Section 1 Hormones Chapter 50 Objectives • Statethe major functions of hormones. • Differentiatebetween endocrine and exocrine glands. • Comparethe structure of amino acid-based hormones with the structure of steroid hormones. • Comparehow amino acid-based hormones act on their target cells with how steroid or thyroid hormones act on their target cells. • Relatehow neuropeptides and prostaglandins act like hormones.

Section 1 Hormones Chapter 50 Function and Secretion • Hormones are substances secreted by cells that act to regulate the activity of other cells in the body. • Hormones affect all cells in the body and are made and secreted by endocrine glands. • Endocrine glandsare ductless organs that secret hormones either into the bloodstream or the fluid around cells.

Section 1 Hormones Chapter 50 Function and Secretion, continued • The endocrine glands can be found through out the body and are collectively known as theendocrine system. • Endocrine glands, such as the pancreas, can also be exocrine glands. • Exocrine glandssecrete substances through ducts to specific locations inside and outside the body.

Section 1 Hormones Chapter 50 The Endocrine System

Section 1 Hormones Chapter 50 Comparing Endocrine and Exocrine Glands Click below to watch the Visual Concept. Visual Concept

Section 1 Hormones Chapter 50 Types of Hormones • Hormones can be grouped into two types based on their structure. Hormones can either be amino acid-based hormones or steroid hormones. • Amino acid based-hormones are made of amino acids, either a single modified amino acid or a protein made of 3-200 amino acids, and are water soluble. • Steroid hormonesare lipid hormones that the body makes from cholesterol and are fat soluble. • Similar to steroid hormones are thyroid hormones.

Section 1 Hormones Chapter 50 Hormone Action • Regardless of which type of hormone is being activated, all hormones affect only their target cells. • Target cells are specific cells to which a hormone travels to produce a specific effect. • On the target cells are receptors.Receptorsare proteins that bind to specific signal molecules, such as hormones, that cause a cell to respond.

Section 1 Hormones Chapter 50 Hormone Action, continued • Amino acid-based hormones • Amino acid-based hormones bind to receptor proteins on the cell membrane and are called first messengers. • Second messengers are then activated. Asecond messengeris a molecule that initiates changes inside a cell in response to the binding of a specific substance to a receptor on the outside of a cell. • Changes to the cell through enzyme action then occur in a cascade fashion.

Section 1 Hormones Chapter 50 How Amino Acid-Based Hormones Work

Section 1 Hormones Chapter 50 Action of Amino Acid-Based Hormones Click below to watch the Visual Concept. Visual Concept

Section 1 Hormones Chapter 50 Hormone Action, continued • Steroid and Thyroid Hormones • Steroid and thyroid hormones are similar because they are both fat soluble. • Because these hormones are fat soluble they can pass through the cell membrane. • Thus, these hormones can enter their target cells and bind directly to receptor sites in the cytoplasm or nucleus and directly activate enzymes.

Section 1 Hormones Chapter 50 How Steroid Hormones Work

Section 1 Hormones Chapter 50 Action of Steroid Hormones Click below to watch the Visual Concept. Visual Concept

Section 1 Hormones Chapter 50 Other Types of Hormones • Two other types of chemical messengers that are classified as hormones are neuropeptides and prostaglandins. • Neuropeptidesare hormones secreted by the nervous system and tend to affect many cells near the nerve cells that release them. • Prostaglandinsare modified fatty acids that are secreted by most cells and tend to accumulate in areas where tissues are disturbed or injured.

Section 1 Hormones Chapter 50 Comparing Hormones and Prostaglandins Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Objectives • Identifythe relationship between the hypothalamus and the pituitary gland in the release of hormones. • Listthe functions of the major endocrine glands and hormones. • Explainthe role of feedback mechanisms in maintaining homeostasis. • Comparehow negative feedback and positive feedback mechanisms are used to regulate hormone. • Summarizehow antagonistic hormones work as pairs to maintain homeostasis.

Section 2 Endocrine Glands Chapter 50 Hypothalamus and Pituitary Gland • Two organs, the hypothalamus and the pituitary gland, control the initial release of many hormones for the endocrine system. • The hypothalamus is the area of the brain that coordinates many activities of the nervous and endocrine systems.

Section 2 Endocrine Glands Chapter 50 Hypothalamus and Pituitary Gland, continued • The hypothalamus responds to information it receives from the body by issuing instructions, as hormones, to the pituitary gland. • Thepituitary glandhas two parts, anterior and posterior, and stores and releases hormones produced by the hypothalamus.

Section 2 Endocrine Glands Chapter 50 Hypothalamus and Pituitary Gland, continued • The nerve cells in the hypothalamus that secrete hormones are calledneurosecretory cells. • These cells secrete two types of hormones to the pituitary gland. • Releasing hormonesstimulate the anterior pituitary to make and secrete hormones. • Release-inhibiting hormonesinhibit production and secretion of anterior-pituitary hormones.

Section 2 Endocrine Glands Chapter 50 The Hypothalamus and the Pituitary Gland

Section 2 Endocrine Glands Chapter 50 The Hormones Secreted by the Pituitary Gland

Section 2 Endocrine Glands Chapter 50 Anatomy of the Human Pituitary Gland Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Thyroid Gland • Thethyroid gland is located near the larynx and helps maintain a normal heart rate, blood pressure, and body temperature by increasing or decreasing cellular metabolic rates. • The thyroid gland is also important for development.

Section 2 Endocrine Glands Chapter 50 Anatomy of the Human Thyroid Gland Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Thyroid Gland, continued • Abnormal thyroid activity can result in hypothyroidism or hyperthyroidism. • Overproduction of thyroid hormones is calledhyperthyroidismand can have symptoms that vary from overactivity to high body temperature. • A deficiency in a thyroid hormone is known ashypothyroidismand can have symptoms that vary from weight gain to retardation.

