Endocrine System: Overview

Endocrine System: Overview
Acts with nervous system to coordinate and integrate activity of body cells Influences metabolic activities via hormones transported in blood Response slower but longer lasting than nervous system Endocrinology Study of hormones and endocrine organs © 2013 Pearson Education, Inc.

Controls and integrates Reproduction Growth and development Maintenance of electrolyte, water, and nutrient balance of blood Regulation of cellular metabolism and energy balance Mobilization of body defenses © 2013 Pearson Education, Inc.

Endocrine glands: pituitary, thyroid, parathyroid, adrenal, and pineal glands Hypothalamus is Neuroendocrine organ Some have exocrine and endocrine functions Pancreas, gonads, placenta Other tissues and organs that produce hormones Adipose cells, thymus, and cells in walls of small intestine, stomach, kidneys, and heart © 2013 Pearson Education, Inc.

Pineal gland Hypothalamus Pituitary gland Thyroid gland
Figure Location of selected endocrine organs of the body. Pineal gland Hypothalamus Pituitary gland Thyroid gland Parathyroid glands (on dorsal aspect of thyroid gland) Thymus Adrenal glands Pancreas Gonads • Ovary (female) • Testis (male) © 2013 Pearson Education, Inc.

Hormones: long-distance chemical signals; travel in blood or lymph
Chemical Messengers Hormones: long-distance chemical signals; travel in blood or lymph Autocrines: chemicals that exert effects on same cells that secrete them Paracrines: locally acting chemicals that affect cells other than those that secrete them Autocrines and paracrines are local chemical messengers; not considered part of endocrine system © 2013 Pearson Education, Inc.

Chemistry of Hormones Two main classes Amino acid-based hormones
Amino acid derivatives, peptides, and proteins Steroids Synthesized from cholesterol Gonadal and adrenocortical hormones © 2013 Pearson Education, Inc.

Mechanisms of Hormone Action
Though hormones circulate systemically only cells with receptors for that hormone affected Target cells Tissues with receptors for specific hormone Hormones alter target cell activity © 2013 Pearson Education, Inc.

Hormone action on target cells may be to Alter plasma membrane permeability and/or membrane potential by opening or closing ion channels Stimulate synthesis of enzymes or other proteins Activate or deactivate enzymes Induce secretory activity Stimulate mitosis © 2013 Pearson Education, Inc.

Hormones act at receptors in one of two ways, depending on their chemical nature and receptor location Water-soluble hormones (all amino acid–based hormones except thyroid hormone) Act on plasma membrane receptors Act via G protein second messengers Cannot enter cell © 2013 Pearson Education, Inc.

Plasma Membrane Receptors and Second-messenger Systems
cAMP signaling mechanism: Hormone (first messenger) binds to receptor Receptor activates G protein G protein activates adenylate cyclase Adenylate cyclase converts ATP to cAMP (second messenger) cAMP activates protein kinases that phosphorylate proteins © 2013 Pearson Education, Inc.

cAMP signaling mechanism Activated kinases phosphorylate various proteins, activating some and inactivating others cAMP is rapidly degraded by enzyme phosphodiesterase Intracellular enzymatic cascades have huge amplification effect © 2013 Pearson Education, Inc.

Figure 16.2 Cyclic AMP second-messenger mechanism of water-soluble hormones.
Slide 1 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Adenylate cyclase Extracellular fluid G protein (Gs) cAMP cAMP activates protein kinases. 5 GTP Receptor GTP ATP GDP Inactive protein kinase Active protein kinase GTP Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Cytoplasm Receptor activates G protein (Gs). 2 G protein activates adenylate cyclase. 3 Adenylate cyclase converts ATP to cAMP (2nd messenger). 4 © 2013 Pearson Education, Inc.

Slide 2 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Extracellular fluid Receptor Cytoplasm © 2013 Pearson Education, Inc.

Slide 3 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Extracellular fluid G protein (Gs) Receptor GTP GDP GTP Cytoplasm Receptor activates G protein (Gs). 2 © 2013 Pearson Education, Inc.

Slide 4 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Adenylate cyclase Extracellular fluid G protein (Gs) GTP Receptor GTP GDP GTP Cytoplasm Receptor activates G protein (Gs). 2 G protein activates adenylate cyclase. 3 © 2013 Pearson Education, Inc.

