II. Regulation of Appetite and Consumption

General Mechanism

• Body regulates food intake to maintain energy balance, homeostasis

• Mechanism: Negative Feedback Control 

• Energy levels sufficient -> appetite suppressed

• Energy low -> appetite stimulated

• Time scales

  • Short term: meal to meal

  • Long term: body fat/ energy stores over time

• Systems involved

  • Hormones

  • CNS: hypothalamus

Example: Glucose Homeostasis

• Involves pancreas: large gland, abdominal cavity 

• Secretes insulin and glucagon 

• 70-100 mg/ml glucose ideal

• Malfunction of glucose regulation

• Diabetes Mellitus

  • Most common endocrine disorder

  • Two types

    • Type 1: insulin deficiency 

    • Type 2: insulin resistance 

  • Both lead to high blood glucose level

• Consequences

  • Cells unable to take up glucose 

    • Fat main fuel 

  • Acidic metabolic byproducts accumulate in blood

  • Lower pH

  • Depletes Na+, K+

  • If severe can cause blindness, kidney disease (polyuria), gangrene

Gherlin

hormone secreted by stomach wall, triggers hunger

PYY

• appetite suppressed from SI

Insulin

• Triggered ny increase blood sugar, suppress appetite 

Leptin

produced by adipose tissue, suppresses appetite long term

Nervous System

• sensory neurons detect stimulus ex food in small intestine blood sugar

• regulates hormone secretion

• hormones target satiety center in brain

• perceived as hungry or full