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BPK 205 Chapter Notes -Anterior Pituitary, Pregnenolone, Lipophilicity


Department
Biomedical Physio & Kines
Course Code
BPK 205
Professor
Parveen Bawa

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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
oAlways synthesized from cholesterol
oMitochondria converts cholesterol to pregnenolone
oSmooth endoplasmic reticulum converts pregnenolone to hormone
testosterone, progesterone, and estrogen in gonads
Aldosterone, and cortisol in adrenal cortex
Storage
oLipophilic so cannot be stored in vesicles
oStored as precursors in cytoplasm of endocrine cells
Circulated
oTransported bound to carrier proteins (extends their half-life)
oWill 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
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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
Hormone examples: Prolactin (release factor: Prolactin releasing hormone, PRH),
growth hormone (release factor: Growth Hormone Releasing Hormone). Cortisol
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