Slide 5 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Adenylate cyclase Extracellular fluid G protein (Gs) cAMP GTP Receptor GTP ATP GDP GTP Cytoplasm Receptor activates G protein (Gs). 2 G protein activates adenylate cyclase. 3 Adenylate cyclase converts ATP to cAMP (2nd messenger). 4 © 2013 Pearson Education, Inc.

Slide 6 Recall from Chapter 3 that G protein signaling mechanisms are like a molecular relay race. Hormone (1st messenger) Receptor G protein Enzyme 2nd messenger Hormone (1st messenger) binds receptor. 1 Adenylate cyclase Extracellular fluid G protein (Gs) cAMP cAMP activates protein kinases. 5 GTP Receptor GTP ATP GDP Inactive protein kinase Active protein kinase GTP Triggers responses of target cell (activates enzymes, stimulates cellular secretion, opens ion channel, etc.) Cytoplasm Receptor activates G protein (Gs). 2 G protein activates adenylate cyclase. 3 Adenylate cyclase converts ATP to cAMP (2nd messenger). 4 © 2013 Pearson Education, Inc.

PIP2-calcium signaling mechanism Involves G protein and membrane-bound effector – phospholipase C Phospholipase C splits PIP2 into two second messengers – diacylglycerol (DAG) and inositol trisphosphate (IP3) DAG activates protein kinase; IP3 causes Ca2+ release Calcium ions act as second messenger © 2013 Pearson Education, Inc.

Other Signaling Mechanisms
Cyclic guanosine monophosphate (cGMP) is second messenger for some hormones Some work without second messengers E.g., insulin receptor is tyrosine kinase enzyme that autophosphorylates upon insulin binding  docking for relay proteins that trigger cell responses © 2013 Pearson Education, Inc.

Intracellular Receptors and Direct Gene Activation
Steroid hormones and thyroid hormone Diffuse into target cells and bind with intracellular receptors Receptor-hormone complex enters nucleus; binds to specific region of DNA Prompts DNA transcription to produce mRNA mRNA directs protein synthesis Promote metabolic activities, or promote synthesis of structural proteins or proteins for export from cell © 2013 Pearson Education, Inc.

Cytoplasm Nucleus mRNA New protein
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 1 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex The receptor- hormone complex enters the nucleus. 2 Receptor Binding region Nucleus The receptor- hormone complex binds a specific DNA region. 3 DNA Binding initiates transcription of the gene to mRNA. 4 mRNA The mRNA directs protein synthesis. 5 New protein © 2013 Pearson Education, Inc.

Steroid hormone Extracellular Plasma fluid membrane
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 2 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex Nucleus © 2013 Pearson Education, Inc.

hormone complex enters the nucleus. 2
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 3 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex The receptor- hormone complex enters the nucleus. 2 Nucleus © 2013 Pearson Education, Inc.

hormone complex enters the nucleus. 2
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 4 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex The receptor- hormone complex enters the nucleus. 2 Receptor Binding region Nucleus The receptor- hormone complex binds a specific DNA region. 3 DNA © 2013 Pearson Education, Inc.

Cytoplasm Nucleus mRNA
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 5 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex The receptor- hormone complex enters the nucleus. 2 Receptor Binding region Nucleus The receptor- hormone complex binds a specific DNA region. 3 DNA Binding initiates transcription of the gene to mRNA. 4 mRNA © 2013 Pearson Education, Inc.

Cytoplasm Nucleus mRNA New protein
Figure Direct gene activation mechanism of lipid-soluble hormones. Slide 6 Steroid hormone Extracellular fluid Plasma membrane The steroid hormone diffuses through the plasma membrane and binds an intracellular receptor. 1 Cytoplasm Receptor protein Receptor- hormone complex The receptor- hormone complex enters the nucleus. 2 Receptor Binding region Nucleus The receptor- hormone complex binds a specific DNA region. 3 DNA Binding initiates transcription of the gene to mRNA. 4 mRNA The mRNA directs protein synthesis. 5 New protein © 2013 Pearson Education, Inc.

Target Cell Specificity
Target cells must have specific receptors to which hormone binds, for example ACTH receptors found only on certain cells of adrenal cortex Thyroxin receptors are found on nearly all cells of body © 2013 Pearson Education, Inc.

Target Cell Activation
Target cell activation depends on three factors Blood levels of hormone Relative number of receptors on or in target cell Affinity of binding between receptor and hormone © 2013 Pearson Education, Inc.

