BIO 311D 2nd Edition Lecture 23 Outline of Last Lecture I. Animal Development and Hox genesII. A look at the classes of vertebratesIII. What is homeostasis?Outline of Current Lecture I. Homeostasis and negative feedback controlII. How do hormone systems work?III. Homeostasis of blood glucose levelCurrent LectureI. Homeostasis and negative feedback controlA. This non-living example exhibits the control elements of homeostasis: a monitoring system and a response system to deviations from the “set point”.B. What is negative feedback control?- Which of the following is an example of the control of blood hormone (H) levels by negative feedback?When blood H level rises above a set point, secretion of H stops - A change in a variable triggers a response that counteracts that change and maintains homeostasisC. Positive Feedback- Deviates faster away from the set point; not a homeostatic mechanism - Which of the following is an example of the control of blood hormone (H) levels by positive feedback?When blood H level rises above a set point, more H is secretedII. How do hormone systems work?A. Hormones are produced by endocrine glands. They travel in blood and affect target cells. - Target cells: receptorsB. Endocrine glands have secretory epithelial cells specialized for secretion. Rough endoplasmic reticulum. Secrete hormone into the blood, not into a duct. - Which of the following distinguishes an endocrine gland from other types of glands?Its products are released directly into the blood - How do peptide (water soluble) and steroid (lipid soluble) hormones differ in receptor location in target cells?Peptide hormone receptors are on the cell surfaceSteroid hormone receptors are intracellular - How do peptide (water soluble) and steroid (lipid soluble) hormones differ in effects on target cells?Steroid hormones bind to receptors to directly affect the target cells- Classic peptide, water-soluble, receptor in plasma membrane; triggers signal transductionBind to membrane receptor Review Signal-Transduction pathways- Classic steroid, lipid-soluble; receptor inside cell nucleus; acts as transcriptionfactorC. Neuron release NT into synapse- Neurosecretory cells: secrete products into bloodIII. Homeostasis of blood glucose levelA. Insulin is a protein hormone secreted by the beta cells of the pancreas. It is in control system that helps keep blood glucose from rising too high. - How can a cell serve as a target cell to insulin: An insulin receptor- What “message” is insulin signaling? – Get rid of glucose- What can cells do to “obey” insulin signal? – Increase glucose uptake, inhibit fat metabolism, stimulate glycogen formation- GLUT 4:
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