Physiology Unit 3 ENDOCRINE SYSTEM

Physiology Unit 3 ENDOCRINE SYSTEM

Amine Hormones Deriva6ves of Tyrosine Catecholamines Epinephrine Thyroid hormones T3, T4 Deriva6ves of Tryptophan Melatonin pineal gland

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, inhibin

Steroid Hormones Cholesterol deriva6ves Produced by Adrenal cortex Androgens Gonads Testosterone Estrogens Estrone Estradiol** Progesterone

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 for sex steroids

Hormone Transport in the Blood

Mechanism of Hormone Ac6on Hormone Receptors Chemical messenger Hormone must be recognized by specific cell receptor Signal- transduc6on mechanism Receptor modula6on Up- regula6on Down- regula6on Loca6on of Receptor Lipid soluble Water soluble

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

The Hypothalamus and Pituitary Gland

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 An,diure,c hormone (ADH)

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

Anterior Pituitary Hormones and the Hypothalamus

Anterior Pituitary Hormones

Hypothalamus Releasing Hormones

Hypothalamic- Anterior Pituitary System

Short- Loop and Long- Loop Nega6ve Feedback

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

Synthesis of Thyroid Hormones

Control of Thyroid Func6on Follicular cells controlled by TSH TSH controlled by TRH Basic control of TSH produc6on is Long- loop nega6ve feedback

Ac6ons of Thyroid Hormones TH receptors present in the nuclei of most cells of the body Receptors in the nucleus can bind to both T 3 and T 4, but has a higher affinity for T 3 Induce gene transcrip6on and protein synthesis Ac6ons of T 3 and T 4 are widespread Many organs and 6ssues T 3 physiologically relevant hormone T 4 major secretory product of the thyroid gland T 4 concentra6ons are higher in the blood involved in long loop nega6ve feedback (pituitary and hypothalamus)

Ac6ons of Thyroid Hormones Metabolic Ac6ons Maintains rela6vely high metabolic rate S6mulate carbohydrate absorp6on from the small intes6ne Increases fa`y acid release from adipocytes S6mulates the ac6vity of Na + /K + /ATPase pumps Permissive Ac6ons Poten6ates the ac6ons of catecholamines Up- regulates beta- adrenergic receptors in the heart and nervous system Growth and Development Poten6ates GH Important for the development of the nervous system Needed for proper nerve/muscle reflexes Needed for normal cogni6on in adults

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

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

Endocrine Control of Growth Insulin- Like Growth Factors Insulin- Like Growth Factor I (IGF- I) Secreted by the liver 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

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

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 Stop bone growth by inducing epiphyseal plate closure Stops growth for life Testosterone exerts a direct anabolic effect on protein synthesis Increases muscle mass

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

99% of total body Ca 2+ is contained in bone 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- Ca 2+ Homeostasis Bone

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

Ca 2+ Homeostasis Gastrointes6nal Tract A considerable amount of Ca 2+ is not absorbed from the intes6ne and leaves the body along with the feces Ac6ve transport that achieves Ca 2+ absorp6on is under hormonal control Calcitonin Thyroid gland Parathyroid hormone (PTH) Parathyroid gland

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

Ca 2+ Homeostasis 1,25- dihydroxyvitamin D 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+ Blood [Vitamin D] are subject to physiological control Synthesis s6mulated by PTH

Ca 2+ Homeostasis Calcitonin Not involved in normal, day- to- day regula6on of plasma [Ca 2+ ] 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

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