Chapter 12
44
homeostasis
The process by which the body's substances and characteristics (such as temperature and glucose level) are maintained at their optimal level.
ingestive behavior
Eating or drinking.
system variable
A variable that is controlled by a regulatory mechanism; for example, temperature in a heating system.
set point
The optimal value of the system variable in a regulatory mechanism.
detector
In a regulatory process, a mechanism that signals when the system variable deviates from its set point.
correctional mechanism
In a regulatory process, the mechanism that is capable of changing the value of the system variable.
negative feedback
A process whereby the effect produced by an action serves to diminish or terminate that action; a characteristic of regulatory systems.
satiety mechanism
A brain mechanism that causes cessation of hunger or thirst, produced by adequate and available supplies of nutrients or water.
intracellular fluid
The fluid contained within cells.
extracellular fluid
All body fluids outside cells: interstitial fluid, blood plasma, and cerebrospinal fluid.
intravascular fluid
The fluid found within the blood vessels.
interstitial fluid
The fluid that bathes the cells, filling the space between the cells of the body (the "interstices").
isotonic
Equal in osmotic pressure to the contents of a cell. A cell placed in an isotonic solution neither gains nor loses water.
hypertonic
The characteristic of a solution that contains enough solute that it will draw water out of a cell placed in it, through the process of osmosis.
hypotonic
The characteristic of a solution that contains so little solute that a cell placed in it will absorb water, through the process of osmosis.
hypovolemia
Reduction in the volume of the intravascular fluid.
nephron
A functional unit of the kidney; extracts fluid from the blood and carries the fluid, through collecting ducts, to the ureter.
ureter
One of two tubes that carries urine from the kidneys to the bladder.
aldosterone
A hormone of the adrenal cortex that causes the retention of sodium by the kidneys.
vasopressin
A hormone secreted by the posterior pituitary gland that causes the kidneys to excrete a more concentrated urine, thus retaining water in the body.
supraoptic nucleus
A hypothalamic nucleus that contains cell bodies of neurons that produce antidiuretic hormone and transport it through their axons to the posterior pituitary gland.
paraventricular nucleus
A hypothalamic nucleus that contains cell bodies of neurons that produce antidiuretic hormone and oxytocin and transport them through their axons to the posterior pituitary gland.
diabetes insipidus
The loss of excessive amounts of water through the kidneys; caused by lack of secretion of vasopressin.
osmometric thirst
Thirst produced by an increase in the osmotic pressure of the interstitial fluid relative to the intracellular fluid, thus producing cellular dehydration.
osmoreceptor
A neuron that detects changes in the solute concentration of the interstitial fluid that surrounds it.
OVLT/organum vasculosum of the lamina terminalis
A circumventricular organ located anterior to the anteroventral portion of the third ventricle; served by fenestrated capillaries and thus lacks a blood-brain barrier.
volumetric thirst
Thirst produced by hypovolemia.
colloid
A soluble, gluelike substance made of large molecules that cannot penetrate cell membranes.
salt appetite
A craving for sodium chloride.
renin
A hormone secreted by the kidneys that causes the conversion of angiotensinogen in the blood into angiotensin.
angiotensinogen
A protein in the blood that can be converted by renin to angiotensin.
angiotensin
A peptide hormone that constricts blood vessels, causes the secretion of aldosterone, and produces thirst and a salt appetite.
saralasin
A drug that blocks angiotensin receptors.
losartan
A drug that blocks angiotensin receptors.
nucleus of the solitary tract
A nucleus of the medulla that receives information from visceral organs and from the gustatory system.
subfornical organ/SFO
A small organ located in the confluence of the lateral ventricles, attached to the underside of the fornix; contains neurons that detect the presence of angiotensin in the blood and excite neural circuits that initiate drinking.
median preoptic nucleus
A small nucleus situated around the decussation of the anterior commissure; plays a role in thirst stimulated by angiotensin.
zona incerta
An oblong extension of the midbrain reticular formation, extending from the midbrain to the medial diencephalon.
furosemide
A diuretic; a drug that increases the production of urine.
esophageal fistula
A diversion of the esophagus so that when an animal eats or drink, the substance does not reach the stomach.
pylorus
The ring of smooth muscle at the junction of the stomach and duodenum that controls the release of the stomach contents.
duodenum
The portion of the small intestine immediately adjacent to the stomach.
hepatic portal vein
The vein that receives blood from the digestive system and passes it to the liver.
atrial natriuretic peptide
A peptide secreted by the atria of the heart when blood volume is higher than normal; increases water and sodium excretion, inhibits renin, vasopressin, and aldosterone secretion, and inhibits sodium appetite.
