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Endocrine system Chapter 45
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Endocrine system Regulation & communication Blood system Glands (ductless) Hormones (chemicals) Target tissues
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Blood vessel Response (a) Endocrine signaling
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Nervous system Regulation & communication Nerves Axon Neurotransmitters Synapse
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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)
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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
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Local regulators Paracrine Messages between neighboring cells 1. Cytokines Regulate immune system 2. Growth factors Regulate cell growth 3. NO Vasodilation (local blood vessels)
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Local regulators 4. Prostaglandins 20-carbon fatty acid Derived from lipids in plasma membrane Found in many organs Released into interstitial fluid
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Local regulators 4. Prostaglandins A. Immune system inflammation B. Reproductive system Labor Semen C. Digestive system Inhibit gastric secretions Increase gut motility
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Local regulators D. Respiratory system Some cause dilation Some cause constriction E. Circulatory system Platelets F. Urinary system Renal vasodilation Increased excretion
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(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
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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)
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Hormone types 4. Steroids Lipids from cholesterol Testosterone Estradiol, progesterone Aldosterone, cortisol
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Water-soluble (hydrophilic) Lipid-soluble (hydrophobic) Polypeptides Steroids Cortisol Insulin Amines Epinephrine Thyroxine 0.8 nm
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Mechanism of regulation 1. Enter the cell Lipophilic Lipid soluble 2. Do not enter the cell Lipophobic Water soluble
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(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
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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
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Lipid-Soluble Hormone
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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
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Water-Soluble Hormone
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Mechanism of regulation
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Mechanism of Regulation Different effects on different target cells Target cells have different Receptors Signal transduction pathways Epinephrine
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(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
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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
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Thyroid
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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
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Parathyroid glands
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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
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Pancreas
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Ovaries Abdomen Estrogen Secondary female characteristics Menstruation Progesterone Prepares/maintains pregnancy
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Testes Inguinal region Testosterone Maintain male characteristics
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Ovaries and Testes
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Steroids
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Adrenal glands Small glands on top of kidneys 1. Adrenal cortex Outer layer 2. Adrenal medulla Inner layer
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Adrenal glands Adrenal cortex A. Corticosteriods Cortisol (glucocorticoid) Increases serum levels of glucose Gluconeogenesis Converts aa to glucose Exercise or fasting
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Adrenal glands B. Mineralcorticoids Aldosterone Stimulates kidneys to reabsorb Na +1 Stimulates kidneys to eliminate K +1 C. Gonadocorticoids Androgens Sex characteristics
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Adrenal glands Adrenal medulla Catacholamines Epinephrine/norepinephrine Increased heart rate, BP, glucose blood levels, Dilation of bronchioles Decreased blood flow to skin and gut
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Adrenal glands
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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
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Pituitary gland
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Anterior pituitary gland All hormones stimulate growth in target organs Tropins A. GH (growth hormone) Somatotropin Stimulates muscle growth (bone)
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Anterior pituitary gland B. ACTH Adrenocorticotropic hormone Corticotropin Stimulates adrenal cortex (cortisol) C. TSH Thyroid-stimulating hormone Thyrotropin Stimulates thryroid to produce thyroxine
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Anterior pituitary gland D. LH Luteinizing hormone Stimulates ovulation & lining of uterus Stimulates testes to produce testosterone
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Anterior pituitary gland E. FSH Follicle stimulating hormone Stimulates the egg development Development of sperm F. Prolactin Stimulates mammary glands to produce milk
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LH, FSH
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Anterior pituitary gland G. MSH Melanocyte-stimulating hormone Regulates skin color in some fish, amphibians & reptiles Regulates pigment distribution in melanocytes Mammals: hunger & pigment
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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
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Pituitary gland
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Pineal gland Small mass of tissue located near center of brain Synthesizes & secretes melatonin (modified aa) Regulates functions related to day and night Seasons
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Hypothalamus Spinal cord Posterior pituitary Cerebellum Pineal gland Anterior pituitary Hypothalamus Pituitary gland Hypothalamus Thalamus Cerebrum
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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
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Hypothalamus Posterior pituitary Anterior pituitary Neurosecretory cells of the hypothalamus Hypothalamus Axon HORMONE Oxytocin ADH Kidney tubulesTARGETMammary glands, uterine muscles
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Hypothalamus control Controls release of AP hormones Neurons in Hypothalamus secrete releasing or inhibiting hormones Anterior Pituitary (negative feedback)
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Hypothalamus
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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 )
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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 ) –
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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
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Problems Thyroid Graves disease Over production of thyroxine Cretinism To little thyroxine in children Leads to delayed skeletal and mental growth
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Hyperthyroidism
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Negative feedback
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Problems Diabetes mellitus Decreased insulin Decreased response to insulin Increased blood sugar
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Diabetes
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Problems Growth hormone (anterior pituitary) Gigantism too much hormone Pituitary dwarfism to little hormone Acromegaly to much hormone after growth plates are fused
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Acromegaly
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Problems Addison’s disease Insufficiency in ACTH Increased pigmentation of skin Imbalance of electrolytes
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