Target Cell Activation
Hormones influence number of their receptors Up-regulation—target cells form more receptors in response to low hormone levels Down-regulation—target cells lose receptors in response to high hormone levels © 2013 Pearson Education, Inc.

Control of Hormone Release
Blood levels of hormones Controlled by negative feedback systems Vary only within narrow, desirable range Endocrine gland stimulated to synthesize and release hormones in response to Humoral stimuli Neural stimuli Hormonal stimuli © 2013 Pearson Education, Inc.

Humoral Stimuli Changing blood levels of ions and nutrients directly stimulate secretion of hormones Example: Ca2+ in blood Declining blood Ca2+ concentration stimulates parathyroid glands to secrete PTH (parathyroid hormone) PTH causes Ca2+ concentrations to rise and stimulus is removed © 2013 Pearson Education, Inc.

Hormone release caused by altered levels of certain critical ions or
Figure 16.4a Three types of endocrine gland stimuli. Slide 1 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Capillary (low Ca2+ in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands PTH Stimulus: Low concentration of Ca2+ in capillary blood. Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+. © 2013 Pearson Education, Inc.

Figure 16.4a Three types of endocrine gland stimuli. Slide 2 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Capillary (low Ca2+ in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands © 2013 Pearson Education, Inc. 36

Figure 16.4a Three types of endocrine gland stimuli. Slide 3 Humoral Stimulus Hormone release caused by altered levels of certain critical ions or nutrients. Capillary (low Ca2+ in blood) Thyroid gland (posterior view) Parathyroid glands Parathyroid glands PTH Stimulus: Low concentration of Ca2+ in capillary blood. Response: Parathyroid glands secrete parathyroid hormone (PTH), which increases blood Ca2+. © 2013 Pearson Education, Inc. 37

Nerve fibers stimulate hormone release
Neural Stimuli Nerve fibers stimulate hormone release Sympathetic nervous system fibers stimulate adrenal medulla to secrete catecholamines © 2013 Pearson Education, Inc.

Hormone release caused by neural input.
Figure 16.4b Three types of endocrine gland stimuli. Slide 1 Neural Stimulus Hormone release caused by neural input. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary Stimulus: Action potentials in preganglionic sympathetic fibers to adrenal medulla. Response: Adrenal medulla cells secrete epinephrine and norepinephrine. © 2013 Pearson Education, Inc.

Figure 16.4b Three types of endocrine gland stimuli. Slide 2 Neural Stimulus Hormone release caused by neural input. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary © 2013 Pearson Education, Inc. 40

Figure 16.4b Three types of endocrine gland stimuli. Slide 3 Neural Stimulus Hormone release caused by neural input. CNS (spinal cord) Preganglionic sympathetic fibers Medulla of adrenal gland Capillary Stimulus: Action potentials in preganglionic sympathetic fibers to adrenal medulla. Response: Adrenal medulla cells secrete epinephrine and norepinephrine. © 2013 Pearson Education, Inc. 41

Hormones stimulate other endocrine organs to release their hormones
Hormonal Stimuli Hormones stimulate other endocrine organs to release their hormones Hypothalamic hormones stimulate release of most anterior pituitary hormones Anterior pituitary hormones stimulate targets to secrete still more hormones Hypothalamic-pituitary-target endocrine organ feedback loop: hormones from final target organs inhibit release of anterior pituitary hormones © 2013 Pearson Education, Inc.

Hormone release caused by another hormone (a tropic hormone).
Figure 16.4c Three types of endocrine gland stimuli. Slide 1 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Hypothalamus Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Stimulus: Hormones from hypothalamus. Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones. © 2013 Pearson Education, Inc.

Figure 16.4c Three types of endocrine gland stimuli. Slide 2 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Hypothalamus Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) © 2013 Pearson Education, Inc. 44

Figure 16.4c Three types of endocrine gland stimuli. Slide 3 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Hypothalamus Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) © 2013 Pearson Education, Inc. 45

Figure 16.4c Three types of endocrine gland stimuli. Slide 4 Hormonal Stimulus Hormone release caused by another hormone (a tropic hormone). Hypothalamus Anterior pituitary gland Thyroid gland Adrenal cortex Gonad (Testis) Stimulus: Hormones from hypothalamus. Response: Anterior pituitary gland secretes hormones that stimulate other endocrine glands to secrete hormones. © 2013 Pearson Education, Inc. 46

Nervous System Modulation
Nervous system modifies stimulation of endocrine glands and their negative feedback mechanisms Example: under severe stress, hypothalamus and sympathetic nervous system activated  body glucose levels rise Nervous system can override normal endocrine controls © 2013 Pearson Education, Inc.

