35-3

35.3 The Endocrine System Bio 30 NWRC

Endocrine Glands • The endocrine system is composed of GLANDS which secrete HORMONES in to the bloodstream • Hormones have 2 classifications Steroid hormones and nonsteroid hormones.

Steroid Hormones • Steroid hormones are crucial substances for the proper function of the body. They mediate a wide variety of vital functions ranging from anti-inflammatory agents to regulating events during pregnancy. They are synthesized and secreted into the bloodstream by endocrine glands such as the adrenal cortex and the gonads (ovary and testis).

Steroid Hormones • Steroid hormones are made on a basis of need. Whenever the body needs a certain process done or needs a certain protein synthesized, the brain releases a signal to produce a certain type of hormone. All steroid hormones work by causing the target cells to initiate protein synthesis.

Steroid Hormones • Progesterone- Regulates events during pregnancy Corticoids- Suppress inflammation reactions and regulates mineral and sugar metabolism. Androgens- Promote male sex development and maintain male sex characteristics. Estrogens- Promote female sex development

Amino Acid Hormones • Also called non-steroid hormones Steroid and non-steroid hormones differ in how they affect target cells. • Made of AAs these hormones cannot diffuse through plasma membrane must bind to receptor on plasma membrane • Once the hormone binds to the receptor , the receptor activates an enzyme found on the inside of the membrane

Negative Feedback • Is essentially a corrective mechanism, consider the following scenarios in a person • The level of glucose in the bloodstream drops • The person requires glucose in cells to meet the demand for ATP • The body detects this with a particular receptor designed for this function • These receptors release hormones, chemical messages that initiate the start of the feedback mechanism • The hormones travel to their target tissue and initiate a corrective response • In this case, the corrective response is the secretion of more glucose into the bloodstream

Negative Feedback

Endocrine Glands and their Hormones • The pituitary gland is sometimes called the "master" gland of the endocrine system, because it controls the functions of the other endocrine glands. The pituitary gland is no larger than a pea, and is located at the base of the brain.

Endocrine Glands and their Hormones • The pituitary gland regulates other glands (thyroid, adrenal, gonads) and also acts on organs and tissues of the body. For example the Human Growth Hormone it secretes stimulates growth by stimulating cell division in muscle and bone tissue.

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Endocrine Glands and their Hormones The THYROID and the thyroid hormone, thyroxine, is a modified amino acid that contains iodine. It accelerates metabolism throughout the body. An abnormal deficiency of thyroxine causes goiter, decreased heart rate, lethargy, obesity, and decreased mental alertness. In contrast, hyperthyroidism (too much thyroxine) is characterized by profuse perspiration, high body temperature, increased basal metabolic rate, high blood pressure, loss of weight, and irritability.

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Endocrine Glands and their Have you ever noticedHormones that the salt we get has iodine added to it? The main reason that you need iodine is because of the thyroid gland. The thyroid gland produces two hormones (thyroxine and triiodothyronine) that your body uses during metabolism Iodine is an important element in these two hormones, so without iodine your thyroid gland cannot produce them. When starved for iodine, the thyroid gland also swells, and when it does it is called goiter

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Endocrine Glands and their Hormones The parathyroid glands are small pealike organs located on the posterior surface of the thyroid. They secrete parathyroid hormone, which regulates the calcium and phosphate balance between the blood and other tissues. Increased parathyroid hormone increases bone reabsorption and elevates plasma calcium.

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The human pancreas has two main functions: [1] to produce pancreatic endocrine hormones (e.g., insulin & glucagon) which help regulate many aspects of our metabolism and [2], to produce pancreatic digestive enzymes. Pancreatic production of insulin,, and glucagon plays an important role in maintaining sugar and salt balance in our bodies and therefore any problem in the production or regulation of these hormones will manifest itself with problems with blood sugar and fluid / salt imbalances.

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Type 1 diabetes is a disease in which the pancreas does not produce insulin or insulin is not used properly by the body. Persons with type 1 diabetes have glucose building up in the blood instead of being used for energy. The cause of type 1 diabetes remains unknown. However, it is not preventable, and it is not caused by eating too much sugar. The body's defense system may attack insulinmaking cells by mistake, but we don't know why. People are usually diagnosed with type 1 diabetes before the age of 20, most often during childhood or their teens.

Endocrine Glands and their Hormones • type 2 diabetes, the body produces insulin. However, the insulin their pancreas secretes is either not enough or the body is unable to recognize the insulin and use it properly. When there isn't enough insulin or the insulin is not used as it should be, glucose can't get into the body's cells.

Endocrine Glands and their Hormones • Each Adrenal gland consists of a medulla (the center of the gland) which is surrounded by the cortex. The medulla is responsible for producing epinephrine (adrenaline). and norepinephrine. These hormones regulate heart rate, blood pressure etc. during stressful times • The adrenal cortex produces other hormones necessary for fluid and electrolyte (salt) balance in the body such as cortisone and aldosterone.

Assessment • 1. Hormones work in the opposite direction to the stimulus; therefore the feedback system is described as negative

Assessment • 2. Insulin is secreted when sugar levels are high. Glucagon is secreted when levels are sugar levels are low

Assessment • 3. Both systems help maintain homeostasis. For example the hypothalamus, a part of the brain secretes ADH which regulates the balance of water in the body.

Assessment • 4. Pituitary hormones regulate many body functions as well as other endocrine glands. • Thyroid hormones increase metabolism • Parathyroid increase blood calcium levels. • Pancreas aids digestion and produces hormones that regulate blood sugar levels • Adrenal hormones aid in reabsorbing sodium, raising blood sugar levels and reducing inflamation.