BIOS 390 Unit 2 Receptors

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BIOS 390 Unit 2 Receptors

• What are the 2 requirements for hormone responsiveness?

–Answer hormone is available and there are receptors

• What is the first order receptor?

–Answer the receptor that the hormone binds to

• What are the two ways hormones can be secreted with regard to synthe- sis?

–Answer

• independent of synthesis
• directly coupled to synthesis
• What does it mean if you upregulate the synthesis of a hormone and see no change in

secretion?–Answer secretion is independent of synthesis

• Which type of hormones is stored in the cells in large quantities?

–Answer peptide and protein hormones

• Which type of hormone has secretion directly coupled to synthesis?

–Answer - steroids (they are produced as needed)

• What occurs in a free standing gland/cell?

–Answer responds to a variety of signals which can increase or decrease synthesis or secretion of the hormone 1 / 3

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• What is negative feedback loop with hormone secretion in a free standing gland/cell?

–Answer as hormone secretion increases the hormone itself or the biological response by the target cells may negatively feedback on the gland to decrease its own secretion

• What are the major endocrine glands regulated by ?

–Answer pituitary tropic hormones

• The pituitary tropic hormones are in turn regulated by what?

–Answer releasing hormones from the hypothalamus in the brain

• Where is the pituitary tropic hormones potential for negative feedback?

–Answer at each part of the hypothalamic-pituitary axis

• How are peptide/protein hormones transported?

–Answer they are soluble so they circulate in the aqueous serum without assistance

• How are steroid and thyroid hormones transported?

–Answer bound to plasma pro- teins because they are not soluble in water

• What happens if the hydrophobic hormones do not have transporting proteins?

–Answer they will not be uniformly distributed in the body, rather they will localize in nearby cells

• What is the free hormone hypothesis (3)?

–Answer

• unbound (free) steroid and TH in the serum can readily enter the cell
• hormone in cytoplasm is at equilibrium with the free hormone in the blood
• hormones simply diffuse into the cell
• Why is the free hormone hypothesis wrong?

–Answer transport proteins play a critical role in steroid and TH uptake, and free hormones in the blood 2 / 3

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and cytoplasm are not necessarily at equilibrium

• What is the more common name for binding proteins?

–Answer distributing proteins

• What is the experiment where they added a steroid to an organ with a radioactive label in

the absence and presence of proteins?–Answer

• in the absence of proteins very little label(and thus hormone) exiting the organ, it portioned

into the PM

• in presence of proteins, there were lots of label leaving the organ
• What are the 3 main reasons binding proteins are important?

–Answer

• distribution (moving hydrophobic hormones)
• maintain a pool of available hormone
• facilitate transporter mediated uptake
• What is an example of how plasma binding/distributor proteins can be significant

modulators of hormone availability and homeostasis?–Answer

• during pregnancy females have significant elevated serum TH levels yet show no signs of

hyperthyroidism

• this increase is due to an increase in thyroxine binding globulin to ensure a larger pool of

available TH which is important for fetal development

• Where do protein hormones typically act when they reach the target cell?-

–Answer on the surface

• If a protein hormone is to enter the cell how are they taken up?

–Answer special transport systems

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