The Endocrine System Second controlling system of the body
Nervous system is the fast-control system Uses chemical messengers (hormones) thatare released into the blood Hormones control several major processes Reproduction Growth and development Mobilization of body defenses Maintenance of much of homeostasis Regulation of metabolism 1 Hormone Overview Hormones are produced by specialized cells
Cells secrete hormones into extracellular fluids Blood transfers hormones to target sites These hormones regulate the activity of othercells 2 The Chemistry of Hormones
Hormones are classified chemically as Amino acidbased, which includes Proteins Peptides Amines Steroidsmade from cholesterol Prostaglandinsmade from highly active lipids 3 Mechanisms of Hormone Action
Hormones affect only certain tissues or organs(target cells or target organs) Target cells must have specific proteinreceptors Hormone-binding alters cellular activity 4 Effects Caused by Hormones
Changes in plasma membrane permeability orelectrical state Synthesis of proteins, such as enzymes Activation or inactivation of enzymes Stimulation of mitosis Promotion of secretory activity 5 The Chemistry of Hormones
Two mechanisms in which hormones act Direct gene activation Second-messenger system 6 Direct Gene Activation (Steroid Hormone Action)
Diffuse through the plasma membrane oftarget cells Enter the nucleus Bind to a specific protein within the nucleus Bind to specific sites on the cells DNA Activate genes that result in synthesis of newproteins 7 Hormone- receptor complex
Cytoplasm Nucleus Steroid hormone Receptor protein 1 2 3 Hormone- receptor complex 4 DNA mRNA 5 New protein Plasma membrane of target cell 6 (a)Steroid hormone action Figure 9.1a 8 Cytoplasm Nucleus Steroid hormone 1 Figure 9.1a, step 1 9 Nucleus Cytoplasm Steroid hormone Receptor protein 1 2
Figure 9.1a, step 2 10 Hormone- receptor complex
Cytoplasm Nucleus Steroid hormone Receptor protein 1 2 3 Hormone- receptor complex Figure 9.1a, step 3 11 Hormone- receptor complex
Cytoplasm Nucleus Steroid hormone Receptor protein 1 2 3 Hormone- receptor complex 4 DNA Figure 9.1a, step 4 12 Hormone- receptor complex
Cytoplasm Nucleus Steroid hormone Receptor protein 1 2 3 Hormone- receptor complex 4 DNA mRNA 5 Figure 9.1a, step 5 13 Hormone- receptor complex
Cytoplasm Nucleus Steroid hormone Receptor protein 1 2 3 Hormone- receptor complex 4 DNA mRNA 5 New protein Plasma membrane of target cell 6 Figure 9.1a, step 6 14 Second-Messenger System (Nonsteroid Hormone Action)
Hormone binds to a membrane receptor Hormone does not enter the cell Sets off a series of reactions that activates anenzyme Catalyzes a reaction that produces a second- messenger molecule (such as cAMP) Oversees additional intracellular changes topromote a specific response 15 Nonsteroid hormone (first messenger) Cytoplasm
Enzyme ATP 1 3 2 Second messenger cAMP 4 Receptor protein Effect on cellular function,such as glycogen breakdown Plasmamembrane of target cell (b)Nonsteroid hormone action Figure 9.1b 16 Nonsteroid hormone (first messenger) Cytoplasm
1 Receptor protein Figure 9.1b, step 1 17 Nonsteroid hormone (first messenger) Cytoplasm
Enzyme 1 2 Receptor protein Figure 9.1b, step 2 18 Nonsteroid hormone (first messenger) Cytoplasm
Enzyme ATP 1 3 2 Second messenger cAMP Receptor protein Figure 9.1b, step 3 19 Nonsteroid hormone (first messenger) Cytoplasm
Enzyme ATP 1 3 2 Second messenger cAMP 4 Receptor protein Effect on cellular function,such as glycogen breakdown Plasmamembrane of target cell Figure 9.1b, step 4 20 Control of Hormone Release
Hormone levels in the blood are mostlymaintained by negative feedback A stimulus or low hormone levels in the bloodtriggers the release of more hormone Hormone release stops once an appropriatelevel in the blood is reached like insulin &thyroid hormones 21 Hormonal Stimuli of Endocrine Glands
