Endocrine system Chapter 45

Endocrine system Regulation & communication Blood system Glands (ductless) Hormones (chemicals) Target tissues

Blood vessel Response (a) Endocrine signaling

Nervous system Regulation & communication Nerves Axon Neurotransmitters Synapse

Both systems (overlap) Neurohormone Released by the nervous system Into blood stream (ADH) Norepinephrine Chemical involved in both Nervous system (cleft) Endocrine system (adrenal gland)

Both systems Neural control of endocrine system Hypothalamus Regulates hormonal secretion of the anterior pituitary Glands derived from nervous tissue Adrenal medulla, posterior pituitary & pineal gland

Local regulators Paracrine Messages between neighboring cells 1. Cytokines Regulate immune system 2. Growth factors Regulate cell growth 3. NO Vasodilation (local blood vessels)

Local regulators 4. Prostaglandins 20-carbon fatty acid Derived from lipids in plasma membrane Found in many organs Released into interstitial fluid

Local regulators 4. Prostaglandins A. Immune system inflammation B. Reproductive system Labor Semen C. Digestive system Inhibit gastric secretions Increase gut motility

Local regulators D. Respiratory system Some cause dilation Some cause constriction E. Circulatory system Platelets F. Urinary system Renal vasodilation Increased excretion

(a) Endocrine signaling Blood vessel RESPONSE (b) Paracrine signaling (c) Autocrine signaling (e) Neuroendocrine signaling (d) Synaptic signaling Neurosecretory cell Blood vessel RESPONSE Neuron Synapse

Hormone types 1. Polypeptide Short, <100 aa, insulin, ADH 2. Glycoprotein >100 aa, carbohydrate attached, FSH, LH 3. Amines Tyrosine & tryptophan Adrenal medulla (NE, Epinephrine) Thyroid (T 3 & T 4 Pineal (Melatonin)

Hormone types 4. Steroids Lipids from cholesterol Testosterone Estradiol, progesterone Aldosterone, cortisol

Water-soluble (hydrophilic) Lipid-soluble (hydrophobic) Polypeptides Steroids Cortisol Insulin Amines Epinephrine Thyroxine 0.8 nm

Mechanism of regulation 1. Enter the cell Lipophilic Lipid soluble 2. Do not enter the cell Lipophobic Water soluble

(a) Water-soluble hormone; receptor in plasma membrane SECRETORY CELL Water- soluble hormone Blood vessel Receptor protein TARGET CELL OR Cytoplasmic response Gene regulation NUCLEUS Gene regulation Cytoplasmic response Receptor protein TARGET CELL Transport protein Blood vessel Lipid- soluble hormone SECRETORY CELL (b) Lipid-soluble hormone; receptor in nucleus or cytoplasm

Mechanism of regulation 1. Lipophilic (Steroids, thyroxine) Not water soluble Plasma attached to protein carriers Target cell-release carrier Cross plasma membrane Bind receptor protein (+/- nucleus) Hormone receptor binds DNA Protein synthesis

Lipid-Soluble Hormone

Mechanism of regulation 2. Lipophobic or too large Bind receptors on target cell membrane A. Triggers second-messenger system cAMP IP 3 /Ca +2 B. Causes change in an ion channel

Water-Soluble Hormone

Mechanism of regulation

Mechanism of Regulation Different effects on different target cells Target cells have different Receptors Signal transduction pathways Epinephrine

(a) Liver cell(b) Smooth muscle cell in wall of blood vessel that supplies skeletal muscle (c) Smooth muscle cell in wall of blood vessel that supplies intestines Epinephrine β receptor Glycogen deposits Glucose Glycogen breaks down and glucose is released from cell. Blood glucose level increases. Blood vessel dilates, increasing flow to skeletal muscle. Cell relaxes. Epinephrine β receptor α receptor Cell contracts. Blood vessel constricts, decreasing flow to intestines. Epinephrine

Thyroid Neck 2 lobes/isthmus T 4 (tetraiodothyronine) thyroxine T 3 (triiodothyronine) Regulates metabolism in the body Calcitonin Stimulates Ca 2+ uptake into bones Decreases serum Ca +2

Thyroid

Parathyroid glands Neck 4 small glands on top of thyroid PTH (parathyroid hormone) Increase in blood calcium levels Stimulates osteoclasts Break down calcium phosphate crystals Stimulates kidneys to reabsorb Ca 2+ Activates Vitamin D

Parathyroid glands

Pancreas Abdomen behind stomach Islets of Langerhans Insulin (  cells) Decreases blood glucose levels Stores in glycogen (liver/muscle) & fat (adipose cells) Glucagon (  cells) Increases glucose blood levels

Pancreas

Ovaries Abdomen Estrogen Secondary female characteristics Menstruation Progesterone Prepares/maintains pregnancy

