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EXSC 224 Week 6 Notes

by: Jane Warther

EXSC 224 Week 6 Notes Exsc 224

Jane Warther
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These notes cover what we went over this past week in class
Anatomy and Physiology 224
Dr. Thompson
Class Notes
Human Anatomy and Physiology
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This 12 page Class Notes was uploaded by Jane Warther on Friday February 19, 2016. The Class Notes belongs to Exsc 224 at University of South Carolina taught by Dr. Thompson in Spring 2016. Since its upload, it has received 43 views. For similar materials see Anatomy and Physiology 224 in Education and Teacher Studies at University of South Carolina.

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Date Created: 02/19/16
CHP. 16 The Endocrine System Lecture 1 2/16/16 The endocrine system  The body’s second great regulatory system  An integrated system of small organs that involve the release of extracellular signaling molecules known as hormones How does this differ from the Nervous System Control?  1. Neurons directly innervate a tissue o Action occurs in synapse  2. Stimulation is direct and immediate  The endocrine system o Regulates cellular activities by means of chemical messengers called hormones o Hormones act at sites independent of secretion o Short and long term regulatory functions o No synapse, diffuse system where hormone circulates throughout the body o No immediate effect  Neurotransmitters and hormones are both chemically signaling molecules o Both cause things to happen at target cells Major endocrine organs  1. Hypothalamus o Has neural and endocrine functions and releases hormones(neuroendocrine)  Part of nervous system but also secretes and regulates hormones  Major site of regulation- pituitary gland which is connected to the hypothalamus by a stalk  2. Pituitary gland- storage site and also regulates secretion of other hormones o 1. Anterior o 2. Posterior  3. Thyroid and parathyroid o Thyroid sits above clavicles o Parathyroid Is embedded in thyroid gland  4. Pancreas o Most lethal types of cancer o Gland that secretes insulin o Also secretes exocrine secretions into the stomach o endocrine and exocrine gland  5. Adrenal glands o On top of kidneys o Also called pyramidal glands o Secrete cluster of hormones  6. Gonads o Ovary- female o Testis- male  7. Other tissues and organs that produce hormones: o 1. Adipose tissue  Leptin o 2. Pockets of cells in the walls of the small intestine o 3. Stomach o 4. Kidneys o 5. Heart o Not called endocrine organs but have endocrine function Hormones  Hormones- chemical messenger secreted by cells in to the extracellular fluids that affect other parts of the body o Secreted in one part of body and exerts affect via receptor in another part of the body and travels via circulatory system o Characteristics  Have lag times ranging from seconds to hours  Tend to have prolonged effects  Because hormone is circulating through body via blood supply it takes a long time to remove hormones from the body o Classifications  Amino acid-based- 1 or more amino acids  Steroids- derived from cholesterol  Eicosanoids- biologically active lipids with local hormone-like activity  NOT a true hormone Autocrines and Paracrines  Autocrines- chemicals that exert effects on the same cells that secrete them o Auto=self o Not hormones because they don’t travel anywhere  Paracrines- locally acting chemicals that affect cells other than those that secrete them o Para=about o Not a hormone because they don’t travel anywhere o These are eicosanoids o Affects the cells surrounding them – their neighbors  These are NOT considered hormones since hormones are long-distance chemical signals o They are chemical messengers that act locally, don’t travel via the circulatory system, act in the area they are secreted Classification of Hormones  1. Amino acid based o Amines  Single modified amino acid  Commonly derived from tyrosine o Peptide  Strings of amino acids from 2-25 amino acids in length o Protein hormones  Large hormones- made of more than 25 amino acids  2. Steroids o Gonadal  Testosterone, estrogen and progesterone o Adrenocortical hormones  Produced in cortex of adrenal gland o All steroid hormones are derivatives of cholesterol  3. Eicosanoids o Leukotrienes and prostaglandins o Not a true hormone o Are paracrines and don’t travel the body via the circulatory system o Made from fatty acids  Ex. Arachidonic acid modified into a prostaglandin How do hormones exert a biological effect on a tissue?  