“ It is the type of coordination present between the cells or different organs within the body of multicellular organisms. In this kind of coordination a group of cells releases specific chemicals, which regulates the activities of other cell of the body.”
DEFINITIONEndocrine glands are organs in thebody that produce hormones whichare released directly into thebloodstream. Together these glandsmake up the endocrine system, whichperforms essential functions likeregulating metabolism, growth andreproduction.
Endocrine derives from the Greek words endo meaning inside, within, and crinis for secrete Chemicals are released by these glands(hormones) hormone derived from Greek word which means „to excite’ The field of study dealing with the endocrine system and its disorders is endocrinology, a branch of internal medicine. In animals glands are of two types Exocrine gland: release products (enzymes) into DUCTS › Ex) Sweat, digestive juices Endocrine glands:– directly to bloodstream; NO DUCTS › Ex) HormonesFeatures of endocrine gland: their ductless nature their vascularity, the presence of intracellular vacuoles or granules storing their hormones.
Endocrine system Nervous system Effects are slow to Effects very fast and initiate quick Response are Responses are short prolonged (few hrs to lived. week) NEUROTRANSMITTERs HORMONES released travel through neurons in blood stream released in synaptic cleft
1. Peptide/ Protein2. Steroid3. Amine (modified amino acids e.g. Thyroxine, Epinephrine, Norepinephrine) PEPTIDE HORMONE May occur as short chain of amino acids e.g., ADH, Oxytocin Or occur as long chain amino acid e.g. Glucagon, Insulin, Prolactin Not lipid soluble Received by receptors external to the cell membrane STEROID HORMONE They are lipid soluble Diffuse easily through the membrane
PEPTIDE HORMONE › React with specific receptors outside the cell › This triggers an enzyme reaction with lead to the formation of a second messenger (cAMP). › cAMP can produce specific intracellular functions: Activates cell enzymes Change in membrane permeability Promote protein synthesis Change in cell metabolism Stimulation of cell secretions
Steroid Hormones › Pass through the cell membrane › Binds to specific receptors › Then enters the nucleus to bind with the DNA which then activates certain genes (Direct gene activation). › mRNA is synthesized in the nucleus and enters the cytoplasm and promotes protein synthesis for: Enzymes as catalysts Tissue growth and repair Regulate enzyme function
Neuroendocrine organ Central part of brain attached by numerous nerves to pituitary gland Weight is about 4g(human) Control the pituitary gland by producing chemicals (releasing/stimulating or inhibiting hormones) Maintains homeostasis(heart rate, body temperature, water balance, and the secretions of the pituitary gland)
Pea size gland hang from the base of brain by stalk (infundibulum) loge in the bone of skull, weigh is about 5gm In past considered as master gland but it itself under the control of hypothalamus It consists of a hormone-producing glandular portion Have two lobes1.Anterior pituitary (Adenohypophysis)2.Posterior pituitary (Neurohypophysis)
Growth /Somatotropin hormone (GH) It is a non- trophic,anabolic hormone which simulates the growth of all body tissue specially skeletal muscles ,bone and cartilage. Control protein synthesis and general metabolism Imbalances 1. Hyperseretion in childhood produces gigantism 2. Hyperseretion after adult-hood produces acromegaly 3. Hypo secretion in childhood produces dwarfism
Posterior Pituitary or NeurohypophysisNeurohypophysis It does not synthesize hormones, however, it stores and releases two hormones produced by the neurosecretory cells of the hypothalamus• It is an extension of hypothalamus• Antidiuretic hormone (ADH)• Oxytocin
Oxytocin › Stimulates smooth muscle contraction of uterus at labour › Stimulates mammary glands during lactation. Antidiuretic H. › Stimulates water reabsorption in collecting ducts. › Decreases urine output › Hypo secretion of ADH produces diabetes insipidus › Excessive thirst and urination
Located at the base of neck in front of trachea Bilobed and butterfly shaped Weigh about 25-40gm Composed of follicles which produce 1. Thyroxine (TetraiodothyronineT4) 2. Triiodothyronine (T3) 3. Calcitonin Both T3 and T4 are important in controlling metabolism and are essential for normal physical growth and mental development. Calcitonin causes excess blood calcium to be deposited in bones.
