Metabolic physiology Flashcards
What is energy balance?
Energy input (food) equals energy output (internal work, external work, and heat) ± stored energy.
Define cellular respiration.
Process converting chemical energy from organic molecules (e.g., glucose) into ATP for cellular functions.
How is BMR measured?
Via direct calorimetry (heat production) or indirect calorimetry (oxygen consumption).
Why is body temperature regulation critical?
Optimizes enzyme activity, maintains immunity, and prevents heat stroke/hypothermia.
List five factors affecting BMR
Body size, composition (muscle vs. fat), age, hormonal levels (thyroxine, adrenaline), health status.
Which hormones regulate appetite?
Stimulate (Orexigenic): Ghrelin, Neuropeptide Y (NPY).
Suppress (Anorexigenic): Leptin, insulin, PYY₃₋₃₆, melanocortins.
How does the hypothalamus control hunger?
Arcuate nucleus: Integrates leptin/insulin signals.
Lateral Hypothalamus (LHA): Releases orexins (hunger).
Paraventricular Nucleus (PVN): Releases CRH (satiety).
What role does CCK play in satiety?
Released from the duodenum during digestion; signals fullness to the nucleus tractus solitarius (NTS)
Compare insulin and glucagon roles.
Insulin: Promotes storage (glycogenesis, lipogenesis).
Glucagon: Mobilizes fuels (glycogenolysis, gluconeogenesis).
What pathways maintain blood glucose during fasting?
Glycogenolysis (liver glycogen → glucose) and Gluconeogenesis (lactate/amino acids → glucose).
What is the Randle Cycle?
High fatty acid oxidation inhibits glucose use in muscles (via acetyl-CoA → citrate → PFK inhibition).
Describe glucose homeostasis in fed vs. fasting states.
Fed: Excess glucose stored as glycogen (liver/muscle) or fat (adipose).
Fasting: Glycogenolysis → gluconeogenesis → ketogenesis (brain fuel).
What causes diabetic ketoacidosis (DKA)?
Insulin deficiency → uncontrolled lipolysis → excess ketones (acetoacetate, β-hydroxybutyrate) → metabolic acidosis.
Why do untreated Type 1 diabetics have acetone breath?
Excess ketones (acetone) are exhaled during DKA.
How does AMPK regulate metabolism during fasting?
Activates catabolism (fat oxidation) and inhibits anabolism (fat synthesis) by phosphorylating ACC.