Receptors – two classes o 1. Membrane bound  Ligand channels  Very few stimulate this  Integral proteins nd  Most hormones exert affect through 2 messenger system o 2. Intracellular  Don’t see with neurotransmitters  If hormones act via receptors, then why do the same hormones affect some tissues/organs differently than others? o Target cell specificity  Hormone only exerts an effect on cells that express the receptor for that specific hormone o Not all cells in the body have the receptor for the hormone Amino Acid-Based Hormone Action: cAMP Second Messenger 1. Hormone(1 messenger) binds receptor a. Drops GDP to GTP 2. Receptor activates G protein 3. G protein activates adenylate cyclase 4. Adenylate cyclase converts ATP to cAMP(2 messenger) 5. cAMP(cyclin adenosine monophosphate) activates protein kinases  amino acid based hormones exert their effect by: o 1. binding to a receptor on the membrane o 2. activating a sequence of events generating a second messenger o 3. The second messenger triggers processes within the cell  Hormones that act via cAMP mechanisms: o Epinephrine o ACTH o FSH o LH o Glucagon o PTH o TSH o Caclitonin  Common system by which hormones exert affect because they don’t enter the cell  Have inhibitory second messenger systems too along with excitatory o Regulate production of cAMP  Phosphodiesterase o Breaks down cAMP o Does automatically o Produce cAMP and then break down cAMP Steroid- Based Intracellular Hormone Signaling  Receptors inside cell o Usually in cytosol o Normally associated with chaperone  Responsibility is to prevent the receptor from doing anything  Forces receptor to remain in cytosol or cytoplasm  When a hormone comes along, crosses membrane, enters cytosol, can bind to receptor, receptor shape changes, chaperone falls off, now the hormone and receptor can move from cytosol to nucleus, in nucleus hormone- receptor binds to regions in the DNA(hormone ndsponse elements),  Rather than activate series of events to activate 2 messenger it just goes into the nucleus via a protein o All hormones that bind to intracellular receptors must be lipid-soluble  Estrogen, testosterone  Made from cholesterol which is lipid-soluble and bind to intracellular receptors  Thyroid hormones(amino acid ) can bind to intracellular receptors How do we regulate hormone activity?  1. Hormone concentration (quantity per volume of solution) o Rate of release  Rate of release into blood affects concentration o Rate of inactivation/ removal while circulating in the blood  Primary function of liver and kidneys  ½ life  The time required for a hormone’s blood level to decrease by half  Not all drugs or hormones have the same half-life  2. Receptor Concentration o Cells can increase or decrease the number of receptors expressed o Or receptor density o The more receptors, the more likely the hormone is to run into the receptor and stimulate something How are hormones removed from the blood?  Degrading enzymes o Kidneys o Liver enzyme systems  Detoxify blood  Breakdown products released into bloodstream, filtered by kidneys into urine Interaction of Hormones at Target Cells  Three types of hormone interaction o 1. Permissiveness- one hormone cannot exert its effects without another hormone being present  Interaction between two hormones  Hormone A causes something to happen but isn’t as effective unless another hormone is present  Growth hormone causes bone growth but isn’t effective unless thyroid hormone is present.  Thyroid is permissive; it allows growth hormone to cause bone growth o 2. Synergism – more than one hormone produces the same effects on a target cell  Additive  Two hormones cause the same thing to happen independently, a larger effect will occur o 3. Antagonism- one or more hormone opposes the action of another hormone  One hormones causes something to happen and the other stops it How are endocrine glands regulated?  