Physiology Unit 3 ENDOCRINE SYSTEM

Transcription

1 Physiology Unit 3 ENDOCRINE SYSTEM

2 Hormone Classifica6on Amine Hormones Tyrosine Tryptophan Pep6de/Protein Hormones Water soluble Steroid Hormones Lipid soluble

3 Amine Hormones Deriva6ves of Tyrosine Catecholamines Epinephrine Thyroid hormones T3, T4 Deriva6ves of Tryptophan Serotonin (5- HT) Melatonin pineal gland

4 Pep6de and Protein Hormones Pep6de Hormones < 200 amino acids ADH, ACTH, insulin, PTH, Calcitonin, ANF, GI tract hormones and others Protein Hormones TSH, LH, FSH, erythropoie6n, renin

5 Steroid Hormones Derived from cholesterol Produced by Adrenal cortex Gonads Testosterone Estrogens Progesterone

6 Aldosterone Regulates blood pressure Cor,sol Steroid Hormones Hormones of the Adrenal Cortex Released in response to stress Increase blood sugar Aid in metabolism Dehydroepiandrosterone (DHEA) Androgen Prohormone (precursor) for sex steroids

7 Hormone Transport in the Blood

8 Mechanism of Hormone Ac6on Hormone Receptors Signal- transduc6on mechanism Receptor modula6on Up- regula6on Down- regula6on Loca6on of Receptor Lipid soluble Water soluble

9 Mechanism of Hormone Ac6on Hormone Interac6ons Synergis6c effects - Epi/NE on heart Permissive/Poten6a6on Hormone A must be present for a full strength of hormone B s effect Antagonis6c effects Insulin/Glucagon Calcitonin/PTH

10 The Hypothalamus and Pituitary Gland

11 Posterior Pituitary Hormones Posterior Pituitary is a neural extension of the hypothalamus Neurons which project from the hypothalamus Hormones synthesized in the hypothalamus Hormones packaged into vesicles move down the axons into the posterior pituitary S6muli of the neurons generate ac6on poten6als which trigger the release of the hormones Hormones released Oxytocin Acts on smooth muscle of the uterus and mammary glands An,diure,c hormone (ADH) Decreases water loss S6mulates thirst

12 Hypothalamus Releasing Hormones TRH stimulates prolactin

13 Anterior Pituitary Hormones and the Hypothalamus Hypothalamus neurons secrete hormones that control the secre6on of all the anterior pituitary hormones Hypothalamus releasing or inhibi6ng hormones Each of the releasing hormones is the first in a three- hormone sequence 1. Hypothalamus releasing hormone 2. Anterior pituitary s6mula6ng hormone 3. Endocrine gland hormone Allows for feedback, amplifica6on of response All are pep6de hormones except DA

14 Anterior Pituitary Hormones and the Hypothalamus A Hypophysiotropic hormone is released from the hypothalamus and binds to receptors in the Anterior Pituitary

15 Anterior Pituitary Hormones A tropic hormone has another endocrine gland as its target organ

16 Hypothalamic- Anterior Pituitary System

17 Short- Loop and Long- Loop Nega6ve Feedback

18 Thyroid Hormones Follicular cells secrete TH Produces two iodine containing molecules Thyroxine (T 4 ) Triiodothyronine (T 3 ) T 4 generally converted into T 3 in target cells Thyroglobulin Thyroid binding hormone in thyroid follicles

19 Synthesis of Thyroid Hormones

20 Control of Thyroid Func6on Basic control of Thyroid Hormone produc6on is long- loop nega6ve feedback The primary role of T 4 in the blood is to feed back to the anterior pituitary AND the hypothalamus

21 Ac6ons of Thyroid Hormones TH receptors present in the nuclei of most cells of the body Metabolic Ac6ons Maintains rela6vely high metabolic rate S6mulates the ac6vity of Na + /K + /ATPase pumps Induces gene transcrip6on and protein synthesis Permissive Ac6ons Poten6ates the ac6ons of catecholamines Growth and Development Poten6ates GH Development and func6on of the nervous system Normal cogni6on in adults