Hormones circulate in blood either free or bound
Hormones in the Blood Hormones circulate in blood either free or bound Steroids and thyroid hormone are attached to plasma proteins All others circulate without carriers Concentration of circulating hormone reflects Rate of release Speed of inactivation and removal from body © 2013 Pearson Education, Inc.

Hormones removed from blood by
Hormones in the Blood Hormones removed from blood by Degrading enzymes Kidneys Liver Half-life—time required for hormone's blood level to decrease by half Varies from fraction of minute to a week © 2013 Pearson Education, Inc.

Onset of Hormone Activity
Some responses ~ immediate Some, especially steroid, hours to days Some must be activated in target cells © 2013 Pearson Education, Inc.

Duration of Hormone Activity
Limited Ranges from 10 seconds to several hours Effects may disappear as blood levels drop Some persist at low blood levels © 2013 Pearson Education, Inc.

Interaction of Hormones at Target Cells
Multiple hormones may act on same target at same time Permissiveness: one hormone cannot exert its effects without another hormone being present Synergism: more than one hormone produces same effects on target cell  amplification Antagonism: one or more hormones oppose(s) action of another hormone © 2013 Pearson Education, Inc.

The Pituitary Gland and Hypothalamus
Pituitary gland (hypophysis) has two major lobes Posterior pituitary (lobe) Neural tissue Anterior pituitary (lobe) (adenohypophysis) Glandular tissue © 2013 Pearson Education, Inc.

Pituitary-hypothalamic Relationships
Posterior pituitary (lobe) Downgrowth of hypothalamic neural tissue Neural connection to hypothalamus (hypothalamic-hypophyseal tract) Nuclei of hypothalamus synthesize neurohormones oxytocin and antidiuretic hormone (ADH) Neurohormones are transported to and stored in posterior pituitary © 2013 Pearson Education, Inc.

Paraventricular nucleus
Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 1 Paraventricular nucleus Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Posterior lobe of pituitary Optic chiasma Supraoptic nucleus Infundibulum (connecting stalk) 2 Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Inferior hypophyseal artery Hypothalamic- hypophyseal tract Axon terminals 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Posterior lobe of pituitary 4 Oxytocin ADH When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood. © 2013 Pearson Education, Inc.

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 2 Paraventricular nucleus Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Posterior lobe of pituitary Optic chiasma Supraoptic nucleus Infundibulum (connecting stalk) Inferior hypophyseal artery Hypothalamic- hypophyseal tract Axon terminals Posterior lobe of pituitary © 2013 Pearson Education, Inc. 56

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 3 Paraventricular nucleus Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Posterior lobe of pituitary Optic chiasma Supraoptic nucleus Infundibulum (connecting stalk) 2 Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Inferior hypophyseal artery Hypothalamic- hypophyseal tract Axon terminals Posterior lobe of pituitary © 2013 Pearson Education, Inc. 57

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 4 Paraventricular nucleus Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Posterior lobe of pituitary Optic chiasma Supraoptic nucleus Infundibulum (connecting stalk) 2 Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Inferior hypophyseal artery Hypothalamic- hypophyseal tract Axon terminals Oxytocin and ADH are stored in axon terminals in the posterior pituitary. 3 Posterior lobe of pituitary © 2013 Pearson Education, Inc. 58

Figure 16.5a The hypothalamus controls release of hormones from the pituitary gland in two different ways (1 of 2). Slide 5 Paraventricular nucleus Hypothalamus 1 Hypothalamic neurons synthesize oxytocin or antidiuretic hormone (ADH). Posterior lobe of pituitary Optic chiasma Supraoptic nucleus Infundibulum (connecting stalk) 2 Oxytocin and ADH are transported down the axons of the hypothalamic- hypophyseal tract to the posterior pituitary. Inferior hypophyseal artery Hypothalamic- hypophyseal tract Axon terminals 3 Oxytocin and ADH are stored in axon terminals in the posterior pituitary. Posterior lobe of pituitary 4 Oxytocin ADH When hypothalamic neurons fire, action potentials arriving at the axon terminals cause oxytocin or ADH to be released into the blood. © 2013 Pearson Education, Inc. 59

