Endocrine System Remember: Your nervous system senses impulses over a system of wire-like neurons that carry messages from one cell to another The term endocrine comes from Greek because endon = within and krinein = to secrete The endocrine system is made up of glands that release their products into the blood stream. These products broadcast messages throughout the body.

Hormones Hormones = “Chemical messengers” Hormones travel through the bloodstream and affect the activities of other cells by binding to specific chemical receptors on those cells Cells that have receptors for a particular hormone = target cells If a cell does not have the specific receptors for a hormone, that hormone will have no effect on that cell Responses to hormones are slower and last longer than responses to nerve impulses

Glands Gland = organ that produces and releases a substance or a secretion Exocrine glands = release their secretions through tube-like structures called ducts (sweat, tears, and digestive juices) Endocrine glands = release their secretions (hormones) directly into the bloodstream

Figure 39–2 The Endocrine Glands Section 39-1 Hypothalamus The hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland. Pineal gland The pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles. Thyroid The thyroid produces thyroxine, which regulates metabolism. Pituitary gland The pituitary gland produces hormones that regulate many of the other endocrine glands. Pancreas The pancreas produces insulin and glucagon, which regulate the level of glucose in the blood. Parathyroid glands These four glands release parathyroid hormone, which regulate the level of calcium in the blood. Ovary The ovaries produce estrogen and progesterone. Estrogen is required for the development of secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg. Thymus During childhood, the thymus releases thymosin, which stimulates Tcell development. Testis The testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics Adrenal glands The adrenal glands release epinephrine and nonepinephrine, which help the body deal with stress.

ENDOCRINE VS. EXOCRINE GLAND (copy chart) 2

EXAMPLES OF ENDOCRINE AND EXOCRINE SECRETIONS SALIVA SWEAT BILE TEARS ENDOCRINE: INSULIN ADRENALINE 2

Feedback Example Thyroid gland produces thyroxine, which affects activity of cells More thyroxine makes cells more active, less thyroxine makes cells less active The thyroid gland is controlled by the hypothalamus and anterior pituitary glands The hypothalamus secretes thyroid-releasing hormone (TRH), which stimulates the anterior pituitary to secrete thyroid-stimulating hormone (TSH), which stimulates the thyroid gland to release thyroxine, which inhibits the hypothalamus to maintain balance

Human Endocrine Glands Pituitary gland Hypothalamus Thyroid gland Parathyroid glands Adrenal glands Pancreas Reproductive glands

Figure 39–2 The Endocrine Glands Section 39-1 Hypothalamus The hypothalamus makes hormones that control the pituitary gland. In addition, it makes hormones that are stored in the pituitary gland. Pineal gland The pineal gland releases melatonin, which is involved in rhythmic activities, such as daily sleep-wake cycles. Thyroid The thyroid produces thyroxine, which regulates metabolism. Pituitary gland The pituitary gland produces hormones that regulate many of the other endocrine glands. Pancreas The pancreas produces insulin and glucagon, which regulate the level of glucose in the blood. Parathyroid glands These four glands release parathyroid hormone, which regulate the level of calcium in the blood. Ovary The ovaries produce estrogen and progesterone. Estrogen is required for the development of secondary sex characteristics and for the development of eggs. Progesterone prepares the uterus for a fertilized egg. Thymus During childhood, the thymus releases thymosin, which stimulates Tcell development. Testis The testes produce testosterone, which is responsible for sperm production and the development of male secondary sex characteristics Adrenal glands The adrenal glands release epinephrine and nonepinephrine, which help the body deal with stress.

Pituitary gland Bean-sized structure that dangles on tissue at the base of the skull within the brain The pituitary gland is divided into two parts: anterior pituitary and posterior pituitary “Master gland” because secretes nine hormones that directly regulate many body functions and controls the actions of several other endocrine glands Growth hormone (GH) Thyroid-stimulating hormone (TSH) Luteinizing hormone (LH) Follicle-stimulating hormone (FSH)

Hypothalamus Part of the brain above and attached to the pituitary gland Controls the secretions of the pituitary gland Connects nervous system and endocrine system

Thyroid gland At the base of the neck and wraps around the upper part of the trachea Regulates the body’s metabolism Produce thyroxine, which affects cellular respiration rates producing energy Hyperthyroidism = too much thyroxine (increased temperature, increased heart and metabolic rates, increased blood pressure, and weight loss) Hypothyroidism = too little thyroxine (low temperature, low metabolic rates, lack of energy, weight gain and sometimes goiter) Needs enough iodine to produce normal amounts of thyroxine

Parathyroid gland Four glands found on the back of the thyroid Maintain homeostasis in blood calcium levels Secrete parathyroid hormone (PTH), which regulates calcium levels in the blood

Adrenal glands Two pyramid-shaped structures that sit on top of the kidneys (one gland on each kidney) Help the body prepare for and deal with stress by secreting adrenaline Has two parts: Adrenal cortex: outer part secretes over 24 hormones (corticosteroids, aldosterone, corisol) Adrenal medulla: inner part secretes epinephrine and norepinephrine producing the “fight or flight” response to stress by increasing heart rate, blood pressure and blood flow

Pancreas Right side of the body behind the stomach Remember: the pancreas secretes enzymes through a duct to help break down food = exocrine gland Different cells in the pancreas release hormones into the blood = endocrine gland Clusters of cells that resemble islands = islets of Langerhans that secrete insulin and glucagon that help keep the level of glucose in the blood stable Insulin stimulates cells in liver and muscles to remove sugar from the blood and store sugar as glycogen or fat Glucagon stimulates the liver to break down glycogen and release glucose back into the blood Diabetes mellitus = too little insulin (high blood glucose levels)