Humoral stimulus o 1. Capillary blood contains low concentration of Ca2+ which stimulates secretion of parathyroid hormone (PTH) by parathyroid glands o Pertaining to elements in the blood or other body fluids o Effector in the blood  Something in the blood triggers the gland to secrete the hormone o Ex. Blood calcium, glucose, Na+/K+  Neural stimulus o 1. Preganglionic sympathetic fibers stimulate adrenal medulla cells to secrete catecholamines (epinephrine and norepinephrine) o Regulated by direct nervous system input o In ANS, neural stimulation synapses with cells in the gland  When neurons fires the gland secretes  Hormonal stimulus o 1. The hypothalamus secretes hormones that stimulate other endocrine glands to secrete hormones o Regulated by hormones  Some hormones regulate the secretion of other hormones Summary  Endocrine system- collection of glands that secrete hormones  Hormones- chemical messengers secreted one place act at another  Hormones act via receptors  Hormone secretion is regulated by other hormones, the nervous system, or factors in blood CHP. 16 Lecture 2 2-18-16 Hypothalamus  Neuroendocrine gland  Secrete variety of hormones  Master regulator of endocrine system  Within it different bunches of nuclei that serve different functions o Axons branch to different regions of hypothalamus or into pituitary gland through the infundibulum or stalk  Two regions- anterior and posterior Neurohypophysis  Posterior lobe (neural tissue) of pituitary gland and the infundibulum o Receives, stores, and secretes hormones from the hypothalamus  Posterior extension of hypothalamus  Axon terminals store the hormones associated with posterior pituitary  Posterior pituitary sometimes not considered true gland because no hormones are made here  Axons with hormones secrete into artery so they can circulate throughout the body  Secrete oxytocin and ADH  Relationship between the posterior pituitary and hypothalamus o 1. Hypothalamic neurons synthesize oxytocin and ADH o 2. Oxytocin and ADH are transported along the hypothalamic- hypophyseal tract to the posterior pituitary o 3. Oxytocin and ADH are stored in axon terminals in the posterior pituitary o 4. Oxytocin and ADH are released into the blood when hypothalamic neurons fire Adenohypophysis  Anterior lobe of pituitary gland, made of glandular tissue  Relationship between anterior pituitary and the hypothalamus o Axons from hypothalamus don’t project into anterior pituitary o It is a proper gland but under control of hypothalamus o Hormones produced in nuclei of hypothalamus, projected into axons in hypothalamus, poject hormones into another circulatory system called the hypophyseal portal system and travel down to anterior pituitary  Stimulate production and secrete of hormones of anterior pituitary o Under hormonal hypothalamic control but is proper gland(produces its own hormones) o TSH, FSH, LH, ACTH, GH, PRL produced here Growth Hormone (GH)  Produced in anterior pituitary  Amino acid based hormone  Produced by somatotropic cells on the anterior lobe that: o Stimulate most cells, but target bone and skeletal muscle o Promote protein synthesis and encourage the use of fats for fuel  Most effects are mediated indirectly by IGF’s (somatomedins) o Doesn’t do all things mentioned above, tells IGF to do some things o Insulin-like growth factor (IGF) o Stimulates bone growth and protein synthesis  GH secretion is regulated by antagonistic hypothalamic hormones o Growth hormone- releasing hormone (GHRH) stimulates GH release  Increase blood concentration of GH o Growth hormone inhibiting hormone-inhibiting hormone (GHIH) inhibits GH release  Decreases blood concentration of GH  Inhibits release or secretion of GH o Under negative feedback control  IGF go up, GHRH is inhibited and GHIH is secreted  IGF go down, stop secreting GHIH and secrete GHRH  Regulation has to do with concentration of GH in the blood  Growth hormone deficiency o Infant- hypoglycemia  Brain needs