metabolic equilibrium actively maintained by several complex biological mechanisms that operate via the autonomic nervous system to offset disrupting changes
eating or drinking
the variable controlled in a regulatory process; for example, temperature in a heating system
The optional value of the system variable in a regulatory mechanism
in a regulatory process, a mechanism that signals when the system variable deviates from its set point
in a regulatory process, the mechanism that is capable of changing the value of the system variable
A process whereby the effect produced by an action serves to diminish of terminate that action; a characteristic of regulatory systems.
A brain mechanism that causes cessation of hunger or thirst, produced by adequate and availaable suppliess of nutrients or water
liquid contained inside the cell membranes (usually containing dissolved solutes)
all body fluid other than that contained within cells; includes plasma and interstitial fluid, cerebrospinal fluidd
the fluid within the circulatory system; blood plasma.
The fluid that bathes the cells, filling the space between the cells of the body (the "interstices")
Equal in osmotic pressure to the contents of a cell. A cell placed in an isotonic solution neither gains nor loses water
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
describes a solution whose solute concentration is lower than the solute concentration inside a cell, which will cause it to absorb water, though the process of osmosis
a blood disorder consisting of a decrease in the volume of circulating blood (intravascular fluid)
thirst produced by an increase in the osmotic pressure of the interstitial fluid relative to the intracellular fluid, thus producing cellular dehydration
A neuron that detects changes in the solute concentration of the interstitial fluid that surrounds it.
A ploysaccharide often referred to as animal starch; stored in liver and muscle; constitutes the short term store of nutrients
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
A pancreatic hormone that promotes the conversion of liver glycogen into glucose
The form of fat storage in adipose cells; consists of a molecule of glycerol joined with three fatty acids.
A substance derived from the breakdown of triglycerides, along with fatty acids; can be converted by the liver into glucose
A substance derived from the breakdown of triglycerides, along with glycerol; can be metabolized by most cells of the body except for the brain
phase of metabolism during which some nutrients are not available from the digestive system: glucose, amino acids, fatty acids derived from glycogen, protein, adipose tissue
phase of metabolism during which nutrients are absorbed from the digestive system; glucose & 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
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
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
A drug that inhibits fatty acid metabolism and produces lipoprivic hunger.
A peptide hormone released by the stomach that increases eating; also produced by neurons in the brain
Hepatic Portal Vein
A large, circulatory channel that conveys nutrient-laden blood from the small intestine to the liver, which regulates the blood's nutrient content
first portion of the small intestine, attached directly to the stomach.
A hormone secreted by the duodenum that regulates gastric mobility and causes the gallbladder (cholecyst) to contract; appears to provide a satiety signal transmitted to the brain through the vagus nerve.
Peptide YY3-36 (PYY)
A peptide released by the gastrointestinal system after a meal in amounts proportional to the size of the meal.
A strain of mice whose obesity and low metabolic rate is caused by a mutation that prevents the production of leptin.
A hormone secreted by adipose tissue; decreases food intake and increases metabolic rate, primarily by inhibiting NPY-secreting neurons in the arcuate nucleus
A surgical procedure that severs the brain stem that disconnects the forebrain from the hindbrain so that the muscles involved in ingestion (out of reflex) can bet studied
Melanin Concentrating Hormone (MCH)
one of two peptide neurotransmitters found in a system of lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate
One of two peptide neurotransmitters found in a system of lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate. Also called hypocretin
A peptide NT found in a system of neurons of the arcuate nucleus that stimulate feeding, insulin and glucocorticoid secretion, decrease the breakdown of triglycerides, and decrease body temperature.
a nucleus in the base of the hypothalamus that controls secretions of the anterior pituitary gland; contains NPY-secretig neurons involved in feeding and control of metabolism
Paraventricular Nucleus (PVN)
A nucleus of the hypothalamus located adjacent to the dorsal third ventricle; contains neurons involved in control of the autonomic nervous system and the posterior pituitary gland.
Agouti-related protein (AGRP)
a neuropeptide that acts as an antagonist at MC-4 receptors and increases eating
Cocaine and amphetamine regulated transcript; a peptide neurotransmitter found in a system of neurons of the arcuate nucleus that inhibit feeding.
a-melanocyte-stimulating hormone (a-MSH)
A neuropeptide that acts as an agonist at MC-4 receptors and inhibits eating
Melanocortin-4 receptor (MC-4R)
A receptor found in the brain that binds with a-MSH and agouti-related protein; plays a role in control of appetite.
