Endocrine System

what kind of gland releases hormones and how do these hormones get to their target cells/organs?

endocrine glands release the hormones, they travel through the blood stream

what kind of hormones are able to pass through the plasma membrane of cells? are these polar or non-polar? examples

lipid-soluble hormones - non-polar

ex: thyroid hormones

because lipid-soluble hormones are non-polar, what does it need to travel through the bloodstream?

transport protein

plasma-membrane receptors vs. intracellular receptors

• where are these located

• what hormones do they receive

1) in the PM of target cells, water-soluble hormones

2) in cytoplasm or nucleus, lipid-soluble hormones

how do plasma-membrane receptors work once binded to a hormone?

water-soluble hormone binds to PM receptor which activates second messengers, like cyclic AMP, to produce a new protein leading to a change in cellular response

how do intracellular receptors work once binded to a hormone?

lipid-soluble hormones bind to receptor inside the cell > which directly influences DNA transcription in nucleus > new protein to alter cell activity in response to hormone

where is the pituitary gland

under the hypothalamus, sits on the hypophysial fossa of sella turcia bone

these hormones belong to ?

• GH: growth hormone

• ACTH: andreno-cortico-tropic hormone

• TSH: tyroid-stimulating hormone

• FSH: follicle-stimulating hormone

• LH: luteinizing hormone

• PRL: prolactin

• MSH: melanocyte-stimulating hormone

anterior pituitary gland

these hormones belong to ?

• oxytocin

• antidiuretic - ADH (vasopressin)

posterior pituitary gland

Mx for releasing hormones from posterior pituitary gland

nerve impulses from hypothalamus stimulate the release of hormones stored in posterior pituitary gland

-posterior pituitary gland does not make its own hormones; the hypothalamus synthesizes these hormones and stores it in posterior pit. (so when its ready to be used, a nerve impulse is sent)

hypothalamus sends a releasing [or inhibiting] hormone to the “gland?” which then stimulates the release of the hormones from this gland.

Mx for releasing hormones from anterior pituitary gland

• growth hormone-releasing hormone (GHRH) > GH

• throtropin-relasing (TRH) > TSH 

• gonadotropin-releasing (GnRH) > FSH, LH 

• prolactin-releasing > PRL 

• corticotropin-releasing > ACTH, MSH

what is the effect of each anterior pituitary hormones on their target cells?

GH:

• liver & other tissues

• growth of tissues, decrease glucose uptake

TSH:

• thyroid

• synthesis and secretion of thyroid hormones

FSH:

• ovaries & testes

• synthesize estrogen and sperm

LH:

• ovaires & testes

• initiate ovulation and synthesize testosterone

PRL:

• mammary glands

• lactation (milk production)

ACTH:

• adrenal gland (aka supra-renal gland)

• release cortisol

MSH:

• brain

• synthesize melanin, darkening of skin if in excess

describe the hypothalamic-pituitary axis

this HPA axis refers to the feedback loop between the hypothalamus and the pituitary gland

• once hypothalamus is triggered, it will send a releasing hormone to the anterior pituitary gland which then triggers secretion of pituitary hormones

• once the body is regulated, it will signal the hypothalamus to stop sending these releasing hormones AND tell the ant. pit. gland to stop sending their hormones