Peripheral Endocrine Glands and Metabolism

Peripheral Endocrine Glands

• Endocrine glands control fuel metabolism, calcium metabolism, and the functions of adrenal and thyroid glands.
• Endocrine pancreas metabolizes nutrients.
• Parathyroid glands are important for calcium metabolism.
• Adrenal glands metabolize nutrients, adapt to stress, and maintain salt balance.
• Thyroid controls the body's basal metabolic rate.

Fuel Metabolism

• Metabolism encompasses all chemical reactions within body cells.
• Fuel metabolism (intermediary metabolism) involves the degradation, synthesis, and transformation of proteins, carbohydrates, and lipids.
• Digestion breaks down macromolecules into absorbable subunits.

Fuel Metabolism (Continued)

• Anabolism synthesizes large organic molecules, requiring ATP.
• Catabolism breaks down large molecules, creating ATP.
• Hydrolysis and oxidation reactions create ATP.
• Smaller subunits from catabolism fuel energy and cellular synthesis.

Nutrient Storage: Glucose

• Nutrients from meals are stored and released.
• Excess glucose is stored as glycogen in the liver and skeletal muscles.
• Glycogen storage is limited; excess glucose is stored as triglycerides in adipose tissue.
• The brain requires a constant glucose supply and cannot store glycogen.
• During fasting, many body cells use fatty acids to conserve glucose for the brain.
• Amino acids can be converted to glucose by gluconeogenesis to supply the brain.

Nutrient Storage: Fatty Acids and Amino Acids

• Excess circulating fatty acids are incorporated into triglycerides primarily in adipose tissue.
• Excess amino acids are converted to glucose and fatty acids, ultimately becoming triglycerides in adipose tissue.
• Muscle tissue is the primary storage site for amino acids, utilized for structural proteins.

Nutrient Storage and Use

• Two metabolic states exist: absorptive (fed) and postabsorptive (fasting).
• The absorptive state occurs when nutrients are absorbed into the blood after meals (approximately 4 hours).
• During this state, metabolic fuels are stored.
• The postabsorptive state occurs between meals when nutrient absorption ceases.
• During this state, stored molecules are broken down to maintain glucose concentration and provide energy.

Insulin Stimulation

• Insulin lowers blood glucose, fatty acid, and amino acid levels.
• Insulin facilitates glucose transport into cells using specific glucose transporters (GLUTs), particularly GLUT-4.
• Insulin stimulates glycogen synthesis in skeletal muscles and the liver.
• Insulin inhibits glycogenolysis and gluconeogenesis.
• Insulin promotes the conversion of glucose to fatty acids and the transport of fatty acids into adipose tissue, and promotes the incorporation of amino acids into cells to synthesize proteins.
• Insulin secretion increases with increased blood glucose during the absorptive state.
• Insulin secretion decreases if glucose levels drop to below a normal level and shifts the metabolism to the postabsorptive state.

Insulin Secretion

• Glucose, amino acids, and gastrointestinal hormones stimulate insulin release.
• Parasympathetic stimulation and blood amino acids increase insulin release.
• Blood glucose, fatty acids, amino acids, protein synthesis, and fuel storage are all regulated by insulin.

Glucagon

• Glucagon's actions are opposite to those of insulin.
• Glucagon promotes glycogenolysis and gluconeogenesis.
• Glucagon increases fat breakdown.
• Glucagon promotes protein breakdown, primarily in the liver.
• Glucagon secretion increases during the postabsorptive state.
• Glucagon secretion increases when blood glucose is low.
• Glucagon, along with other hormones like growth hormone, cortisol, and epinephrine, acts as an antagonist to insulin in raising blood glucose levels.

This quiz explores the functions of various peripheral endocrine glands, including the pancreas, parathyroid, and adrenal glands, in regulating metabolism and nutrient storage. It also covers the processes of anabolism and catabolism as they relate to energy production. Test your knowledge on how these systems interact and contribute to overall health.