Hypothyroidism results › Myxedema (in adults)lethargy, weight gain, dry- skin, hair loss, cold intolerant, confused and depressed. › Goiter—low intake of iodine in diet › Cretinism (in children)mental retardation,dwarfism,lack of sexual maturity. Hyperthyroidism results › Graves disease (enlargement of overall gland along with › Exopthalamic goiter(excess accumulation of fat and mucus in eye orbit)
Two pairs of pea-sized glands embedded on the surface of thyroidWeigh about 0.05g-0.3gParathyroid hormone (PTH)Antagonistic to CalcitoninStimulated by falling Ca2+ in blood and inhibited by rising blood Ca2+Stimulates osteoclasts to free Ca2+ from boneStimulates Ca2+ uptake from intestine & kidney
Consists of two major types of secretory tissues which reflects its dual function › Exocrine gland secretes digestive juice › Endocrine gland releases hormones Patches of pancreatic cells (Islets of Langerhans) secretes › Insulin from beta cells in response to high blood glucose level › Glucagon from alpha cells in response to low blood glucose level
Triangular structure located at the top of kidney Weight of each gland is 5gm Have two parts1. Adrenal medulla2. Adrenal cortex Adrenal cortex produces three kinds of steroid hormones Glucocorticoid(cortisol) Mineralocorticoid (aldosterone) Small amount of sex hormone (Androgens).
Cortex › Activity stimulated by ACTH › Controls prolonged responses by secreting corticosteroids. 1. Glucocorticoid(Cortisol) regulate glucose metabolism and the immune system. 2. Mineralocorticoids(Aldosterone) regulate salt and water balance 3. Gonad corticoids(Androgens) development of secondary sexual characteristics in male like growth of facial hair and deepening of voice. It is produced in both sexes and its excessive secretion in females causes masculinization i.e,appearance of beard
Hyper secretion leads to Cushing’s Disease Weight gain Hypertension Reduced sex drive Diabetes Depression/inability to think clearlyHypo secretion leads to Addison’s DiseaseFatigue, weakness, loss of appetiteWeight lossGastrointestinal problems (nausea, vomiting, etc.)Darkening of the skinLow blood pressure and low blood sugar
Medulla › The adrenal medulla mediates short–term responses under the influence of sympathetic nervous system. › It secretes two emergency hormones under stress conditions to bring about fight or flight response. Epinephrine(adrenaline) increases blood glucose, heart beat, breathing rate and metabolic rate. directs blood to the heart, brain, and skeletal muscles. Norepinephrine (noreadrenaline) Works like epinephrine Sustains blood pressure
TYPE I Diabetes Beta cells are destroyed by lymphocytes as a result of autoimmune disorder. No insulin is produced.TYPE II (Diabetes mellitus) Insulin is produced Target cells lose insulin receptors Excess glucose excreted in urine As a result of fat metabolism ketone bodies accumulates in blood Blood Level Regulation in Diabetics
It is present in the upper part of chest behind the breast bone. It consists of two lobes that join infront of trachea. It secretes a hormone, Thymosin, which stimulates the development and differentiation of T lymphocytes after they leave the thymus. It plays a role in regulating the immune system by stimulating other kinds of immune cells.
It is a tiny cone-shaped body located in diencephalon (fore brain) It secretes Melatonin which › Influences growth and development of gonads › Controls Day/night cycles › Timing of sleep, body temperature, appetite › Participates in setting the body’s clock
Ovaries › Estrogens › Maintains female reproductive cycle › Development of secondary sexual characters › Progesterone › Preparation and maintenance of uterus for the development of embryo Testes › Testosterone › Stimulates bones and muscles growth › Development of secondary sexual characters