Chapter 9 Internal Regulation

Endothermic

(Homeothermic) The use of internal physiological mechanisms to maintain an almost constant body temp. -Some species become ectothermic during hibernation

Ectothermic

(Poikilothermic) Maintaining the body at the same temp. as the environment.

Vagus nerve

(cranial nerve X) Conveys information about the stretching of the stomach walls, providing a major basis for satiety -The stomach conveys satiety messages to the brain via this

Thirst

-70% of the mammalian body -Water in the body must be regulated within narrow limits -Sufficient fluid needed in circulatory system -The concentrations of chemicals in water determines the rate of all chemical reactions in the body

POA/AH

-Receives input from temp. receptors in the skin, in the organs, and in the brain. -Heating it leads to panting or sweating; cooling leads to shivering -Receives input from the immune system, which reacts to an infection by steps that deliver chemicals to produce fever -The body temp. regulations are dependent in the areas of it

Osmotic thirst

-Results from eating salty foods -Thirst triggered by certain neurons that detect the loss of their own water -Water must be absorbed through the digestive system -Delivered by the blood to the brain -Takes 15min

Sodium-specific hunger

-Strong craving for salty foods -Depends partly on hormones -When sodium reserves are low, the adrenal glands produce aldosterone, a hormone that causes the kidneys, salivary glands, and sweat glands to retain salt.

· OVLT Receptors (Organum Vasculosum Laminae Terminals)

-Those axons combine with input from the OVLT, the stomach, and elsewhere to provide input to the hypothalamus -The lateral preoptic area and surrounding parts of the hypothalamus control drinking -The supraoptic nucleus and the paraventricular nucleus (PVN) control the rate at which the posterior pituitary releases vasopressin.

What is some advantages of having a constantly high body temperature?

-We spend about 2/3 of our total energy maintaining body temp. (basal metabolism) -If we didn't maintain a constant, high body temp., we could eat less & spend less effort finding food. -Reproductive cells require a cooler environment than the rest of the body.

Bulimia nervosa

A condition in which people alternate between binges of overeating and period of strict dieting. Some force vomiting after eating. -Show a variety of biochemical abnormalities, including increased production of ghrelin.

Vassopressin (ADH)

A hormone released by the posterior pituitary -Raises blood pressure by constricting blood vessels -Helps to compensate for decreased water volume -Enables the kidneys to reabsorb water & excrete highly concentrated urine

Set point

A single value that the body works to maintain (ex. Levels of water, oxygen, glucose, calcium, protein, fat, and acidity in the body)

Hypovolemic thirst

A thirst resulting from loss of fluids due to bleeding or sweating. -Thirst associated with low volume of body fluids

Small intestines

After the stomach stores food then it is released into the small intestine -Has enzyme that digest proteins, fats, and carbs, and absorbs digested materials into the blood -Large Intestine -Absorbs water & minerals & lubricates the remaining materials to pass as feces

Hunger

Animals vary in their eating strategies

Glucose, Insulin, and Glucagon

Digestion converts much of a meal into glucose -Pancreatic hormones, insulin and glucagon, regulate the flow of glucose into cells -Immediately before, during, and after a meal, the pancreas increases release of insulin, which enables glucose to enter the cells, except for brain cells, where glucose doesn't need insulin to enter. -Some of the excess glucose produced by a meal enters the liver, which converts it to glycogen & stores it -Some enters fat cells, which convert it to fat & store it -The pancreas increases release of glucagon, stimulating the liver to convert some of its stored glycogen back to glucose. -Glucagon: Hormone released by the pancreas when glucose levels fall -Stimulates the liver to convert some of its stored glycogen to glucose -When glucose levels rise, the pancreas releases insulin, which helps glucose enter cells, including liver cells and fat cells that store fuel for future use.

Anorexia nervosa

Disorder characterized by refusal to eat enough to remain healthy -Reveal abnormalities in the brain of dopamine release and other variables, these abnormalities are probably the result of prolonged weight loss rather than the cause. -Not due to depression

CCK (cholecystokinin)

Distension of the duodenum releases this hormone which limits the meal size in 2 ways: -Constricts the sphincter muscle between the stomach & the duodenum, causing the stomach to hold its contents & fill more quickly than usual -Speeds up stomach distension -Stimulates the vagus nerve to send signals to the hypothalamus to release CCK to trigger decreased feeding.

