Endocrine (hormone) System Hendra Wijaya

Hormones are chemical messengers secreted by certain tissues into the blood or institial fluid, serving to regulate the activity of other tissues.

Chemical Classification of Hormones Amine hormones are derived from tyrosine or tryptophan Include NE, Epi, thyroxine, melatonin Polypeptide/protein hormones are chains of amino acids Include ADH, GH, insulin, oxytocin, glucagon, ACTH, PTH Glycoproteins Long polypeptide bound to a carbohydrate group Include LH, FSH, TSH Steroids are lipids derived from cholesterol Include testosterone, estrogen, progesterone & cortisol 11-7

Chemical Classificaton of Hormones Steroid Hormones: Lipid soluble Diffuse through cell membranes Endocrine organs Adrenal cortex Ovaries Testes placenta

Chemical Classification of Hormones Nonsteroid Hormones: Not lipid soluble Received by receptors external to the cell membrane Endocrine organs Thyroid gland Parathyroid gland Adrenal medulla Pituitary gland pancreas

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 ducts Neurosecretory cells~ actual cells that secrete hormones Feedback mechanisms ~ negative and positive

Endocrine System

Major Endocrine Glands Pineal Gland Hypothalamus Pituitary Gland Anterior Posterior Thyroid Gland Parathyroid Glands Adrenal Glands Cortex Medulla Thymus Gland Pancreas Gonads Ovaries Testes Instructor to read slide. Go to next slide.

There is a hierarchical chain of command in hormonal signaling. Coordination center of the endocrine system. Via direct neuronal connection

Hypothalamus-pituitary axis

Feedback control

Feedback control of thyroid function

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

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

Hypotalamus Hypothalamus and pituitary gland secrete hormones and regulate other endocrine organs. They are the main regulatory organs of the endocrine system.

Hypothalamus Located below the thalamus and above the pituitary gland (=epiphysis) Regulates the pituitary gland secretions through two different mechanisms

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)

Pituitary Gland Releasing and inhibiting hormones Anterior pituitary: Growth (GH)~bones √gigantism/dwarfism √acromegaly Prolactin (PRL)~mammary glands; milk production Follicle-stimulating (FSH) & Luteinizing (LH)~ovaries/testes Thyroid-stimulating (TSH)~ thyroid Adrenocorticotropic (ACTH)~ adrenal cortex Melanocyte-stimulating (MSH) Endorphins~natural ‘opiates’; brain pain receptors

Hormones of the Anterior Pituitary

Hypothalamus & Pituitary Gland

Posterior Region of the Pituitary Gland The posterior pituitary: Oxytocin~ uterine and mammary gland cell contraction Antidiuretic (ADH)~ retention of water by kidneys

The Pineal, Thyroid, & Parathyroid Melatonin~ pineal gland; biological rhythms Thyroid hormones: Calcitonin~ lowers blood calcium Thyroxine~ metabolic processes Parathyroid (PTH)~ raises blood calcium

The thyroid gland - Chp 21 p 623-625 Located in the neck, just below the larynx Secrete 2 types of hormone: - thyroid hormones  stimulate cell metabolism, triiodothyronine (T3) and thyroxine (T4) – iodine is needed to synthesize these hormones - calcitonin  decrease blood calcium Figure 6.8a

Thyroid hormones T3 and T4 secreted by the follicular cells Stored as colloid Parafollicular cells (C cells) secrete calcitonin (Chp 19)

Thyroid Hormones T3 and T4 Target organs: all cells Role: Increase cell metabolism, oxygen consumption Permissive role for some other hormones (growth hormone)

Thyroid hormone regulation Figure 6.7

Goiter Both hypo and hyperthyroidism can have goiter as a symptom Goiter is a swelling of the neck due to hypertrophy of the thyroid gland How can one explain that?

Goiter in hypothyroidism Most often due to a lack of dietary iodine The thyroid hormone is unable to synthesize a functional thyroid hormone (T3 and T4) The person express symptoms of hypothyroidism The 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

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

Parathyroid glands Four nodules located in the back of the thyroid gland Secreted parathyroid hormone or parathormone or PTH Action of PTH opposes action of calcitonin Both hormones play a role in calcium metabolism

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 regulation Vitamin D helps PTH activity

Calcium regulation: Calcitonin promotes blood calcium decrease, by: 1. calcium deposition on bone 2. calcium dumping by the kidney PTH promotes blood calcium increase by: 1. bone resorption 2. calcium reabsorption by kidney 3. increase calcium absorption by intestine

Figure 23-20: Calcium balance in the body Calcium Metabolism: Figure 23-20: Calcium balance in the body

Figure 19.20

The Pancreas Islets of Langerhans Alpha cells: •glucagon~ raises blood glucose levels Beta cells: •insulin~ lowers blood glucose levels Type I diabetes mellitus (insulin-dependent; autoimmune disorder) Type II diabetes mellitus (non-insulin-dependent; reduced responsiveness in insulin targets)

The pancreas Located in the left upper abdominal cavity Exocrine and endocrine glands The endocrine function is due to the cells of the islets of the Langerhans -- α cells  glucagon -- β  insulin -- δ  somatostatin

Glucose regulation Glucose level controlled by insulin and glucagon Insulin promotes a decrease in blood glucose Glucagon promotes an increase in blood glucose

Glucose regulation

Fate of glucose Figure 3.21

Diabetes mellitus Type I: autoimmune disease  beta cells of the islets of Langerhans are destroyed by antibodies Type II: The cells become insulin-resistant  glucose does not enter the cells as readily http://faculty.weber.edu/nokazaki/Human_Physiology/Class%20notes/diabetes.htm

The Adrenal Glands Adrenal 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+

The Gonads Steroid hormones: precursor is cholesterol Androgens (testosterone) sperm formation male secondary sex characteristics; gonadotropin Estrogens (estradiol) uterine lining growth female secondary sex characteristics gonadotropin Progestins (progesterone)

The Gonads Steroid hormones: precursor is cholesterol androgens (testosterone)~ sperm formation; male secondary sex characteristics; gonadotropin estrogens (estradiol)~uterine lining growth; female secondary sex characteristics; gonadotropin progestins (progesterone)~uterine lining growth

Revision: Major endocrine conditions Endocrine Gland Hormones Endocrine Disorders Hyper Hypo Anterior Pituitary Growth Hormone Gigantism, acromegaly Dwarfism Thyroid Thyroxine (T4) Triodothronine (T3) Thyrotoxicosis Goitre Exopthalmos Hypothroidism Cretinism Myxoedema Parathyroid Parathormone Osteoporosis Kidney stones Tetany Adrenal Cortex Glucacorticoids Cushings syndrome Addisons disease Adrenal Medulla Epinephrine Norepinephrine Increased metabolism Hypertension Pancreatic Islets Insulin Diabetes mellitus

Pituitary Dwarfism

Hyper secretion of Growth hormone: Gigantism