copyright © 2008 pearson allyn & bacon inc. 1 chapter 11 ingestive behavior this multimedia...

Copyright © 2008 Pearson Allyn & Bacon Inc.1

Chapter 11

Ingestive Behavior

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• Chapter 11 Outline

• Physiological Regulatory Mechanisms

• Drinking

• Eating: Some Facts about Metabolism

• What Starts a Meal?

• What Stops a Meal?

• Brain Mechanisms

• Eating Disorders



• Object – maintain the ____________________.

• ________________• The process by which the body’s substances and

characteristics (such as temperature and glucose level) are maintained at their _______________.

• Ingestive behavior• Eating or drinking.



• Regulatory mechanisms contain 4 components:

• 1. ______________• A variable that is controlled by a regulatory

mechanism; for example, temperature in a heating system.

• 2. ___________• The optimal value of the system variable in a

regulatory mechanism.



• 3. ______________• In a regulatory process, a mechanism that signals

when the system variable deviates from its set point.

• 4. ___________________• In a regulatory process, the mechanism that is

capable of changing the value of the system variable.



• _____________feedback – an essential characteristic of all regulatory mechanisms

• A process whereby the effect produced by an action serves to diminish or terminate that action.

• _________________• A brain mechanism that causes cessation of hunger or

thirst, produced by adequate and available supplies of nutrients or water.


Correctional mechanism – in a regulatory process, the mechanism capable of ___________________ of the system variable (fluid volume).


• Drinking

• Some facts about fluid balance• 4 fluid compartments

• 1. Intracellular fluid• The fluid contained within cells. (___%)

• Extracellular fluid• All body fluids outside cells: interstitial fluid, blood

plasma, and cerebrospinal fluid.

• 2. Intravascular fluid• The fluid found within blood vessels. (__%)


• Drinking

• Some facts about fluid balance

• 3. Interstitial fluid• The fluid that bathes the cells, filling the space

between the cells of the body (interstices). (__%)

• 4. Cerebral spinal fluid (1%)

• Isotonic• Equal in ______________________ to the contents of

a cell. A cell placed in an isotonic solution neither __________________________.


Relative size of fluid compartments.


• Drinking

• Some facts about fluid balance

• Hypertonic (may endanger cells)• The characteristic of a solution that contains enough

solute that it will _________________of a cell placed in it, through the process of osmosis.

• Hypotonic (may endanger cells)• The characteristic of a solution that contains so little

solute that a cell placed in it will ________ water, throughthe process of osmosis.

• _________________• Reduction in the volume of the intravascular fluid.


Movement of water molecules.


• Drinking

• Two types of thirst: • The body needs two sets of receptors, one for blood

volume, and one for cell volume.

• 1. __________________ thirst• Thirst produced by an increase in the osmotic

pressure of the interstitial fluid relative to the intracellular fluid, thus producing ________________.

• Osmoreceptor• A neuron that detects changes in the solute

concentration of the interstitial fluid that surrounds it. If this volume is too low – ________________.


The detectors in the ___________________________ respond to changes in the interstitial fluids that surround them.


MRI of brain stimulation from osmotic thirst.


• Drinking

• Two types of thirst

• Volumetric Thirst• Thirst caused by hypovolemia; occurs when the

___________________________________.• Loss of blood causes volumetric thirst. In this case

there is a loss of (1) salt as well as (2) water. The loss of salt produces a salt appetite.

• Two sets of receptors accomplish this dual function:

Set 1 is located in the kidneys (angiotensinogen).

Set 2 is located in the heart (atrial baroreceptors).


• Drinking

• Two types of thirst: (1) When the flow of blood to the kidneys decreases, the detector cells secrete an enzyme called renin.

• Renin• An enzyme secreted by the kidneys that causes the

conversion of a protein (angiotensinogen) in the blood into a hormone called angiotensin.

• Role of angiotensin

This hormone causes _______________________ (increasing blood pressure), it causes the kidneys to conserve water and sodium, and it initiates drinking and a ______________.


Detection of hypovolema.


• Neural Mechanisms of Thirst

• Subfornical organ (SFO) – the receptor site the initiates drinking.

• 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 ____________________.


• Neural Mechanisms of Thirst

• Receptor neurons in the SFO send their axons to the median preoptic nucleus.

• Median preoptic nucleus• A small nucleus situated around the decussation of

the anterior commissure; plays a role in thirst stimulated by angiotensin. Stimulation initiates ______________.


The subfornical organ and its connection to the median preoptic nucleus.

• Atrial Baroreceptors: the second set of receptors for volumetric thirst.

• When the blood volume falls, the atria of the heart becomes less full, and stretch receptors located in the atria detect this change. The decrement in blood volume is sent to the brain, and drinking behavior is stimulated in about 30 minutes (dogs).


