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Unformatted text preview: The Endocrine System The Endocrine System: Overview Overview Endocrine system – the Endocrine body’s second great controlling system controlling which influences metabolic activities of cells by means of hormones hormones Endocrine System: Overview Overview Endocrine glands – Endocrine pituitary Endocrine System: Overview Endocrine Endocrine glands – thyroid, thyroid, Endocrine System: Overview Endocrine Endocrine glands – parathyroid, parathyroid, Endocrine System: Overview Endocrine Endocrine glands –, adrenal, Endocrine Endocrine System: Overview Overview Endocrine glands –pineal, Endocrine Endocrine System: Overview Endocrine Endocrine glands –pineal, Endocrine Endocrine System: Overview Endocrine Endocrine glands – thymus Hormone Hormone The term hormone, derived from a Greek The hormone derived phrase meaning "to set in motion," aptly describes the dynamic actions of these circulating substances as they elicit cellular responses and regulate physiologic processes through feedback mechanisms. Endocrine System: Overview Endocrine The pancreas and gonads produce both hormones and The exocrine products exocrine Endocrine System: Overview Overview The hypothalamus has The both neural functions and releases hormones and Thank GOD we had ADH Endocrine System: Overview Endocrine Other tissues and Other organs that produce hormones – adipose cells, Endocrine System: Overview Endocrine Other tissues and organs that produce hormones –pockets Other of cells in the walls of the small intestine, Endocrine System: Overview Overview Other tissues and Other organs that produce hormones –stomach Endocrine System: Overview Endocrine Other tissues and organs Other that produce hormones –kidneys –kidneys Endocrine System: Overview Endocrine Other tissues and organs Other that produce hormones –heart –heart Major Endocrine Organs Organs Autocrines and Paracrines Autocrines Autocrines – Autocrines chemicals that exert their effects on the same cells that secrete them that Autocrines and Paracrines Autocrines Paracrines – locally acting chemicals that affect cells Paracrines other than those that secrete them other Autocrines and Paracrines Paracrines These are not These considered hormones since hormones are long-distance chemical signals signals Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Hormones Hormones Hormones – chemical Hormones substances secreted by cells into the extracellular fluids extracellular Regulate the Regulate metabolic function of other cells other Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Have lag times ranging from seconds to hours Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Have lag times ranging from seconds to hours Hormones Hormones Hormones – chemical substances secreted by cells into Hormones the extracellular fluids the Tend to have prolonged effects Hormones Hormones Hormones – chemical Hormones substances secreted by cells into the extracellular fluids extracellular Are classified as Are amino acid-based hormones, or steroids hormones, Hormones Hormones Eicosanoids – Eicosanoids biologically active lipids with local hormone–like activity activity Hormones Hormones Eicosanoids – biologically active lipids with local Eicosanoids hormone–like activity hormone–like leukotrienes and prostaglandins Types of Hormones Types Amino acid based – Amino most hormones belong to this class, including: including: Amines, thyroxine, Amines, peptide, and protein hormones hormones Types of Hormones Types Amino acid based – most hormones belong to this class, Amino including: including: Amines, thyroxine, peptide, and protein hormones Types of Hormones Hormones Steroids – Steroids gonadal and adrenocortical hormones hormones Types of Hormones Types Steroids – gonadal and adrenocortical hormones Hormone Action Hormone Hormones alter target cell activity by one of two Hormones mechanisms mechanisms Second messengers involving: Regulatory G proteins Amino acid–based hormones Hormone Action Hormone Hormones alter target Hormones cell activity by one of two mechanisms two Direct gene activation Direct involving steroid hormones hormones Hormone Action Hormone The precise response depends on the type of The the target cell the Mechanism of Hormone Action Mechanism Hormones produce one or more of the following cellular Hormones changes in target cells changes Alter plasma membrane permeability Mechanism of Hormone Action Mechanism Hormones produce one or more of the following Hormones cellular changes in target cells cellular Stimulate protein synthesis Stimulate Mechanism of Hormone Action Mechanism Hormones produce one Hormones or more of the following cellular changes in target cells target Activate or deactivate Activate enzyme systems enzyme Mechanism of Hormone Action Mechanism Hormones produce Hormones one or more of the following cellular changes