Feeding terms
30
glycogen
A polysaccharide often referred to as _animal starch;_ stored in liver and muscle; constitutes the short-term store of nutrients.
insulin
A pancreatic hormone that facilitates entry of glucose and amino acids into the cell, conversion of glucose into glycogen, and transport of fats into adipose tissue.
glucagon
A pancreatic hormone that promotes the conversion of liver glycogen into glucose.
triglyceride
The form of fat storage in adipose cells; consists of a molecule of glycerol joined with three fatty acids.
glycerol
A substance (also called glycerine) derived from the breakdown of triglycerides, along with fatty acids; can be converted by the liver into glucose.
fatty acid
A substance derived from the breakdown of triglycerides, along with glycerol; can be metabolized by most cells of the body except for the brain.
fasting phase
The phase of metabolism during which nutrients are not available from the digestive system; glucose, amino acids, and fatty acids are derived from glycogen, protein, and adipose tissue during this phase.
absorptive phase
The phase of metabolism during which nutrients are absorbed from the digestive system; glucose and amino acids constitute the principal source of energy for cells during this phase, and excess nutrients are stored in adipose tissue in the form of triglycerides.
sensory-specific satiety
Satiety for a specific food that has been ingested recently in the absence of general satiety for all foods.
conditioned flavor aversion
The avoidance of a relatively unfamiliar flavor that previously caused (or was followed by) illness.
glucoprivation
A dramatic fall in the level of glucose available to cells; can be caused by a fall in the blood level of glucose or by drugs that inhibit glucose metabolism.
lipoprivation
A dramatic fall in the level of fatty acids available to cells; usually caused by drugs that inhibit fatty-acid metabolism.
methyl palmoxirate/MP
A drug that inhibits fatty-acid metabolism and produces lipoprivic hunger.
mercaptoacetate/MA
A drug that inhibits fatty-acid metabolism and produces lipoprivic hunger.
capsaicin
An ingredient in hot peppers that can destroy small, unmyelinated sensory axons that innervate the internal organs.
2,5-AM
A drug that inhibits carbohydrate metabolism in the liver by making phosphate unavailable, thus blocking the production of ATP.
L-ethionine
A drug that inhibits carbohydrate metabolism in the liver by making adenosine unavailable, thus blocking the production of ATP.
sham feeding
Feeding behavior of an animal with an open gastric or esophageal fistula that prevents food from remaining in the stomach.
cholecystokinin/CCK
A hormone secreted by the duodenum that regulates gastric motility and causes the gallbladder (cholecyst) to contract; appears to provide a satiety signal transmitted to the brain through the vagus nerve.
ob mouse
A strain of mice whose obesity and low metabolic rate is caused by a mutation that prevents the production of leptin.
leptin
A hormone secreted by adipose tissue; decreased food intake and increased metabolic rate, primarily by inhibiting NPY-secreting neurons in the arcuate nucleus.
lateral parabrachial nucleus
A nucleus in the pons that receives gustatory information and information from the liver and digestive system and relays it to the forebrain.
neuropeptide Y/NPY
A peptide neurotransmitter whose release stimulates feeding, insulin and glucocorticoid secretion, decreased breakdown of triglycerides, and a decrease in body temperature.
arcuate nucleus
A nucleus in the base of the hypothalamus that controls secretions of the anterior pituitary gland; contains NPY-secreting neurons involved in feeding and control of metabolism.
galanin
A peptide neurotransmitter whose release stimulates ingestion of fats.
fenfluramine/FEN
A drug that causes the release of serotonin and inhibits eating.
agouti mouse
A strain of mice whose yellow fur and obesity are caused by a mutation that causes the production of a peptide that blocks MC4 receptors in the brain.
melanocortin-4 receptor/MC4-R
A receptor normally stimulated by the hormone melanocortin; responsible for the production of melanin; also plays a role in control of appetite.
anorexia nervosa
A disorder that most frequently afflicts young women; exaggerated concern with overweight that leads to excessive dieting and often compulsive exercising; can lead to starvation.
bulimia nervosa
Bouts of excessive hunger and eating, often followed by forced vomiting or purging with laxatives; sometimes seen in people with anorexia nervosa.