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Honors biology Reading Guide Chapter 26 Chemical signals coordinate body functions. Endocrine glands secrete hormones that are carried by the blood to target cells. Neurons secrete neuro-­‐transmitters that signal nearby neurons. Neurosecretory cells perform both functions by secreting their chemical signals into the blood In vertebrates two classes of molecules function as hormones. Amino acid derived hormones bind to receptors in the target cell membrane. This activates a set of relay molecules, which activate a protein that carries out a response. Steroid hormones enter the target cell and bind to a receptor inside. The receptor-­‐hormone complex turns genes on or off. This has a somewhat slower, loner-­‐lasing effect. A hormone can bind to a variety of receptors in carious cells, so one hormone can have many effects In vertebrates, there are more than a dozen endocrine glands. The hypothalamus connects the nervous and endocrine systems and controls many glands. Releasing and inhibiting hormones from the anterior pituitary, controlling growth, metabolism, and reproduction. Hormone of the posterior pituitary are produced in the hypothalamus, and nerve impulses from the hypothalamus trigger their secretion Two hormones form the thyroid gland regulate development and metabolism. Secretion is triggered by thyroid stimulating hormone from the anterior pituitary damping thyroid secretion. This kind of negative feedback maintains constant levels of many hormones. The thyroid and parathyroid glands regulate blood calcium Antagonistic pancreatic hormone regulates blood glucose. When blood glucose rises the pancreas increases its secretion of insulin, which causes cells to taking and stores glucose. When blood glucose drops, insulin secretion drops and the pancreas put out more glucagon. This causes the liver to release glucose from storage maintaining blood glucose level The adrenal gland mobilizes response to stress. Nerve impulses can quickly trigger the adrenal medulla to release the fight or flight hormones epinephrine and norepinephrine. Which raise blood pressure breathing rate and metabolic rate. In response to longer term stress the hypothalamus signals the anterior pituitary to release ACTH, which stimulates the adrenal cortex to secrete mineralocorticoids and glucocorticoids, which act on slat and water balance and fuel mobilization The gonads secrete sex hormones. The female ovaries produce estrogens and progestin, which maintain the reproductive system, stimulate the development of female characteristics and prepare the uterus for pregnancy. The male testes secrete androgens. Mainly testosterone tat shape male sexual development and function secretion of sex hormones is regulated by the hypothalamus and anterior pituitary Neurotransmitter from a nerve cell Hormone from an endocrine cell Endocrine v Function involves chemical signals v Signals carries by body fluids v Signals carried by blood v Slower messages v Longer lasting responses v More pinpoint localized effects Nervous v Function involves electrical signals v Signals carries by neurons v Rapid messages v Split second responses v Widespread whole body effects Both v A system of internal communication Gland Pituitary Hormone(s) Thyroxin Triiodothyronine Calcitonin Adrenal medulla Adrenaline Noradrenaline Mineralocorticoids Adrenal cortex v
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Pancreas Glucagon Insulin Parathyroid glands Parathyroid hormone Anterior lobe Growth hormone Thyroid stimulating hormone Adrenocorticotropic Action Control metabolic processes Lower blood calcium level Trigger fight or flight response Regulate reabsorption of Na and loss of K by kidneys Raises blood glucose Lowers blood glucose Raises blood calcium level Stimulates growth Stimulated thyroid gland Stimulates adrenal cortex Posterior pituitary Antidiuretic hormone Promotes water retention by kidneys Thymus Thymosin Stimulated T cell development The pancreas makes two opposing hormones insulin and glucagon Ø Diabetics have high blood sugar so many of them have to take insulin Ø Insulin makes blood sugar go down and it makes cells take sugar out of the blood and use it or store it Ø Glucagon must make blood sugar go up by causing cells to get it out of storage and put it into the blood Ø Increase in blood sugar triggers insulin secretion (to make sugar go down) Epinephrine and norepinephrine Ø Increase breathing rate Ø Respond to short term stress Ø Triggered by nerve impulses from the hypothalamus Ø Secreted by adrenal medulla Ø Suppressed the inflammatory response and immune system Ø Dilate and or constrict blood vessels redirecting blood flow Mineralocorticoids Ø Secreted by adrenal cortex Ø Also triggered by ACTH from the pituitary Ø Cause retention of sodium and water by kidneys Ø Increase metabolic rate Glucocorticoids Ø Often prescribed to relieve pain from athletic injuries Ø Triggered by ACTH from the pituitary Ø Cause proteins and fats to be broken down to make glucose Ø Increase blood volume and pressure in response to long term stress Ø Secreted by adrenal cortex