Lecture slides for PSY-2 Ch09 Homeostasis

1. Ch09: Homeostasis
➔Principles of Homeostasis
➔Fluid Regulation
➔Food Regulation

2. PRINCIPLES OF HOMEOSTASIS
HOMEOSTASIS: physiological & behavioral maintenance of a
stable, balanced, internal environment
MOTIVATION: the psychological process that can induce or
suppress a certain behavior

3. • ENDOTHERMS: generate most of their own
heat through internal processes
AKA warm-blooded
• ECTOTHERMS: get most of their heat from the
environment
AKA cold-blooded
PRINCIPLES OF HOMEOSTASIS

4. • NEGATIVE FEEDBACK SYSTEMS: the
output of the system feeds back to reduce
the effect of input signals
• SET POINT: a desired value in a feedback
system
• SET ZONE: refers to the range of tolerance
in a system
PRINCIPLES OF HOMEOSTASIS
1. Internal states are governed by negative feedback.

5. PRINCIPLES OF HOMEOSTASIS

6. • REDUNDANCY: homeostatic systems are
monitored by more than one mechanism
• Regulatory systems in the hypothalamus
–Physiological responses (POA – preoptic area)
–Behavioral responses (lateral hypothalamus)
PRINCIPLES OF HOMEOSTASIS
2. Redundancy is a feature of many homeostatic systems.

7. Figure 9.2 Multiple Thermostats in
the Nervous System
PRINCIPLES OF HOMEOSTASIS
2. Redundancy is a feature of many homeostatic systems.

8. 1. Changing exposure of the
body surface
2. Changing external
insulation
3. Changing surroundings
PRINCIPLES OF HOMEOSTASIS
3. Behavioral mechanisms are crucial for homeostasis.

9. PRINCIPLES OF HOMEOSTASIS

10. PRINCIPLES OF HOMEOSTASIS

11. Ch09: Homeostasis
➔Principles of Homeostasis
➔Fluid Regulation
➔Food Regulation

12. FLUID REGULATION
• INTRACELLULAR
COMPARTMENT: the fluid
part of the body contained
within cells
• EXTRACELLULAR
COMPARTMENT: the fluid
space outside of cells

13. FLUID REGULATION
• DIFFUSION: molecules
of a substance (solute)
dissolved in another
substance (solvent) will
move to reach a
uniform concentration
Forces driving water movement:
• OSMOSIS: movement of water
across a semipermeable membrane

14. • The extracellular fluid indicates the state of the
intracellular space, and is monitored by the
nervous system
• The concentration of salt in the extracellular
fluid is about 0.9%.
–PHYSIOLOGICAL SALINE
–ISOTONIC
FLUID REGULATION

15. HYPOVOLEMIC THIRST
• Low extracellular volume from a loss
of bodily fluids
• Triggered by a loss of water volume—
the concentration is not changed as
salt and ions are also lost
FLUID REGULATION

16. HYPOVOLEMIC THIRST
• Baroreceptors: detect changes in blood pressure;
located in heart & blood vessels
– Brain activates thirst and salt hunger
– Sympathetic nervous system constricts arteries,
activates hormone systems
FLUID REGULATION

17. HORMONE:
RELEASED BY
THE: EFFECTS ON THE BODY:
BLOOD VOLUME LOSS
LEADS TO:
Atrial Natriuretic
Peptide (ANP)
Heart Reduced BP, increased urine
production
Decreased release
Vasopressin Posterior
Pituitary
Increased BP, slowed urine
production
Increased release
Angiotensin II Kidneys Increased BP, drinking
behavior
Increased release
HYPOVOLEMIC THIRST
The drop in blood volume triggers hormonal reactions:
FLUID REGULATION

18. HYPOVOLEMIC THIRST
• CIRCUMVENTRICULAR ORGANS: located in the cerebral
ventricle; monitor the composition of cerebrospinal fluid
FLUID REGULATION

19. OSMOTIC THIRST
• High extracellular solute
concentration
• Volume of the extracellular fluid
is decreased AND the solute
concentration is increased
FLUID REGULATION

20. OSMOSENSORY NEURONS:
• Monitor changes in concentration of the
extracellular fluid
• Located in the hypothalamus & the OVLT
FLUID REGULATION

21. FLUID
REGULATION

22. Ch09: Homeostasis
➔Principles of Homeostasis
➔Fluid Regulation
➔Food Regulation

23. FOOD REGULATION
• NUTRIENTS: chemicals required for function,
maintenance, and growth of the body
• GLUCOSE: the principal sugar used for energy

24. FOOD REGULATION
Short-term Energy Storage
• GLYCOGEN: energy stored in the liver and muscles
• INSULIN: pancreatic hormone that converts glucose
into glycogen
• GLUCAGON: pancreatic hormone that converts
glycogen back into glucose, when glucose levels drop

