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Hormone - a specific messenger molecule synthesized and secreted by a group of specialized cells called an endocrine gland. These glands are ductless, which means that their secretions (hormones) are released directly into the bloodstream and travel to elsewhere in the body to target organs, upon which they act
Collection of glands that secrete chemical messages we call hormones hormones and glands- foundation of the endocrine system Hormones are grouped into three classes based on their structure: steroids peptides amines
steroid hormones including prostaglandins which function especially in a variety of female functions (aspirin inhibits synthesis of prostaglandins, some of which cause “cramps”) and the sex hormones all of which are lipids made from cholesterol, • amino acid derivatives (like epinephrine) which are derived from amino acids, especially tyrosine, and • peptide hormones (like insulin) which is the most numerous/diverse group of hormones.
Steroid hormones • crucial substances for the proper function of the body; has a lipid nature • They mediate a wide variety of vital physiological functions ranging from anti-inflammatory agents to regulating events during pregnancy. • synthesized and secreted into the bloodstream by endocrine glands such as the adrenal cortex and the gonads
Steroids hormones • characterized by the steroid nucleus which is composed of three six member rings and one five member ring, ingeniously labeled A, B, C, and D respectively
Cholesterol- precursor for steroid hormones • sterol which is a natural product derived from the steroid nucleus • component of the cell membrane • precursor for bile acids (bile acids aid in fat digestion), steroid hormones, and provitamin D (When irradiated by sunlight it changes to vitamin D3.
Glucocorticoids • originate in the adrenal cortex and affect mainly metabolism in diverse ways; decrease inflammation and increase resistance to stress. • Mineralocorticoids • originate in adrenal cortex and maintain salt and water balance.
Estrogens • originate in the adrenal cortex and gonads and primarily affect maturation and function of secondary sex organs (female sexual determination) • Androgens • originate in the adrenal cortex and gonads and primarily affect maturation and function of secondary sex organs (male sexual determination).
Steroids hormones • Progestins • originate from both ovaries and placenta, and mediate menstrual cycle and maintain pregnancy
Amino acids hormones • Thyroid hormones - primarily derived from the amino acid tyrosine with the incorporation of iodine atoms • Catecholamines which include neurotransmitter hormones - epinephrine and nor epinephrine are also derivatives of the amino acid tyrosine • Serotonin and melatonin are derived from the amino acid Tryptophan • Histamine is derived from the amino acid Glutamic Acid.
Peptide hormones • protein hormones • vary considerably in size and can be as short as a three amino acids chain or as large as a glycoprotein. Most of the peptide hormones are prohormones (i.e. precursors of the mature form of hormones)
1. Luteinizing Hormone and Follicle Stimulating Hormone: Both these hormones are secreted by the pituitary gland and have an action on the gonads. In females, these hormones bring about the maturation of the ovarian follicle and aid in secreting progesterone. While in males, these hormones stimulate the production of sperms and help in the production of the male hormone-testosterone. Further, these hormones also contribute in development of secondary sexual characteristics for both the sexes
Prolactin: secreted by the pituitary, it works on the mammary glands and stimulates the release of breast milk from the breast tissue. • ACTH (Adrenocorticotrophic Hormone): secreted by the pituitary gland, it stimulates the adrenal glands and regulates the production of glucocorticoids and the growth hormone which subsequently act on muscles, bones and the liver.
Anti Diuretic Hormone (ADH): has essential functions of retaining fluid in the body. • Insulin: secreted by the pancreas, controlling blood sugar levels by aiding the absorption of glucose by the body cells. • Gastrin: secreted by the G- cells (located in the stomach and duodenum), gastrin facilitates the release of gastric juices by the parietal cells in the gastric mucosa and enhances gastro intestinal mobility.
Endocrine vs.nervous • The endocrine system acts with nervous system to coordinate the body's activities. • Both systems enable cells to communicate with others by using chemical messengers. • The endocrine system uses chemical messengers called hormones that are transported by the circulatory system (blood). They act on target cells that may be anywhere in the body. • The endocrine system is slower than the nervous system because hormones must travel through the circulatory system to reach their target. • Target cells have receptors that are specific to the signaling molecules. The binding of hormones to the receptors on or within the target cell produces a response by the target cell.
