Understanding The Function of The Endocrine System PDF

Understanding The Function of The Endocrine System By: Mary Alexis Baliguat & Dolfus Ritchie Bernal Objectives Define the Endocrine System and explain its general function. Explain how does the endocrine system maintain the homeostasis in the body. Explain the relationship between the endoc...

Understanding The Function of The Endocrine System By: Mary Alexis Baliguat & Dolfus Ritchie Bernal Objectives Define the Endocrine System and explain its general function. Explain how does the endocrine system maintain the homeostasis in the body. Explain the relationship between the endocrine system and the nervous system. Distinguish between endocrine and exocrine glands. Define the term hormone and explain its functions and number of types. Ways on how to keep our endocrine system healthy Definition of the Endocrine System The endocrine system is the collection of glands that produce hormones that regulate metabolism, growth and development, tissue function, sexual function, reproduction, sleep, and mood, among other things. The word endocrine derives from the Greek words "endo," meaning within, and "crinis," meaning to secrete. Although the hormones circulate throughout the body, each type of hormone is targeted toward certain organs and tissues. The General Function The endocrine system gets some help from organs such as the kidney, liver, heart and gonads, which have secondary endocrine functions. The kidney, for example, secretes hormones such as erythropoietin and renin. General Function of Hormones It helps regulate: extracellular fluid, metabolism, biological clock contraction of cardiac & smooth muscle, glandular secretion and some immune functions. Growth & development Reproduction ​  How does the endocrine system maintains the HOMEOSTASIS? Homeostasis is happening constantly in our bodies. We eat, sweat, drink, dance, eat some more, have salty fries, and yet our body composition remains almost the same. If someone were to draw your blood on ten different days of a month, the level of glucose, sodium, red blood cells and other blood components would be pretty much constant, regardless of your behavior (assuming fasting before drawing blood, of course). This is the main way we maintain homeostasis actually, since the endocrine system releases chemicals known as hormones. These hormones are sent via the blood to specific spots in the body to control things like blood sugar, heart rate, etc. The Endocrine system is responsible for homeostasis. The Endocrine system secrete hormones that the body needs to perform certain functions.  How does the endocrine system maintains the HOMEOSTASIS? When glands create hormones, they get transported through either the bloodstream or the lymph. Hormones help the body to act or react to any threat to homeostasis. Hormones aid throughout reproduction and birth. They help people sleep and wake up. The adrenal glands give off adrenaline to help a person perform in potential danger, and they release dopamine linked with the body's reward system. In general, the endocrine system plays a major role in helping the body maintain homeostasis because it gives off the messengers to help the body to react to any threats to homeostasis.  Relationship Between Nervous System & Endocrine System The nervous system and the endocrine system are both essential to the communication and relay of messages throughout the body. They work together to regulate (homeostasis) the activities of the other organs. Both systems use chemical signals when they respond to changes that might alter (homeostasis)  Feature Nervous System Endocrine System Signals Electric impulses Chemical impulses (hormones) Pathways Transmission by Transported by blood neurons Speed of information fast Slow Duration of effect Short lived Long lived Example: In a fight or flight response, there is a coordination of both the nervous and endocrine systems. The nervous system detects stimuli, either inside or out, for example, danger like an oncoming car about to run someone over, and that in turn sends an impulse to the endocrine system where a response is carried out. The response in this case is the release of adrenaline into the bloodstream, by the endocrine glands called adrenal glands. Once in the bloodstream, this hormone can cause the heart rate to increase, the muscles to become ready to either react to an emergency situation by fighting or by flight.  The Difference Between Endocrine & Exocrine Glands ENDOCRINE GLAND: a gland that secretes hormones directly into the bloodstream; a ductless gland. EXOCRINE GLAND: a gland that secretes substances into ducts which then leave the body (i.e. sweat/sebaceous glands) or into an internal space or lumen (i.e. digestive glands).  Exocrine glands are not part of the endocrine system! Definition of Hormones Hormones are chemical substances that act like messenger molecules in the body. After being made in one part of the body, they travel to other parts of the body where they help control how cells and organs do their work.  