Endocrine system Chapter 45 Endocrine system n n

Endocrine system Chapter 45

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

(a) Endocrine signaling Blood vessel Response

Nervous system n n n Regulation & communication Nerves Axon Neurotransmitters Synapse

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

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

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

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

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

Figure 45. 2 Blood vessel RESPONSE (a) Endocrine signaling Synapse Neuron RESPONSE (d) Synaptic signaling (b) Paracrine signaling Neurosecretory cell RESPONSE (c) Autocrine signaling Blood vessel (e) Neuroendocrine signaling RESPONSE

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

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

Water-soluble (hydrophilic) Lipid-soluble (hydrophobic) Polypeptides Steroids Figure 45. 4 0. 8 nm Insulin Cortisol Amines Epinephrine Thyroxine

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

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

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

Water-Soluble Hormone

Mechanism of regulation

Mechanism of regulation

Mechanism of regulation

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

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

Thyroid n n n n 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 n n n n 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 n n n n 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 n n n Abdomen Estrogen Secondary female characteristics Menstruation Progesterone Prepares/maintains pregnancy

Testes n n n Inguinal region Testosterone Maintain male characteristics

Ovaries and Testes

Steroids

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

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

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

Adrenal glands n n n 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) n n n n n 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 n n n All hormones stimulate growth in target organs Tropins A. GH (growth hormone) Somatotropin Stimulates muscle growth (bone)

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

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

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

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

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

Hypothalamus control n n n 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 Neurosecretory cells of the hypothalamus Axon Posterior pituitary Anterior pituitary HORMONE ADH Oxytocin TARGET Kidney tubules Mammary glands, uterine muscles

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

Hypothalamus

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

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

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

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

Problems n n Hashimoto’s thyroiditis Autoimmune disorder Underactive thyroid Hypothyroidism

Hyperthyroidism

Negative feedback

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

Diabetes

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

Acromegaly

Problems n n n n Addison’s disease Insufficiency in ACTH Increased pigmentation of skin Imbalance of electrolytes Cushing’s syndrome Too much cortisol Round face, weight gain, increase BP