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Assigned readings:Chapters 1-3 in Griffin & Ojeda; Chapter 1 in Bentley

Explore the two general patterns of hormone effects on cells: the protein-amne effect on membrane receptors and the direct action of steroid hormones on nuclear DNA. Gain insights into the role of hormones in cellular control through feedback loops and persistent secretion patterns. Understand the regulation of blood calcium levels by hormone pairs and the complex feedback loops involved in hormone secretion. Dive into the functions of the pituitary gland and the hypothalamus in hormone regulation.

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Assigned readings:Chapters 1-3 in Griffin & Ojeda; Chapter 1 in Bentley

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  1. Assigned readings:Chapters 1-3 in Griffin & Ojeda; Chapter 1 in Bentley • Lecture: Tuesdays 6-8:45 PM • Professor: Dr. Frank V. Paladino • Office: SB G-56 • Phone: 481-6304 or 6305 • Lecture 2

  2. Thus there are 2 general patterns of hormone effects on cells • Protein – amine effect on membrane receptors:

  3. Second messenger cAMP causes responses in cytoplasm

  4. Specific Example Antidiuretic (argenine vasopressin or ADH) hormone a nonapeptide (9 aa): regulates water levels in body by action on nephron distal tubule: very close relationship of the nonapetides secreted from the Posterior Pituitary or neurohypophysis.

  5. 2. Steroid hormones act directly on nuclear DNA, chromosomes puff shows areas of DNA where steroid hormone has induced new mRNA production

  6. Cholesterol is a 17 ketosteroid and an important precursor for all steroid hormones.

  7. Ca also an important cell regulator and Ca – Calmodulin system for cellular control:

  8. Hormone control: Usually done by feedback loops but other general patterns; • Pattern 1 – On/off --- For this pattern hormone secretion is initiated by some factor (may be neural) For this case the hormone us usually not found in the general circulation – some factor turns on the secretion i.e. Ext stim>neural signalGland> hormone secreted>H in blood>Target organ> response> Stimulus removed>

  9. Example: Food bolus in duodenum> neural receptors Intestinal plexus> Endocrine cells in intestinal mucosa >Secretin Hormone dumped into blood> Receptors in pancreas> secretin cause release of digestive enzymes from pancreas> Food digested and absorbed> bolus gone> Stimulus gone> Neural signal off> secretin gone from blood • This is an example of On/off

  10. Persistent secretion pattern: There is always a certain level of the hormone in the blood and feedback control regulates the amount and level. Usually there are hormone pairs that work in concert to maintain a constant level (homeostasis) of some chemical in system. • SIMPLE feedback control: steady state hormone levels control some variable • Specific example: Regulation of blood Ca levels

  11. Parathormone (PTH) produced by Parathyroid glands regulates blood Ca levels in concert with Thyrocalcitonin (TCT) secreted from the thyroid Levels of Ca are relatively constant in blood. PTH cells monitor [Ca] > when [Ca]^ PTH secretion is reduced and blood [Ca]v PTH causes Bone cells to reabsorb Ca from bone matrix and deposit free Ca in Blood , Stimulates gut to absorb Ca and reduces Ca secretion in Kidney tubules

  12. Thyrocalcitonin (TCT) produced by cells in thyroid nodules has an opposite effect and opposes the action of PTH • As [Ca]^ > TCT cells in thyroid [TCT]^ • TCT causes bone cells to deposit Ca in bone matrix, Kidney tubules secrete Ca, and gut cells reduce absorption of Ca from food. • Thus these 2 hormones are persistently secreted at low levels in the blood and regulate very closely the levels of free Ca in the blood. They are known as a simple negative feedback hormone pair Feedback loop is negative because the hormone removes the stimulus [Ca] change and thus the system comes into steady state or homeostasis

  13. Multistep feedback loops: more complex and now have feedback at more than 1 level • It was thought that the Pituitary gland located at the base of the brain was the “Master Gland” • Embryologically derived from neural tissue and a pouch from the oral tube (Rathke’s pouch)

  14. Special circulation between Pituitary and Hypothalamus called Hypothalmo-hypophoseal portal system. Capillary’s in hypothalamus go to adenohypophysis

  15. Tropic hormones from the Anterior Pituitary (Adenohypophysis) and Regulating Factors (RF’s) from the Hypothalamus put multiple levels of control and feedback in the feedback loops

  16. Study and know all the Pituitary hormones and actions • Know the hypothalmus nuclei and regulating factors • Know the unique anatomy of these 2 structures • Understand now the multiple levels of control and feedback • i.e. control of gonad function – • Hypothalamus produces GnRF (gonadotropin reg Factor – goes via special circulation to Ant. Pit. Effects release of Gonadotropin (like FTH foliculotropin AKA FSH) FSH effects ovary – ovary produces estrogen (Female sex hormone) estrogen effects uterus, breasts etc… and can now feed back to hypothalamus as well as Pituitary, and the ovary at multiple levels

  17. Hypersecretion of thyroid causes enlarged goiter Exopthalmus (Bug eyes) and Graves Disease Hyposecretion as a child can cause cretin as an adult Myxedema

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