Important Functions of Hormones include: Growth and development of Prompting cell or tissue Food metabolism Initiating and maintaining sexual development and reproduction Maintaining body temperature Controlling thirst Regulating mood and cognitive functioning  Types of Hormones Hormones are classified by various criteria: By Proximity of their site of synthesis to their site of action. By their chemical structure. By their degree of solubility in aqueous medium.  3 classes of hormones based on proximity of site of Synthesis to Site of Action: 1. Autocrine Hormones: those that act on the same cells that synthesize them. 2. Paracrine Hormones: those that are synthesized very close to their site of action. 3. Endocrine Hormones: those that are synthesized by endocrine glands and transported in the blood to target cells that contain the appropriate receptors. 4 classes of hormones based on chemical structure: 1. Peptides or Protein hormones: made of amino acids joined by peptide bonds, most hormones belong to this group except hormones secreted by the gonads (testis and ovary) and the adrenal cortex. Examples: Thyrotropin Releasing Hormone (TRH), made up of three amino acid residues Insulin, made up of 51 amino acid residues. 4 classes of hormones based on chemical structure: 2. Steroid hormones - made of fatty acids using cholesterol as a functional group. only hormones secreted by the gonads and adrenal cortex belong to this group. 3. Amino acid derivatives. 4. Fatty acid derivatives.  Two classes of hormones based on solubility in aqueous medium: 1. Hydrophilic Hormones - Hormones that are soluble in aqueous medium. They cannot cross the cell membrane. Examples: Insulin, Glucagon, Epinephrine. 2. Lipophilic Hormones - Hormones that are not soluble in aqueous medium, but soluble in lipid. They can easily cross the cell membrane. Location of receptors for each class of hormone is different. Examples: Thyroid hormones & Steroid hormones  Control of Hormone Release Endocrine Gland Stimuli - The stimuli that activate the endocrine organs fall into three major categories- hormonal, humoral, and neural. 1. Hormonal stimuli - The most common stimulus is a hormonal stimulus, in which endocrine organs are prodded into action by other hormone. 2. Humoral stimuli - Changing blood levels of certain ions and nutrients may also stimulate hormone release  Control of Hormone Release 3. Neural stimuli - In isolated cases, nerve fibers stimulate hormone release, and the target cells are said to respond to neural stimuli. The classic example is sympathetic nervous system stimulation of the adrenal medulla to release norepineplarine and epinephrine during periods of stress.  Hormone Transport in Blood Hormones flow through the blood and then bind to their receptors within the capillaries or diffuse out to reach the receptors at the target cell. Water insoluble hormones must bind to plasma protein to be carried into the plasma, hormones remain bind to these protein for some time which act as a reservoir for the hormones Water soluble hormones which can dissolve into the plasma by itself and can easily diffuse out to their site of action. Water soluble hormones act faster in a short period of time. Pituitary Gland The main endocrine gland. It is a small structure in the head. The pituitary gland is about the size of a bean. and it hangs by a stalk from the hypothalamus. It is called the master gland because it produces hormones that control other glands and many body functions including growth. The pituitary consists of the anterior and posterior pituitary. The pituitary glands are made of the anterior lobe and posterior lobe. The anterior lobe produces and releases hormones. The posterior lobe does not produce hormones, this is done by nerve cells in the hypothalamus - but it does release  The Anterior Pituitary The anterior lobe releases hormones upon receiving, releasing or inhibiting hormones from the hypothalamus. These hypothalamic hormones tell the anterior lobe whether to release more of a specific hormone or stop production of the hormone. Anterior Lobe Hormones: Growth hormone – GH is essential in early years to maintaining a healthy body composition and for growth in children. In adults, it aids healthy bones and muscle mass. It also affects fat distribution and increase protein synthesis. Prolactin - It stimulates breast milk production after childbirth.  