Homeostasis: Energy Regulation

Made by @agreyr

Basal metabolism

The majority of food energy is spent on things like heat, cellular activity, and maintenance of membrane potentials

Energy metabolism is under strict homeostatic control and can be adjusted

Short term storage

Insulin converts glucose to glycogen to store as reserve fuel

Glucagon converts glycogen back into glucose when stores are low

Long term storage

Insulin triggers lipid (far) storage in adipose tissues, liver, and muscles

Glucagon produces free fatty acids and ketones

Three phases of energy metabolism

Cephalic phase, Absorptive phase, Fasting phase

Cephalic phase

Preparatory phase, which is initiated by the sight, smell, or expectation of food

Insulin levels high; glucagon levels low

Absorptive phase

Nutrients from a meal meeting the body’s immediate energy requirements, with the excess being stored

Insulin levels high; glucagon levels low

Insulin levels high; glucagon levels low

Promotes utilization of blood glucose as a source of energy

Promotes conversion of excess glucose to glycogen and fat

Promotes conversion of amino acids to proteins

Promotes storage of glycogen in liver and muscle, fat in adipose tissue, and protein in muscle

Inhibits conversion of glycogen, fat, and protein into directly utilizable fuels (glucose, free fatty acids, and ketones)

Fasting phase

Energy being withdrawn from stores to meet the body’s immediate needs

Glucagon levels high; insulin levels low

Glucagon levels high; insulin levels low

Promotes conversion of fats to free fatty acids and the utilization of free fatty acids as a source of energy

Promotes conversion of glycogen to glucose, free fatty acids to ketones, and protein to glucose

Inhibits utilization of glucose by the body but not by the brain

Inhibits conversion of glucose to glycogen and fat, and amino acids to protein

Inhibits storage of fat in adipose tissue

Insulin

Required by glucose transporters in the body to allow use of glucose in the body

Diabetes Mellitus

Lack of insulin production or reduced sensitivity to insulin

Theories of hunger

Set point theory and Positive-incentive theory

Set point theory assumption

Hunger is a response to an energy need; we eat to maintain an energy set point

Set point theory problems

Not everyone is the same size

It doesn’t fit evolutionary pressures; energy storage necessary for survival

Reductions in blood glucose or body fat do not reliably induce eating

It doesn’t account for the influence of external factors on eating and hunger (taste, learning, social cues)

Positive incentive theory

We are drawn to eat by the anticipated pleasure of eating

We have evolved to “crave” food

Eating has a positive-incentive value; multiple factors interact to determine this

Accounts for the impact of external factors on eating behavior