• Eating and Fasting

• The control of eating is more complicated than the control of drinking and sodium intake.

• To stay alive all cells in the body must have a constant supply of fuel and oxygen.

• Metabolism has two phases:• Absorptive phase occurs when ______________ in the

digestive tract.• Fasting phase occurs when the digestive tract is ______.• Fuel reservoirs are necessary to keep the cells nourished

when the gut is empty.

The short-term reservoir stores _______________.

The long-term reservoir stores_____.Copyright © 2008 Pearson Allyn & Bacon Inc.24

• Liver, Insulin & Glycagen: (Short-term _____ calory capacity). The liver soaks up excess glucose and stores it as glycogen, and releases glucose from its reservoir when the digestive tract is empty.• When glucose and insulin are present in the blood, some of

the glucose is __________________________________.• Cells in the liver convert glucose into glycogen, and

glycogen is stored in the liver. Insulin, a pancreatic hormone regulates this process.

• When blood glucose begins to drop, the pancreas responds by stopping the _________________________________

• _______________________________________________.• The effect of glucagon is the reverse of that of insulin. It

stimulates the conversion of glycogen into glucose.


• When the short-term glucose resevoir becomes empty the body taps into the long-term reservoir (adipose tissue).• Adipose tissue is filled with fats (triglycerides).• Stimulation by the sympathetic branch of the ANS innervate

adipose tissue, the pancreas and the adrenal medulla..• ANS stimulation causes the triglycrides to be broken down

by glucagon and catecholamines into glycerol, & fatty acids.• Fatty acids can be metabolized by all the cells in the body

__________________.• The brain can only metabolize __________. The liver

takes up the _________________________________.• The brain can absorb glucose in the absence of _______.

All the other cells in the body require insulin to absorb glucose.




• ____________• A polysaccharide often referred to as ____________;

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 ________________.

• Triglyceride• 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_________________.

• 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 _________________________________________.



• Absorptive phase• The phase of metabolism during which nutrients are

absorbed from the digestive system; ____________• ___________________________________________

_______________________________________________________________________________________________________________________________________________________________________.


Absorptive & fasting phase.



• One mechanism is needed to start feeding when the fuel reservoir is being depleted, and a second mechanism is needed to stop ingestion when we eat more calories than needed.

• Signals from the environment

• An empty stomach is an important signal to eat.

• However, many environmental factors motivate us to eat including:

Sight of foodSmell of foodBehaviors related to food preparation



• Signals from the stomach

• ______________• A peptide hormone released by the stomach that

increases eating, also produced by neurons in the brain.

• Duodenum• The first portion of the small intestines, attached

directly to the stomach. The ghrelin receptors are in the duodenum.

• The secretion of ghrelin is suppressed when ghrelin receptors detect the presence of food in the duodenum. This system is not sensitive to _________________________.


Ghrelin levels & the onset of feeding.



• Metabolic signals

• ________________• 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.

• What detectors monitor the level of metabolic fuels?

• There are two sets of detectors:• 1. Located in the __________• 2. Located in the___________

• The liver receives blood from the intestines via the hepatic portal vein. Receptors in the liver are sensitive to glucoprivation, and lipoprivation. The vagus nerve sends this signal to the brain.

• Receptors in the _________ also detect glucoprivation.




• Metabolic signals

• 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.

• Hepatic portal vein• The vein that transports blood from the digestive

system to the liver.


Blood flow to the liver via the hepatic portal vein exposes receptors in the liver to changes in lipid and glucose levels.


• What Stops a Meal?

• Short-term regulation of the sense of satiety.

• 1. Liver sends satiety signals to the brain via the vagus nerve.

• 2. Insulin receptors in the brain serve to indicate that the

body is in the ________________of carbohydrate ingestion.

• 3. Cholecystokinin• A hormone secreted by the duodenum that regulates

gastric motility and causes the gallbladder (cholecyst)to contract; appears to provide a satiety signaltransmitted to the brain through the vagus nerve. Receptors are between the stomach & duodenum.


• Long-Term Satiety: Signals from Adipose Tissue

• __ mouse• A strain of mice whose obesity and low metabolic

rate is caused by a mutation that prevents theproduction of leptin.

• Leptin• A hormone secreted by ______________; decreases

food intake and increases metabolic rate, primarilyby inhibiting NPY-secreting neurons in the arcuate nucleus.


Untreated ob mouse ob mouse treated with leptin



• Brain Stem

• Decerebration• A surgical procedure that severs the brain stem,

disconnecting the _________________________.

• The only behaviors that a decerebrate animal can display are those that are directly controlled by neural circuits located within the ______________________.

• Animal studies indicate that the brain stem contains neural circuits that can control at least some aspects of food intake.



