Chapter 12 - Ingestive behaviours Flashcards
the process by which the body’s substances and characteristics are maintained at their optimal level
homeostasis
a variable that is controlled by a regulatory mechanism
ex: temperature in a heating system
system variable
the optimal value of the system variable in a regulatory mechanism
set point
a polysaccharide often referred to as animals starch; stored in the liver and muscle; constitutes the short-term store of nutrients
- complex, insoluble carbohydrate
glycogen
a pancreatic hormone that facilitates entry of glucose and amino acids into the cell, conversion of glucose into glycogen, and transport of fates into adipose tissue
- a peptide hormone produced by the pancreas
- Promotes use of glucose as 1o energy source.
- Promotes conversion of fuels to storable forms; glucose to glycogen and fat, amino acids to proteins.
- Promotes storage of glycogen in liver and muscle, fat in adipose tissue, and protein in muscles.
insulin
a pancreatic hormone that promotes the conversion of liver glycogen into glucose
- opposite effects of insulin
- stimulates conversion of glycogen to glucose
glucagon
a substance derived from the breakdown of triglycerides, along with fatty acids; can be converted by liver into glucose
glycerol
the form of fat storage in adipose cells; consists of a molecule of glycerol joined with three fatty acids
triglyceride
a substance derived from the breakdown of triglycerides, along with glycerol; can be metabolized by most cells of the body expect the brain
fatty acid
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
- decrease in insulin
- increase in glucagon
fasting phase
the phase of metabolism during which nutrients are absorbed from the digestive system; glucose and amino acids constitute the principle source of energy for cells during this phase, and excess nutrients are stored in adipose tissue in the form of triglycerides
- nutrients absorbed from the bloodstream to meet body needs (energy source)
- increase in insulin, decrease in glucagon
absorptive phase
preparoty stage, begins with sensory (head) cues) ie: sight, smell, thought of food. ends with beginning of absorption in bloodstream.
- increase in insulin
- decrease in glucagon
cephalic phase
a peptide hormone release by the stomach that increases eating; also produced by neurons in the brain
- stimulate thoughts about food
- released by digestive system
- levels go up before a meal, down after
ghrelin
the first portion of the small intestine, attached directly to the stomach
- contains receptors that control secretion of ghrelin
duedenum
internal state of an animal seeking food
hunger
animals are drawn to eat not by energy deficits but, by the anticipated pleasure of eating
positive incentive theory
anticipated pleasure of a behaviour
positive incentive value
a dramatic fall in the level of glucose avaliable to cells; can be caused by a fall in the blood level of glucose or by drugs that inhibit glucose metabolism.
glucoprivation
a dramatic fall in the level of fatty acids available to cells; usually caused by drugs that inhibit fatty acid metabolism
lipoprivation
the vein that transports blood from the digestive system to the liver
hepatic portal vein
a tube that drains out the contents of the stomach
gastric fistula
a hormone secreted by the duodenum that regulates gastric motility and causes the gallbladder to contract; appears to provide a satiety signal transmitted to the brain through the vagus nerve
- released by small intestine in response to presence of fats that control the rate of stomach emptying
- inhibits gastric contractions, causes plyorus to constrict
- acts on receptors between stomach and duodenum.
CCK
a peptide released by the gastrointestinal system after a meal in amounts proportional to the size of the meal
- only nutrients cause release
PYY
a strain of nice whose obesity and low metabolic rate are caused by a mutation that prevents the production of leptin
ob mouse
a hormone secreted by adipose tissue; decreases food intake and increases metabolic rate, primarily by inhibiting NPY-secreting neurons in the arcuate nucleus
- weight gained, increase in fat mass, more released
- weight lost, fatty tissue reduces, decreased amount circulating in body
leptin
small amounts of food consumed before a meal increase hunger rather than reduce it
appetizer effect
as you eat one food, the positive-incentive value of all foods declines a bit, but plummets for that particular food. You will be satiated for that food but are likely to begin eating again if offered a different food
Two kinds of effects:
1) brief effects that influence food selection within a meal 2) enduring effects influencing selection from meal to meal.
Some foods immune: rice, bread, potatoes, sweets, green salads can be eaten daily with only slight drop in palatability (is the hedonic reward provided by foods or fluids that are agreeable to the “palate” in regard to the homeostatic satisfaction of nutritional, water, or energy needs.)
Sensory-specific satiety
Mechanism for adjustment of energy efficiency in response to body fat levels is
diet-induced thermogenesis
levels at which factors that contribute to body weight reach an equilibrium
settling (balance) point
a surgrical procedure that severs the brain stem, disconnecting the hindbrain from the forebrain
decerebration
a peptide neurotransmitter found in a system of the lateral hypothalamic neurons that stimulate appetite and reduce metabolic rate
MCH (melanin-concentrating hormone)
a peptide neurotransmitter found in a system of the lateral hypothamic neurons that stimulate appetite and reduce metabolic rate
orexin
a peptide neurotransmitter 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
NPY
a nucleus in the base of the hypothalamus that controls secretion of the anterior pituitary gland; contains NPY-secreting neurons involved in feeding and control of metabolism
arcuate nucleus
a nucleus of the hypothalamus located adjacent to the dorsal third ventricle; contains neurons involved in the control of autonomic nervous system and the posterior pituitary gland
PVN
a neuropeptide that acts as competitive antagonist at MC-4 receptors and increases eating
AGRP
cocaine and amphetamine-regulated transcript; a peptide neurotransmitter found in a system of the arcuate nucleus that inhibits feeding
CART
a neuropeptide that acts as an agonist at MC-4 receptors and inhibits eating
a-MSH
a receptor found in the brain that binds with a-MSH and agouti-related protein; plays a role in control of appetite
MC-4R
appetite supressing chemicals
anorexigens
a disorder that most frequntly afflicts young women; exaggerated concern with being overweight that leads to excessive dieting and often compulsive exercising; can lead to starvation
anorexia nervosa
bouts of excessive hunger and eating, often followed by forced vomiting or purging with laxatives; sometimes seen in people with anorexia nervosa
bulimia nervosa
regulates cell cycling, growth and division according to nutrient availability.
mTOR
potent inhibitor of mTORC1.
RAP
We showed that acute injection of RAP, which induces a transient suppression of mTOR, can have a long-lasting effect on the set point for body weight, suggesting a novel role of mTOR in body weight regulation.
Moreover, a single injection has distinct advantage as it can avoid side effects of chronic RAP administration such as glucose intolerance.
We propose that RAP and related compounds could be used as tools to investigate how the defended level (apparent set point) of body weight is determined and to complement other weight loss strategies.
mTOR/RAP/body weight summary
deletion of several genes in segment of chromosome 15
involved in production of proteins critical to normal functioning of the hypothalamus
- caused by random accident that occur during production of fathers sperm
Prader-Willi Syndrome
brain recieves hunger signals through
vagus nerve
fall in blood glucose levels, stimulates hunger
hypoglycemia