Pituitary-hypothalamic Relationships
Anterior Lobe: Originates as out-pocketing of oral mucosa Vascular connection to hypothalamus Hypophyseal portal system Primary capillary plexus Hypophyseal portal veins Secondary capillary plexus Carries releasing and inhibiting hormones to anterior pituitary to regulate hormone secretion © 2013 Pearson Education, Inc.

they stimulate or inhibit
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 1 Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. Anterior lobe of pituitary Superior hypophyseal artery When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1 2 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. Hypophyseal portal system • Primary capillary plexus In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. 3 A portal system is two capillary plexuses (beds) connected by veins. • Hypophyseal portal veins • Secondary capillary plexus GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary © 2013 Pearson Education, Inc.

A portal system is two capillary plexuses (beds) connected by veins.
Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 2 Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. Anterior lobe of pituitary Superior hypophyseal artery When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1 Hypophyseal portal system • Primary capillary plexus A portal system is two capillary plexuses (beds) connected by veins. • Hypophyseal portal veins • Secondary capillary plexus GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary © 2013 Pearson Education, Inc. 62

Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 3 Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. Anterior lobe of pituitary Superior hypophyseal artery When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1 2 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. Hypophyseal portal system • Primary capillary plexus A portal system is two capillary plexuses (beds) connected by veins. • Hypophyseal portal veins • Secondary capillary plexus GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary © 2013 Pearson Education, Inc. 63

Figure 16.5b The hypothalamus controls release of hormones from the pituitary gland in two different ways (2 of 2). Slide 4 Hypothalamus Hypothalamic neurons synthesize GHRH, GHIH, TRH, CRH, GnRH, PIH. Anterior lobe of pituitary Superior hypophyseal artery When appropriately stimulated, hypothalamic neurons secrete releasing or inhibiting hormones into the primary capillary plexus. 1 2 Hypothalamic hormones travel through portal veins to the anterior pituitary where they stimulate or inhibit release of hormones made in the anterior pituitary. Hypophyseal portal system • Primary capillary plexus 3 A portal system is two capillary plexuses (beds) connected by veins. In response to releasing hormones, the anterior pituitary secretes hormones into the secondary capillary plexus. This in turn empties into the general circulation. • Hypophyseal portal veins • Secondary capillary plexus GH, TSH, ACTH, FSH, LH, PRL Anterior lobe of pituitary © 2013 Pearson Education, Inc. 64

Posterior Pituitary and Hypothalamic Hormones
Oxytocin and ADH Each composed of nine amino acids Almost identical – differ in two amino acids © 2013 Pearson Education, Inc.

Strong stimulant of uterine contraction Released during childbirth
Oxytocin Strong stimulant of uterine contraction Released during childbirth Hormonal trigger for milk ejection Acts as neurotransmitter in brain © 2013 Pearson Education, Inc.

Inhibits or prevents urine formation Regulates water balance
ADH (Vasopressin) Inhibits or prevents urine formation Regulates water balance Targets kidney tubules  reabsorb more water Release also triggered by pain, low blood pressure, and drugs Inhibited by alcohol, diuretics High concentrations  vasoconstriction © 2013 Pearson Education, Inc.

Syndrome of inappropriate ADH secretion (SIADH)
Diabetes insipidus ADH deficiency due to hypothalamus or posterior pituitary damage Must keep well-hydrated Syndrome of inappropriate ADH secretion (SIADH) Retention of fluid, headache, disorientation Fluid restriction; blood sodium level monitoring © 2013 Pearson Education, Inc.

Anterior Pituitary Hormones
Growth hormone (GH) Thyroid-stimulating hormone (TSH) or thyrotropin Adrenocorticotropic hormone (ACTH) Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) Prolactin (PRL) © 2013 Pearson Education, Inc.

Anterior Pituitary Hormones
All are proteins All except GH activate cyclic AMP second-messenger systems at their targets TSH, ACTH, FSH, and LH are all tropic hormones (regulate secretory action of other endocrine glands) © 2013 Pearson Education, Inc.

Growth Hormone (GH, or Somatotropin)
Produced by somatotropic cells Direct actions on metabolism Increases blood levels of fatty acids; encourages use of fatty acids for fuel; protein synthesis Decreases rate of glucose uptake and metabolism – conserving glucose  Glycogen breakdown and glucose release to blood (anti-insulin effect) © 2013 Pearson Education, Inc.