The Anterior Pituitary Follicle-stimulating hormone (FSH): FSH works with LH to ensure normal functioning and development of the ovaries and testes. It stimulates the production of egg and sperm. Luteinizing hormone (LH): LH works with FSH to ensure normal functioning of the ovaries and testes. It triggers ovulation in females and stimulates testosterone production in male Adrenocorticotropic hormone (ACTH): ACTH stimulates the adrenal glands to produce hormones. Thyroid-stimulating hormone (TSH): TSH stimulates the thyroid gland to produce hormones  The Posterior Pituitary The posterior pituitary (or neurohypophysis) comprises the posterior lobe of the pituitary gland and is part of the endocrine system. The posterior lobe contains the ends of nerve cells coming from the hypothalamus. The hypothalamus sends hormones directly to the posterior lobe via these nerves, and then the pituitary gland releases them. Posterior Lobe Hormones: Antidiuretic hormone (ADH): Antidiuretic hormone, also known as vasopressin, acts to maintain blood pressure, blood volume and tissue water content by controlling the amount of water and hence the concentration of urine excreted by the kidney This hormone prompts the kidneys to increase water absorption in the blood. Oxytocin: Oxytocin is involved in a variety of processes, such as contracting the uterus during childbirth and stimulating breast milk The Pineal Gland Definition: The pineal gland, also known as the "pineal body, is a small endocrine gland. Location: It is located on the back portion of the third cerebral ventricle of the brain, which is a fluid-filled space in the brain. This gland lies in- between the two halves of the brain. The gland is named for its shape, włuch resembles a pinecone (in Latin, "pinea").  The Pineal Gland The pineal gland's function in the body is not clearly understood yet. However, it is known to play a role in regulating female reproduction and sexual maturation. It also has a part in controlling circadian rhythms (biological processes), the body's internal clock that affects such actions as when we wake and sleep. The pinealocytes create and secrete melatonin a hormone that helps maintains the body's internal clock. Melatonin also helps regulate female reproductive hormones, including when women menstruate. Thyroid Gland Location: The thyroid gland is located at the base of the throat, just inferior to the Adam's apple. Structure: It is a fairly large gland consisting of two lobes joined by a central mass, or isthmus. Hormones: Thyroid hormone (thyroxine [T4] and triodothyronine [T3]) Calcitonin Thyroid Gland Thyroid gland is composed of hollow structures called follicles, which store a sticky colloidal material. Thyroid hormone is derived from this colloid. But calcitonin hormone is made by the parafollicular cells found in the  The Thyroid Gland Thyroxine (T4); is the major hormone secreted by the thyroid tollicles. Trilodothyronine (T3): is formed at the target tissues by conversion of thyroxine to triiodothyronine. Each is constructed from two tyrosine amino acids linked together, but thyroxine has four bound iodine atoms, whereas triodothyronine has three Function: It is the body's metabolic hormone Thyroid hormone controls the rate at which glucosens "barried," of oxidized, and converted to body heat and chemical energy. Parathyroid Gland The parathyroid glands are four small glands located on the posterior aspect of the thyroid gland Low blood levels of calcium stimulate the parathyroid glands to release parathyroid hormone (PTH). It causes bone calcium to be liberated into the blood. PT also stimulates the kidneys and intestine to absorb more Hypothalam us The hypothalamus is a secretion of the brain responsible for the production of many of the body's essential hormones It's not an endocrine gland but regulates the secretion of some pituitary gland hormones Location: The hypothalamus is located below the thalamus and above the pituitary gland  Hypothalamus Functions of hypothalamus : The primary function of the hypothalamus is homeostasis The hypothalamus govern temperature regulation The hypothalamus also governs thirst and hunger It also governs sleep, mood, and blood pressure Gonads The female and male gonads produce sex cells (an exocrine function). They also produce sex hormones that are identical to those produced by adrenal cortex cells. The major differences from the adrenal sex hormone production are the source and relative amounts of hormones produced. Ovaries The female sex organ that serves as an endocrine gland. The female gonads or ovaries, are paired, almond-sized organs located in the pelvic cavity. Ovaries produce female sex cells (ova or eggs) and two groups of steroids hormones estrogens and  Ovaries PRODUCTION An ovarian follicle (and ovum) start to mature each month following puberty under the influence of FSH (Follicle-stimulating hormone) The developing follicle secretes estrogen. Luteinizing hormone (LH) causes the follicle to rupture and release the ovum (ovulation); the follicle becomes the corpus luteum. The corpus luteum secretes progesterone.  Ovaries ESTROGENS: A) The estrogens are responsible for the development of sex characteristics in women (primarily growth and maturation of the reproductive organs) and the appearance of secondary sex characteristics (hair in the pubic and axillary regions)at puberty. B)Acting with progesterone, estrogens promote breast development and cyclic changes in the uterine lining (the menstrual cycle).  