• Hypothalamus : Role in hunger • Lesions of ___________hypothalamus produce cessation of

eating and drinking. • Lesions of _____________hypothalamus produce gross

obesity.

• Melanin-concentrating hormone (MCH)• A peptide neurotransmitter found in a system of

lateral hypothalamic neurons that stimulate appetiteand reduce metabolic rate.

• Orexin (AKA hypocretin involved in sleep regulation)• A peptide neurotransmitter found in a system of lateral

hypothalamic neurons that stimulate appetite andreduce metabolic rate.

Revision 2006 PSB

Hypothalamic Centers

Ventromedial hypothalamus (VMH) depresses hunger (stimulation). Destroy it

and the animal eats excessively.

Richard H

oward


Feeding circuit



• Hypothalamus : Role in hunger

• Neuropeptide Y (NPY)• A peptide neurotransmitter found in a system of

neurons of the arcuate nucleus that:

______________feeding

Stimulates insulin and glucocorticoid secretion

Stimulates the breakdown of triglycerides

Decreases body _______________



• Hypothalamus : Role in hunger

• _____________ nucleus• A nucleus in the base of the hypothalamus that

controls secretions of the _____________ pituitary gland; contains NPY-secreting neurons involved in feeding and control of metabolism.

• ________________ nucleus• A nucleus of the hypothalamus located adjacent to the

dorsal third ventricle; contains neurons involved in control of the autonomic nervous system and the _____________ pituitary gland.


Hunger signal pathway to the lateral hypothalamus.

Infusion of NPY to the arcuate nucleus induces ______________.



• Hypothalamus: Role in hunger

• NPY neurons in hypothalamus release AGRP at their terminals. This peptide induces eating for intervals up to 6 days in duration.

• Agouti-related peptide (AGRP)• A potent and extremely long-lasting orexigen; A

neuropeptide that acts as an antagonist at MC-4 receptors and increases eating.

• THC may stimulate the AGRP pathway. Used to stimulate ________________________.


Satiety signal pathway.

Leptin receptors induce an inhibitory effect on feeding, & prevent a decrease in metabolic rate. The satiety signal from adipose tissue ________________ the brain to ________________.



• Hypothalamus: Role in satiety

• CART (arcuate nucleus)• Cocaine and amphetamine-regulated transcript; a

peptide neurotransmitter found in a system of neurons of the arcuate nucleus that inhibits feeding.

Revision 2006 PSB

Set-Point Theory

Manipulating lateral and ventromedial hypothalamus and alters the body’s

“weight thermostat.”

If weight is lost – food intake increases and energy expenditure decreases. If weight is

gained – the opposite takes place.

Revision 2006 PSB

Hunger

• Under feeding – malnourishment

• Over feeding – obesity• If you eat just one extra carrot a day (20 calories), you will

gain 2 pounds a year, 20 pounds a decade. Thus the regulation of food intake must to very precise to defend a set body weight.



• Obesity

• Obesity is a widespread problem that can have serious medical consequences.

• In the United States, 67% of males and 62% of females overweight (exceed a body mass index of 25).

• Known health hazards of obesity include ___________________________________________________________________________________.


11.21

2008 Data


Change in Obesity Rates


Revision 2006 PSB

Hunger and Eating

Body Weights of Twins• Identical twins are more similar in body weight than are fraternal twins.

• Genetic factors play a large role in body weight.

Revision 2006 PSB

Stress, food cues and appetite

• Stress: ____________body weight individuals lose appetite with increases in stress while __________ individuals show the reverse pattern.

• ____________________________: overweight individuals feel hungrier to food-related cues than do average weight individuals.

Revision 2006 PSB

Can you “catch” obesity?

• There is a lot of good advice to help us avoid becoming fat, such as eat less and exercise. But if some researchers are right, you may soon be hearing a surprising new piece of advice:

_________________.

Revision 2006 PSB

Catching Obesity

• There is growing evidence that some viruses may cause obesity, thus making obesity contagious, said Leah Whigham of the University of Wisconsin, Madison, lead researcher in a new study on the subject.

•Her study found that a ______________________ AD-37 causes _____________.



• Obesity• People with sedentary occupations eat slightly less than

active people (2400 kcal/day), but burn only about 300 k cal in physical activity.

• If calories in exceed calories out, then obesity is the result.

• Uncoupling protein (UCP)• A mitochondrial protein that facilitates the conversion

of nutrients into heat. It strongly influences metabolic efficiency.



• Anorexia Nervosa and Bulimia Nervosa

• ____________________• A disorder that most frequently afflicts young women;

exaggerated concern with being overweight that leads to excessive dieting and often compulsive exercising; can lead to starvation.

• _____________________• Bouts of excessive hunger and eating; often followed

by forced vomiting or purging with laxatives; sometimes seen in people with anorexia nervosa.

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