in target cells changes Induce secretory Induce activity activity Mechanism of Hormone Action Mechanism Hormones produce one Hormones or more of the following cellular changes in target cells target Stimulate mitosis Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Hormone (first messenger) binds to its receptor, which then binds to a G Hormone protein protein Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP The G protein is then activated as it binds GTP, displacing GDP Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Activated G protein activates the effector enzyme adenylate cyclase Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP Adenylate cyclase generates cAMP (second messenger) from ATP Amino Acid-Based Hormone Action: cAMP Second Messenger cAMP cAMP activates protein kinases, which then cause cellular effects Amino Acid-Based Hormone Action: cAMP Second Messenger Second Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Hormone binds to the receptor and activates Hormone G protein protein Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium G protein binds and activates a phospholipase enzyme protein Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Phospholipase splits the phospholipid PIP2 into diacylglycerol (DAG) and IP3 (both act as second diacylglycerol messengers) messengers) Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium DAG activates protein kinases; IP3 triggers release of Ca2+ stores Ca Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Ca2+ (third messenger) alters cellular responses Amino Acid-Based Hormone Action: PIP-Calcium PIP-Calcium Steroid Hormones Steroid Steroid hormones and thyroid hormone diffuse easily into their Steroid target cells target Steroid Hormones Steroid Once inside, they bind and activate a specific intracellular Once receptor receptor Steroid Hormones Steroid The hormone-receptor complex travels to the nucleus and binds The a DNA-associated receptor protein DNA-associated Steroid Hormones Steroid This interaction prompts DNA transcription to produce mRNA Steroid Hormones Steroid The mRNA is translated into proteins, which bring about a The cellular effect cellular Steroid Hormones Figure 16..3 Target Cell Specificity Specificity Hormones circulate to Hormones all tissues but only activate cells referred to as target cells to Target Cell Specificity Target Target cells must have specific receptors to which the Target hormone binds hormone Target Cell Specificity Specificity These receptors may be These intracellular or located on the plasma membrane membrane Target Cell Specificity Target Examples of hormone Examples activity activity ACTH receptors are only ACTH found on certain cells of the adrenal cortex the Target Cell Specificity Specificity Examples of hormone Examples activity activity Thyroxin receptors are Thyroxin found on nearly all cells of the body the Target Cell Activation Activation Target cell activation depends on three Target factors factors Blood levels of the hormone Target Cell Activation Target Target cell activation depends on three factors Relative number of receptors on the target cell Target Cell Activation Target Target cell activation depends on Target three factors three The affinity of those receptors The for the hormone for Target Cell Activation Target Upregulation: The hormones Upregulation: increases the number or sensitivity of the receptors sensitivity Thyroid hormone increases the Thyroid number of cardiac β1 receptors Clinical relevance: During thyrotoxicosis, Propranolol During can be used for treating tachycardia tachycardia why? Because propranolol will have why? enough β1 receptors Target Cell Activation Target Downregulation: A hormone Downregulation: decreases the number or affinity of receptors for itself or other hormones or prolonged use of propranolol prolonged can DECREASE the number of β1 receptors Clinical relevance: A patient’s response to drug patient’s therapy may change over time therapy Rats! Where did they all go?!? Hormone Concentrations in the Blood the Hormones circulate in Hormones the blood in two forms – free or bound free Hormone Concentrations in the Blood Blood Steroids and thyroid Steroids hormone are attached to plasma proteins to All others are All unencumbered unencumbered Hormone Concentrations in the Blood Blood Concentrations of circulating hormone reflect: Concentrations Rate of release Speed of inactivation and removal from the body Hormone Concentrations in the Blood Blood Hormones are removed Hormones from the blood by: from Degrading enzymes Hormone Concentrations in the Blood Blood Hormones are removed Hormones from the blood by: from The kidneys Hormone Concentrations in the Blood Blood Hormones are removed from the blood by: Liver enzyme systems Interaction of Hormones at Target Cells Target Three types of hormone interaction Permissiveness – one hormone cannot Permissiveness exert its