Ovaries PROGESTERONES A) Progesterone as already noted, acts with estrogen to bring about the menstrual cycle. B) During pregnancy, it quiets the muscles of the uterus so that an implanted embryo will not be aborted and helps prepare breast tissue for lactation, Testes The male sex organ that also serves as an endocrine gland The paired oval testes of the male are suspended in a sac, the scrotum, outside the pelvic cavity. Testes produce male sex cells or sperm and male sex hormones testosterone. PRODUCTION FSH follicle stimulating hormone) causes the production of sperm LH causes the  Testes Testosterone At puberty, testosterone promotes the growth and maturation of the reproductive system organs to prepare the young man for reproduction. It also causes the male's secondary sex characteristics (growth of facial hair, development of heavy bones and muscles, and lowering of the voice) to appear and stimulates the male sex drive. In adults, testosterone is necessary for continuous production of sperm. Adrenal Glands Location: They are flat pyramidal shaped, curved over the top of each kidney. Structure: Although it looks like a single organ, they are actually two endocrine organs; Adrenal Medulla and Adrenal Cortex.  Adrenal Glands Hormones of Adrenal cortex are collectively called corticosteroids. 1. Mineralocorticoids: (mainly Aldosterone). Regulates the mineral (or salt) content of the blood. Their target is the kidney tubules. When aldosterone is released, Na ions are reabsorbed and K are released into the urine When Na' are reabsorbed, water, is reabsorbed too(osmosis). In this way, blood volume and BP are adjusted  Adrenal Glands 2. Glucocorticoids (corticosterone, cortisone but mainly cortisol) Maintain normal cell metabolism. Promote Protein breakdown. lipolysis and gluconeogenesis Helps the body fight long term stressors. When glucocorticoids are released, fats and even proteins are broken down to glucose Anti-Inflammatory: Inhibit WBC hence they slow down wound healing Depression of Immune system: High doses can depress immune response hence they are prescribed during organ  Adrenal Glands 3. Sex hormones: (or Androgens) In both male and female Androgens are released but in relatively small quantities. Mainly testosterone, but some estrogen is also produced. In females after menopause, ovarian secretion of estrogen ecases and all estrogen is derived from adrenal androgens.  Adrenal Glands Function of Adrenal Medulla hormones 1. Epinephrine (Adrenaline) and Norepinephrine (noradrenaline) Enhances and prolongs the effects of " fight or flight" response of the sympathetic nervous system Increases Heart rate. B.P. Blood glucose level and dilate small passageways of the lungs These events, result in more oxygen and faster cucullation of blood, mainly to brain, heart and muscles  Adrenal Glands Regulation Epinephrine and norepinephrine are released when adrenal medulla is stimulated by the sympathetic nervous system during "fight or flight response Glucocorticoids are released from adrenal cortex in response to rising levels of ACTH in blood. ACTH is secreted from the anterior pituitary lobe by the release of CRF from hypothalamus, which is controlled by steroid level in blood. Aldosterone release is stimulated by humoral factors, such as fewer Na + ions in blood. Renin from kidneys also causes release of aldosterone when Blood pressure drops. A hormone of heart ANP prevents aldosterone release, to reduce blood pressure Thymus Gland Location: The thymus gland is located in the thoracic cavity, behind the sternum. Thymosin and other hormones: Thymic humoral factor, thymic factor and Thymopoietin.  Thymus Gland Function of Thymus gland: Promotes the maturation of T-cells WBC’s Other endocrine tissues and Organs: Placenta: Human Chorionic Gonadotrophin Estrogen and Progesterone  Kidney Renin - restore normal blood pressure, thereby increasing filtration rates of water and solutes in the kidney tubules. Erythropoietin - stimulates the production of red blood cells. Calcitriol - stimulates active transport of dietary calcium across intestinal cell membranes in the intestine  Stomach Gastrin-stimulates glands to release hydrochloric acid. Intestine Secretin-Pancreas: stimulates release of bicarbonate-rich juice. Liver: increases release of bile. Cholecystokinin-Pancreas: stimulates release of enzyme-rich juice. Gallbladder: stimulates expulsion of stored bile Duodenal papilla: causes sphincter to relax, allowing bile and pancreatic juice to enter duodenum. Atrial natriuretic peptide (ANP) - Kidney: inhibits sodium ion reabsorption and renin release. Heart Adrenal cortex: inhibits secretion of aldosterone, thereby decreasing blood volume and blood pressure. Adipose tissues Leptin - suppresses appetite and increases energy expenditure in the brain. Resistin - causes resistance of peripheral tissues to insulin. Thanks 