Ch 7 study questions

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Biomedical Physio & Kines
BPK 205
Parveen Bawa

Practice Questions Chapter 7 1. Briefly describe the steps in the synthesis, storage and release of a peptide hormone. [~ 1 page, 15 minutes]. • Occurs in cells that synthesize peptide hormones • mRNA leaves nucleus and attaches to ribosome, starting production of pre- prohormone (contains copies of final hormone, and signal sequences to take it to endoplasmic reticulum) • Once pre-prohormone reaches ER, enzymes cut off signal sequences leaving it as just a prohormone. • From ER to golgi apparatus, where prohormone is packaged along with proteolytic enzymes into vesicles • Once packaged, the now secretory vesicle contains active hormone and peptide fragments. These vesicles are stored in the cell • When cell receives appropriate signal, Ca++ increases in cell, and secretory vesicle releases contents into ECF • Peptide hormones are water soluble and travel through ECF, and go into capillaries into the plasma of blood 2. How is steroid hormone synthesized, stored and circulated? [ ~ a page, 15 minutes] • Synthesis o Always synthesized from cholesterol o Mitochondria converts cholesterol to pregnenolone o Smooth endoplasmic reticulum converts pregnenolone to hormone  testosterone, progesterone, and estrogen in gonads  Aldosterone, and cortisol in adrenal cortex • Storage o Lipophilic so cannot be stored in vesicles o Stored as precursors in cytoplasm of endocrine cells • Circulated o Transported bound to carrier proteins (extends their half-life) o Will either:  Enter a cell and bind to DNA in the nucleus to turn on or off a gene (turning on a gene can lead to a slow protein synthesis)  Bind to receptor located on plasma membrane of a cell (non genomic, and rapid response) 3. Why can't steroid hormones be stored in a typical vesicle? Because they are lipophilic. They must be stored in lipids, but vesicles typically aren’t filled with lipids 4. With the help of a figure, describe the relationship of the hypothalamus to pituitary, naming at least two hormones entering the systemic circulation from the posterior and anterior pituitary. Provide the names of associated hypothalamic releasing factors where applicable. [1 figure + at least one page of clear writing]. Do not describe feedback effects here. Posterior Pituitary: • Neurons in magnocellular region of hypothalamus secretes oxytocin and vasopressin (ADH) • Hormones are transported down the neuron via vesicles to the neurohypophysis • At the terminals of the neuron, the hormones are stored • When hypothalamus receives a signal, hormones are released from terminal into blood stream • Oxytocin targets the uterus, and is a factor in pregnancy, and breast feeding • ADH increases reabsorption of water at the kidneys Anterior Pituitary: • Neurons in parvocellular region of hypothalamus synthesize and release “releasing hormones” among capillary plexuses • Portal blood system carries releasing hormones to anterior hypophysis (pituitary). Releasing hormones control inhibition or excitation of trophic hormone release
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