Most common stimuli Endocrine glands are activated by otherhormones Examples: Anterior pituitary hormones travel to targetglands, such as the thyroid gland, to prompt therelease of a particular hormone, such as thyroidhormone 22 (a) Hormonal stimulus 1 The hypothalamus secretes hormones that
2 stimulate the anterior pituitarygland tosecrete hormones that Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) stimulate other endocrineglands to secrete hormones 3 Figure 9.2a 23 Humoral Stimuli of Endocrine Glands
Changing blood levels of certain ions stimulatehormone release Humoral indicates various body fluids such asblood and bile Examples: Parathyroid hormone and calcitonin areproduced in response to changing levels ofblood calcium levels Insulin is produced in response to changinglevels of blood glucose levels 24 (b) Humoral stimulus 1 Capillary blood contains low concentration of Ca2+, which stimulates Capillary (low Ca2+in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands PTH 2 secretion of parathyroidhormone (PTH) by parathyroid glands Figure 9.2b 25 Neural Stimuli of Endocrine Glands
Nerve impulses stimulate hormone release Most are under the control of the sympatheticnervous system Examples: The release of norepinephrine and epinephrineby the adrenal medulla 26 (c) Neural stimulus 1 Preganglionic sympathetic fiber stimulates adrenal medullacells CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary to secrete catecholamines (epinephrine and norepinephrine) 2 Figure 9.2c 27 Major Endocrine Organs
Pituitary gland Thyroid gland Parathyroid glands Adrenal glands Pineal gland Thymus gland Pancreas Gonads (Ovaries and Testes) Hypothalamus 28 Pineal gland Hypothalamus Pituitary gland Thyroid gland
Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3 29 Pituitary Gland Size of a pea
Hangs by a stalk from the hypothalamus in thebrain Protected by the sphenoid bone Has two functional lobes Anterior pituitaryglandulartissue(adenohypophysis.) Posterior pituitarynervoustissue(neurohypophysis) Often called the master endocrine gland 30 Hormones of the Anterior Pituitary
Six anterior pituitary hormones Two affect non-endocrine targets Growth hormone Prolactin Four stimulate other endocrine glands (tropichormones) Thyroid-stimulating hormone (thyrotropichormone)TSH Adrenocorticotropic hormone(ACTH) Two gonadotropic hormones(FSH, LH) 31 Hormones of the Anterior Pituitary
Characteristics of all anterior pituitaryhormones Proteins (or peptides) Act through second-messenger systems Regulated by hormonal stimuli, mostlynegative feedback 32 Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Releasing hormones secreted into portal circulation Hypothalamus Hypothalamus Hypothalamus Anterior pituitary Posterior pituitary Hypophyseal portal system Adrenocorticotropic hormone (ACTH) Growth hormone (GH) Bones and muscles Prolactin (PRL) Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Thyrotropic hormone (TH) Adrenal cortex Mammary glands Thyroid Testes or ovaries Figure 9.4 33 Hormones of the Anterior Pituitary
Growth hormone General metabolic hormone Major effects are directed to growth of skeletalmuscles and long bones Plays a role in determining final body size Causes amino acids to be built into proteins Causes fats to be broken down for a source ofenergy 34 Hormones of the Anterior Pituitary
Growth hormone (GH) disorders Pituitary dwarfism results from hyposecretionof GH during childhood Gigantism results from hypersecretion of GHduring childhood Acromegaly results from hypersecretion of GHduring adulthood 35 Pituitary dwarf (left), Giant (center), Normal height woman (right)
Figure 9.5 36 Hormones of the Anterior Pituitary
Prolactin (PRL) Stimulates and maintains milk productionfollowing childbirth by increasing # of milk ducts& milk glands, no realse of milk Adrenocorticotropic hormone (ACTH) Regulates endocrine activity of the adrenalcortex Thyroid-stimulating hormone (TSH) Influences growth and activity of the thyroidgland 37 Hormones of the Anterior Pituitary
