1. The document outlines various physiological regulatory mechanisms involved in eating and drinking behaviors, including homeostatic processes that maintain optimal levels of substances and characteristics in the body. 2. Key factors that start and stop meals are discussed, such as metabolic signals like glucoprivation and lipoprivation that stimulate eating when fuel levels drop, as well as gastric and intestinal factors that provide satiety signals. 3. Brain mechanisms centered in the hypothalamus that control hunger and satiety are examined, including neurons that secrete factors like NPY, CART, and AGRP that stimulate or inhibit feeding behaviors. The hypothalamus contains circuits that regulate metabolism and defend a set point for body weight.

1. 1
REVIEW

2. 2
Chapter 11 Outline
• Physiological Regulatory Mechanisms
• Drinking
• Eating: Some Facts about Metabolism
• What Starts a Meal?
• What Stops a Meal?
• Brain Mechanisms
• Eating Disorders

3. 3
• Physiological Regulatory Mechanisms
• Object – maintain the constancy of some internal
characteristic of the organism in the face of external
variability.
• 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
• 1. Eating
• 2. Drinking
•

4. 4
• Physiological Regulatory Mechanisms
• Regulatory mechanisms contain 4 components:
• 1. System Variable
• A variable that is controlled by a regulatory mechanism; for
example, temperature in a heating system.
• 2. Set Point
• The optimal value of the system variable in a regulatory
mechanism.

5. 5
• Physiological Regulatory Mechanisms
• 3. Detector
• In a regulatory process, a mechanism that signals when the
system variable deviates from its set point.
• 4. Correlational Mechanism
• In a regulatory process, the mechanism that is capable of
changing the value of the system variable.

6. 6
• Physiological Regulatory Mechanisms
• Negative feedback – an essential characteristic of all regulatory
mechanisms
• A process whereby the effect produced by an action serves to diminish
or terminate that action.
• Satiety Mechanism
• A brain mechanism that causes cessation of hunger or thirst, produced
by adequate and available supplies of nutrients or water.

7. 7
Correctional mechanism – in a regulatory process, the
mechanism capable of Changing of the system variable
(fluid volume).

8. 8
• Drinking
• Some facts about fluid balance
• 4 fluid compartments
• 1. Intracellular fluid
• The fluid contain in cell. (67%)
• Extracellular fluid
• All body fluids outside cells: interstitial fluid ,
Blood plasma, cerebrospinal fluid
• 2. Intravascular fluid
• The fluid found within blood vessels. (7%)

9. 9
• Drinking
• Describe some facts about fluid balance!
• 3. Interstitial fluid
• The fluid that bathes the cells, filling the space between the cells of the
body (interstices). (26%)
• 4. Cerebral spinal fluid (1%)
• one of the extracellular fluid
• Isotonic
• Equal in osmotic pressure to the contents of a cell. A cell placed in an
isotonic solution neither gains nor loses water.

10. 10
Relative size of fluid
compartments.
Describe the fluid
works!

11. 11
• Drinking
• Hypertonic (may endanger cells)
• 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 (may endanger cells)
• 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.

12. 12
Describe the Movement of water molecules!

13. 13
• Drinking
• Two types of thirst:
• The body needs two sets of receptors, one for blood volume,
and one for cell volume.
• 1. 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. If this volume is too low – they will
lose water through osmosis.

14. 14
The detectors in the existence of neurons respond to changes
in the interstitial fluids that surround them.

15. 15
What behavior that stimulates this brain works?

16. 16
• Drinking
• Two types of thirst
• Volumetric Thirst
• Thirst caused by hypovolemia; occurs when the volume of the blood
plasma-the intravascular volume-decreases.
• Loss of blood causes pure volumetric thirst. In this case there is a loss
of (1) salt as well as (2) water. The loss of salt produces a sodium.
• Two sets of receptors accomplish this dual function:
• Set 1 is located in the kidneys (angiotensin).
• Set 2 is located in the heart (renin).

17. 17
• 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 the retention of sodium and water (increasing blood
pressure), it causes the kidneys to conserve water and sodium, and it initiates
drinking and a salt appetite.

18. 18
Describe how to detect
hypovolema, using this
picture!

19. 19
• 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
initiate drinking.

20. 20
• 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 thirst.

21. • Atria Baroreceptor: 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 20 minutes (dogs).
21

22. • 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 food is present in the digestive tract.
• Fasting phase occurs when the digestive tract is empty.
• Fuel reservoirs are necessary to keep the cells nourished when the gut is
empty.
• The short-term reservoir stores carbohydrates.
• The long-term reservoir stores fats.
22

23. • Liver, Insulin & Glycagen: (Short-term reservoir 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 used as a fuel, and some of it stored as glycogen .
• 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 secretion of insulin and start secreting glucagon .
• The effect of glucagon is the reverse of that of insulin. It
stimulates long term fat reservoir .
23

24. • When the short-term glucose reservoir becomes empty the
body taps into the long-term reservoir (adipose tissue).
• Adipose tissue is filled with fat or the other name is fat tissue.
• 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 except the brain,
which needs glucose.
• The brain can only metabolize glycerol. The liver takes up the glycerol and
converts it to glucose.
• The brain can absorb glucose in the absence of insulin. All the other cells in
the body require insulin to absorb glucose.
24

25. 25
• Eating: Some Facts about Metabolism
• Glycolygen
• 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.

26. 26
• Eating: Some Facts about Metabolism
• 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.

27. 27
• Eating: Some Facts about Metabolism
• Glycerol
• A substance 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.