glucose to develop properly  Can lead to retardation of CNS development o Childhood- pituitary dwarfism  Roughly proportional  As long as growth plate hasn’t sealed, can now give synthetic GH to increase vertical height  Lesion that inhibits the release of GH o Adult- loss of lean tissue mass  Because don’t promote protein synthesis as much  Growth hormone excess o Childhood- pituitary gigantism  Usually result of anterior pituitary tumor causing over production of GH  Can be treated by killing the tumor( don’t kill will never stop growing) o Adults- acromegaly (extremities enlargement)  Tumor happens after growth plates are sealed Anterior Pituitary  Thyroid stimulating hormone (thyrotropin) o Stimulates the normal development and secretory activity of the thyroid o Triggered by hypothalamic peptide thyrotropin-releasing hormone (TRH)  Secreted by hypothalamus o Rising blood levels of thyroid hormones act on the pituitary and hypothalamus to block the release of TSH (thyroid stimulating hormone- secreted by anterior pituitary)  Causes thyroid gland to secrete T3 and T4 o Hypothalamus regulates thyroid gland by anterior pituitary o Under negative feedback control o Amino acid based hormones  Adrenocorticotropic (ACTH) o Stimulates the adrenal cortex to release corticosteroids o Part of stress hormone pathway  When stressed ,ACTH goes up o Triggered by hypothalamic corticotropin- releasing hormone (CRH) in a daily rhythm  Secreted by hypothalamus  Causes anterior pituitary to secrete ATCH which travels to adrenal gland that stimulates production of another hormone  ATCH stimulates secretion of cortisol (steroid) by adrenal gland  Important stress hormone  Under negative feedback loop  Peaks around 9 or 10 am o Internal and external factors such as fever, hypoglycemia, and stressors can trigger the release of CRH o CRH and ATCH are amino acid based  Gonadotropins o Follicle-stimulating hormone(FSH)  Stimulates gamete (egg or sperm) production o Luteinizing hormone (LH)  Regulate the function of the ovaries and testes o Both FSH and LH are absent from the blood in prepubertal boys and girls o Triggered by the hypothalamic gonadotropin-releasing hormone (GnRH) during and after puberty  Hypothalamus secretes GnRH causes secretion and production of LH and FSH  FSH and LH travel to gonads to exert their effects o Deficiency- failure of sexual maturation o FSH and LH  Produced and secreted by anterior pituitary which is under hormonal regulation of hypothalamus  Amino-acid based hormones that secretions of steroids  Normally under negative feedback control  Testosterone or estrogen increases it inhibits the hypothalamus  Exception is ovulation with LH surge and it becomes positive feedback loop  Functions of Gonadotropins o In females  LH works with FSH to cause maturation of the ovarian follicle  LH works alone to trigger ovulation (expulsion of the egg from the follicle)  LH promotes synthesis and release of estrogens and progesterone o In males  LH stimulates interstitial cells of the testes to produce testosterone  LH is also referred to as interstitial cell-stimulating hormone (ICSH)  Prolactin (PRL) o In females, stimulates milk production by the breasts o Triggered by the hypothalamic prolactin-releasing hormone (PRH)  Travels to anterior pituitary , stimulates secretion of prolactin which travels to mammary glands which produces milk  Production of milk does not inhibit hypothalamus o Inhibited by prolactin-inhibiting hormone (PIH)  Aka dopamine( a neurotransmitter)  Inhibits hypothalamus from secreting PRH o Blood levels rise toward the end of pregnancy o Suckling stimulates PRH release and encourages continued milk and production  Stops secretion of PIH, allows hypothalamus to secrete PRH  To stop milk production, stop suckling(the stimulus), PIH is released, inhibits hypothalamus and no longer secrete prolactin o Deficiency- poor milk production o Overproduction  Inappropriate milk production- female  Impotence and breast enlargement- male Posterior Pituitary Hormones  Oxytocin o Stimulates uterine contraction  Cause birth o Positive feedback mechanism  Leads to increased intensity