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.
- 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.
- 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
- 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