effects without another hormone being present e.g. Absence of Thyroid hormone e.g. results in Cretinism Interaction of Hormones at Target Cells Target Three types of hormone Three interaction interaction Synergism – more than Synergism one hormone produces the same effects on a target cell cell e.g. Glucagon, GH and e.g. Norepinephrine all cause Glycogenolysis Glycogenolysis Interaction of Hormones at Target Cells Target Three types of hormone interaction Antagonism – one or more hormones opposes the action of Antagonism another hormone another Control of Hormone Release Control Blood levels of hormones: Blood Are controlled by negative feedback systems Vary only within a narrow desirable range Control of Hormone Release Control Hormones are Hormones synthesized and released in response to: in Humoral stimuli Neural stimuli Hormonal stimuli Humoral Stimuli Humoral Humoral stimuli – secretion of hormones in direct Humoral response to changing blood levels of ions and nutrients response Humoral Stimuli Stimuli Humoral stimuli – Humoral secretion of hormones in direct response to changing blood levels of ions and nutrients of Neural Stimuli Neural Neural stimuli – nerve Neural fibers stimulate hormone release release Preganglionic Preganglionic sympathetic nervous system (SNS) fibers stimulate the adrenal medulla to secrete catecholamines Hormonal Stimuli Hormonal Hormonal stimuli – Hormonal release of hormones in response to hormones produced by other endocrine organs endocrine Hormonal Stimuli Stimuli The hypothalamic The hormones stimulate the anterior pituitary In turn, pituitary In hormones stimulate targets to secrete still more hormones more Nervous System Modulation Nervous The nervous system The modifies the stimulation of endocrine glands and their negative feedback mechanisms Nervous System Modulation Nervous The nervous system can The override normal endocrine controls controls For example, control of For blood glucose levels blood Normally the endocrine Normally system maintains blood glucose Nervous System Modulation Modulation For example, control For of blood glucose levels levels Under stress, the Under body needs more glucose The hypothalamus The and the sympathetic nervous system are activated to supply ample glucose glucose Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Pituitary gland – two-lobed organ that secretes nine major Pituitary hormones hormones Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Neurohypophysis – posterior lobe (neural Neurohypophysis tissue) and the infundibulum tissue) Receives, stores, and releases hormones Receives, from the hypothalamus from Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Adenohypophysis – anterior lobe, made up of glandular tissue Adenohypophysis Synthesizes and secretes a number of hormones Major Endocrine Organs: Pituitary (Hypophysis) Pituitary Pituitary-Hypothalamic Relationships: Posterior Lobe Posterior The posterior lobe is a downgrowth of hypothalamic neural tissue Has a neural connection with the hypothalamus (hypothalamic-hypophyseal tract) Pituitary-Hypothalamic Relationships: Posterior Lobe Posterior Nuclei of the hypothalamus synthesize oxytocin and antidiuretic hormone Nuclei (ADH) (ADH) These hormones are transported to the posterior pituitary Level Pituitary-Hypothalamic Relationships: Anterior Lobe opment of Pituitary Anterior 5­6 wks The anterior lobe of the pituitary is an The outpocketing of the oral mucosa outpocketing There is no direct neural contact with There the hypothalamus the Level Pituitary-Hypothalamic Relationships: Anterior Lobe opment of Pituitary Anterior The anterior lobe of the The pituitary is an outpocketing of the oral mucosa of There is no direct neural There contact with the hypothalamus hypothalamus Pituitary-Hypothalamic Relationships: Anterior Lobe Anterior There is a vascular There connection, the hypophyseal portal system, consisting of: portal The primary capillary plexus The hypophyseal portal veins The secondary capillary plexus Pituitary-Hypothalamic Relationships: Anterior Lobe Anterior Adenophypophy Adenophypophy seal Hormones The six hormones of the The adenohypophysis: adenohypophysis: Are abbreviated as GH, Are TSH, ACTH, FSH, LH, and PRL and Regulate the activity of Regulate other endocrine glands other Adenophypophyseal Hormones Adenophypophyseal The six hormones of the The adenohypophysis: adenohypophysis: Are abbreviated as GH, Are TSH, ACTH, FSH, LH, and PRL and Regulate the activity of Regulate other endocrine glands other Adenophypophyseal Hormones Adenophypophyseal In addition, pro-opiomelanocortin (POMC): Has been isolated from the pituitary Is enzymatically split into ACTH, opiates, and MSH Is Activity of the Adenophypophysis Activity The hypothalamus sends a chemical stimulus to the The anterior pituitary anterior Releasing hormones stimulate the synthesis and release of Releasing hormones hormones