2 Hormones are chemical messengers secreted by certain tissues into the blood or institial fluid, serving to regulate the activity of other tissues.
3 Chemical Classification of Hormones Amine hormones are derived from tyrosine or tryptophanInclude NE, Epi, thyroxine, melatoninPolypeptide/protein hormones are chains of amino acidsInclude ADH, GH, insulin, oxytocin, glucagon, ACTH, PTHGlycoproteinsLong polypeptide bound to a carbohydrate groupInclude LH, FSH, TSHSteroids are lipids derived from cholesterolInclude testosterone, estrogen, progesterone & cortisol11-7
4 Chemical Classificaton of Hormones Steroid Hormones:Lipid solubleDiffuse through cell membranesEndocrine organsAdrenal cortexOvariesTestesplacenta
5 Chemical Classification of Hormones Nonsteroid Hormones:Not lipid solubleReceived by receptors external to the cell membraneEndocrine organsThyroid glandParathyroid glandAdrenal medullaPituitary glandpancreas
6 Regulatory Systems Target cells~ body cells that respond to hormones Endocrine system/glands~ hormone secreting system/glands (ductless); exocrine glands secrete chemicals (sweat, mucus, enzymes) through ductsNeurosecretory cells~ actual cells that secrete hormonesFeedback mechanisms ~ negative and positive
8 Major Endocrine Glands Pineal GlandHypothalamusPituitary GlandAnteriorPosteriorThyroid GlandParathyroid GlandsAdrenal GlandsCortexMedullaThymus GlandPancreasGonadsOvariesTestesInstructor to read slide.Go to next slide.
9 There is a hierarchical chain of command in hormonal signaling. Coordination centerof the endocrinesystem.Via direct neuronal connection
13 Mode of Action: Chemical Signaling 1- Plasma membrane reception • signal-transduction pathways (neurotransmitters, growth factors, most hormones)2- Cell nucleus reception • steroid hormones, thyroid hormones, some local regulators
14 Hypothalamus Part of brain Regulates ANS, emotions, feeding/satiety, thirst, body temperature, etc.Hormones related to these functions“Releasing hormones”Axonal transport to posterior lobe
15 HypotalamusHypothalamus and pituitary gland secrete hormones and regulate other endocrine organs. They are the main regulatory organs of the endocrine system.
16 HypothalamusLocated below the thalamus and above the pituitary gland (=epiphysis)Regulates the pituitary gland secretions through two different mechanisms
17 Hypothalamus - neurohypophysis 1- Neurons, receiving information from receptors, fire APs which travel down to the post pituitary gland and stimulate the release of stored neurohormones – Oxytocin (OT) and anti-diuretic hormone (ADH)
24 The thyroid gland - Chp 21 p 623-625 Located in the neck, just below the larynxSecrete 2 types of hormone:- thyroid hormones stimulate cell metabolism, triiodothyronine (T3) and thyroxine (T4) – iodine is needed to synthesize these hormones- calcitonin decrease blood calciumFigure 6.8a
25 Thyroid hormones T3 and T4 secreted by the follicular cells Stored as colloidParafollicular cells (C cells) secrete calcitonin (Chp 19)
26 Thyroid Hormones T3 and T4 Target organs: all cellsRole: Increase cell metabolism, oxygen consumptionPermissive role for some other hormones (growth hormone)
28 Goiter Both hypo and hyperthyroidism can have goiter as a symptom Goiter is a swelling of the neck due to hypertrophy of the thyroid glandHow can one explain that?
29 Goiter in hypothyroidism Most often due to a lack of dietary iodineThe thyroid hormone is unable to synthesize a functional thyroid hormone (T3 and T4)The person express symptoms of hypothyroidismThe nonfunctional T3/T4 cannot promote a negative feedback on TRH and TSH the hypotalamus and pituitary gland increase their secretions the thyroid gland is stimulated to secrete more T3 and T4 …In children, the lack of functional T3/T4 result in cretinism, a form a mental retardation
30 Goiter in hyperthyroidism The cells secreting TRH or TSH on the hypothalamus and pituitary gland (respectively) have become abnormal and no longer are sensitive to the negative feedback they continue to secrete TRH or TSH continuous stimulation of the thyroid gland with excess thyroid hormones being formed symptoms of hyperthyroidism
31 Parathyroid glandsFour nodules located in the back of the thyroid glandSecreted parathyroid hormone or parathormone or PTHAction of PTH opposes action of calcitoninBoth hormones play a role in calcium metabolism
32 Roles of calcium Most calcium ions are stored in the bones Calcium is an important cofactor for enzymatic activity, plays a role in blood coagulation and action potentials.Calcitonin and PTH participate in calcium regulationVitamin D helps PTH activity
33 Calcium regulation: Calcitonin promotes blood calcium decrease, by: 1. calcium deposition on bone2. calcium dumping by the kidneyPTH promotes blood calcium increase by:1. bone resorption2. calcium reabsorption by kidney3. increase calcium absorption by intestine
34 Figure 23-20: Calcium balance in the body Calcium Metabolism:Figure 23-20: Calcium balance in the body
36 The Pancreas Islets of Langerhans Alpha cells: •glucagon~ raises blood glucose levelsBeta cells: •insulin~ lowers blood glucose levelsType I diabetes mellitus (insulin-dependent; autoimmune disorder)Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)
37 The pancreas Located in the left upper abdominal cavity Exocrine and endocrine glandsThe endocrine function is due to the cells of the islets of the Langerhans-- α cells glucagon-- β insulin-- δ somatostatin
38 Glucose regulation Glucose level controlled by insulin and glucagon Insulin promotes a decrease in blood glucoseGlucagon promotes an increase in blood glucose
41 Diabetes mellitusType I: autoimmune disease beta cells of the islets of Langerhans are destroyed by antibodiesType II: The cells become insulin-resistant glucose does not enter the cells as readily
42 The Adrenal GlandsAdrenal medulla (catecholamines): •epinephrine & norepinephrine~ increase basal metabolic rate (blood glucose and pressure)Adrenal cortex (corticosteroids): •glucocorticoids (cortisol)~ raise blood glucose •mineralocorticoids (aldosterone)~ reabsorption of Na+ and K+