Endocrine System - Hormones & Glands PDF

18-6 The paired adrenal glands secrete several hormones that affect electrolyte balance and stress responses. - Lie along superior border of each kidney. **Superficial adrenal cortex** - Stores lipids, especially cholesterol and fatty acids. - Manufactures steroid hormones (**corticosteroi...

18-6 The paired adrenal glands secrete several hormones that affect electrolyte balance and stress responses. - Lie along superior border of each kidney. **Superficial adrenal cortex** - Stores lipids, especially cholesterol and fatty acids. - Manufactures steroid hormones (**corticosteroids**). **Inner adrenal medulla** - Secretory activities controlled by sympathetic division of ANS. - Produces epinephrine and norepinephrine (**catecholamines**). **Adrenal cortex** - Subdivided into three zones... - Outer zona glomerulosa - Middle zona fasciculata - Inner zona reticularis **Zona glomerulosa (SALT)** - Outer region of adrenal cortex - Produces mineralocorticoids. Ex. *aldosterone* - Stimulates conservation of sodium ions and elimination of potassium ions - Increases sensitivity of salt receptors in taste buds - Secreted in response to... - Drop in blood Na+, blood volume, or blood pressure - Rise in blood K+ concentration **Zona fasciculata (SUGAR)** - Produces glucocorticoids. Ex. *cortisol, corticosterone, and cortisone* - Secretion is regulated by negative feedback Glucocorticoids have inhibitory effect on production of... - Corticotropin-releasing hormone (CRH) in hypothalamus - ACTH in anterior pituitary - Effects of glucocorticoids - Accelerate glucose synthesis and glycogen formation, especially in liver - Have anti-inflammatory effects - Inhibit activities of white blood cells and other components of immune system **Zona reticularis (SEX)** - Branching network of endocrine cells - Forms narrow band bordering each adrenal medulla - Produces small quantities of androgens under stimulation by ACTH - Some are converted to estrogens in bloodstream - Stimulate development of pubic hair before puberty **Adrenal medulla (ADRENALINE)** - Contains two types of secretory cells... - One produces epinephrine (E). - 75--80 percent of medullary secretion. - The other produces norepinephrine (NE). - 20--25 percent of medullary secretion. Results of activation of adrenal medulla - In skeletal muscles, E and NE trigger mobilization of glycogen reserves. - And accelerate breakdown of glucose. - In adipose tissue, stored fats are broken down into fatty acids. - In the liver, glycogen molecules are broken down. - In the heart, stimulation of β1 receptors speeds and strengthens cardiac muscle contraction. 18-7 The pineal gland secretes melatonin, which affects the circadian rhythm. - Lies in posterior portion of roof of third ventricle. - Contains [ **pinealocytes**]. - Synthesize hormone **[melatonin]**. **Functions of melatonin** - Influence circadian rhythms. - Inhibit reproductive functions. - Protect against damage by free radicals. **[PANCREAS]** 18-8 The pancreas is both an exocrine organ and an endocrine gland that produces hormones affecting the blood glucose level. - Large gland. - Lies in loop between inferior border of stomach and proximal portion of small intestine. - Mostly retroperitoneal. - Contains exocrine and endocrine cells. **Exocrine Pancreas** - Consists of clusters of gland cells called pancreatic acini and their attached ducts. - Takes up roughly 99 percent of pancreatic volume. - Gland and duct cells secrete alkaline, enzyme-rich fluid. - Passes through a network of ducts to lumen of digestive tract. **Endocrine Pancreas** - Consists of cells that form clusters known as **[pancreatic islets (*islets of Langerhans*)]**. - **[Alpha (α) cells]** produce **glucagon**. - **[Beta (β) cells]** produce **insulin**. - **[Delta (δ) cells]** produce peptide hormone identical to GH--IH (somatostatin). - **[Pancreatic polypeptide cells (PP cells)]** produce pancreatic polypeptide (PP). When blood glucose level increases... - Beta cells secrete insulin. - Stimulating transport of glucose into target cells. When blood glucose level decreases... - Alpha cells secrete glucagon. - Stimulating glycogen breakdown and glucose release by liver. **Insulin** - Released by beta cells. - Effects on target cells... - Accelerating glucose uptake. - Accelerating glucose use and enhancing ATP production. - Stimulating glycogen formation. - Stimulating amino acid absorption and protein synthesis. - Stimulating triglyceride formation in adipocytes. **Glucagon** - Released by alpha cells. - Mobilizes energy reserves. - Effects on target cells... - Stimulating breakdown of glycogen in skeletal muscle fibers and liver cells. - Stimulating breakdown of triglycerides in adipocytes. - Stimulating production and release of glucose in liver cells (gluconeogenesis). **[Hyperglycemia:]** abnormally high glucose levels in the blood. **[Diabetes mellitus:]** characterized by high glucose concentrations that overwhelm reabsorption capabilities of kidneys. - Glucose appears in urine. **[Polyuria:]** urine volume becomes excessive. **Type 