The Endocrine System By: Morgan, Leandra, Emma & Andreas
What is the Endocrine System? • The endocrine system is composed of organs and glands which are responsible for transferring information and instructions from one group of cells to another • The endocrine system uses hormones to transfer these messages • Glands are responsible for secreting these hormones. A gland is a group of cells that produces and secrets chemicals. A gland selects and removes materials from the blood, processes them, and secretes the finished chemical product for use somewhere else in the body. • The pancreas, although a main part of the digestive system, also secretes hormones • Although the endocrine glands are the body’s main hormone producers some non-endocrine organs – such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta – also produce and release hormones
What is a Hormone? • A hormone is a chemical messenger whose job it is to transfer information and instruction from one set of cells to another. • Once a hormone is secreted, it travels from the endocrine gland through the bloodstream to their target cells (cells designed to receive that hormones specific message). • These target cells have receptors that only latch onto specific hormones, and each hormone has its own receptor, so that each hormone can only communicate with its specified target cells. • When the hormones reach their target cells, they lock into their matching receptors and transmit their chemical instructions into the cell.
The Pituitary Gland…along with the hypothalamus… • Is located at the base of the brain just beneath the hypothalamus. These two glands are considered the most important part of the endocrine system • This “master gland” makes hormones that control several of the system’s other glands • Pituitary hormones can be influenced by emotions and seasonal changes • The pituitary is made up of the anterior and posterior lobes… • Anterior Lobe: - regulates the activity of the thyroid, adrenals, & reproductive glands) • - growth hormones (responsible for bone & tissue growth) • - prolactin (activates milk production in women who are breastfeeding) • - thyrotropin (stimulates the thyroid to produce thyroid hormones) • - corticotropin (stimulates the adrenal gland to produce hormones) • Posterior Lobe: - antidiuretic hormones (which help control body water balance) • - oxytocin (triggers contractions of the uterus that occur during labor) **The pituitary also secretes endorphins which are chemical that act on the nervous system to reduce sensitivity to pain.
The Adrenal Glands • Two triangular shaped glands located one on top of each kidney • The adrenal glands have two parts, each of which produces a set of hormones and has a different function. • The Adrenal Cortex • produces corticosteriods that influence and regulate salt and water balance in the body, the body’s response to stress, metabolism, the immune system, and sexual development. • **The adrenal cortex is regulated by hormones from the anterior pituitary gland • The Adrenal Medulla • produces catecholamines such as epinephrine, also known as adrenaline, which increase blood pressure and heart rate when the body experiences stress (used to counteract allergic reactions). • **The adrenal medulla is regulated by the nervous system
The Thyroid Gland • Is located in the front of the neck and is shaped like a bowtie or butterfly • Produces thyroxine and triiodothyronine. These hormones control the rate at which cells burn fuels from food to produce energy by stimulating increased sugar utilization by body cells (metabolism). • These hormones play an important role in bone growth and the development of the brain and nervous system in children. • The production and release of thyroid hormones is controlled by thyrotropin (which is secreted by the pituitary gland) • The Parathyroids (attached to the thyroid gland) • are four tiny glands that function together releasing the parathyroid hormone which regulates the calcium levels in the blood with the help of calcitonin which is produced in the thyroid.
Secretion of Thyroid Hormones TRH anterior pituitary Negative feedback loop of Thyroxine TRH = thyroid-releasing hormone TSH = thyroid-stimulating hormone hypothalamus T3 T4 thyroid TSH Negative Feedback
Blood Calcium Levels Low levels of blood calcium stimulate the release of parathyroid hormones (PTH) from the parathyroid glands. PTH causes the kidneys and gut to retain calcium while promoting calcium release from bone. This causes blood calcium levels to rise, which in turn inhibits the release of PTH from the parathyroid glands. Hormones That Affect Metabolism
The Pineal Gland • is located in the middle of the brain and is responsible for secreting melatonin, a hormone that may help regulate the wake-sleep cycle.
