| Hormones and Feedback Mechanisms |
| 03.01.05 | |
| How the endocrine system controls everything |
| The Endocrine System |
| General Overview | |
| Basic Anatomy | |
| Control of the endocrine system | |
| Specific endocrine events |
| Slide 3 |
| I. A General Overview |
| ES (endocrine system) and homeostasis | ||
| Anatomy | ||
| Endocrine glands, cells, neurosecretory cells | ||
| Hormones | ||
| Target cells | ||
| ES as a Control System | ||
| Hormone + target = change in cell function (return to homeostasis) | ||
| ES and Homeostasis |
| Homeostasis | |
| Feedback Mechanisms |
| Stimulus | ||
| change in homeostatic environment | ||
| signal sent to CNS | ||
| Response | ||
| signal sent from CNS | ||
| produce effect | ||
| body returns to homeostasis | ||
| Basic ES cont. |
| ES and NS = 2 main control systems of body | ||
| Endocrine organs located throughout body | ||
| Actions mediate all tissues | ||
| Control of ES through feedback mechanisms | ||
| II. ES anatomy basics |
| Exocrine gland | ||
| Ducts | ||
| Lumen and surfaces | ||
| Endocrine gland | ||
| Chemical messengers | ||
| Blood stream | ||
| C. Hormones |
| Chemical messenger | ||
| Secreted by endocrine gland | ||
| Specific to target | ||
| Activate cellular change | ||
| Of 4 different chemical types | ||
| C. 4 Classes of Hormones |
| Peptide/ Protein | |
| Steroid | |
| Amine | |
| Eicosanoid |
| Hormone + Receptor |
| Protein/Peptide Hormones |
| Hydrophilic | |
| Large | |
| Can't fit through membrane | |
| Second messenger mechanism of action | |
| Most hormones | |
| Example: Insulin |
| Steroid Hormones |
| Small | |
| Hydrophobic/Lipophilic | |
| Travel in blood w/carrier | |
| Cytoplasmic or nuclear receptors | |
| change protein synthesis | |
| Example: estradiol | |
| Amine |
| Eicosanoid |
| Hormone + Receptor |
| Where are Hormones Made ? |
| The H-P-A Hypothalamic-Pituitary Axis |
| Most feedback loops run through this axis | |
| HPA mediates growth, metabolism, stress response, reproduction. | |
| is secondarily in charge of almost everything else. |
| Slide 19 |
| D. Neurosecretory Cells |
| Specialized neurons | ||
| Synthesize and secrete hormones | ||
| Extend from HYPOTHALAMUS to POSTERIOR PITUITARY | ||
| 2. Neurosecretory cells in Hypothalamus |
| Nuclei synthesize and secrete hormones | |
| Neuronal connection to POSTERIOR pituitary | |
| Antidiuretic Hormone (ADH), Oxytocin | |
| E. Hypothalamus (general) |
| Connection to pituitary | |||
| Neuronal to POSTERIOR PITUITARY | |||
| Endocrine to ANTERIOR PITUITARY | |||
| RH = Pituitary releasing hormones | |||
| RIH = Pituitary release inhibiting hormones | |||
| Why is the Hypothalamus so Important? |
| Secretes regulatory homones | ||
| RH | ||
| RIH | ||
| "Directs" pituitary | ||
| Slide 24 |
| Hypothalamic Hormomes |
| Release Inhibiting Hormones | ||
| Somatostatin | ||
| Prolactin release inhibiting hormone-PIH | ||
| Releasing Hormones | ||
| Thyrotropin releasing hormone-TRH | ||
| Growth hormone releasing hormone-GHRH | ||
| Slide 26 |
| 1. Posterior Pituitary Hormones |
| Manufactured in Hypothalamus, released from Post. Pit. | ||
| Oxytocin | ||
| Target = smooth ms. Uterus and Breast (&brain) | ||
