The Endocrine System Chapter 11

Introduction The endocrine system is made up of the cells, tissues and organs that secrete hormones into body fluids. The body has two types of glands: Exocrine Secretes products into ducts Endocrine Secretes products into body fluids

General Characteristics of Endocrine System Endocrine glands and their hormones regulate a number of metabolic processes within cells, as well as reproduction, development and growth. Endocrine glands include the pituitary gland, thyroid gland, parathyroid glands, adrenal glands, pancreas and other hormone-secreting glands and tissues.

Hormone Action A hormone is a biochemical secreted by one cell that affects a specific target cell with appropriate cell surface receptors. Prostaglandins are locally produced lipids that affect the organ in which they are produced.

Control of Hormonal Secretions Hormone levels are very precisely regulated. Negative Feedback Systems Commonly control hormonal releases. When the concentration of the regulated substance reaches a certain level (high or low), it inhibits the gland from secreting more hormone until the concentration returns to normal (if the level is too high), or releases more (if the level is too low).

Pituitary Gland Is attached to the base of the brain and has an anterior lobe (anterior pituitary) and a posterior lobe (posterior pituitary) The pituitary gland is controlled by the brain. Releasing hormones from the hypothalamus control the secretions of the anterior pituitary. The posterior pituitary releases hormones into the bloodstream in response to nerve impulses from the hypothalamus.

Pituitary Gland

Anterior Pituitary Hormones Growth Hormone (GH) Stimulates body cells to grow and reproduce and speeds the rate at which cells use carbohydrates and fats Prolactin (PRL) Promotes milk production following the birth of an infant. Thyroid-Stimulating Hormone (TSH) Controls the secretion of hormones from the thyroid gland.

Posterior Pituitary Hormones Anti-Diuretic Hormone (ADH) Causes the kidneys to conserve water (prevents dehydration) Oxytocin Plays a role in childbirth by contracting muscles in the uterine wall and in milk-letdown by forcing milk into ducts from the milk glands.

Thyroid Gland Located below the larynx and consists of two broad lobes connected by an isthmus.

Hormones of the Thyroid Gland Thyroid Hormones Increase the rate at which cells release energy from carbohydrates, enhance protein synthesis, and stimulate the breakdown and mobilization of lipids. These hormones are essential for normal growth and development. The hypothalamus and pituitary gland control release of thyroid hormones.

Hormones of the Thyroid Gland Calcitonin Lowers blood levels of calcium and phosphate ions when they are too high. Increases the rate at which calcium is stored in bones and excreted in the urine.

Parathyroid Glands The four, tiny parathyroid glands are located on the posterior of the thyroid.

Hormones of the Parathyroid Gland Parathyroid Hormone (PTH) Increases blood calcium ion concentration and decreases phosphate ion concentration. Stimulates bone breakdown by osteoclasts, which releases calcium into the blood. Influences the kidneys to conserve calcium and causes increased absorption of calcium in the intestines. Calcitonin and PTH have opposite effects in regulating calcium ion levels in the blood.

Adrenal Glands Sit atop the kidneys enclosed in a layer of fat.

Hormones of the Adrenal Gland Aldosterone Causes the kidneys to conserve sodium ions and thus, water and to excrete potassium ions. Cortisol Influences the metabolism of glucose, protein and fat in response to conditions that stress the body and require a greater supply of energy in the bloodstream. Adrenal Sex Hormones Hormones that supplement those released by the gonads and may stimulate early development of reproductive organs.

Pancreas Secretes hormones as an endocrine gland and digestive juices to the digestive tract as an exocrine gland.

Hormones of the Pancreas Glucagon Increases blood levels of glucose by stimulating the breakdown of glycogen and the conversion of non-carbohydrates into glucose. Responds to low blood glucose levels Insulin Decreases blood levels of glucose by stimulating the liver to form glycogen, increasing protein synthesis and stimulating adipose cells to store fat. Responds to high blood glucose levels.

Pineal Gland Located near the upper portion of the thalamus of the brain

Hormones of the Pineal Gland Melatonin Involved in the regulation of the circadian rhythms of the body Circadian rhythms regulate our sleep/awake cycle.

Thymus Gland Located between the lungs, under the sternum

Hormones of the Thymus Gland Thymosins Affect production and differentiation of T-Lymphocytes that are important in immunity.

Reproductive Glands Ovaries Testes Produce estrogen and progesterone in females Testes Produce testosterone in males

Disease Definitions Pathology: the science of causes and effects of diseases Hyper-: more than normal Hypo-: less than normal

Adrenal Gland Disorders Addison’s Disease Pathology: hypersecretion of all adrenal cortex hormones Symptoms: Bronze skin tone, muscles are weak, burnout, susceptibility to infection, hypoglycemia

Adrenal Gland Disorders Cushing’s Syndrome Pathology: tumor in adrenal gland; hypersecretion of adrenal cortex Symptoms: extreme obesity, hirsutism (excessive hair growth), “moon face”, “buffalo hump”

Diseases of the Pituitary Giantism Pathology: hypersecretion of GH (growth hormone) Symptoms: overgrowth of long bones leading to excessive tallness

Diseases of the Pituitary Acromegaly Pathology: hypersecretion of GH Symptoms: Overdevelopment of bones in face, hands, and feet; cartilge is attacked; chin protudes, lips, nose, and extremities enlarge

Disease of the Pituitary Dwarfism Pathology: Hyposecretion of GH in childhood (genetic) Symptoms: small size (body proportions and intellect are normal) sexual immaturity

Diseases of Thyroid Hyperthyroidism Pathology: hypersecretion of thyroxine Symptoms: consumption of large quantities of food but loss of body fat and weight; enlargement of the gland (GOITER) and bulging of the eyeballs (EXOPTHALMOS)

Diseases of the Thyroid Hypothyroidism Pathology: hyposecretion of thyroxine in adulthood Symptoms: dry and itchy skin, dry and brittle hair, muscle cramps at night Cretinism Pathology: hyposecretion of thyroxine in childhood Symptoms: dwarfism during childhood

Diseases of the Parathyroid Gland Tetany Pathology: hyposecretion of parathyroid hormone Symptoms: development of convulsive twitching

Sex Related Endocrine Diseases Central Hypogonadism Pathology: hyposecretion of FH and LH from the pituitary gland Females: (BEFORE PUBERTY) no menstruation or breast development; (AFTER PUBERTY) hot flashes, loss of body hair Males: breast enlargement, decreased beard and body hair, muscle loss

Diseases of Pancreas Diabetes Mellitus Type 1 (“Juvenile Diabetes”) Pathology: body’s immune system attacks and destroys cells in Islets of Langerhans Effect: Pancreas unable to secrete enough insulin Treatment: Insulin shots

Diseases of Pancreas Diabetes Mellitus Type 2 Pathology: muscle, fat, and liver cells become unable to respone to insulin properly (as a result of poor diet, low activity level, excess body weight around the waist) Effect: Cells unable to use blood sugar for cellular respiration Treatment: strict diet and exercise; doctor may prescribe medication that lowers blood sugar Long term effects: blindness, infection needing amputation, nerve damage, damage to blood vessels and nerves

Disease of Pineal Gland SADS (Seasonal Affective Disorder) Pathology: hypersecretion of melatonin Symptoms: cells prepare for winter, sleepy, sad, tired, gain weight, depression

Diseases of the Thymus Gland Relatively rare and potentially serious Mainly Genetic Severe Combined Immunodeficiency disorder (SCID) Pathology: mutation in a gene that affects the development of T cells and other immune cells Symptoms: compromised immune system; inability to fight off infections