1 diabetes mellitus** - Characterized by inadequate insulin production by pancreatic beta cells. - Patients require daily injections or continuous infusion of insulin. - Approximately 5 percent of cases. - Usually develops in children and young adults. **Type 2 diabetes mellitus** - **\*\*\* Most common form \*\*\*** - Usually, normal amounts of insulin are produced, at least initially. - **[Insulin resistance:]** tissues do not respond properly. - Associated with obesity. - Weight loss can be an effective treatment. Complications of untreated or poorly managed diabetes mellitus include... - Kidney degeneration. - Retinal damage (diabetic retinopathy). - May lead to blindness. - Early heart attacks (3--5 times more likely). - Peripheral nerve problems (diabetic neuropathies). - Peripheral tissue damage due to reduced blood flow. - Tissue death, ulceration, infection, and amputation. **[OTHER ENDOCRINE ORGANS]** 18-9 Many organs have secondary endocrine functions. **Organs with secondary endocrine functions** - Intestines (digestive system) - Kidneys (urinary system) - Heart (cardiovascular system) - Thymus (lymphatic system) - Gonads (reproductive system) **Intestines** - Release hormones that coordinate digestive activities. **Kidneys** - Release the hormones **[calcitriol]** and **[erythropoietin (EPO)]**. - Release the enzyme **[renin]**. - Renin converts **[angiotensinogen]** to **[angiotensin I]**. - In the lungs, **[angiotensin-converting enzyme]** converts angiotensin I to **[angiotensin II]**. **Heart** - Produces **[natriuretic peptides (ANP and BNP)]**. - When blood volume becomes excessive. - Actions opposes those of angiotensin II. - Resulting in reduction in blood volume and blood pressure. **Thymus** - Produces **[thymosin]** (blend of several hormones). - Promotes development and maturation of lymphocytes. **Testes** - **[Interstitial endocrine cells:]** produce androgens. - **[Testosterone]** is an important androgen. - **[Nurse cells (Sertoli cells):]** support differentiation and physical maturation of sperm. - Secrete inhibin for negative feedback. **Ovaries** - Produce **[estrogens]**. - Principal estrogen is **[estradiol]**. - After ovulation, follicle cells. - Reorganize into corpus luteum. - Release estrogens and progesterone. **Adipose tissue** - Produces **[leptin]**. - Provides feedback control of appetite. - Maintains normal levels of GnRH and gonadotropin synthesis. 18-10 Hormones interact over our lifetime to produce coordinated physiological responses. When a cell receives instructions from two hormones at the same time, four outcomes are possible. **[Antagonistic effect:]** result depends on balance between two hormones. **[Synergistic effect:]** additive effect. **[Permissive effect:]** one hormone is needed for another to produce effect. **[Integrative effect:]** hormones produce different but complementary results. **Hormones important to growth** - Growth hormone - Thyroid hormones - Insulin - Parathyroid hormone and calcitriol - Reproductive hormones **Growth hormone (GH)** - In children... - Supports muscular and skeletal development. - In adults... - Maintains normal blood glucose concentrations. - Mobilizes lipid reserves. **Thyroid hormones** - If absent during fetal development or for first year after birth... - Nervous system fails to develop normally. - Developmental delay results. - If T4 concentrations decline before puberty... - Normal skeletal development does not continue **Insulin** - Allows passage of glucose and amino acids across plasma membranes. - Important for growing cells. **Parathyroid hormone (PTH) and calcitriol** - Promote absorption of calcium salts from bloodstream for deposition in bone. - Inadequate levels result in weak, flexible bones. **Reproductive hormones** Androgens in males, estrogens in females. - Stimulate cell growth and differentiation in target tissues. - Produce gender-related differences in. - Skeletal proportions. - Secondary sex characteristics. **[Stress:]** any condition that threatens homeostasis. **[General adaptation syndrome (GAS), *stress response*:]** how body responds to stress-causing factors. - Divided into three phases... - Alarm phase - Resistance phase - Exhaustion phase **Alarm phase** - Immediate response to stress. - Directed by sympathetic division of ANS. - Energy reserves (mainly glucose) are mobilized. - Body prepares "fight or flight" responses. - **Epinephrine is dominant hormone**. **Resistance phase** - Occurs if stress lasts longer than a few hours. - May last for weeks or months. - Lipids and amino acids are mobilized for energy. - Glucose is conserved for use by nervous tissue. - **Glucocorticoids are dominant hormones**. **Exhaustion Phase** - Begins when homeostatic regulation breaks down. - Drop in K+ levels due to aldosterone produced in resistance phase. - Failure of one or more organ systems will be fatal. **Hormone changes** - Can affect behavior, intellectual capabilities, memory, learning, and emotional states. **Few functional changes occur with age** - Reproductive hormones decline in concentration. -