Transcript Hormones
Hormones Hormones • Peptides- combine with receptors in the cell membrane production of cAMP, leads to activation of a particular enzyme • Steroids (small and lipid soluable) – pass through the membrane to combine with receptors and this activates genes and protien synthesis. Endocrine Glands • secrete products internally directly into blood. Have no ducts – blood transport but only a specific target organ is affected. ADH Negative feedback ( Antidiuretic Hormone - vasopressin) Produced in hypothalamus and released by posterior pituitary Promotes reabsorption of water in collecting duct of kidney Hypothalamus contains osoreceptors (hyper osmolality) that are sensitive to the amount of water in blood. ADH is released from the posterior pituitary, thirst increases and the blood becomes more dilute. Dilute blood shuts down the release of the hormone. a Oxytocin • Causes uterus to contract • Used to induce labor • Stimulates release of milk from breast when nursing. • Produced by hypothalamus and released by posterior pituitary. Inability to produce ADH causes diabetes insipidus ( watery urine) Growth Hormone ( GH) somatotrophin • Produced by anterior pituitary. • Determines the height of the individual. • Promotes cell division, protein synthesis and bone growth. • GH causes liver to release somatatomedins which actually have the effect on cartilage plates and causes osteoblasts to form bone. Midget • too little GH Giant • too much GH If GH increases in an adult after full height has been reached • Only certain bones respond • Jaw, eyebrow ridges, nose, fingers and toes. - acromegaly Lactogenic Hormone ( LTH) Prolactin • Produces after childbirth causing mammary glands to develop and produce milk. TSH – thyroid stimulating hormone Hypothalamus ( TRH) Anterior Pituitary ( THS Thyroid produces thyroxin - feedback turns off pituitary release of TSH TSH feedback controls hypothalamus to turn off TRH Thyroid Gland • Is located in the neck, attached to trachea just below larnyx. • The gland contains follicles filled with thyroglobulin the storage form of thyroxin. • Iodine is needed for both. • Thyroxin increases the metabolic rate. No target organ. Respiratory enzymes and oxygen intake increases in most cells. • Produces calcitonin – toregulate calcium level in blood and opposes parathyroid hormone. Hypothyroidism • If iodine is lacking in the diet, thyroid enlarges – Goiter • Low level of thyroxin • Anterior pituitary stimulated to produce TSH • TSH causes the thyroid to increase in size until enough thyroxin is produced. So it continues because enough thyroxin is never produced. Hypothyroidism - myxedema • Too much thyroxin • Lethargy, weight gain, loss of hair, slow pulse, decreased body temp and thickness and puffiness of skin. Cretinism • short stocky persons who have hypothyroidism since childhood • Tongue enlargement – difficulty breathing and swallowing • Skeletal growth inhibited. Adrenal Gland • Near kidneys. • Cortex ( hormonal control) and medulla ( nervous control) portions. • Hypothalamus Adrenal Medulla • Stress causes the hypothalamus to produce a a releasing hormone that stimulates anterior pituitary t produce ACTH. Which activates the adrenal glands • Adrenalin causes – metabolic rate increases as do breathing and heart rate. Blood vessels in intestine constrict and muscle vessels dilate. Increased circulation to the muscles can cause more strength than normal. Wide eyed look and extreme alertness occur. • A heart that has stopped beating is injected with adrenalin to stimulate contraction Adrenal Medulla • is a source of the catecholamines epinephrine and norepinephrine. And is part of the sympathetic nervous system. • In emergencies, adrenaline is released by the body to override the homeostatic control of glucose. This is done to promote the breakdown of glycogen into glucose to be used in the emergency. These emergencies are often known as 'fight or flight reactions'. • Adrenaline is secreted by the adrenal glands. The secretion of it leads to increased metabolism, breathing and heart rate. Once the emergency is over, and adrenaline levels drop, the homeostatic controls are once again back in place Effects of Epinephrine and norepinephrine • Increased rate & force of contraction of heart muscle: • Constriction of blood vessels: • norepinephrine, resulting in increased resistance and hence arterial blood pressure. Dilation of bronchioles:more air • Stimulation of lipolysis in fat cells: – energy production when glucose dwindles • Increased metabolic rate: oxygen consumption and heat production increase throughout the body in response to epinephrine. Breakdown of glycogen in skeletal muscle to provide glucose for energy production. Inhibition of certain "non-essential" processes: an example is inhibition of gastrointestinal secretion and motor activity. “Runner’s High” • ACTH and opioids ( endorphins and enkephalins are chemically rlated. • Can produce a feeling of euphoria and a higher threshold of pain. • Physical activity causes the release of endorphin and can elevate the mood. • Despite their organization into a single gland, the medulla and cortex are functionally different endocrine organs, and have different embryological origins. The medulla derives from ectoderm , while the cortex develops from mesoderm. • In some species, amphibians and certain fish, for example, two separate organs are found. • cortex, which secretes several classes of steroid hormones (glucocorticoids and mineralocorticoids, plus a few others). • Small amount of male and even smaller amount of female sex hormones • Adrenal cortex produces cortisol • Cortisol causes gluconeogenesis ( raises level of amino acids in blod which leads to an increased level of glucose when liver converts these to glucose. Production of glucose from non glucose substances) to relieve stress. • In low diet glucose provides glucose to brain. AA not converted to glucose can be used for repair of tissue, should injury occur. Cortisol • Also counteracts the inflammatory response. • Capillaries become permeable and fluid leaks out, causing swelling. – Pain and swelling of joints in arthritis and bursitis can be administered cortisol. mineralocorticoids • Aldosterone • The target organ is the kidney. They promote renal absorbtion of sodium and potassium. Levels of these ions are critical for nerve conduction and muscle contraction. Cardiac failure can result from too low level of potassium. • Levels of sodium maintain blood pressure and concentration of sodium regulates secretion of aldosterone. • When sodium levels are low, kidneys secrete renin. Renin is an enzyme that leads to the conversion of angiotensinogen to angiotensis and stimulates the adrenal cortex to release aldosterone. This raises blood pressure. • Angiotensin constricts the arteries and • Aldsterone causes the kidneys to reabsorb sodiumand blood volume is rainsed as water is reabsorbed.