16.4 Endocrine System

• Veins have valves along their length that prevent backflow of blood away from the heart, since pressure is lower.
• The major veins take blood from the same parts of the body.

• The arteries of the body start at the aortic arch and branch to supply the organs and muscles of the body with oxygenated blood.
• The veins of the body return blood to the heart.
• The pulmonary arteries are blue to show that they are deoxygenated, and the pulmonary veins are red to show that they are oxygenated.

• The hormones produced by the endocrine system control and regulate many body processes.
• The nervous system controls the functions of the other organ systems.
• hormones are produced by cells of the endocrine system.
• The OpenStax book is available for free at http://cnx.org/content/col11487/1.9 and may be located in organs or tissues that have functions in addition to hormone production.
• Hormones circulate throughout the body, stimulating a response in cells that have the ability to bind with them.
• Changes in the receiving cells affect the functioning of the organ system that they belong to.
• The nervous system and hormones act in concert to change the body.

• The coordination of many different systems and organs is needed to maintain the body's equilibrium.
• One mechanism of communication between neighboring cells and between cells and tissues in distant parts of the body is the release of chemicals called hormones.
• The endocrine organs include the pancreas, which makes hormones that regulate blood-glucose levels, the adrenal glands, which make hormones that regulate responses to stress, and the hypothyroidism, which makes hormones that regulate metabolism.

• The exocrine glands have different functions.
• sweat is released into ducts that carry it to the surface of the skin The exocrine functions of the pancreas include releasing hormones into the blood.
• The juices are carried by the ducts into the small intestine.

• An endocrinologist is a doctor who specializes in treating disorders of the endocrine system.
• The surgical treatment of diseases of the endocrine system is done by an endocrine surgeon.
• Disorders of the pancreas, acromegaly, and pituitary dwarfism are some of the diseases that are managed by endocrinologists.

• Endocrinologists use a lot of laboratory tests to diagnose and assess patients.
• Many diseases are diagnosed using tests that affect the functioning of the endocrine system.
• The effect of stimulating or suppressing an organ on the production of hormones can be determined with the help of blood samples.
• To diagnose diabetes, patients need to fast for 12 to 24 hours.
• They are given a drink that stimulates the pancreas to make moreinsulin, which lowers blood-glucose levels.
• After the sugar drink is consumed, a blood sample is taken.
• The blood-glucose level will be within a normal range if the pancreas is functioning properly.
• The A1C test can be done during blood screening.
• The A1C test is an indicator of how well the blood sugar is being managed.

• Once a disease such as diabetes has been diagnosed, endocrinologists can prescribe lifestyle changes and medications to treat the disease.
• Some cases of diabetes can be managed by exercise, weight loss, and a healthy diet; in other cases, medications may be required.
• If the disease can't be controlled with these methods, the endocrinologist may prescribe injections.

• In addition to clinical practice, endocrinologists may also be involved in primary research and development activities.
• Diabetes islet transplant research is investigating how healthy islet cells may be used.
• Patients with islet transplants may be able to stop taking injections.

• Even though hormones circulate throughout the body and come into contact with many different cell types, they only affect cells that possess the necessary receptors.
• It is possible for a specific hormone to be found in many different cells or in a small number of specialized cells.
• THe hormones act on many different tissue types, stimulating metabolism.

• The number of cells that respond to a hormone is determined by the number of receptors that respond.
• Increased or decreased cell sensitivity can be caused by the number of receptors available to respond to a hormone.

• The hormones that are released into the surrounding fluid are carried to various organs and tissues within the body.
• The hormones include the pituitary, thyroid, parathyroid, adrenal, gonads, pineal, and pancreas.

• The hypothalamus is attached to it.
• The hypothalamus produces the antidiuretic hormone.

• Most of the hormones that regulate other hormones are produced by the hypothalamus.