Uncoupling Protein (UCP)
A mitochondrial protein that facilitates the conversion of nutrients into heat.
eating disorder; severe weight loss accompanied by obsessive worrying about weight gain despite the fact the person is 10-15% below normal body weight; symptoms include: absence of 3 menstrual periods (females), distorted body image, intense fear of weight gain, dull eyes, baggy skin, dull hair, sallow skin, listlessness, overexercises, obsession about amount of food eaten; Onset: early adolescence, more white middle-class females; often comorbid with OCD
eating disorder; recurrent episodes of binging and purging (massive eating in private, hiding out then throwing up or laxative usage), looks normal in weight (often) and is obsessed with maintaining weight not necessarily losing weight ; symptoms include: bruising on hand, suspicious behavior, binging/purging, smell from skin and mouth, lank hair, rotting teeth (eventually), puffy skin; Onset: late adolescence, more white middle-class females, but rising in white males
overfatness to the point of injuring health. Obesity is often defined as 20 percent or more above the appropriate weight for height
goal: achieve on optimal level of balance, homeostasis, via adaptive internal self regulation mechanisms
achieved by: potentiation~ making particular behaviors, perceptions & feelings MORE probable
Physiological Regulation Mechanisms for Feeding Behavior
System variable & set point
nutrients monitored: carbohydrates, fats, amino acids, vitamins & minerals
hunger due: glucoprivation (glucose deprived) or lipoprivation (fewer fatty acids available)
ST reservoir: carbs in liver & muscles, glucose is converted to glycogen for ST storage
LT reservoir: Carbs & amino acids get stored LT in adipose tissue (triglycerides ~ fat cells)
Physiological Regulation Mechanisms for Feeding Behavior
Nutrient related detectors
Absorptive phase (PNS active):
nutrients being ABSORBED in digestive tract, pancreas secretes insulin so nutrient storage, ST: liver & muscles, LT: triglycerides ~ fat brain detects insulin, liver detects nutrients, CNS & body cells use glucose as a fuel
Fasting phase (SNS activity increases):
digestive tract is empty, glucose levels drop, fall detected by cells in pancreas & brain, pancreas then stops insulin secretion & secretes glucagon so glycogen to glucose no insulin so only CNS can be fed by liver
eating initiation due to GHRELIN, social, enviro factors (clock, smell of food, time w/ friends) physiological hunger signals: fall in blood glucose levels (glucoprivation) & lipoprivation liver receptors send info about low glucose & fatty acids to brain via the vagus nerve
Anticipatory Satiety Mechanisms
ST info: gut (stomach, small intestine, liver) & blood levels insulin, insulin receptors in brain
ST: CCK secreted when ingesting fat whereas PYY released in amount proportional to calories
LT: signals arising from adipose tissue (leptin) may alter brain sensitivity, stop eating sooner
Lateral Hypothalamus (LH)
~Role: hunger center, activity increases eating, stimulates hunger & reduces metabolic rate
~LH cells have OREXIN or melanin-concentrating hormone (MCH): eating initiation role, infusion NPY into LH will trigger ravenous eating via stimulating LH NPY receptors, if bilaterally destroy LH (electrolytic or ibotenic acid) then refuse to eat so anorexic
Paraventricular Nucleus (PVN)
~Role: carb & general consumption, NPY, NE & 5-HT receptors, also ANS regulation
~Carbs: NE or 5-HT antagonist increases carb intake, 5-HT/agonist decreases card intake
~General eating: NPY potent stimulator eating, if block NPY receptors then block feeding NPY levels increase when animal is food deprived, NPY levels decrease when eats again
Arcuate Nucleus (ARC)
~Role: satiety effects, inhibits eating: leptin (LT) & PPY (ST) receptors, NPY neurons ARC
~ARC NPY Neurons have ghrelin receptors; stimulate NPY neurons so initiates eating, leptin inhibits NPY/AGRP-secreting neurons: increases metabolic rate, suppresses eating neurons secrete CART, a peptide that suppresses eating, leptin activates these neurons, CART neurons have inhibitory connections with LH OREXIN & MCH neurons so SATIETY
Biology matters for metabolism: evidence from twin & adoption studies, UCP3 research too environment matters: Pima indians of southwestern USA v. Northwestern Mexico very obese: metabolically efficient readily store nutrients into their adipose tissue, Ghrelin animal models/leptin insensitivity: 3 obese rodent types all have leptin receptor gene issues
preoccupied with food yet refuse to eat, exercise excessively, intense fear of becoming obese
cinnamon roll study: insulin levels higher than thin non-anorexic girls who readily eat food,
fMRI research results: food is perceived as threatening as well as disgusting since food stimuli activated left medial PFC & anterior cingulate cortex (like OCD & substance abuse).
bouts of eating binges, often followed by purging by vomiting or laxatives (some anorexic), although overall "normal" or slightly overweight on average so harder for others to detect
PROZAC (SSRI)~ effective remedy for some; likely due to decreased pressure to consume carbs