Chapter 16
                                          Endocrine System

Endocrinology:
The study of hormones, their effects...
Tumors: Some cancerous tumors of lungs, pancreas… synthesized hormones identical to those made by
glands but in uncontroll...
6. For “Direct gene activation” by steroid hormones, how is it that only this part of the DNA is
      affected so that on...
Control of Hormone Release

1. Negative Feedback (2401) – Most hormones

   Be able to explain what a negative feedback sy...
MSH – Melanin stimulating hormone - a neurotransmitter in humans
       Enkephalins and Endorphins which are natural opiat...
Draw in
                                                                                        the




Gonadotropins are ...
Homeostatic Imbalance:
  ADH deficiency ________________________________________________________________
     Cause – ____...
The Parathyroid gland is located on posterior of thyroid gland
Chief cells – secretes PTH

PTH – elevates blood Calcium le...
a. Keeps blood sugar constant
         b. Maintains blood volume

         Excessive amounts: ____________________________...
Cause: usually a tumor
                                              Pancreas

Acinar cells – produce enzyme rich juice th...
peak levels at night – makes us drowsy
                 lowest levels near “noon”
               Exposure to bright light ...
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Chapter 16

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Chapter 16

  1. 1. Chapter 16 Endocrine System Endocrinology: The study of hormones, their effects and the organs that produce them. Endocrine System: Interacts with nervous system Influences metabolic activity with hormones Hormones: are chemical messengers Lag time: seconds or even days Response is more prolonged Widespread and diverse effects Widespread and Diverse Effects One hormone can affect more than one of these at the same time. Several hormones Reproduction may work together to affect one of these. We Growth and development will learn these as we go. Body defenses Electrolyte, water and nutrient balance Metabolism Our job here is to learn which hormone does what. An Overview Exocrine glands: 1. have ducts 2. produce nonhormonal substances 3. released in localized areas examples: ______________________________________________________ Endocrine glands: 1. have no ducts 2. produce hormones 3. circulate all over the body examples: _____________________________________________________ Local Hormones Autocrines – chemicals that exert effects on the same cells that secrete them ex: prostaglandins Paracrines – affects cell types other than those that secrete them (but these cells are very close) ex: Somatostatin Are these hormones part of the endocrine system? Hormones Hormones chemical substances (chemical messengers) Amino acid based – amino acids, peptides or proteins. Examples: _____________________ Steroids – made from cholesterol. Examples: ______________________________________ Eicosanoids – biologically active lipids. Examples __________________________________
  2. 2. Tumors: Some cancerous tumors of lungs, pancreas… synthesized hormones identical to those made by glands but in uncontrolled and excessive amounts. Assignment: for every chapter: Mechanisms of Hormone Action about all the diseases! read How is it that hormones circulate throughout the body but effect only certain target cells? What are target cells? ______________________________________________ The same hormone can cause different effects in different cells. Explain. __________________________________________________________ Hormones alter a target cells normal activity by increasing or decreasing it. ex: Epinephrine causes smooth muscle to contract, but causes sweat cells to increase production of sweat. How is the target cell one time stimulated and another time inhibited? _______________ What if a cell does not have a receptor for that hormone? _________________________ Two Main Mechanisms Hormones Communicate to Target Cells 1. Amino acid based hormones involve the G proteins - 2nd messenger Mechanism (a.) cAMP signaling mechanism (b.)PIP-calcium signaling mechanism Be able to explain how each 2. Steroid Hormones: involve Direct Gene Activation of these systems work Questions: 1. Why such a complicated mechanism? Hormones that are proteins cannot pass through the cell membrane. The signal is greatly amplified with each step, One molecule of TSH can cause the thyroid gland to produce millions of molecules of thyroid hormone! 2. What stops the reaction caused by a hormone once it is started? Degradation of hormone, or hormone slips out of the receptor and AMP is rapidly degraded within the cell 3. What keeps the reaction going longer, if that is needed? More of the hormone is released. 4. How is it that all cells are not affected by hormones that circulate throughout the body? The cell has different receptors for different hormones 5. What if a cell does not have a receptor for that hormone? The cell will be unaffected by that particular hormone
