Endocrine system Flashcards
What does the endocrine system regulate?
Metabolism, growth and development, reproduction, water and electrolyte balance, and behavior.
Types of endocrine receptors:
Cytoplasmic or nuclear receptors for lipophilic hormones and cell surface receptors for hydrophilic proteins.
How do second messengers in the endocrine system function?
Second messengers are short-lived intracellular signaling molecules that lead to rapid changes in the activity of cellular enzymes, with their concentration increasing to amplify signals.
What happens when a hormone binds to a G-protein coupled receptor?
It activates adenyl cyclase to produce cAMP from ATP, which then activates cAMP-dependent protein kinase, leading to the cell’s response.
What are the two main types of white adipose tissue ?
Subcutaneous adipose tissue (beneath the skin) and intra-abdominal adipose tissue (around inner organs).
What are the primary functions of white adipose tissue ?
Energy storage, temperature insulation, mechanical protection, and functioning as an endocrine organ.
Where is brown adipose tissue found in newborns and adults?
In newborns, BAT is found between the shoulder blades and around the adrenal glands. In adults, it is found in the cervical, supraclavicular, and paravertebral regions.
What is the main function of brown adipose tissue ?
To generate heat through thermogenesis, especially important for maintaining body temperature in cold environments.
What is the role of insulin produced by pancreatic beta cells?
Insulin lowers blood glucose levels by facilitating glucose uptake into tissues.
What is the significance of glucagon produced by pancreatic alpha cells?
Glucagon increases blood glucose levels by promoting glucose release from the liver.
What triggers glucose-stimulated insulin secretion (GSIS) in pancreatic beta cells?
A rise in blood glucose levels leads to increased intracellular calcium, triggering the exocytosis of insulin-containing granules.
What is lipotoxicity and what causes it?
Lipotoxicity is damage caused to organs and tissues by excessive lipid accumulation, often due to limited lipid storage capacity in organs other than adipose tissue.
What are the main functions of the liver?
Storage of glycogen, vitamins, and minerals, bile production, protein synthesis, hormone breakdown, and detoxification of harmful substances.
What is the role of hepatocytes in the liver?
Hepatocytes perform synthesis, storage, and detoxification functions, and have a high capacity for regeneration.
How do cytoplasmic and nuclear receptors in the endocrine system function with lipophilic hormones?
Lipophilic hormones bind to cytoplasmic or nuclear receptors, which then bind to the promoter of hormone-response elements on DNA, affecting gene expression and leading to changes in cellular activity.
What are bile acids and their function?
Bile acids, produced by the liver, help in fat digestion and absorption and play a hormonal role in regulating metabolism.
Explain how cell surface receptors induce intracellular signaling in the endocrine system.
Cell surface receptors, such as G-protein coupled receptors and ion channels, bind to hydrophilic hormones, which activate intracellular signaling pathways involving second messengers like cAMP, IP3, and DAG. These messengers lead to the activation of enzymes and changes in cell function.
What is the physiological regulation of thermogenesis in brown adipose tissue?
A: The preoptic area of the brain senses cold and activates the hypothalamus, which increases sympathetic nervous system (SNS) activity. Norepinephrine released from sympathetic nerve terminals binds to β-adrenergic receptors on brown adipocytes, activating pathways that increase cAMP and protein kinase A (PKA), leading to the activation of UCP1 and heat production.
What roles do white adipose tissue play as an endocrine organ?
WAT secretes hormones called adipokines, such as leptin and adiponectin, which are involved in regulating energy balance, metabolism, and insulin sensitivity. It also plays a role in inflammation through cytokine production.
What is the difference between healthy and unhealthy expansion of white adipose tissue?
Healthy expansion involves increased adipogenesis, cell volume, and insulin sensitivity with reduced inflammation. Unhealthy expansion is characterized by decreased adipogenesis, increased cell hypertrophy, reduced insulin sensitivity, heightened low-grade inflammation, and macrophage infiltration, leading to complications like insulin resistance and type 2 diabetes.
Describe the structure and cellular composition of white adipose tissue.
WAT consists primarily of adipocytes that store triglycerides and secrete hormones, preadipocytes that serve as a regenerative reservoir, immune cells that contribute to inflammation, endothelial cells, vascular smooth muscle cells, and fibroblasts that provide structural integrity and cell communication.
How does brown adipose tissue contribute to thermogenesis and energy metabolism?
BAT generates heat by metabolizing lipids through the action of UCP1 in mitochondria. This process uncouples oxidative phosphorylation, allowing energy from fat oxidation to be released as heat, aiding in body temperature regulation and protection against cold.
What is the role of insulin signaling in various tissues?
In muscle and adipose tissue, insulin promotes glucose uptake by translocating GLUT4 to the cell membrane. In the liver, it stimulates glycogen synthesis and inhibits gluconeogenesis. In adipose tissue, it increases lipogenesis, converting glucose into fatty acids for storage.
Explain the roles of different cell types in the islets of Langerhans in the pancreas.
Beta cells produce insulin, alpha cells secrete glucagon, delta cells produce somatostatin to regulate insulin and glucagon secretion, PP cells secrete pancreatic polypeptide involved in hormone regulation, and epsilon cells produce ghrelin to regulate satiety and metabolic rate.