Basal metabolism

Energy used to maintain a constant body temperature while at rest.

Digestion begins in the mouth

Enzymes in saliva break down carbs. -Function: -Break down food into smaller molecules that the cells can use

Hydrochloric acid (HCL)

Enzymes in the stomach digest proteins.

Sham feeding experiments

Everything an animal eats leaks out of a tube connected to the stomach or esophagus -Doesn't produce satiety

The lateral hypothalamus

Feeding related functions: -Controls insulin secretion -Alters taste responsiveness Stimulation of the lateral hypothalamus increases the drive to eat -Damage to this area causes aversion to food

Negative feedback

Homeostatic processes that reduce discrepancies from the set point.

Orexin (animals)

Increases animals' persistence in seeking food -If orexin receptors are blocked, an animal becomes less active and less likely to work reinforcement of any kind -Stimulation of orexin receptors increase activity & motivation

Ventromedial hypothalamus

Inhibits feeding -Damage to this nucleus leads to overeating & weight gain -Increased stomach motility; stomach empties faster than normal

Type I Diabetes

Insulin levels remain constantly low, but blood glucose levels are high -Excrete most of glucose

Consumption of Dairy Products

Most mammals at about the age of weaning lose the intestinal enzyme lactase, which is necessary for metabolizing lactose, the sugar in milk -The declining level of lactase may be an evolved mech.

Shivering

Muscle contractions that generate heat -Decreased blood flow to the skin prevents the blood from cooling too much. Warm internal organ = Cold skin

Monogenic obesity

Occurs when a single gene leads to obesity without other physical or mental abnormalities

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

Paraventricular nucleus (PVN)

Output from the arcuate nucleus goes to the PVN of the hypothalamus -Inhibits the lateral hypothalamus, an area important for eating -Hunger cells in the arcuate nucleus inhibit the PVN and the PVN inhibits the Lateral Hypothalamus -Inhibiting an inhibitor produces net excitation, and that is how the stimuli for hunger increase eating & arousal

Duodenum

Part of the small intestine adjoining the stomach; first digestive site that absorbs nutrients. -Nerves from it inform the brain about distension, and the type and amount of nutrition

Gastric bypass surgery

Part of the stomach is removed or sewed off so that food cannot enter -Stomach distension is a major contributor to satiety -10-20% of people experience serious side effects, including infections, bowel obstruction, leakage of food, and nutritional deficiencies

Fever

Reflects an increased body temp. set point, directed by the hypothalamus. -Benefits: Certain bacteria grow less vigorously -Immune system works more vigorously -Fever above 39C (103F) does the body more harm than good -Fever above 41C (109F) is life threatening

Polygenic or common obesity

Relates to many genes, each of which slightly increases the probability of obesity

Homeostasis

Temperature regulation and other biological processes that keep certain body variables within a fixed range.

Osmotic pressure

Tendency of water to flow across a semi-permeable membrane from the area of low solute concentration to the area of high solute concentration. - (High Concentration) Solutes inside & outside a cell create this pressure -Occurs when solutes are more concentrated on one side of the membrane -The brain detects this pressure from: -Receptors around the third ventricle including the OVLT and the SFO (subfornical organ) -Detect op & sodium content of the blood -Weak blood brain barrier

Allostasis

The adaptive way in which the body anticipates needs depending on the situation. -Adjustment of the range, increasing it or decreasing it as circumstances change.

Leptin

The body's fat cells produce it which signals the brain to increase or decrease eating -Low levels of it increase hunger -High levels reduce eating & increase physical & immune system activity -The more fat cells, the more leptin -Almost all overweight people already produce plenty of leptin -Leptin sensitivity declines during pregnancy and in animals preparing for hibernation, also declines as a result of obesity.

Ghrelin

The hunger sensitive cells receive excitatory input from the taste pathway and from axons releasing this neurotransmitter -Acts on the hypothalamus to increase appetite

Syndromal obesity

When a gene causes a medical problem that includes obesity -Prader Willi syndrome: a genetic condition marked by mental retardation, short stature, and obesity -Problem relates to an inability to turn off ghrelin release -Ghrelin acts on the hypothalamus to increase appetite

raphe nucleus

controls mech. such as shivering, sweating, changes in heart rate and metabolism, and changes in blood flow to the skin.