Gonadotropic hormones Regulate hormonal activity of the gonads Follicle-stimulating hormone (FSH) Stimulates follicle development in ovaries, thegrafian follicle that secretes estrogen Stimulates sperm development in testes Luteinizing hormone (LH) Triggers ovulation of an egg in females, it actson the corpus lutium to secrete progestron Stimulates testosterone production in males 38 PituitaryHypothalamus Relationship
Hormonal release is regulated by releasingand inhibiting hormones produced by thehypothalamus Hypothalamus produces two hormones These hormones are transported toneurosecretory cells of the posterior pituitary Oxytocin Antidiuretic hormone The posterior pituitary is not strictly anendocrine gland, but does release hormones 39 Hormones of the Posterior Pituitary
Oxytocin Stimulates contractions of the uterus duringlabour, sexual relations, and breastfeeding Causes milk ejection in a nursing woman aftersuckling 40 Hormones of the Posterior Pituitary
Antidiuretic hormone (ADH) Inhibits urine production by promoting waterreabsorption by the kidneys In large amounts, causes vasoconstrictionleading to increased blood pressure Also known as vasopressin 41 Hypothalamic neurosecretory cells Optic chiasma Hypothalamus Axon
terminals Arterial blood supply Posterior lobe Capillary bed Venous drainage Anterior lobe of the pituitary ADH Oxytocin Kidney tubules Mammary glands Uterine muscles Figure 9.6 42 Thyroid Gland Found at the base of the throat
Consists of two lobes and a connectingisthmus Produces two hormones Thyroid hormone Calcitonin 43 (a) Gross anatomy of the thyroid gland, anterior view
Thyroid cartilage Epiglottis Common carotid artery Isthmus of thyroid gland Trachea Left subclavian artery Brachiocephalic artery Left lobe of thyroid gland Aorta (a) Gross anatomy of the thyroid gland, anterior view Figure 9.7a 44 Thyroid Gland Thyroid hormone Major metabolic hormone
Composed of two active iodine-containinghormones Thyroxine (T4)secreted by thyroid follicles Triiodothyronine (T3)conversion of T4 attarget tissues 45 (b) Photomicrograph of thyroid gland follicles (125)
Colloid-filled follicles Follicle cells Parafollicular cell (b) Photomicrograph of thyroid gland follicles (125) Figure 9.7b 46 Thyroid Gland Thyroid hormone disorders Goiters
Thyroid gland enlarges due to lack of iodine Salt is iodized to prevent goiters Types:simple nodular, toxic(Graves disease) &malignant Cretinism Caused by hyposecretion of thyroxine duringchildhood 47 Figure 9.8 48 Thyroid Gland Thyroid hormone disorders (continued) Myxedema
Caused by hypothyroidism in adults Results in physical and mental slugishnesswith rapid increase in weight Graves disease( toxic goiter) Caused by hyperthyroidism Results in increased metabolism, heatintolerance, rapid heartbeat, weight loss, andexophthalmos 49 Figure 9.9 50 Thyroid Gland Calcitonin
Decreases blood calcium levels by causing itsdeposition on bone Antagonistic to parathyroid hormone Produced by parafollicular cells Parafollicular cells are found between thefollicles 51 (b) Photomicrograph of thyroid gland follicles (125)
Colloid-filled follicles Follicle cells Parafollicular cell (b) Photomicrograph of thyroid gland follicles (125) Figure 9.7b 52 Parathyroid Glands Tiny masses on the posterior of the thyroid
Secrete parathyroid hormone (PTH) Stimulate osteoclasts to remove calcium frombone Stimulate the kidneys and intestine to absorbmore calcium Raise calcium levels in the blood 53 Calcium homeostasis of blood: 911 mg/100 ml
Calcitonin Calcitonin stimulates calcium salt deposit in bone. Thyroid gland releases calcitonin. Stimulus Rising blood Ca2+ levels IMBALANCE Calcium homeostasis of blood: 911 mg/100 ml BALANCE BALANCE Stimulus Falling blood Ca2+ levels IMBALANCE Thyroid gland Osteoclasts degrade bone matrix and release Ca2+ into blood. Parathyroid glands Parathyroid glands release parathyroid hormone (PTH). PTH Figure 9.10 54 Adrenal Glands Sit on top of the kidneys Two regions
