Endocrine+System

=__Endocrine System__=
 * The system of glands, each of which secretes a type of hormone directly into the bloodstream to regulate the body.
 * Information signal system like the nervous system, yet its effects and mechanism are classifiably different.
 * Effects are slow to initiate, and prolonged in their response , lasting from a few hours up to weeks.
 * Made of a series of glands that produce chemicals called hormones.
 * Only target cells can respond to hormones
 * Target cells have receptors that are proteins that have shapes complementary to the hormones.

=__Hypothalamus__=
 * The **hypothalamus** is a portion of the brain that contains a number of small nuclei (nucleuses) with a variety of functions.
 * One of the most important functions of the hypothalamus is to link the nervous system to the endocrine system via the pituitary gland (hypophysis).
 * Located just above brain stem [Thalamus( Relay/Motor Signals/Alertness)]
 * The hypothalamus controls body temperature, hunger, thirst, fatigue, sleep, and circadian cycles.[[image:http://www.elp.manchester.ac.uk/pub_projects/2000/mnby6kas/pitdiag.jpg]]


 * The hypothalamus is responsive to:**
 * Light: daylength and photoperiod for regulating circadian and seasonal rhythms
 * Olfactory stimuli, including pheromones
 * Steroids, including gonadal steroids and corticosteroids
 * Neurally transmitted information arising in particular from the heart, the stomach, and the reproductive tract
 * Autonomic inputs
 * Blood-borne stimuli, including leptin, ghrelin, angiotensin, insulin, pituitary hormones, cytokines, plasma concentrations of glucose and osmolarity etc.
 * Stress
 * Invading microorganisms by increasing body temperature, resetting the body's thermostat upward.


 * Influences Include;**
 * 1) Control of food intake
 * 2) Sexual dimorphism
 * 3) Responses to ovarian steroids
 * 4) Gonadal steroids in neonatal life of rats
 * 5) Androgens in primates
 * 6) Human sexual orientation and the hypothalamus

Sex steroids are not the only important influences upon hypothalamic development; in particular, pre-pubertal stress in early life (of rats) determines the capacity of the adult hypothalamus to respond to an acute stressor.Unlike gonadal steroid receptors, glucocorticoid receptors are very widespread throughout the brain; in the paraventricular nucleus, they mediate negative feedback control of CRF synthesis and secretion, but elsewhere their role is not well understood.
 * Other influences upon hypothalamic development **

=__Pituitary gland__= The anterior pituitary synthesizes and secretes the following important endocrine hormones: Somatotrophins: These hormones are released from the anterior pituitary under the influence of the hypothalamus. Hypothalamic hormones are secreted to the anterior lobe by way of a special capillary system, called the hypothalamic-hypophysial portal system. The anterior pituitary is divided into anatomical regions known as the pars tuberalis, pars intermedia, and pars distalis. It develops from a depression in the dorsal wall of the pharynx (stomodial part) known as Rathke's pouch.
 * The pituitary is functionally connected to the hypothalamus by the median eminence via a small tube called the infundibular stem (Pituitary stalk).
 * The pituitary gland secretes nine hormones that regulate homeostasis.
 * The pituitary gland consists of two components: the anterior pituitary (or adenohypophysis) and the posterior pituitary (or neurohypophysis),[[image:http://2.bp.blogspot.com/-GSh5QxCrotw/TgdUk3u2T6I/AAAAAAAAAEM/iG4H_QMCv2A/s1600/pituitary_gland.jpg]]
 * Anterior pituitary (Adenohypophysis) **
 * Growth hormone released under influence of hypothalamic Growth Hormone-Releasing Hormone ,inhibited by hypothalamic Somatostatin
 * Thyroid-stimulating hormone released under influence of hypothalamic Thyrotropin-Releasing Hormone
 * Adrenocorticotropic hormone released under influence of hypothalamic Corticotropin-Releasing Hormone
 * Beta-endorphin, released under influence of hypothalamic Corticotropin-Releasing Hormone
 * Prolactin also known as 'Luteotropic' hormone, whose release is inconsistently stimulated by hypothalamic, oxytocin, vasopressin, vasoactive intestinal peptide, angiotensin II, neuropeptide Y, galanin, substance P, bombesin-like peptides, and neurotensin, and inhibited by hypothalamic dopamine.
 * Luteinizing hormone
 * Follicle-stimulating hormone, both released under influence of Gonadotropin-Releasing Hormone
 * Melanocyte–stimulating hormones or "intermedins," as these are released by the pars intermedia, which is "the middle part"; adjacent to the posterior pituitary lobe, pars intermedia is a specific part developed from the anterior pituitary lobe.