  3. 3. 6. For “Direct gene activation” by steroid hormones, how is it that only this part of the DNA is affected so that only this particular protein is synthesized? The receptors are located on this specific segment of the DNA strand so that only this part of the DNA is activated. All three are dynamic Target Cell Activation Depends on: 1. Blood levels of hormone and can change! 2. Relative numbers of target receptors 3. Affinity (strength) of bond between hormone and receptor High affinity receptors hold tight to the hormone, once bonded, so that the hormone stays there for a long time while the cell becomes more and more affected. Low affinity receptors: hormone slips out of the receptors before the cell has been fully affected by the hormone. Large numbers of high affinity receptors produce increased hormonal affects and smaller number of low affinity receptors result in reduced target cell response a. Up regulation - target cell forms more receptors and/or exchanges low affinity for high affinity ones b. Down regulation - target cell loses receptors and/or exchanges high affinity for low affinity ones Why would cells do this up or down regulation? __________________________________________ Half Life, Onset and Duration of Hormone Activity Concentration of hormone in the blood depends on: 1. Rate of release 2. Speed of deactivation and removal a. Some are degraded quickly by enzymes within target cells b. Most are removed by kidney or liver Each hormone has its own half life, Half-life – Length of time hormone remains in the blood onset and duration and must be Onset – time required for hormone effects to appear very precisely controlled. Duration – how long the effects last Interaction of Hormones at Target Cells Several different hormones may be acting on the same target cells at the same time: (3 ways) Permissiveness one hormone is necessary for another hormone to be produced. Example: TH effect on production of sex hormones Synergism: More than one hormone produces the same effects on target cells and their combined effect is greater than either one alone. Example: Glucagon and epinephrine Antagonism: hormones with opposite effects or one hormone inhibits the effect of another. Example: glucagon and insulin. Example: progesterone-estrogen interaction in the uterus.
  4. 4. Control of Hormone Release 1. Negative Feedback (2401) – Most hormones Be able to explain what a negative feedback system is: Study the picture of insulin and glucagon production in response to blood sugar levels and be able to explain how it all works. 2. Endocrine stimuli a. Humoral – in response to changing levels of ions or nutrients in the blood b. Neuronal – Neural fibers stimulate hormone release c. Hormonal – Glands release hormone in response to hormone released by another endocrine gland. Nervous System Modulation Give an example of a hormone for each of these controls completely explaining each one. All those things that stimulate or inhibit (humoral, hormonal or neural) can be modulated by the nervous system.If they were not, the endocrine system would be no better than a thermostat - maintaining a set value, taking nothing else into consideration. Explain this. 1. Body temperature: negative feedback systems keep body temperature at 37C. However, when we are exercising or sleeping, temperature is modified so metabolism can keep pace with our activities 2. Blood glucose is maintained at 88-120, but in times of stress, the brain can over-ride by stimulating a gland to release a hormone that increases blood sugar. Pituitary gland (Hypophysis) Anterior Pituitary (adenohypophysis) Summary Posterior Pituitary (neurohypophysis) Produces 6 major hormones and some minor ones Adenohypophyseal Hormones TSH – Thyroid Stimulating Hormone (anterior pituitary) ACTH – Adrenocorticotropic Hormone FSH – Follicle Stimulating Hormone LH – Leutinizing Hormone TSH GH – Growth Hormone ACTH Tropic Hormones PRL – Prolactin FSH POMC - Pro-opiomelanocortin LH Can be split into: GH ACTH PRL MSH – Melanin Stimulating Hormone POMC ACTH Enkephalins and endorphins MSH Enkephalins and endorphins POMC can be split into ACTH _______________________________________________________