Adrenal cortexouter glandular region hasthree layers Mineralocorticoids secreted by outermostlayer(zona glumerulosa) Glucocorticoids secreted by middle layer(z.faciculata) Sex hormones secreted by innermost layer(z.reticularis) Adrenal medullainner neural tissue region 55 Adrenal gland Capsule Mineralocorticoid- secreting area Kidney
Glucocorticoid- secreting area Adrenal gland Adrenal cortex Medulla Cortex Cortex Sex hormone secreting area Kidney Adrenal medulla Medulla Figure 9.11 56 Hormones of the Adrenal Cortex
Mineralocorticoids (mainly aldosterone) Produced in outer adrenal cortex Regulate mineral content in blood Regulate water and electrolyte balance, itkeeps Na &release K Target organ is the kidney Production stimulated by renin Production inhibited by atrial natriuretichormon (ANH) 57 Figure 9.12 58 Decreased Na+ or increased K+ in Stress blood
Hypothalamus Decreased blood volume and/or blood pressure Corticotropin- releasing hormone Anterior pituitary Increased blood pressure or blood volume ACTH Kidney Renin Heart Indirect stimulating effect via angiotensin Atrial natriuretic peptide (ANP) Angiotensin II Direct stimulating effect Inhibitory effect Mineralocorticoid- producing part of adrenal cortex Enhanced secretion of aldosterone targets kidney tubules Increased absorption of Na+ and water; increased K+ excretion Increased blood volume and blood pressure Figure 9.12 58 Hormones of the Adrenal Cortex
Glucocorticoids (including cortisone andcortisol) Produced in the middle layer of the adrenalcortex Promote normal cell metabolism(anti- inflammatory)& antiallergic Help resist long-term stressors(antidepressant) Released in response to increased bloodlevels of ACTH 59 Corticotropic cells of anterior pituitary
Short term Stress More prolonged Hypothalamus Releasing hormones Nerve impulses Spinal cord Corticotropic cells of anterior pituitary ACTH Adrenal cortex Preganglionic sympathetic fibers Adrenal medulla Mineralocorticoids Glucocorticoids Short-term stress response Long-term stress response Catecholamines (epinephrine and norepinephrine) 1. Increased heart rate 2. Increased blood pressure 3. Liver converts glycogen to glucose and releases glucose to blood 4. Dilation of bronchioles 5. Changes in blood flow patterns, leading to increased alertness and decreased digestive and kidney activity 6. Increased metabolic rate 1. Retention of sodium and water by kidneys 2. Increased blood volume and blood pressure 1. Proteins and fats converted to glucose or broken down for energy 2. Increased blood sugar 3. Suppression of immune system Figure 9.13 60 Hormones of the Adrenal Cortex
Sex hormones Produced in the inner layer of the adrenalcortex Small amounts are made throughout life Mostly androgens (male sex hormones) aremade but some estrogens (female sexhormones) are also formed 61 Adrenal Glands Adrenal cortex disorders Addisons disease
Results from hyposecretion of all adrenal cortexhormones Bronze skin tone, muscles are weak, burnout,susceptibility to infection Hyperaldosteronism May result from an ACTH-releasing tumor Excess water and sodium are retained leading tohigh blood pressure and edema 62 Adrenal Glands Adrenal cortex disorders Cushings syndrome
Results from a tumor in the middle cortical area ofthe adrenal cortex Moon face, buffalo hump on the upper back,high blood pressure, hyperglycemia, weakening ofbones, depression Masculinization Results from hypersecretion of sex hormones Beard and male distribution of hair growth 63 Hormones of the Adrenal Medulla
Produces two similar hormones(catecholamines) Epinephrine (adrenaline) Norepinephrine (noradrenaline) These hormones prepare the body to deal withshort-term stress (fight or flight) by Increasing heart rate, blood pressure, bloodglucose levels Dilating small passageways of lungs 64 Adrenal gland Capsule Mineralocorticoid- secreting area Kidney