28. 28
• Eating: Some Facts about Metabolism
• 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.

29. 29
• Eating: Some Facts about Metabolism
• Describe about 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.

30. 30
What Starts a Meal?
• One mechanism is needed to start feeding when the
long-term nutrient is becoming depleted, and a second
mechanism is needed to stop ingestion when we take
callories than we need.
• Signals from the environment
• Hunger signal is an important signal to eat.
• However, many environmental factors motivate us to eat including:
• 1. The sight of a plates of the food.
• 2. The smell of the food.
• 3. The pressence of other people sitting around the table or the words
“It’s time to eat!”

31. 31
• What Starts a Meal?
• Signals from the stomach
• Ghrelin
• 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
pylorus.

32. 32
• What Starts a Meal?
• Metabolic signals
• 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.

33. • What detectors monitor the level of metabolic fuels?
• There are two sets of detectors:
• 1. Located in the brain.
• 2. Located in the liver.
• 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 liver also detect glucoprivation.
33

34. 34
• What Starts a Meal?
• Metabolic signals
• Methyl palmoxirate (MP)
• Drugs used to stimulate eating.
• Mercaptoacetate (MA)
• Drugs used to deprived ability to metabolize fatty acids.
• Hepatic portal vein
• The vein that transports blood from the digestive system to liver.

35. 35
What is the meaning of
this picture?

36. 36
What Stops a Meal?
Short-term regulation of the sense of satiety.
• 1. Head factors, gastric factors and intestinal.
• 2. Insulin receptors in the brain serve to indicate that the body is
in the absorptive phase of carbohydrate ingestion.
• 3. Cholecystokinin
appears to provide a satiety signal transmitted to the brain
through the vagus nerve.

37. 37
Long-Term Satiety: Signals from Adipose Tissue
• 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; decreases
food intake and increases metabolic rate, primarily
by inhibiting NPY-secreting neurons in the arcuate nucleus.

38. Copyright © 2008 Pearson Allyn & Bacon Inc. 38
Untreated ob mouse ob mouse treated with leptin

39. 39
Brain Mechanisms
• Brain Stem
• Decerebration
• A surgical procedure that severs the brain stem, disconnecting the
hindbrain from the forebrain.
• The only behaviors that a decerebrate animal can display are those
that are directly controlled by neural circuits located within the brain
stem.
• Animal studies indicate that the brain stem contains neural circuits that
can control at least some aspects of food intake.

40. 40

41. 41
Brain Mechanisms
• Hypothalamus : Role in hunger
• Lesions of ventromedial hypothalamus produce cessation of eating
and drinking.
• Lesions of ventromedial hypothalamus produce gross obesity.
• Melanin-concentrating hormone (MCH)
• A peptide neurotransmitter found in a system of lateral hypothalamic
neurons that stimulate appetite and reduce metabolic rate.
• Orexin (AKA hypocretin)
• A peptide neurotransmitter found in a system of lateral hypothalamic
neurons which has a function to stimulate appetite and reduce metabolic
rate.

42. 42
What is the
picture describe
about?

43. 43
Brain Mechanisms
• Hypothalamus : Role in hunger
• Neuropeptide Y (NPY)
• A peptide neurotransmitter found in a system of neurons of the
arcuate nucleus that:
• Stimulate feeding
• Stimulates insulin and glucocorticoid secretion
• Stimulates the breakdown of triglycerides
• Decreases body temperature.

44. 44
Brain Mechanisms
• Hypothalamus : Role in hunger
• 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.
• Paraventricular 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 posterior pituitary gland.

45. Copyright © 2008 Pearson Allyn & Bacon Inc. 45
Hunger signal pathway to
the lateral hypothalamus.
Infusion of NPY to the
arcuate nucleus induces
frantic eating.

46. 46
Brain Mechanisms
• Hypothalamus: Role in hunger
• NPY neurons in hypothalamus release AGRP at their terminals.
This peptide induces eating for intervals up to six 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 eating.

47. 47
Satiety signal pathway.
Leptin receptors induce an
inhibitory effect on feeding, &
prevent a decrease in
metabolic rate. The satiety
signal from adipose tissue
desentize the brain to hunger
signal .

48. 48
Brain Mechanisms
• 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
which has a function to inhibit feeding.

49. Set-Point Theory
Manipulating lateral and ventromedial
hypothalamus and alters the body’s “weight
thermostat.”
If weight is lost our metabolic rate will slowing down. If
weight is gained – our metabolic rate will increase.

50. Hunger
• Under feeding – a condition where you don’t eat
enough food.
• Over feeding – a condition where you eat too much of
food.
• 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.

51. 51
Eating Disorders
• 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 . cardiovascular disease,
diabetes, stroke, arthritis, and some forms of cancer

52. Hunger and Eating
Body Weights of Twins
• Identical twins are
more similar in body
weight than are
fraternal twins.
• play a large role in
body weight.

53. Stress, food cues and appetite
• Stress: underweight body weight individuals lose appetite
with increases in stress while overweight individuals show
the reverse pattern.
• Obesity : overweight individuals feel hungrier to food-
related cues than do average weight individuals.

54. 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 human AD-37
• causes obesity in chickens.

55. 55
Eating Disorders
Anorexia Nervosa and Bulimia Nervosa
• Anorexia 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.
• Bulimia nervosa
• Bouts of excessive hunger and eating; often followed
by forced vomiting or purging with laxatives; sometimes seen in
people with anorexia nervosa.