BackEndocrine System and Hormone Physiology
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1/24BackSkip to main contentBackPineal gland function
Produces serotonin by day and converts it to melatonin at night to regulate circadian rhythm. Melatonin may regulate puberty timing and is increased in Seasonal Affective Disorder. Thymus gland role
Located in the mediastinum above the heart, it shrinks after puberty and secretes hormones that regulate T-cell development. Parathyroid hormone (PTH) effect
Released in response to low blood calcium levels and increases calcium concentration in the blood. Pancreas endocrine vs exocrine function
2% of pancreas cells (islets) produce hormones like insulin and glucagon; 98% produce digestive enzymes (exocrine). Insulin secretion triggers and effects
Secreted by β cells after meals with carbohydrates/proteins; stimulates glucose and amino acid uptake and antagonizes glucagon. Glucagon secretion and function
Secreted by α cells during fasting or low carbohydrate intake; stimulates glycogen breakdown and fat catabolism, antagonizing insulin. Symptoms of diabetes mellitus
Polyuria, polydipsia, polyphagia, hyperglycemia, glycosuria, ketonuria, and osmotic diuresis due to insulin hyposecretion. Type I diabetes mellitus characteristics
Autoimmune destruction of β cells, usually diagnosed around age 12, requires insulin injections and blood glucose monitoring. Type II diabetes mellitus characteristics
Due to insulin resistance; risk factors include heredity, age over 40, and obesity; treated with diet, exercise, and oral medications. Long-term diabetes complications
Vascular damage causing heart and kidney disease, retinal damage leading to blindness, and poor wound healing possibly causing amputations. Hyperinsulinism causes and symptoms
Caused by excess insulin injection or pancreatic tumor; leads to hypoglycemia, weakness, hunger, anxiety, sweating, and increased heart rate. Gestational diabetes features
Occurs during pregnancy due to placental hormones deactivating insulin receptors; reverses after birth but increases type II diabetes risk. Gonadal hormone functions
Ovaries secrete estrogens and progesterone for female reproductive development; testes produce androgens for male reproductive system and sperm production. Heart endocrine function
Produces atrial natriuretic peptide (ANP) in response to increased blood pressure, which decreases blood volume and pressure. Hormone chemical nature
Most hormones are protein-based and water-soluble; steroid hormones are lipid-soluble. Lipid-soluble hormone mode of action
Penetrate plasma membrane, bind intracellular receptors, enter nucleus, and initiate gene transcription for protein synthesis. Water-soluble hormone mode of action
Bind to cell-surface receptors and activate second messenger systems to trigger cellular responses. Hormone clearance mechanisms
Hormones are degraded by liver and kidneys, excreted in bile or urine; metabolic clearance rate and half-life determine removal speed. Up-regulation and down-regulation of hormone receptors
Up-regulation increases receptor density and sensitivity; down-regulation decreases receptor density and response to hormones. Negative feedback control of pituitary hormones
Target organ hormones inhibit hypothalamus and pituitary to regulate hormone secretion and maintain homeostasis. General Adaptation Syndrome stages
Body's response to stress occurs in alarm (mobilize resources), resistance (cope with stressor), and exhaustion (reserves depleted) phases. Paracrine secretions
Chemical messengers that act locally on nearby cells, e.g., histamine causes vasodilation during allergies. Eicosanoids functions
Mediate allergic and inflammatory reactions, regulate smooth muscle contraction, clotting, and sensitize neurons to pain. Examples of anti-inflammatory drugs
Non-steroidal: aspirin, ibuprofen; Steroidal: prednisone; they inhibit eicosanoid pathways to reduce inflammation.
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