Activity of the Adenophypophysis Activity The hypothalamus sends a chemical stimulus to the anterior The pituitary pituitary Inhibiting hormones shut off the synthesis and release of hormones Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Thyroid-stimulating hormone (TSH) Thyroid-stimulating Activity of the Adenohypophysis Activity The tropic hormones The that are released are: that Adrenocorticotropic Adrenocorticotropic hormone (ACTH) hormone Activity of the Adenophypophysis Adenophypophysis The tropic hormones The that are released are: that Follicle-stimulating Follicle-stimulating hormone (FSH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Follicle-stimulating hormone (FSH) Follicle-stimulating Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are The released are: released Follicle-stimulating hormone Follicle-stimulating (FSH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones The that are released are: that Luteinizing hormone Luteinizing (LH) (LH) Activity of the Adenophypophysis Adenophypophysis The tropic hormones that are released are: Luteinizing hormone (LH) Growth Hormone (GH) Growth Produced by somatotropic Produced cells of the anterior lobe that: that: Stimulate most cells, but Stimulate target bone and skeletal muscle muscle Promote protein synthesis Promote and encourage the use of fats for fuel for Growth Hormone (GH) (GH) Produced by Produced somatotropic cells (acidophils) of the anterior lobe that: anterior Most effects are Most mediated indirectly by somatomedins somatomedins Anterior pituitary Growth Hormone (GH) Growth Antagonistic hypothalamic Antagonistic hormones regulate GH hormones Growth hormone–releasing Growth hormone (GHRH) stimulates GH release GH Growth hormone–inhibiting Growth hormone (GHIH) inhibits GH release GH Metabolic Action of Growth Hormone Hormone GH stimulates liver, GH skeletal muscle, bone, and cartilage to produce insulin-like growth factors factors Metabolic Action of Growth Hormone Metabolic Metabolic Action of Growth Hormone Metabolic Direct action promotes lipolysis and inhibits glucose uptake Metabolic Action of Growth Hormone Hormone Ponce de Leon Ponce Fountain of Youth Acromegaly Acromegaly Acromegaly Acromegaly Acromegaly Acromegaly Gigantism Gigantism Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Tropic hormone Tropic that stimulates the normal development and secretory activity of the thyroid gland thyroid Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Triggered by Triggered hypothalamic peptide thyrotropin-releasing hormone (TRH) hormone Thyroid Stimulating Hormone (Thyrotropin) (Thyrotropin) Rising blood levels of Rising thyroid hormones act on the pituitary and hypothalamus to block the release of TSH the Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Stimulates the adrenal Stimulates cortex to release corticosteroids corticosteroids Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Triggered by Triggered hypothalamic corticotropin-releasing hormone (CRH) in a daily rhythm daily Adrenocorticotropic Hormone (Corticotropin) (Corticotropin) Internal and external Internal factors such as fever, hypoglycemia, and stressors can trigger the release of CRH release Gonadotropins Gonadotropins Gonadotropins – folliclestimulating hormone stimulating (FSH) and luteinizing hormone (LH) hormone Regulate the function of Regulate the ovaries and testes the Gonadotropins Gonadotropins Gonadotropins – folliclestimulating hormone (FSH) stimulating and luteinizing hormone (LH) (LH) FSH stimulates gamete (egg FSH or sperm) production or What would be the blood levels of FSH in this group of students? FSH Gonadotropins Gonadotropins Gonadotropins – follicle-stimulating hormone (FSH) Gonadotropins and luteinizing hormone (LH) and Absent from the blood in prepubertal boys and girls Gonadotropins Gonadotropins Gonadotropins – Gonadotropins follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (LH) Triggered by the Triggered hypothalamic gonadotropin-releasing hormone (GnRH) during and after puberty and Functions of Gonadotropins Functions In females LH works with FSH to LH cause maturation of the ovarian follicle ovarian Functions of Gonadotropins Functions In females LH works alone to LH trigger ovulation (expulsion of the egg from the follicle) follicle) Functions of Gonadotropins Functions In females LH promotes LH synthesis and release of estrogens and progesterone progesterone Functions of Gonadotropins Gonadotropins In females LH promotes synthesis LH and release of estrogens and progesterone and Functions of Gonadotropins Functions In females LH promotes LH synthesis and release of estrogens and progesterone progesterone Functions of Gonadotropins Functions In males LH stimulates LH interstitial cells of the testes to produce testosterone testosterone Functions of Gonadotropins Functions In males LH is al...
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