| Function = labor and delivery, milk ejection,(pair bonding) | ||
| ADH (Vasopressin AVP) | ||
| Target = kidneys | ||
| Function = water reabsorption | ||
| How about in frogs ? |
| Hormone structure/function tightly conserved | ||
| Mesotocin | ||
| yolking of eggs | ||
| egg-laying | ||
| Vasotocin (AVT) | ||
| water balance | ||
| REPRODUCTIVE BEHAVIORS | ||
| Slide 29 |
| Slide 30 |
| Slide 31 |
| 2. Anterior Pituitary Hormones |
| Hormones To Study |
| Hypothalamic Hormones | ||
| Posterior Pituitary (Neurohypophysis) | ||
| Anterior Pituitary (Adenohypophysis) | ||
| Thyroid | ||
| Growth | ||
| Sex Steroid | ||
| III.Control of Endocrine Function |
| Positive | |
| or Negative Feedback mechanisms | |
| Self-regulating system | |
| Slide 35 |
| A. Positive Feedback |
| Not common | |
| Classic example: | |
| Action of OXYTOCIN on uterine muscle during birth. |
| Positive Feedback |
| Baby pushes on cervix | |
| Nervous signal to Hypothalamus | |
| Hypothal. manufactures OXY | |
| OXY transported to POSTERIOR PITUITARY & released | |
| OXY stimulates uterine contraction | |
| Loop stops when baby leaves birth canal |
| Same with frogs? |
| B. Negative Feedback |
| Most common control mechanism | |
| Level of hormone in blood or bodyÕs return to homeostasis shuts off loop at hypothalamus and pituitary |
| Negative Feedback: Thyroid |
| Basic Structure of Feedback Loop |
| Environmental Stimulus | |
| Stimulates Control Center (Brain-hypothal.) | |
| Hypothalamic hormones stim. Pituitary | |
| Pituitary hormone stim. Target area | |
| Target area produces change | |
| Change acts negatively or positively on the cycle. | |
| IV. Specific Endocrine Events |
| Thyroid Hormone | |
| Growth Hormone | |
| Adrenal Cortex Hormones | |
| Sex Steroids | |
| A. Thyroid Hormone |
| ø T3 & T4 stim. Or environmental stim. Hypothalamus | |
| TRH stim. Anterior Pituitary | |
| TSH stim. Thyroid | |
| T3 & T4 shuts off TRH and TSH production |
| Slide 44 |
| Slide 45 |
| Slide 46 |
| Thyroid Problems |
| What would happen if the thyroid could no longer produce T3 and T4? | |
| No negative feedback to hypothalamus and anterior pituitary |
| Goiter |
| Hypersecretion of TSH or TH |
| Hyposecretion of TH |
| B. Growth Hormone |
| Stimulus = Tissue growth/ repair | |
| Hypothalamus releases GHRH | |
| Anterior Pituitary releases GH | |
| Protein synthesis, growth, etc. | |
| GH and release of somatostatin shuts off GHRH and GH release | |
| What happens with excess GH? |
| GH as Juvenile |
| GH as an Adult |
| How Does Hypersecretion of GH Happen? |
| øGH = pituitary dwarfism |
| Slide 57 |
| Adrenal Gland |
| Adrenal gland located atop kidney | ||
| Outer part = cortex | ||
| Secretes Cortisol (stress), Androgens, Aldosterone (electrolytes) | ||
| Inner part = medulla | ||
| SNS control | ||
| Secretes EPI & NEPI (fight or flight) | ||
| Adrenal Insufficiency |
| AddisonÕs disease--hyposecretion of cortisol | |
| JFK | |
| Darkened skin (ACTH mimics MSH) | |
| Weight loss, hypoglycemia | |
| Find the anomaly in the feedback loop. | |
| Inability to handle stress |
| 4. Sex Steroids |
| Stimulus = low circulating T or E | |
| Hypothalamus = GnRH | |
| Anterior Pituitary = FSH & LH | |