  5. 5. MSH – Melanin stimulating hormone - a neurotransmitter in humans Enkephalins and Endorphins which are natural opiates (pain killers) Growth Hormone GH stimulates cells to increase in size and divide (mostly bone and skeletal muscle cells a. Promotes protein synthesis b. Encourages use of fats for fuel (conserving glucose) c. Raises blood glucose levels GH secretion is highest during sleep. GH peaks during adolescence and Growth hormone is mediated by IGFs * declines with age. Growth hormone is regulated by GHRH and GHIH* Insulin-like Growth Factors IGFs (insulin-like growth factors) are produced by the liver, skeletal muscle and other tissues. Production of IGFs is stimulated by GH. 1. Stimulate the uptake of amino acids from blood to make proteins 2. Stimulates uptake of sulfur for chondroitin sulfate for cartilage construction 3. Increases blood levels of fatty acids 4. Decreases rate of glucose uptake 5. Encourages glycogen à glucose in the liver to raise glucose levels in the blood Homeostatic Imbalance of Growth Hormone – Read more! Gigantism ________________________________________________________________ Acromegaly _______________________________________________________________ Pituitary dwarfism __________________________________________________________ Draw in the Draw in the
  6. 6. Draw in the Gonadotropins are virtually absent from prepubertal children. At puberty, these cells of the adenohypophysis activate and gonadotropin levels rise and gonads are stimulated to mature. What produces GnRH? _______________________________________ Prolactin (PRL) High estrogen levels PRL Stimulates milk production stimulates the release of ____ Low estrogen levels PRH (Prolactin Releasing Hormone) Stimulates release of prolactin stimulates the release of ____ PIH (Prolactin Inhibiting Hormone) Inhibits the release of prolactin. PIH dominates in males Homeostatic Imbalance: of PRL Hypersecretion of PRL (more common) _______________________________________________ Symptoms - __________________________________________________________________ Cause - ______________________________________________________________________ Hyposecretion of PRL _____________________________________________________________ Symptoms - __________________________________________________________________ Posterior Pituitary and Hypothalamic Hormones 1. ADH - Antidiruetic Hormone: influences water balance. How? Makes you retain water. 2. Oxytocin – stimulates smooth muscle contraction of uterus and breasts (ejection of milk) Read other effects of oxytocin in both males and in females
  7. 7. Homeostatic Imbalance: ADH deficiency ________________________________________________________________ Cause – ____________________________________________________________________ Hypersecretion of ADH __________________________________________________________ Cause – ____________________________________________________________________ Differentiate between diabetes insipidus and diabetes mellitus. ______________________________ Thyroid Hormone (Is really two hormones) T4 – has four bound iodine atoms T3 – has three bound iodine atoms 1. Increases metabolism and heat production of nearly all cells My 2. Maintains blood pressure. Baby Plays & 3. Proper skeletal proportions, Sings 4. Development of nervous system Nursery 5. Maturation of reproductive capabilities Rhymes Homeostatic Imbalance (Thyroid hormones) Hypothyroidism – ______________________________________________________ Hypethyroidism – ______________________________________________________ Goiter - ______________________________________________________________ Calcitonin Calcitonin is secreted by parafollicular cells in thyroid gland Decreases calcium levels in blood (learned this in 2401) Parathyroid Gland Calcitonin Secreted by parafollicular cells in thyroid gland Rising Ca2+ Thyroid gland Encourages deposition of levels releases calcitonin Ca2+ in bone to decrease Ca2+ levels in blood Release Ca2+ from Parathyroid Falling blood bone into blood releases PTH Ca2+ levels
  8. 8. The Parathyroid gland is located on posterior of thyroid gland Chief cells – secretes PTH PTH – elevates blood Calcium levels (be able to explain how it works) 1. Takes calcium out of bones 2. Kidneys activate vitamin D so intestine can absorb Calcium 3. Kidneys reabsorb Calcium Homeostatic Imbalance (of Parathyroid hormone) Hyperparathyroidism _______________________________________________________ Hypoparathyroidism ________________________________________________________ Adrenal Glands There are over a dozen corticoid hormones. All adrenal hormones help us cope with stress 1. Top of kidneys 2. Each are two glands a. adrenal medulla (inner part) b. adrenal cortex (outer part) Mineralocorticoids (aldosterone) – secreted from zona glomerulosa Glucocorticoids (cortisol) – secreted from zona fascicularis Gonadocoricoids (androgen and progesterone) – secreted from zona reticularis Aldosterone Maintains Na balance, thus maintains water balance by stimulating Na in the blood. Increasing water will increase blood