ENDOCRINE VS.NERVOUS SYSTEM • 1.SIMILARITIES • A. both maintain homeostasisB. both secrete chemicals- such as: • 1. Nervous System: secretes neurotransmitters • 2. Endocrine System: secretes hormones
differences • • A nerve travels very fast around the body however a hormone travels very slowly around the body.• Hormones are produced by glands and nerves are produced by the nervous system.
• Nerves die out very quickly whereas hormones live longer.• Hormones travel around the body as chemicals but nerves travel by electrical impulses.• Hormones are regenerated but nerves are not.• Hormones have slow effects but last longer.• Nerves have fast effects but don’t last long • The effects of the endocrine system are widespread in the body while the nervous system has a localised effect
conclusion • , the body often combines the speed of the nervous system with the specificity of the endocrine system to create the neuroendocrine system. Neuroendocrine cells receive neurally transmitted information and release hormones in response which is carried via blood the the target cells. The neuroendocrine system is mainly organised by the hypothalamus.
Starting Material/Origin Cholesterol Precursor Molecules Processed in Endoplasmic Reticulum and Golgi Bodies Processes Biochemical Reaction Series Hormones Steroid Hormones Non-Steroid Hormones Where Does It Go? Direct into the Bloodstream Stored in Secretory Granules until Needed Target and Nature Nucleus/Stimulate or inhibit protein synthesis Membrane proteins/amplified responses
Bloodstream Hormones Endocrine Glands Target Tissue or Cell Receptor Cells Basic Hormone Pathway
Bloodstream Cell membrane Steroid Cytoplasm Nucleus Cell receptor mRNA New proteins Ribosomes
Hormone Plasma membrane Receptor molecule Adenylatecyclase GTP G-protein AMP ATP Activates many enzymes in the cytoplasm
Endocrine Systems and Feedback Cycles (Response) • Imagine your body as a house with a thermostat. When the weather gets cold, the thermostat is turned to heat up, but when the weather is hot the air conditioning is turned on. • The same is true with the endocrine system, when there is an imbalance, the endocrine glands will control and maintain homeostasis. Stress Adrenal Medulla Cate-cholamines Increase in blood pressure and heart rate
Pituitary gland • a tiny organ, the size of a pea, found at the base of the brain. As the master gland of the body, it produces and secretes many hormones that travel throughout the body, directing certain processes stimulating other glands to produce different types of hormones. • Also called hypophysis.
Anterior pituitary • the front portion of the pituitary, also called adenohypophysis
Posterior Pituitary • the back portion of the pituitary, also called neurohypophysis
Pituitary Gland • this gland secretes the maximum number of hormones in the human body that regulate growth and development.
Diabetes insipidus • caused due to insufficient secretion of vasopressin secreted by the posterior pituitary gland. • acondition characterized by excessive thirst and excretion of large amounts of severely diluted urine.
Acromegaly • is caused due to an overproduction of growth hormone.
acromegaly • cheekbones are obvious • forehead bulge • jaw is enlarged • facial lines prominent • forehead and overlying skin is thickened
Prolactinoma • is a tumor that causes increased secretion of prolactin. • can be observe in males and females
Sex hormone disorders • pituitary gland secretes various sex hormones, thus altered secretion of these affects the sexual development or regulation of sexual characteristics.
HYPOTHALAMUS • the "hypo-thalamus" (literally, the under-thalamus)
FUNCTIONS • Maintains homeostasis • links the nervous system to the endocrine system via the pituitary gland • responsible for certain metabolic processes and other activities of the autonomic nervous system. The ANS affects heart rate, digestion, respiration rate, salivation, perspiration, diameter of the pupils, micturition (urination), and sexual arousal. • controls body temperature, hunger, thirst, fatigue, sleep, and circadian cycles.
synthesizes and secretes certain neurohormones, often called hypothalamic-releasing hormones, and these in turn stimulate or inhibit the secretion of pituitary hormones.