The posterior pituitary stores and secretes the following important endocrine hormones: Magnocellular Neurons: Oxytocin is one of the few hormones to create a positive feedback loop. For example, uterine contractions stimulate the release of oxytocin from the posterior pituitary, which, in turn, increases uterine contractions. This positive feedback loop continues throughout labor.
 * Posterior pituitary (Neurohypophysis) **
 * Oxytocin, most of which is released from the paraventricular nucleus in the hypothalamus
 * Antidiuretic hormone the majority of which is released from the supraoptic nucleus in the hypothalamus

=__**Thymus**__=
 * The thymus is a specialized organ of the immune system
 * The thymus "educates" T- lymphocytes ( T cells ), which are critical cells of the adaptive immune system.
 * Each T cell attacks a foreign substance which it identifies with its receptor
 * T cells that attack the body's own proteins are eliminated in the thymus.
 * The thymus is of a pinkish-gray color, soft, and lobulated on its surfaces.
 * In children the thymus is grayish-pink in colour and in adults it is yellow.
 * Disease associations; Hypersensitivity Immunodeficiency, DiGeorge Syndrome, SCID, HIV/AID, Autoimmune Disease, Autoimmune Polyendocrinopathy-Candidiasis-Ectodermal Dystrophy

__**Two different types of Hormones**__


 * Polypeptide and proteins**: Hormones that are chains of amino acids of less than or more than about 100 amino acids, respectively. Some protein hormones are actually glycoproteins, containing glucose or other carbohydrate groups. They are soluble so that they can enter the target cells. They combine receptors in the cytoplasm.


 * Lipid-soluble:** hormones (steroid hormones and hormones of the thyroid gland) diffuse through the cell membranes of target cells. The lipid-soluble hormone then binds to a receptor protein that, in turn, activates a DNA segment that turns on specific genes. The proteins produced as result of the transcription of the genes and subsequent translation of mRNA act as enzymes that regulate specific physiological cell activity. They cannot get through the cell membrane.


 * __Endocrine System and how it works with other body systems__**

The endocrine system works with the nervous system by sending hormones to cells and therefore having a reaction. It also works with the digestive system with the pancreas producing insulin. The urinary system because it works with water absorption in the kidneys. The glands of the endocrine system and the hormones they release influence almost every cell, organ, and function of our bodies. The endocrine system is instrumental in regulating mood, growth and development, tissue function, and metabolism, as well as sexual function and reproductive processes. In general, the endocrine system is in charge of body processes that happen slowly, such as cell growth. Faster processes like breathing and body movement are controlled by the nervous system. But even though the nervous system and endocrine system are separate systems, they often work together to help the body function properly. The foundations of the endocrine system are the hormones and glands. As the body's chemical messengers, hormones transfer information and instructions from one set of cells to another. Although many different hormones circulate throughout the bloodstream, each one affects only the cells that are genetically programmed to receive and respond to its message. Hormone levels can be influenced by factors such as stress, infection, and changes in the balance of fluid and minerals in blood.

__**Weird and Gross facts about the Endocrine System**__


 * There are almost 30 hormones on our body that are being produced by various glands of the endocrine system.
 * The sense of thirst and hunger is triggered in our body by the hypothalamus gland.
 * The pineal gland induces sleep in our body. It produces a hormone named melatonin which controls the sleep cycle of our body.
 * The secret behind activities like overactivity or sluggishness of an individual depends on functioning of the thyroid gland.
 * The behavior and the characteristic of a person is largely influenced by the endocrine system

=The role of insulin in the body=
 * **Regulate sugar in your bloodstream.** The main job of insulin is to keep the level of sugar in the bloodstream within a normal range. After you eat, carbohydrates break down into sugar and enter the bloodstream in the form of glucose, a sugar that serves as a primary source of energy. Normally the pancreas responds by producing insulin, which allows sugar to enter the tissues.
 * **Storage of excess glucose for energy.** After you eat — when insulin levels are high — excess glucose is stored in the liver in the form of glycogen. Between meals — when insulin levels are low — the liver releases glycogen into the bloodstream in the form of sugar. This keeps blood sugar levels within a narrow range.

