MUSCLE PHYSIOLOGY

Detailed explanation-1: -Gluconeogenesis. During short-term fasting periods, the liver produces and releases glucose mainly through glycogenolysis. During prolonged fasting, glycogen is depleted, and hepatocytes synthesize glucose through gluconeogenesis using lactate, pyruvate, glycerol, and amino acids (Fig. 1).

Detailed explanation-2: -Gluconeogenesis occurs after around 8 hours of fasting when liver glycogen stores start to deplete and an alternative source of glucose is required. It occurs mainly in the liver and to a lesser extent in the cortex of the kidney.

Detailed explanation-3: -The liver supplies sugar or glucose by turning glycogen into glucose in a process called glycogenolysis. The liver also can manufacture necessary sugar or glucose by harvesting amino acids, waste products and fat byproducts. This process is called gluconeogenesis.

Detailed explanation-4: -Gluconeogenesis occurs in liver and kidneys. The precursors of gluconeogenesis are lactate, glycerol, amino acids, and with propionate making a minor contribution. The gluconeogenesis pathway consumes ATP, which is derived primarily from the oxidation of fatty acids.

Detailed explanation-5: -In contrast to glycogen synthesis, glycogenolysis is the release of glucose 6-phosphate from glycogen stores. It can occur in both the liver and the skeletal muscle but under two different conditions (figures 5.6 and 5.7). As noted above, this is a pathway active in the fasted state.