes that digest protein, fat, and carbs. Also absorbs digested materials in bloodstream, and carries those chemicals to body cells that use them or store them for later. The large intestine absorbs water and minerals and lubricates the remaining materials to pass as feces.

Hypovolemic thirst

Needed whenever you loose actual fluid content, due to bleeding, diarrhea, or sweating.

Arcuate nucleus

Of the hypothalamus, has one set of neurons sensitive to hunger signals, and a second set sensitive to satiety signals. (Damage to one set or the other can lead to starvation or excessive eating.)

Poikilothermic

Organisms whose body temperature matches the temperature of their environment. (synonym: ectothermic, meaning dependent on external sources for body heat.) Animals like amphibians, reptiles and most fish.

What are the different types of thirst?

Osmotic thirst and hypovolemic thirst.

Ventromedial Hypothalamus (VMH)

Output from the ventromedial hypothalamus inhibits feeding, and therefore damage to this nucleus lead to overeating and weight gain.

Why is gastric bypass surgery effective in reducing weight?

Part of the stomach is sewed off so that food cannot enter, and because stomach distension is a large factor in satiety, this makes it possible for a much smaller meal to induce satiety. However, because of serious side effects, people should only consider this in serious case of obesity.

Negative Feedback

Processes that reduce discrepancies from the set point. (Much of motivated behavior can be described as negative feedback: something causes a disturbance and behavior proceeds until it relieves the disturbance.)

What receptors detect Hypovolemic thirst?

Receptors in the large veins that monitor blood pressure. (Drop in blood pressure releases Angiotensin II, which constricts blood vessels, compensating for a drop in blood pressure.) The angiotensin goes to the third ventricle which respond to angiotensin.

What is the advantage of maintaining our temperature?

Staying warm keeps us constantly ready for vigorous activity. (A warmer animal with warmer muscles can run or move faster.)

Ghrelin

Stomach releases ghrelin during a period of food deprivation, where it triggers stomach contractions. Also acts on the hypothalamus to increase appetite.

What also help to regulate the onset and offset of a meal

Taste, stomach distension, duodenum distension and insulin.

What receptors detect Osmotic Thirst?

The OVLT (organum vasculosum laminae terminalis) and the subfornical organ (SFO) detects osmotic thirst. They detect osmotic pressure and sodium content of the blood. OVLT also receives input from the receptors in the digestive tract, enabling it to anticipate osmotic need before the rest of the body experiences it.

Allostasis

The adaptive way in which the body anticipates needs depending on the situation, avoiding errors rather than just correcting them. (Ex: The body sweats before it overheats, anticipating a certain or future need.)

Satiation mechanism for thirst

The body monitors swallowing and detects the distension of the stomach and upper part of the small intestine, those messages limit drinking to not much more than you need at a given time.

Homoestasis

The process by which the body regulates temperature and other biological processes to keep the body variables within a fixed range. (Think of it like a thermostat fixed to a temperature.)

Osmotic thirst

The type of thirst caused when eating salty foods; when water is needed to rebalance equilibria of solutes within the body.

Vagus Nerve and Splanchnic Nerve

The vagus nerve (cranial nerve X) conveys information about the stretching of the stomach walls for satiety, and the splanchnic nerves convey information about the nutrient contents of the stomach.

What exactly do the temperature receptors assess?

They asses cooling/heating of the skin or organs. (Differences in temperature.)

What evidence do we have of genetics playing in obesity?

Thin parents usually have thin children, and large parents usually have large children. People with a mutation for the receptor for melanocortin can overeat for the rest of their lives. Those with Prader-Willi, a genetic condition marked by mental retardation, have high blood levels of ghrelin. (4-5x higher than average.)

Insulin

immediately before and after a meal, the pancreas releases this in order to enable glucose to enter the cells, except for brain cells, where glucose does not need insulin to enter.