• Growth hormone, prolactin, thyroid-stimulating hormone, adrenocorticotropic hormone, and follicle-stimulating hormone are produced by the pituitary.
• Growth hormone stimulates cellular activities.
• The production of milk is stimulated by prolactin.
• The production of hormones by other tissues is regulated by hormones produced by the anterior pituitary.
• There is a book available for free at http://cnx.org/content/col11487/1.9 It is a part of the brain that extends down from the hypothalamus.

• There are two lobes connected to the butterflyshaped gland.
• T4 and triiodothyronine, also known as T3 and T4 respectively, are hormones produced by the thyroid follicle cells.
• T3 and T4 have the effect of stimulating metabolism in the body and increasing energy use, as well as being released by the thyroid in response to the hormone produced by the anterior pituitary.
• The third hormone is produced by the thyroid.
• Calcitonin is released in response to rising calcium ion concentrations in the blood and has the effect of reducing those levels.

• The glands are located on the surface of the thyroid.

• The parathyroid hormone is produced by the parathyroid glands.
• When calcium ion levels fall below normal, parathyroid hormone increases blood calcium concentrations.

• Different hormones are produced by these regions.

• Mineralocorticoids are produced by the adrenal cortex.
• The main mineralocorticoid is aldosterone, which regulates the concentration of ion in urine, sweat, and saliva.
• The release of Aldosterone from the adrenal cortex can be stimulated by a decrease in blood concentrations of sodium ion, blood volume, or blood pressure.
• The blood-glucose levels are maintained by the glucocorticoids.
• They control a response to stress by increasing the synthesis of fats and proteins and interacting with the drug epinephrine.

• Sex hormones produced in small amounts by the adrenal cort can be used to supplement sex hormones released from the gonads.
• There are two types of secretory cells in the adrenal medulla.

• The fightor-flight response is caused by immediate, short-term changes in response to stressors.
• Increased heart rate, breathing rate, and cardiac muscle contraction are some of the responses.
• They speed up the breakdown of glucose in muscles and fat in fat in the body, as well as redirecting blood flow away from skin and viscera.
• The sympathetic nervous system that comes from the hypothalamus stimulates the release of epinephrine and norepinephrine.

• It contains exocrine cells that release hormones.

• The islets of Langerhans are formed by the cells of the pancreas.
• The alpha cells, which produce the hormone glucagon, are one of the cell types in the islet.
• The hormones regulate blood-glucose levels.
• Glucagon causes the release of sugar from the body's cells to the blood.

• The male testes and female ovaries produce steroid hormones.
• Testes produce androgens, testosterone being the most prominent, which allow for the development of secondary sex characteristics and the production of sperm cells.
• The hormones produced by the ovaries cause secondary sex characteristics, control production of eggs, and prepare the body for childbirth.

• There are several organs that have non-endocrine functions.
• The organs include the heart, kidneys, intestines, and adipose tissue.
• The walls of the atria contain cells that respond to increased blood volume.
• It causes a reduction in blood pressure and blood volume.

• Several hormones are produced in the gastrointestinal tract.
• The GI tract contains the endocrine cells.
• The release of gastric juices helps to break down and digest food in the GI tract.

• The kidneys have functions.
• The hormones regulate blood pressure and ion concentrations.
• Erythropoietin is released in response to low oxygen levels.
• Red blood cells are formed in the bone marrow.
• Athletes use erythropoietin to improve performance.
• The risks of erythropoietin do not end there, since it increases the strain on the heart and increases the risk of blood clot.

• The development of the immune response in infants is influenced by the hormones produced by the thymus.
• The hormone leptin is produced in fat tissue.
• The feeling of satiety is caused by leptin.

• Negative feedback controls the production and release of hormones.
• The concentration of hormones in blood can be maintained within a narrow range.
• The anterior pituitary is the one that signals the release of hormones.

• T3 and T4 are hormones that are released into the air by the anterior pituitary.
• Increased levels of these hormones in the blood result in feedback to the hypothalamus and anterior pituitary.

• The body tries to compensate by producing more TSH.