If your pancreas secretes little or no insulin (type 1 diabetes) or your body produces too little insulin or has become resistant to insulin's action (type 2 diabetes), the level of sugar in your bloodstream increases. This is because it's unable to enter cells. Left untreated, high blood sugar can lead to complications such as blindness, nerve damage (neuropathy) and kidney damage.

The goals of insulin therapy
If you have type 1 diabetes, insulin therapy replaces the insulin your body is unable to produce. Insulin therapy is sometimes needed for type 2 diabetes and gestational diabetes when other therapies have failed to keep blood glucose levels within the desired range. If your doctor says that you need insulin therapy, take the recommendation seriously. Insulin therapy can help prevent diabetes complications by helping keep your blood sugar within your target range.

Insulin Basics: How Insulin Helps Control Blood Glucose Levels
Insulin and glucagon are hormones secreted by islet cells within the pancreas. They are both secreted in response to blood sugar levels, but in opposite fashion!

The stimulus for insulin secretion is a HIGH blood glucose...it's as simple as that! Although there is always a low level of insulin secreted by the pancreas, the amount secreted into the blood increases as the blood glucose rises. Similarly, as blood glucose falls, the amount of insulin secreted by the pancreatic islets goes down. Insulin has an effect on a number of cells, including muscle, red blood cells, and fat cells. In response to insulin, these cells absorb glucose out of the blood, having the net effect of lowering the high blood glucose levels into the normal range. Glucagon is secreted by the alpha cells of the pancreatic islets in much the same manner as insulin...except in the opposite direction. If blood glucose is high, then no glucagon is secreted. When blood glucose goes LOW, however, (such as between meals, and during exercise) more and more glucagon is secreted. Like insulin, glucagon has an effect on many cells of the body, but most notably the liver.

The Role of Glucagon in Blood Glucose Control
The effect of glucagon is to make the liver release the glucose it has stored in its cells into the bloodstream, with the net effect of increasing blood glucose. Glucagon also induces the liver (and some other cells such as muscle) to make glucose out of building blocks obtained from other nutrients found in the body (eg, protein). Our bodies desire blood glucose to be maintained between 70 mg/dl and 110 mg/dl (mg/dl means milligrams of glucose in 100 milliliters of blood). Below 70 is termed "hypoglycemia." Above 110 can be normal if you have eaten within 2 to 3 hours. While you are fasting it should be between 70 and 110. Even after you have eaten, however, your glucose should be below 180. Above 180 is termed "hyperglycemia" (which translates to mean "too much glucose in the blood"). If your 2 two blood sugar measurements above 200 after drinking a sugar-water drink (glucose tolerance test), then you are diagnosed with diabetes.

The human body wants blood glucose (blood sugar) maintained in a very narrow range. Insulin and glucagon are the hormones which make this happen. Both insulin and glucagon are secreted from the pancreas, and thus are referred to as pancreatic endocrine hormones. The picture on the left shows the intimate relationship both insulin and glucagon have to each other. Note that the pancreas serves as the central player in this scheme. It is the production of insulin and glucagon by the pancreas which ultimately determines if a patient has diabetes, hypoglycemia, or some other sugar problem.

=How Insulin Works to Regulate Blood Glucose= Insulin Helps Glucose Get Into Your Body's Cells If the glucose can't get into your cells, it builds up in your blood stream. If left untreated, high blood glucose can cause long-term complications. ||  ||
 * Insulin is like a key that opens up the locks on your body's cells so that glucose (blood sugar) can get inside and be used for energy.

Additionally, when blood sugar reaches a certain level, the kidneys try to get rid of it through urine - which means that you'll need to urinate more often. Frequent urination can make you feel tired, thirsty, or hungry. You may also start losing weight. Your body also gets energy from a complex sugar called glycogen, which is stored in your liver and muscles. The liver converts glycogen to glucose and releases it into your bloodstream when you're under stress and/or when you're extremely hungry. When enough insulin is present, muscles can use their glycogen for energy, but cannot release it directly into the blood. In type 2 diabetes, the liver releases too much glucose, especially at night (when the liver normally releases some glucose), resulting in high blood sugar levels in the morning. Insulin injections help bring down the amount of glucose released by the liver during the night, bringing morning blood sugars levels back to normal. Carbohydrates are broken down into glucose, which is the "fuel" that gives our bodies energy. Insulin's important job is to help glucose get into the body's cells.