of uterine contractions, ending in birth o Doesn’t kick unless the contractions are five minutes or less apart regularly o Triggers milk ejection (“letdown” reflex) o Used to induce labor o Role in sexual arousal and satisfaction in males and non-lactating females  Men who don’t produce oxytocin are more likely to cheat  ADH o Hypothalamus doesn’t have a blood-brain barrier  Wants to detect level sodium and electrolyte in blood  Sodium high, dehydrated, save water, don’t pee o Allows nuclei to directly detect salt concentrations in the blood o Secrete ADH o Anti-diuretic- makes you not have to pee o Regulates production of urine by causing you to conserve or save water o Amino-acid based o Helps to avoid dehydration  Prevents urine formation o Osmoreceptors o High osmolarity  ADH preserves water  High sodium concentration o Low osmolarity  ADH is not released  Causing water loss  Low sodium concentration o Alcohol inhibits ADH release and causes copious urine output o ADH deficiency  Diabetes insipidus (tasteless urine)  Abnormal increase in urine output, fluid intake and often thirst  Symptoms o Dilute urine (low osmolarity)  Low sodium concentration  Urine has no taste at all  Don’t produce ADH o Increased urinary frequency  Nocturia- frequent awakening at night to urinate  Enuresis- involuntary urination during sleep of bedwetting  Cause o Death of ADH producing cells in hypothalamus/posterior pituitary gland o ADH Overproduction  Syndrome of inappropriate ADH secretion (SIADH)  Compound problem  Symptoms:  Hyponatremia- low blood concentration of sodium o Dilute blood, salt concentrations go down  Inappropriately elevated urine osmolarity (>200 mOsm/kg)  Excessive urine sodium excretion (Una >30 mEq/L)  Decreased serum osmolarity  Cause  Hypovolemia  ADH-secreting tumor (non-pituitary) Thyroid Gland  Secretes 2 hormones o Thyroid hormone  Major metabolic hormone o Calcitonin  Lowers blood calcium  Consists of two related iodine-containing compounds o T4- thyroxine  Has two tyrosine molecules plus four bound iodine atoms o T3- triiodothyronine  Has two tyrosines with three bound iodine atoms  TH is concerned with o Glucose oxidation o Increasing metabolic rate o Heat production  TH plays a role in: o Maintaining blood pressure o Regulating tissue growth o Developing skeletal and nervous systems o Maturation and reproductive capabilities o Permissive hormones  Hypo-thyroid disorder o Cretinism- children  Low metabolic rate  Growth retardation  Developmental delay  Other abnormal features  Can be due to deficiency of iodine in the mother’s diet during pregnancy o Myxedema- adults  Low metabolic rate  Skin ad tissue disorder usually due to severe prolonged hypothyroidism o Goiter- swollen thyroid gland  Hyper- thyroid disorder o Grave’s disease  Autoimmune disorder  Over activity of the thyroid gland  Inflammation of the tissues around the eyes causing swelling  Increased metabolic rate, sweating, rapid and irregular heartbeat, nervousness, weight loss, protruding eyeballs (exophthalmos) Humoral  Calcium ion concentration in the blood  Negative feedback mechanism Parathyroid Gland  Parathyroid hormone (PTH)  Cells are arranged in cords containing oxyphil and chief cells  Chief (principal) cells secrete PTH  PTH raises blood calcium levels (antagonistic to calcitonin)  Humoral (calcium ion concentration in the blood )- negative feedback mechanism  Hyper-parathyroidism o Rare- leach bone minerals  Hypo-parathyroidism o Deficiency o Causes hypocalcemia o Increases spontaneous membrane depolarization Quiz 3 1. Define hormone. Chemical messenger, secreted into the blood or extracellular cells, acts somewhere other where it is secreted. 2. What are the classes of hormones? Amino-based, steroids 3. What class of hormones binds to intra-cellular receptors? Steroids 4. What is target cell specificity? A hormone only exerts an effect on cells that have the appropriate receptor 5. What is 2 of the 3 mechanisms regulating glandular secretion of a hormone. Humoral, Neural, Hormonal 6. Name the master regulator of the endocrine system. Hypothalamus


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