volume which increases BP Cells: stimulates transcription of Na+/K+ pump Where Na goes, water follows. Kidneys: reduces excretion and increases re-absorption of Na+ So aldosterone indirectly causes: from kidney and increases output of K+ into urine 1. Water retention Sweat: resbsorption of Na+ from sweat back into blood 2. Decreased urine output Stomach: resorption of Na+ from gastric juice back into blood 3. Increased blood pressure Other tissues: resorption of Na+ from saliva back into blood 4. pH changes Homeostatic Imbalance of corticoids Hypersecretion – aldosteronism __________________________________________________ Hyposecretion – Addison’s Disease _______________________________________________ Glucocorticoids (Cortisol) 1. Influence energy metabolism 2. Essential to life:
  9. 9. a. Keeps blood sugar constant b. Maintains blood volume Excessive amounts: ___________________________________________________ Treatment: _______________________________________________________ Hyposecretion: _______________________________________________________ Treatement: ______________________________________________________ Stress, hemorrhage, Release of Increase glucose, fatty acids and amino or infection glucocorticoids acids in blood stimulates fluid retention. What are the consequences for long term stress? _______________________________ Gonadocorticoids (Sex hormones) Androgens – converted to testosterone in males These hormones are secreted in converted to estrogens in females very small quantities. Much more are produced by the gonads. They Homeostatic Imbalance of Gonadocorticoids only become important in older age Hypersecretion – _________________________ when the gonads are no longer Hyposecretion - __________________________ producing these hormones. Summary Hormones of the Adrenal Cortex Mineralocorticoids: Aldosterone (Long acting hormones) Glucocorticoids: Cortisol Aldosterone Glucocorticoids: Cortisol Gondadocorticoids: Sex Hormones Adrenal Medulla (Catecholamines) Catecholamines – epinephrine and norepinephrine* (Brief acting hormones) Raises blood sugar Vasoconstriction (elevates BP) Increased heart rate and respiration rate Stimulates sweat glands Blood shunted to brain, heart and skeletal muscles Hyperglycemia Increased metabolic rate Homeostatic Imbalance of Rapid heart beat and Catecholamines palpatations Hypertension Deficiency – not a problem (read why) Intense Nervousness Hypersecretion – uncontrolled sympathetic nervous system activity * Sweating
  10. 10. Cause: usually a tumor Pancreas Acinar cells – produce enzyme rich juice that is ducted to small intestine Pancreatic islets (Islets of Langerhans) α cells – produce glucagon * β cells – produce insulin * Glucose uptake into cells ∆ cells – produce somatostatin β cells release Excess glucose converted to insulin glycogen in liver & skeletal muscles Rising blood glucose levels Glucose is converted to fat 1. Glycogen à glucose Blood glucose 2. Release of glucose declines from liver α cells 3. Synthesis of glucose release from lactic acid … Imbalance of Pancreatic Hormones Homeostatic glucagon Hypoglycemia – hyperinsulinism ___________________________________________________ Hyperglycemia (diabetes mellitus) __________________________________________________ Type I diabetes _______________________________________________________________ Type II diabetes_______________________________________________________________ Gonads Produce sex hormones Ovaries – estrogens and progesterone estrogens – 1. maturation of reproductive organs 2. Appearance of secondary sexual characteristics estrogens + progesterone – breast development & menstrual cycle 3. Sex drive 4. Normal egg production 5. Maintains organs in mature functional state Testes – testosterone: 1. maturation of reproductive organs Hypersecretion of 2. Appearance of secondary sexual characteristics testosterone over long 3. Sex drive periods of time ultimately 4. Normal sperm production results in feminization. 5. Maintains reproductive organs in mature functional state Explain this. Pineal Gland Melatonin – derived from seratonin
  11. 11. peak levels at night – makes us drowsy lowest levels near “noon” Exposure to bright light suppresses melatonin Thymus Deep to sternum Large in children – small and atrophied in adults Thymopoietin Normal development of Thymic factor T-Lymphocytes Thymosins Other Hormone Producing Structures Heart ANP (atrial natiuretic peptide) Gastrointestinal tract Gastrin, Serotonin, Intestinal gastrin, Secretin, Cholecystokinin Placenta progesterone, hCG (human chorionic gonadotropin Kidneys EPO (Erythropoietin) Skin Cholecalciferol Will study these hormones in the Adipose Leptin, Resistin chapters that cover these topics.

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