Testes Inguinal region Testosterone Maintain male characteristics

Ovaries and Testes

Steroids

Adrenal glands Small glands on top of kidneys 1. Adrenal cortex Outer layer 2. Adrenal medulla Inner layer

Adrenal glands Adrenal cortex A. Corticosteriods Cortisol (glucocorticoid) Increases serum levels of glucose Gluconeogenesis Converts aa to glucose Exercise or fasting

Adrenal glands B. Mineralcorticoids Aldosterone Stimulates kidneys to reabsorb Na +1 Stimulates kidneys to eliminate K +1 C. Gonadocorticoids Androgens Sex characteristics

Adrenal glands Adrenal medulla Catacholamines Epinephrine/norepinephrine Increased heart rate, BP, glucose blood levels, Dilation of bronchioles Decreased blood flow to skin and gut

Adrenal glands

Pituitary gland (hypophysis) In the brain Hangs by a stalk from hypothalamus 1.Anterior Adenohypophysis Developed from epithelial tissue 2. Posterior Neurohypophysis Developed from the neural tissue Nerve axons from hypothalamus end here

Pituitary gland

Anterior pituitary gland All hormones stimulate growth in target organs Tropins A. GH (growth hormone) Somatotropin Stimulates muscle growth (bone)

Anterior pituitary gland B. ACTH Adrenocorticotropic hormone Corticotropin Stimulates adrenal cortex (cortisol) C. TSH Thyroid-stimulating hormone Thyrotropin Stimulates thryroid to produce thyroxine

Anterior pituitary gland D. LH Luteinizing hormone Stimulates ovulation & lining of uterus Stimulates testes to produce testosterone

Anterior pituitary gland E. FSH Follicle stimulating hormone Stimulates the egg development Development of sperm F. Prolactin Stimulates mammary glands to produce milk

LH, FSH

Anterior pituitary gland G. MSH Melanocyte-stimulating hormone Regulates skin color in some fish, amphibians & reptiles Regulates pigment distribution in melanocytes Mammals: hunger & pigment

Posterior pituitary gland A. ADH Antidiuretic hormone (vasopressin) Stimulates water retention in the kidneys B. Oxytocin Milk ejection from mammary glands Stimulates uterine contractions in labor

Pituitary gland

Pineal gland Small mass of tissue located near center of brain Synthesizes & secretes melatonin (modified aa) Regulates functions related to day and night Seasons

Hypothalamus Spinal cord Posterior pituitary Cerebellum Pineal gland Anterior pituitary Hypothalamus Pituitary gland Hypothalamus Thalamus Cerebrum

Hypothalamus control Posterior pituitary (direct) Stimulation in hypothalamus Causes release of hormone from axon in pp ADH released increased blood osmolality Oxytocin released due to baby suckling

Hypothalamus Posterior pituitary Anterior pituitary Neurosecretory cells of the hypothalamus Hypothalamus Axon HORMONE Oxytocin ADH Kidney tubulesTARGETMammary glands, uterine muscles

Hypothalamus control Controls release of AP hormones Neurons in Hypothalamus secrete releasing or inhibiting hormones Anterior Pituitary (negative feedback)

Hypothalamus

thyroid Cold Pathway Stimulus Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Example Sensory neuron Neurosecretory cell Blood vessel + Anterior pituitary secretes thyroid-stimulating hormone (TSH or thyrotropin )

thyroid Cold Pathway Stimulus Hypothalamus secretes thyrotropin-releasing hormone (TRH ) Negative feedback Example Sensory neuron Neurosecretory cell Blood vessel Anterior pituitary secretes thyroid-stimulating hormone (TSH or thyrotropin ) Target cells Response Body tissues Increased cellular metabolism – Thyroid gland secretes thyroid hormone (T 3 and T 4 ) –

Anterior pituitary Hypothalamic releasing and inhibiting hormones Neurosecretory cells of the hypothalamus HORMONE TARGET Posterior pituitary Portal vessels Endocrine cells of the anterior pituitary Pituitary hormones Tropic effects only: FSH LH TSH ACTH Nontropic effects only: Prolactin MSH Nontropic and tropic effects: GH Testes or ovaries Thyroid FSH and LHTSH Adrenal cortex Mammary glands ACTHProlactinMSHGH MelanocytesLiver, bones, other tissues

Problems Thyroid Graves disease Over production of thyroxine Cretinism To little thyroxine in children Leads to delayed skeletal and mental growth

Hyperthyroidism

Negative feedback

Problems Diabetes mellitus Decreased insulin Decreased response to insulin Increased blood sugar

Diabetes

Problems Growth hormone (anterior pituitary) Gigantism too much hormone Pituitary dwarfism to little hormone Acromegaly to much hormone after growth plates are fused

Acromegaly

Problems Addison’s disease Insufficiency in ACTH Increased pigmentation of skin Imbalance of electrolytes