Section 2 Endocrine Glands Chapter 50 Hyperthyroidism

Section 2 Endocrine Glands Chapter 50 Hypothyroidism

Section 2 Endocrine Glands Chapter 50 Adrenal Glands • Humans have anadrenal glandlocated above each kidney. Each adrenal gland has an inner core, the medulla, and an outer core, also called the cortex. • The medulla and the cortex function as separate endocrine glands. • The medulla is controlled by the nervous system, and the cortex is controlled by the anterior pituitary.

Section 2 Endocrine Glands Chapter 50 Adrenal Glands, continued • Adrenal Medulla • The adrenal medulla secretes the hormones that stimulate a “flight-or-fight” response to a stress. • In this response, the hormonesepinephrine,also called adrenaline, andnorepinephrine are released. • These hormones increases heart rate, blood pressure, blood glucose levels, and blood flow into the heart and lungs so the body can respond to the initial stress.

Section 2 Endocrine Glands Chapter 50 Adrenal Glands, continued • Adrenal Cortex • In the presence of some stresses the pituitary gland will secrete the adrenocorticotropic hormone (ACTH). • This hormone stimulates the adrenal cortex to produce the hormone cortisol. • Cortisolpromotes the production of glucose from proteins to help cells make usable energy.

Section 2 Endocrine Glands Chapter 50 The Adrenal Gland

Section 2 Endocrine Glands Chapter 50 Adrenal Gland Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Gonads • Gonads are the gamete-producing organs that also produce a group of steroid sex hormones. • Gonads, ovaries in females and the testes in males, are regulated by sex hormones, which begin production at puberty. • Pubertyis the adolescent stage during which the sex organs mature and secondary sex characteristics appear.

Section 2 Endocrine Glands Chapter 50 Gonads, continued • The production of sexhormones is stimulated by the release of two hormones by the pituitary. • The first hormone is luteinizing hormone (LH).This hormone stimulates ovulation and the release ofprogesteronein females and the release of androgens, such astestosterone,in males. • The second hormone isfollicle-stimulating hormone (FSH).This hormone stimulates the growth and maturation of the ovarian follicles in females and sperm production in males.

Section 2 Endocrine Glands Chapter 50 Gonads Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Pancreas • The pancreas contains both exocrine and endocrine cells. The endocrine cells are calledislets of Langerhans. • These cells secrete hormones that regulate the level of sugar in the blood. The hormone insulin is one of the hormones produced. • Insulinlowers the blood sugar level by stimulating body cells to store glucose or use it for energy.

Section 2 Endocrine Glands Chapter 50 Pancreas Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Pancreas, continued • A condition calleddiabetes mellitusoccurs when cells are unable to obtain glucose from the blood. This results in a high glucose level in the blood • There are two types of diabetes: Type I and Type II. • Type I occurs when immune cells attack and destroy the islet of Langerhans cells. • Type II occurs when cells don’t have sufficient insulin levels or when the organism’s cells have become less responsive.

Section 2 Endocrine Glands Chapter 50 Pancreas, continued • A condition calledhypoglycemiaoccurs when excessive insulin is stored and not properly delivered to body cells. • This leads to a lowered blood glucose concentration, which can cause such symptoms as overactivity and dizziness.

Section 2 Endocrine Glands Chapter 50 Other Endocrine Glands • There are several other glands in the endocrine system, including thymus gland, the pineal gland and the parathyroid glands. • Thymus Gland • The thymus gland is located beneath the sternum and plays a role in the development of the immune system by secretingthymosin. • This amino acid-based hormone stimulates formation of T cells.

Section 2 Endocrine Glands Chapter 50 Other Endocrine Glands, continued • Pineal Gland • The pineal gland is located near the base of the brain and helps regulate sleep patterns by secretingmelatonin.

Section 2 Endocrine Glands Chapter 50 Pineal Gland Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Other Endocrine Glands, continued • Parathyroid Gland • The parathyroid glands is made up of four glands embedded in the two thyroid glands. • These glands secrete theparathyroid hormone,which stimulates the transfer of calcium ions from the bones to the blood.

Section 2 Endocrine Glands Chapter 50 Parathyroid Gland Click below to watch the Visual Concept. Visual Concept

Section 2 Endocrine Glands Chapter 50 Other Endocrine Glands, continued • Digestive Cells • Some of the digestive organs also act as endocrine cells by secreting a variety of hormones that control digestive processes. Two hormones that are secreted are gastrin and secretin. • Gastrinis released by the stomach when food is eaten. • Secretinis released by the small intestine and helps stimulates the release of various digestive fluids from the pancreas.

Section 2 Endocrine Glands Chapter 50 Feedback Mechanisms • The endocrine system plays an important role in the maintenance of a stable internal environment, or homeostasis. • Maintenance of homeostasis is controlled by feedback mechanisms. A feedback mechanism is one in which the last step in a series of events controls the first. • Feedback mechanisms can be either negative or positive.

Section 2 Endocrine Glands Chapter 50 Feedback Mechanisms, continued • Negative Feedback • When the final step in a series of events inhibits the initial signal in the series it is callednegative feedback. • An example of negative feedback is the regulation of thyroid hormones.

Section 2 Endocrine Glands Chapter 50 Negative Feedback

Section 2 Endocrine Glands Chapter 50 Feedback Mechanisms, continued • Positive Feedback • Positive feedback occurs when the release of an initial hormone stimulates release or production of other hormones or substances. • An example of positive feedback is the stimulation and increase in luteinizing hormone by estrogen.

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