| Gonads produce T and E | |
| High T and E shut off GnRH and FSH/LH |
| Importance |
| Reproduction/Mating Behavior (duh) | ||
| Formation of reproductive organs | ||
| gonads | ||
| brain | ||
| Slide 62 |
| Too many steroids |
| Slide 64 |
| Invertebrates |
| Hormones involved in: | ||
| Molting | ||
| Pupation | ||
| Metamorphosis | ||
| Insect Hormones |
| Juvenile Hormone | ||
| maintains juvenile cuticle for pre-adulthood molts | ||
| secreted by corpus allatum near brain | ||
| Ecdysone | ||
| Molting Hormone | ||
| Prothoracic Glands (in thorax of insect) | ||
| PTTH = Brain hormone that stimulates Prothoracic Glands | ||
| Slide 67 |
| Points |
| History | |
| Anatomy | |
| Terms | |
| Hormones | |
| Feedback control | |
| Specific Points discussed |
| I. Endocrine History |
| Claude Bernard (mid 1800s) | ||
| pancreas, liver | ||
| brain, smooth ms. | ||
| internal environ. | ||
| A.A. Berthold (1849) | ||
| repro hormones and | ||
| behavior | ||
| Endocrine History |
| Charles Brown-Sequard (1889) | ||
| Harvard 1864-1868 | ||
| M.D. in NY 1873-1878 | ||
| bull testis extracts | ||
| Important Physiologists |
| Walter Cannon | |||
| homeostasis | |||
| sympathetic nervous system | |||
| Bodily Changes in Hunger, Fear, and Rage | |||
| 1. Peptide/Protein Hormones |
| Most common hormone | |
| translated, packaged, & sent | |
| Hydrophilic/Lipophobic | |
| Bind surface receptors at target | |
| Binding mediates signal transduction/2nd messenger system | |
| Peptide Hormones cont. |
| Short 1/2-life | ||
| Pancreas | ||
| Insulin/glucagon | ||
| Hypothalamus | ||
| RH (releasing hormones) | ||
| RIH (release inhibiting hormones) | ||
| Slide 74 |
| 2. Steroid Hormones |
| Derived from cholesterol | ||
| Hydrophobic/Lipophilic | ||
| Travel with a protein carrier | ||
| Long 1/2-life | ||
| Binds to cytoplasmic or nuclear receptor | ||
| 1st Messenger | ||
| Steroid hormones cont. |
| Genomic effect | ||
| Activates genes | ||
| Directs synthesis of new proteins | ||
| Lag time between hormone binding and effect = long time. | ||
| Gonads & placenta | ||
| Adrenal cortex | ||
| Slide 77 |
| 3. Amine Hormones |
| Synthesized from a single amino acid | |
| Melatonin from tryptophan | |
| Thyroid hormone from tyrosine | |
| Catecholamines (EPI, DA) from tyrosine | |
| 4. Eicosanoid hormones |
| Produced from 20-carbon fatty acid, arachadonic acid | |
| Produced in all cells except RBCs | |
| 2nd messenger | |
| Prostaglandins and leukotrienes | |
| inflammation |
| Slide 80 |
| Slide 81 |
| Slide 82 |
| Slide 83 |
| Negative Feedback |
| Low levels of T3 or T4 in blood or low BMR = stimulus | |
| Hypothalamus releases TRH | |
| TRH stimulates the ANTERIOR PITUITARY to release TSH | |
| TSH stim. Thyroid to release T3 & T4 | |
| Levels of T3 & T4 shut off Hypothal. & Anterior Pituitary |
| Slide 85 |
| Adrenal cortex feedback |
| Low glucocorticoid (cortisol) levels or low blood sugar | |
| Stim. Hypothal. = CRH | |
| CRH stim. Anterior Pit. = ACTH | |
| ACTH stim. Adrenal Cortex. | |
| Increase glucocort. Level then blood sugar level |
| Adrenal gland |
| Adrenal Problems |
| Hypersecretion of Adrenal Cortex |
| What Would the Feedback Loop Look Like for CushingÕs Syndrome? |