5+Endocrine+physiology.pdf

Exercise Physiology KINS 4940 Dongwoo Hahn, PhD 5 Endocrine physiology Endocrine disorder in history Pre-Colombian stone carving of a woman shows a mass at her neck. This mass is an enlarged thyroid...

Exercise Physiology KINS 4940 Dongwoo Hahn, PhD 5 Endocrine physiology Endocrine disorder in history Pre-Colombian stone carving of a woman shows a mass at her neck. This mass is an enlarged thyroid gland, a condition known as goiter. It was considered as a sign of beauty among the people who lived high in the Andes mountains. What cause goiter? Lack of sufficient iodine in the water and soil on which food crops are grown What makes a chemical a hormone? A hormone is a chemical signal Hormones are secreted by a cell or group of cells Hormones are secreted into the blood Secretion from a cell to ECF or external environment Phermones are specialized ectohormones Hormones are transported to a distant target Transported by blood Growth factors act at short distance Hormones exert their effect at very low concentrations Hormones act by binding to receptors Cellular mechanism of action Depends on binding to target cell receptors Initiates biochemical responses Hormone action must be terminated Half-life indicates length of activity Hormones act by binding to receptors Ions as signal molecule +Pi, -Pi Kinase Phosphorylase, phosphatase Peptide, steroid, amino acid derived hormone Simple endocrine pathways Anterior pituitary gland Thyroid gland  Thyroid gland & Iodine pills Normal condition: thyroid needs iodine → I-127: negligible radioactivity Uranium atoms shatter in core of nuclear reactor → I-131: radioactive (DNA damage), highly mobile, 8 days half-life Posterior pituitary gland Posterior pituitary gland-Antidiuretic hormone ADH Reduces water loss from the body to maintain plasma volume Favors reabsorption of water from kidney tubules to capillaries Release stimulated by high plasma osmolality and low plasma volume, due to sweat loss without water replacement Increases during exercise >60% VO2 max To maintain plasma volume Portal system: hypothalamus – anterior pituitary Portal system consists of two sets of capillaries connected in series by a vein Hypothalamic-hypophyseal (pituitary) portal system Hypothalamic neurons produce trophic hormones Released into 1st capillary bed in portal system to anterior pituitary Anterior pituitary endocrine cells produce trophic hormones Released into 2nd capillary bed in portal system to target tissues Ensures that small amount of concentrated hormone is directed to its target Negative feedback in complex endocrine pathway Response stimulus Homeostasis? Baroreflex? Positive feedback? Hormones in hypothalamic-anterior pituitary Negative feedback from exogenous hormone Endocrine pathology Endocrine pathologies Hypersecretion Hyposecretion Abnormal tissue responsiveness Normal feedback mechanisms do not work on the abnormal gland when there is a problem Primary problem: last gland Secondary problem: trophic gland  Thyroid action Not necessary for life Primary function: metabolism, protein synthesis In children, permissive for growth hormone needed for synapse formation  Hyperthyroidism Hypothyroidism Increased O2 consumption decreased metabolism heat intolerant cold intolerant psych disturbances brittle hair & nails diminished reflexes fatigue Exophthalmos Myxedema Marty Feldman  Cortisol Necessary for life Catabolic: gluconeogenesis (“glucocorticoid”) muscle breakdown, lipolysis Suppresses the immune system - therapeutics Affects brain function (mood, memory) Negative Ca balance Circadian rhythm  The deeper the snow, the more men were admitted for heart attacks. For example, for snowfalls of more than eight inches, there was a 16% increase in hospital admissions compared to days with no snow. The deeper the snow, the more men died of heart attacks. A 34% increase was observed the day after an eight-inch snowfall, and higher rates were noted when even more snow fell. Similar observations were made for duration of snowfall. The longer it snowed, the higher the rates of heart attack and related deaths among men. A link between snowfall and heart attack was not observed among women. WHY?  Shoveling snow (or perhaps other means of snow removal, including pushing a heavy snow blower) can raise your heart rate and blood pressure more quickly and more dramatically than many other types of exercise. Snow shoveling requires use of arm muscles, which for most people is more strenuous than other exercise. Snow removal happens in a cold environment. That’s important because cold temperatures may cause blood vessels to constrict. Many snow shovelers are ordinarily sedentary. The sudden, strenuous workout may tax a system that is not prepared for it. Epidemiologic studies have previously suggested that premenopausal females have reduced incidence of cardiovascular disease (CVD) when compared to age-matched males, and the incidence and severity of CVD increases postmenopause. The lower incidence of cardiovascular disease in women during reproductive age is attributed at least in part to estrogen (E2). … This review summarizes the protective role of E2 and its receptors in the cardiovascular system and discusses its underlying mechanisms with an emphasis on oxidative stress, fibrosis, angiogenesis, and vascular function.... Targeting specific ERs in the cardiovascular system may result in novel and possibly safer therapeutic options for cardiovascular protection. Cortisol – adrenal gland  Primary & secondary hypersecretion of cortisol “stress hormone” Pathology Hypersecreting Anterior (hyper- Adrenal cortex tumor in pituitary secretion) hypothalamus CRH ACTH Cortisol ↓, , ↑?  Hypercortisolism “Moon face” Trunkal obesity Protein breakdown Plasma Glucose, Insulin, Diabetes Summary of hormonal responses & substrate mobilization Effect on Fuel Hormone Gland Exercise Response Action Utilization ↑ Muscle and liver Epinephrine Mobilizes both fat and Adrenal medulla ↑ glycogenolysis ↑ FFA Norepinephrine carbohydrate fuels mobilization ↑ FFA mobilization ↑ Mobilizes fat fuels Cortisol Adrenal cortex ↑ Gluconeogenesis ↓ Preserves blood Glucose uptake glucose ↑ FFA mobilization ↑ Mobilizes fat fuels Growth hormone Anterior pituitary ↑ Gluconeogenesis ↓ Preserves blood Glucose uptake glucose ↑ FFA mobilization ↑ Mobilizes fat fuels Glucagon Pancreas (α-cells) ↑ Glycogenolysis ↓ Preserves blood Glucose uptake glucose ↑ Glucose, amino Stores fuels Lowers Insulin Pancreas (β-cells) ↓ acid, and FFA uptake blood glucose into tissues Muscle as an endocrine gland Skeletal muscle produces myokines during contractions Stimulate glucose uptake and fatty acid oxidation Promote blood vessel growth in muscle Promote liver glucose production and triglyceride breakdown Interleukin 6 (IL-6) Both proinflammatory and anti-inflammatory IL-6 produced during exercise promotes anti-inflammatory effect Regular exercise promotes anti-inflammatory environment Reduction in chronic inflammation and reduced risk of heart disease, type 2 diabetes, and certain cancers  Glycogen depletion during exercise Plasma epinephrine is a powerful simulator of glycogenolysis Role of cortisol in the maintenance of blood glucose Role of growth hormone in the maintenance of plasma glucose Role of catecholamines in substrate mobilization Insulin and glucagon during exercise Summary of the hormonal responses to exercise