Glucocorticoid- secreting area Adrenal gland Adrenal cortex Medulla Cortex Cortex Sex hormone secreting area Kidney Adrenal medulla Medulla Figure 9.11 65 Pancreatic Islets The pancreas is a mixed gland and has bothendocrine and exocrine functions The pancreatic islets produce hormones Insulinallows glucose to cross plasmamembranes into cells from beta cells Glucagonallows glucose to enter the bloodfrom alpha cells These hormones are antagonists that maintainblood sugar homeostasis 66 Stomach Pancreas (a) Figure 9.14a 67 Exocrine cells of pancreas Pancreatic islets (b) Figure 9.14b 68 Cord of beta () cells secreting insulin into capillaries
Exocrine cells of pancreas Alpha () cells Capillaries Cord of beta () cells secreting insulin into capillaries (c) Figure 9.14c 69 BALANCE: Normal blood glucose level (about 90 mg/100 ml)
Uptake of glucose from blood is enhanced in most body cells Insulin-secreting cells of the pancreas activated; release insulin into the blood Insulin Tissue cells Pancreas Glucose Glycogen Blood glucose falls to homeostatic set point; stimulus for insulin release diminishes Elevated blood sugar level Liver takes up glucose and stores as glycogen IMBALANCE Stimulus Blood glucose level (e.g., after eating four jelly doughnuts) BALANCE: Normal blood glucose level (about 90 mg/100 ml) Stimulus Blood glucose level (e.g., after skipping a meal) IMBALANCE Blood glucose rises to homeostatic set point; stimulus for glucagon release diminishes Low blood sugar level Glucagon-releasing cells of pancreas activated; release glucagon into blood Liver breaks down glycogen stores and releases glucose to the blood Glucose Glycogen Liver Glucagon Figure 9.15 70 Pineal Gland Found on the third ventricle of the brain
Secretes melatonin Helps establish the bodys wake and sleepcycles Believed to coordinate the hormones of fertilityin humans 71 Pineal gland Hypothalamus Pituitary gland Thyroid gland
Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3 72 Thymus Gland Located posterior to the sternum
Largest in infants and children Produces thymosin Matures some types of white blood cells Important in developing the immune system 73 Gonads Ovaries Produce eggs Produce two groups of steroid hormone
Estrogens Progesterone Testes Produce sperm Produce androgens, such as testosterone 74 Pineal gland Hypothalamus Pituitary gland Thyroid gland
Parathyroid glands Thymus Adrenal glands Pancreas Ovary (female) Testis (male) Figure 9.3 75 Hormones of the Ovaries
Estrogens Stimulate the development of secondaryfemale characteristics Mature female reproductive organs With progesterone, estrogens also Promote breast development Regulate menstrual cycle 76 Hormones of the Ovaries
Progesterone Acts with estrogen to bring about themenstrual cycle Helps in the implantation of an embryo in theuterus Helps prepare breasts for lactation 77 Hormones of the Testes Produce several androgens
Testosterone is the most important androgen Responsible for adult male secondary sexcharacteristics Promotes growth and maturation of malereproductive system Required for sperm cell production 78 Other Hormone-Producing Tissues and Organs
Parts of the small intestine Parts of the stomach Kidneys Heart Many other areas have scattered endocrinecells 79 Endocrine Function of the Placenta
Produces hormones that maintain thepregnancy Some hormones play a part in the delivery ofthe baby Produces human chorionic gonadotropin(hCG) in addition to estrogen, progesterone,and other hormones 80 Developmental Aspects of the Endocrine System
Most endocrine organs operate smoothly untilold age Menopause is brought about by lack ofefficiency of the ovaries Problems associated with reduced estrogenare common Growth hormone production declines with age Many endocrine glands decrease output withage 81