Growth Hormone (GH, or Somatotropin)
Indirect actions on growth Mediates growth via growth-promoting proteins – insulin-like growth factors (IGFs) IGFs stimulate Uptake of nutrients  DNA and proteins Formation of collagen and deposition of bone matrix Major targets—bone and skeletal muscle © 2013 Pearson Education, Inc.

GH release chiefly regulated by hypothalamic hormones
Growth Hormone (GH) GH release chiefly regulated by hypothalamic hormones Growth hormone–releasing hormone (GHRH) Stimulates release Growth hormone–inhibiting hormone (GHIH) (somatostatin) Inhibits release Ghrelin (hunger hormone) also stimulates release © 2013 Pearson Education, Inc.

Homeostatic Imbalances of Growth Hormone
Hypersecretion In children results in gigantism In adults results in acromegaly Hyposecretion In children results in pituitary dwarfism © 2013 Pearson Education, Inc.

Figure 16.6 Growth-promoting and metabolic actions of growth hormone (GH).
Hypothalamus secretes growth hormone–releasing hormone (GHRH), and GHIH (somatostatin) Feedback Inhibits GHRH release Stimulates GHIH release Anterior pituitary Inhibits GH synthesis and release Growth hormone (GH) Indirect actions (growth- promoting) Direct actions (metabolic, anti-insulin) Liver and other tissues Produce Insulin-like growth factors (IGFs) Effects Effects Fat metabolism Carbohydrate metabolism Skeletal Extraskeletal Increases, stimulates Reduces, inhibits Increased protein synthesis, and cell growth and proliferation Initial stimulus Increased cartilage formation and skeletal growth Increased fat breakdown and release Increased blood glucose and other anti-insulin effects Physiological response Result © 2013 Pearson Education, Inc.

Thyroid-stimulating Hormone (Thyrotropin)
Produced by thyrotropic cells of anterior pituitary Stimulates normal development and secretory activity of thyroid Release triggered by thyrotropin-releasing hormone from hypothalamus Inhibited by rising blood levels of thyroid hormones that act on pituitary and hypothalamus © 2013 Pearson Education, Inc.

Hypothalamus TRH Anterior pituitary TSH Thyroid gland
Figure 16.8 Regulation of thyroid hormone secretion. Hypothalamus TRH Anterior pituitary TSH Thyroid gland Thyroid hormones Stimulates Target cells Inhibits © 2013 Pearson Education, Inc.

Adrenocorticotropic Hormone (Corticotropin)
Secreted by corticotropic cells of anterior pituitary Stimulates adrenal cortex to release corticosteroids © 2013 Pearson Education, Inc.

Adrenocorticotropic Hormone (Corticotropin)
Regulation of ACTH release Triggered by hypothalamic corticotropin-releasing hormone (CRH) in daily rhythm Internal and external factors such as fever, hypoglycemia, and stressors can alter release of CRH © 2013 Pearson Education, Inc.

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Gonadotropins Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) Secreted by gonadotrophs of anterior pituitary FSH stimulates gamete (egg or sperm) production LH promotes production of gonadal hormones Absent from the blood in prepubertal boys and girls © 2013 Pearson Education, Inc.

Regulation of gonadotropin release
Gonadotropins Regulation of gonadotropin release Triggered by gonadotropin-releasing hormone (GnRH) during and after puberty Suppressed by gonadal hormones (feedback) © 2013 Pearson Education, Inc.

Secreted by prolactin cells of anterior pituitary
Prolactin (PRL) Secreted by prolactin cells of anterior pituitary Stimulates milk production Role in males not well understood © 2013 Pearson Education, Inc.

Regulation of PRL release
Prolactin (PRL) Regulation of PRL release Primarily controlled by prolactin-inhibiting hormone (PIH) (dopamine) Blood levels rise toward end of pregnancy Suckling stimulates PRL release and promotes continued milk production Hypersecretion causes inappropriate lactation, lack of menses, infertility in females, and impotence in males © 2013 Pearson Education, Inc.

Endocrine System: Overview

Similar presentations

Presentation on theme: "Endocrine System: Overview"— Presentation transcript:

Similar presentations

About project

Feedback

Log in

Auth with social network:

Endocrine System: Overview

Similar presentations

Presentation on theme: "Endocrine System: Overview"— Presentation transcript:

Similar presentations

About project

Feedback