25. FOOD REGULATION
Long-term Energy Storage
• LIPID (fat) molecules are
stored in adipose tissue for
long-term storage
• Fat can be converted into
glucose and KETONES, which
can be used as fuel

26. BASAL METABOLISM: energy used for heat production,
maintenance of membrane potentials, and life-sustaining
processes
FOOD REGULATION

27. FOOD REGULATION

28. FOOD REGULATION

29. • The body needs INSULIN to import glucose from the blood
into most cells
FOOD REGULATION
INSULIN IS ESSENTIAL FOR OBTAINING, STORING, &
USING FOOD ENERGY

30. • DIABETES MELLITUS: excess glucose in blood & urine, reduced
glucose use by body cells
FOOD REGULATION
INSULIN IS ESSENTIAL FOR OBTAINING, STORING, &
USING FOOD ENERGY

31. FOOD REGULATION

32. Insulin release is triggered by several mechanisms:
1. Cephalic Phase: insulin released when you perceive food
2. Digestive Phase: insulin released when food enters the
digestive tract
3. Absorptive Phase: liver cells–GLUCODETECTORS—signal
the pancreas to release even more insulin
FOOD REGULATION
INSULIN IS ESSENTIAL FOR OBTAINING, STORING, &
USING FOOD ENERGY

33. FOOD REGULATION
How does the brain know it is hungry and trigger eating?
GLUCOSE
02
● Available energy supply in the
bloodstream
● BUT in untreated diabetes glucose
levels are high, but hunger is also very
high
INSULIN
01
● Lowering insulin increases hunger &
eating (and vice versa)
● BUT, injecting very large amounts of
insulin increases hunger & eating

34. FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER
• DUAL CENTER
HYPOTHESIS two
areas of the
hypothalamus work
together, in
opposition

35. Figure 9.12 Lesion Studies
Revealed That the Hypothalamus Is
Involved in Appetite (Part 2)
FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER

36. The hypothalamus contains
an appetite control network.
FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER

37. • ARCUATE NUCLEUS:
–hypothalamic appetite controller
–integrates hormone signals
• LEPTIN:
–hormone released by fat cells
–info about long-term energy
FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER

38. • GHRELIN: hormone
appetite stimulant
– reaches high levels
before eating
– drops off after eating
– released by the
stomach
FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER
• PYY: hormone appetite
suppressant
– reaches high levels
after eating
– Released by the
intestine

39. NPY NEURONS:
• hunger neurons
• stimulate appetite
• reduce metabolism
FOOD REGULATION
THE HYPOTHALAMUS COORDINATES MULTIPLE SYSTEMS
THAT CONTROL HUNGER
POMC NEURONS:
• satiety neurons
• inhibit appetite
• increase metabolism
Appetite control neurons within the arcuate nucleus:

40. FOOD REGULATION

41. • NUCLEUS OF THE SOLITARY TRACT (NST):
–brainstem nucleus
–receives gut and taste info from a variety of sources
• CHOLECYSTOKININ (CCK)
–peptide released by the gut after feeding
–acts on the vagus nerve to inhibit appetite
FOOD REGULATION
OTHER SYSTEMS INVOLVED IN FOOD REGULATION

42. • ENDOCANNABINOIDS:
–endogenous ligands that mimic THC
–affect the reward system AND hypothalamic
appetite mechanisms
–inhibit satiety signals
FOOD REGULATION
OTHER SYSTEMS INVOLVED IN FOOD REGULATION

43. FOOD REGULATION
The Obesity
Epidemic

44. The Obesity
Epidemic
FOOD REGULATION

45. The Obesity
Epidemic
FOOD REGULATION

46. Several emerging strategies for treatment:
• Appetite Control: drugs to dampen the hypothalamic
appetite controller
• Increased Metabolism: cause the body’s metabolic
rate to increase and burn more calories
• Inhibition of Fat Tissue: interfere with the formation
of new fat tissue
FOOD REGULATION

47. Several emerging strategies for treatment:
• Reduced Absorption: drugs that interfere
with the digestion of fat (Orlistat)
• Reduced Reward: use drugs to reduce
the brain’s reward circuitry
• Anti-obesity Surgery:
• Liposuction is the surgical removal of fat tissue
• Bariatric procedures bypass part of the
stomach or intestinal tract to reduce
absorption
FOOD REGULATION

48. EATING DISORDERS
• ANOREXIA NERVOSA: sufferers become dangerously
thin and have distorted body image
• BULIMIA NERVOSA: sufferers are not underweight,
but have distorted body image and engage in
unhealthy efforts to compensate for consumed
calories
• BINGE EATING DISORDER: people gorge themselves
with excess food, to the point of illness
FOOD REGULATION