22 Endocrine Control of Growth Bone Growth Growth Hormone Insulin- Like Growth Factors I and II Thyroid hormones Insulin Testosterone Estrogens Pep6de growth factors Paracrine/autocrine agents to s6mulate differen6a6on, cell division

23 Endocrine Control of Growth Growth Hormone Growth hormone (GH) Most important hormone for post- natal growth S6mulus: exercise, stress, fas6ng, low plasma glucose, sleep S6mulates cell division in many 6ssues Promotes bone lengthening S6mulates protein synthesis in muscle S6mulates liver cells to secrete IGF- I

24 Endocrine Control of Growth Insulin- Like Growth Factors Insulin- Like Growth Factor I (IGF- I) Poten6ates GH effects on bone growth S6mulates chondrocytes Required for fetal total body growth, matura6on of fetal nervous system Insulin- Like Growth Factor II (IGF- II) Important mitogen during prenatal period

25 Endocrine Control of Growth Thyroid Hormones and Insulin Thyroid hormones Poten6ates growth hormone Insulin Uptake of glucose and amino acids by cells S6mulates storage of fat Inhibits protein degrada6on Promotes cell division and differen6a6on in fetal development

26 Endocrine Control of Growth Sex Hormones Sex hormone secre6on begins to increase between the ages of 8 and 10 and plateaus over the next 5-10 years Pubertal growth spurt Growth of long bones, vertebrae S6mulates the secre6on of GH and IGF- I Testosterone exerts a direct anabolic effect on protein synthesis Increases muscle mass

27 Endocrine Control of Ca 2+ Homeostasis Ca 2+ homeostasis is vital for survival Low plasma [Ca 2+ ] Increase excitability of nerve, muscle membranes High plasma [Ca 2+ ] Causes cardiac arrhythmias Causes depressed neuromuscular excitability Ca 2+ homeostasis involves bone, kidneys, parathyroid gland, skin, thyroid gland, GI tract

28 Endocrine Control of Ca 2+ Homeostasis Bone 99% of total body Ca 2+ is contained in bone Osteoclast/osteoblast ac6vity Ca 2+ flux into/out of bone is paramount in controlling plasma [Ca 2+ ] Hydroxyapa6te is where minerals are deposited Ca 2+, PO 4 3-

29 Endocrine Control of Ca 2+ Homeostasis Kidneys Control of Ca 2+ excre6on is exerted mainly in the kidneys Reabsorp6on decreases when plasma [Ca 2+ ] increases, and vis versa Hormonal controls of Ca 2+ also regulate PO 4 3- balance

30 Endocrine Control of Ca 2+ Homeostasis Parathyroid Gland Normal, day- to- day regula6on of plasma [Ca 2+ ] Decreased plasma [Ca 2+ ] s6mulates Parathyroid Hormone (PTH) secre6on S6mulates osteoclast ac6vity S6mulates 1,25- dihydroxy vitamin D Increases absorp6on of Ca 2+ and PO 4 3- by the intes6nes Increases Ca 2+ reabsorp6on in the kidneys

31 Endocrine Control of Ca 2+ Homeostasis Skin Normal, day- to- day regula6on of plasma [Ca 2+ ] 1,25- dihydroxyvitamin D (calcitrol) is the ac6ve form of Vitamin D Vitamin D is synthesized in the skin Dietary supplement S6mulates intes6nal absorp6on of Ca 2+

32 Endocrine Control of Ca 2+ Homeostasis Thyroid Gland Not involved in normal, day- to- day regula6on of plasma [Ca 2+ ] Calcitonin Pep6de hormone secreted by parafollicular cells of the thyroid S6mulated by an increase in plasma [Ca 2+ ] Results in a decreases plasma [Ca 2+ ] Inhibits osteoclasts

33 Endocrine Control of Glucose Homeostasis Pancreas Insulin Produced by pancrea6c islet β cells S6mulated by increased blood glucose S;mulates cellular uptake (liver, skeletal muscle, adipocytes) and u6liza6on of glucose Glucagon Produced by pancrea6c islet α cells S6mulated by decreased blood glucose S;mulates liver to release glucose S;mulates skeletal muscle, adipocytes to decrease glucose uptake and u6liza6on