Examples of Hormone Disorders • If the pituitary gland secretes too much hormone a child could grow too tall. If too secretes not enough, child could be much too short. • Adrenal Insufficiency: is the decreased function of the adrenal cortex. This results in a lack of adrenal corticosteroid hormones. Symptoms of this insufficiency can include weakness, fatigue, abdominal pain, nausea, dehydration, and skin changes. This can be treated by receiving replacement corticosteroid hormones. • Cushing Syndrome: an excess of steroid hormones in your blood that can be caused by taking large doses of steroid drugs or a large tumor in the adrenal gland. Symptoms include round and red face, pad of fat that develops between your shoulder blades, bruises and fatigue. • Hyperthyroidism: a condition in which the levels of thyroid hormones in the blood are too high. A person suffering from this condition can experience weight loss, nervousness, tremors, excessive sweating, increased heart rate and blood pressure, protruding eyes, and a swelling in the neck from an enlarged thyroid gland (goiter). In children and teens the condition is usually caused by Graves' disease, an autoimmune disorder in which specific antibodies produced by the child's immune system stimulate the thyroid gland to become overactive.
Examples of Hormone Disorders Continued • Hypothyroidism: a condition in which the levels of thyroid hormones in the blood are abnormally low. The hormone deficiency can slow body processes and may lead to fatigue, a slow heart rate, dry skin, weight gain, constipation, and, in children, slowing of growth and delayed puberty. Hashimoto's thyroiditis, which results from an autoimmune process that damages the thyroid and blocks thyroid hormone production. • Diabetes (Type 1): when the pancreas is incapable of producing proper amounts of insulin. The disease can cause long-term complications including kidney problems, nerve damage, blindness, and early coronary heart disease and stroke. • Diabetes (Type 2): when the body is unable to respond to insulin properly and the sufferer experiences obesity and many of the same symptoms as type 1. This can be treated by injecting the body with insulin. The Effects of Chemotherapy • Chemotherapy increases the rate of hypothyroidism in children. On the contrary, radioactive therapy is used in the treatment of hyperthyroidism.
Thermal Regulation Sensors send messages to nerve cells which are coordinated with the hypothalamus to trigger negative feedback… • *When the body gets too hot (due to environment, exercise, etc.): • Blood vessels dilate • Body is signaled to sweat & when sweat evaporates, the body cools • …Blood is rushed to hot area for re-nourishment (eg. rosy cheeks) • *When the body gets too cold: • Arteries near the skin constrict to allow blood to go to essential body parts (eg. Organs, heart, brain) • Hair stands on end (goose bumps) when nerves tell muscles near hairs to contract. The erect hairs trap warm air. • Shivering produces heat by muscle and skeletal contractions • …Fat can be burned up in body for energy
Effects of Food on Endocrine System • Hormones are used in young animals to help them gain weight faster, or to produce milk faster. The Food and Drug Administration (FDA) set a tolerance level for certain steroid hormone residue in foods. • Studies say that hormones left in animal meat or milk are within the normal range. It is difficult to determine if such hormones are natural or not. • Early puberty in girls has been found with various factors, exposure to higher than natural levels of steroid hormones have never been documented though. • It has been suspected that beef and poultry in a school cafeteria caused breast enlargement in boys and girls. Such meat had hormone residue. • In 1980, some chicken samples in Puerto Rico were found to have had higher levels of estrogen. As well, girls in Puerto Rico who had early puberty showed higher levels of hormone residue in their blood. • The FDA scientists though have concluded that eating foods with higher levels of recombinant bovine growth hormone (rbGH) will not affect human health.
Water Balance • Osmoreceptors – detect changes in osmotic pressure of blood and extra cellular fluids • Antidiuretic hormone (ADH) • 1. Released when hypothalamus cells shrink • 2. Causes kidneys to reabsorb water when there is a higher osmotic pressure in body fluids (eg. Body sweats or losses water, osmotic pressure increases) • 3. Results in more concentrated urine • 4. Produced by nerve cells in hypothalamus and stored in pituitary glands
Disruptors in the Endocrine System Agonists - Act as natural hormones by binding to the cell’s receptor site Antagonists - Inhibit binding receptors - Have opposite effect as that of natural hormones ex. Anti-estrogen emasculates an organism. - Other factors can simultaneously have an effect on the endocrine system while affecting other systems. ex. Mercury poisoning affects the brain and therefore can interfere with hormones **Some examples of antagonist chemicals and what they effect:
Disruptors in the Endocrine System • These compounds change the effects of hormones on the body • ex. Daughters of treated patients with DES were found to have an increased risk of vaginal cancer. • ex. Long exposure to estrogen causes an increased risk of breast cancer. • There are different methods to screen, modify or treat the chemicals so that they are less harmful to humans Will you be the Target Cell?