= Endocrine System Diseases = The endocrine system is composed of a network of organs and glands responsible for producing, storing, and secreting hormones that help to maintain and control vital functions such as growth, reproduction, and energy levels. There are several endocrine system diseases that result from disruptions in this complex system:
 * Diabetes** - Condition in which the pancreas does not produce enough of the hormone insulin or the body does not effectively use the insulin it does produce. Because insulin is instrumental in helping the body convert sugars and starches into necessary energy, there can be serious consequences if diabetes is left undiagnosed and/or untreated.
 * **Growth Disorders** - Given that the endocrine system regulates growth processes, endocrine system diseases often result in growth disorders. If the body produces too much growth hormone (GH), gigantism or acromegaly (gigantism in adults) can occur; too little growth hormone results a condition called growth hormone deficiency, or GHD, which can cause children to grow more slowly than normal.
 * **Osteoporosis** - Osteoporosis, which occurs in both women and men (although the former are four times more likely to develop the disease), is a condition in which bones becomfragile and more likely to break. This can be the result of many factors including a decrease in the hormone estrogen occurring during menopause in women, or a decrease in testosterone occurring in men as they age. Because osteoporosis often has no obvious symptoms, it is often left undiagnosed until the person affected suffers a broken or fractured bone during a minor fall.
 * **Polycystic Ovary Syndrome** Also referred to as PCOS, polycystic ovary syndrome is one of the more common endocrine system diseases, affecting between 7% to 10% of women aged 15 to 45. PCOS is a condition associated with symptoms of infrequent or irregular menstruation, male hormone excess symptoms like hirsutism (increased and unwanted hair growth) and acne and difficulty to conceive. Patients with PCOS can also have multiple egg-containing cysts on the ovaries. They are higher risk for metabolic complications like diabetes and hypertension.
 * **Thyroid Disorders** - Thyroid hormones, hormones produced by the thyroid gland, influence nearly all of the body's symptoms. Thyroid problems include hyperthyroidism (too much thyroid hormone), hypothyroidism (too little thyroid hormone), thyroid nodules, thyroid cancer, and more.

Cushing's Syndrome
Cushing's syndrome, less common than the endocrine system diseases discussed above, occurs as the result of too much cortisol in the blood for an extended period of time. Cortisol is a hormone that, in normal amounts, helps the body perform a number of important functions including converting fat into energy, maintaining immune system function, and responding to stress.People with Crushing's disease have to much adrenocorticotropic hormone (ACTH). ACTH stimulates the production and release of cortisol, a stress hormone. Too much ACTH means too much cortisol. Cortisol is normally released during stressful situations. It controls the body's use of carbohydrates, fats, and proteins, and also helps reduce the immune system's response to inflammation. The two types of Cushing's syndrome, exogenous (from an outside source) and endogenous (from a source within the body), share a common list of symptoms but different causes. Exogenous Cushing's syndrome occurs in patients taking cortisol-like medications, and is temporary, ceasing when the patient has finished the course of medication. The endogenous form of this endocrine system disease is far rarer, and results from a tumor or tumors either on the adrenal glands or the pituitary gland, which is located at te base of the brain. Cushing's syndrome symptoms include the following:
 * Weight gain
 * Muscle loss and weakness
 * Easily-bruised, fragile skin
 * Reduced sex drive
 * Depression/inability to think clearly

Addison's Disease
Addison's disease, also among the rare endocrine system diseases, occurs in fewer than 150 people in a million. Also referred to as primary adrenal insufficiency, Addison's disease occurs when the adrenal glands, which are located at the top of each kidney, produce an insufficient amount of steroid hormones despite the presence of an adequate amount of ACTH, the hormone that triggers the adrenal glands to release steroids. The steroid hormones produced by the adrenal glands, and deficient during Addison's disease, hold many important functions including the regulation of blood sugar levels, helping the body fight infection and stress, and maintaining normal sexual drive. Addison's disease symptoms include the following:
 * Fatigue, weakness, loss of appetite
 * Muscle and joint pain
 * Gastrointestinal problems (nausea, vomiting, etc.)
 * Darkening of the skin on the face, neck, and back of hands
 * Low blood pressure
 * A craving for salt

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