Ch 5 - The Endocrine System Flashcards Preview

Biology > Ch 5 - The Endocrine System > Flashcards

Flashcards in Ch 5 - The Endocrine System Deck (76)
Loading flashcards...


signaling molecules that are secreted directly into the bloodstream to travel to a distant target tissue


Peptide hormones

made up of amino acids; derived from larger precursor polypeptides that are cleaved into subunits during posttranslational modification which are then sent to Golgi appar to activate hormone and direct it. then released by exocytosis after packaging in vesicles. Effects are usually rapid and short lived; water soluble and usually do not require carriers in the bloodstream


first messenger

peptide hormone itself; binds to the receptor and triggers transmission of a second signal. this is because peptide hormones are charged and cannot pass through the plasma membrane


second messenger

the second signal generated by first messenger binding to a receptor


signaling cascade

connection bt hormone at the surface and the effect brought about by second messengers within the cell



can occur at each step of signaling cascade; increased intensity in signal


Common second messengers

cyclic adenosine monophosphate (cAMP), inositol triphosphate (IP3) and calcium


activation of G protein-coupled receptor

binding of a peptide hormone triggers activation or inhibition of the enzyme adenylate cyclase which raises or lowers levels of cAMP


steroid hormones

from cholesterol and produced mainly by gonads and adrenal cortex; derived from nonpolar molecules and can pass the cell membrane easily - receptors usually in nucleus or cytosol. receptor binding causes conformational changes to hormone-receptor complexes and then the receptor can bind directly to DNA causing increased or decreased transcription of particular genes; effects are slower but longer lived than peptide hormones bc alterations in amount of mRNA and protein present in a cell by direct action on DNA



form of conformational change of steroid hormone-receptor complexes in which two receptor-hormone complexes pair


amino acid-derivative hormones

less common than peptide and steroid hormones but include epi, norepi, triiodothyronine, and thyroxine; derived from one or two amino acids



include epi and norepi - bind to G protein-coupled receptors; secreted by adrenal medulla


direct hormones

classification of hormone by target tissue; secreted and then act directly on a target tissue (ex - insulin from pancreas causes increased uptake of glucose by muscles)


tropic hormones

classification of hormone by target tissue; require an intermediary to act (ex - gonadotropin-releasing hormone GnRH from hypothalamus stimulates release of luteinizing hormone LH and follicle-stimulating hormone FSH. FSH acts on gonads to produce testosterone or estrogen; GnRH and LH cause release of other hormones). These usually originate in the brain and anterior pituitary gland


endocrine glands

hypothalamus, pituitary, thyroid, parathyroid glands, adrenal glands, pancreas, gonads, pineal gland



located in the forebrain, directly above the pituitary gland and below the thalamus; bridge bt the nervous and endocrine system. controls the pituitary through paracrine release of hormones into a portal system that directly connects the two organs.


suprachiasmatic nucleus

part of the hypothalamus that receives a portion of light input from the retinae and controls sleep-wake cycles


negative feedback

occurs when a hormone (or product) later in pathway inhibits hormones or enzymes earlier in the pathway; the release of hormones by the hypothalamus is regulated by this.


hypophyseal portal system

a blood vessel system that directly connects the hypothalamus with the anterior pituitary so that hormones released from the hypothalamus travel directly to the anterior pituitary stimulating release of other hormones



alternative term for pituitary


Gonadotropin-releasing hormone (GnRH) is released by what and causes release of what?

released by hypothalamus, causes a release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in pituitary


Growth hormone-releasing hormone (GHRH) is released where and causes the release of what

released by the hypothalamus and stimulates release of growth hormone (GH) in pituitary


Thyroid-releasing hormone (TRH) is released where and causes the release of what?

released by the hypothalamus and causes a released of thyroid stimulating hormone (TSH) in the pituitary


Corticotropin-releasing factor (CRF) is released by what and causes a release of what?

released by the hypothalamus and causes a release of adrenocorticotropic hormone (ACTH) in the pituitary


Exception to pattern of release and stimulation by hypothalamus to pituitary hormones

prolactin-inhibiting factor (PIF) is dopamine and is released by the hypothalamus and causes a decrease of prolactin secretion which is what stimulates milk production in mammary glands; direct hormone



three-organ systems such as hypothalamic-pituitary-adrenal (HPA) axis and hypothalamic-pituitary-ovarian axis; hormones released by hypothalamus to pituitary and from pituitary to respective target organs


Hypothalamic negative feedback mechanism (HPA)

hypothalamus releases CRF to anterior pituitary which releases ACTH to adrenal cortex which releases cortisol


path of connection from hypothalamus to posterior pituitary

posterior does not receive tropic hormones through the hypophyseal portal system like the anterior but neurons in the hypothalamus send their axons down the pituitary talk directly into the posterior pituitary which can then release oxytocin and antidiuretic hormone



peptide hormone released by posterior pituitary that stimulates uterine contractions during labor as well as milk letdown during lactation and possibly is involved with bonding behavior; positive feedback loop: release promotes uterine contraction which promotes more oxytocin release which continues this cycle - endpoint is delivery


antidiuretic hormone (ADH) or vasopressin

increases reabsorption of water in the collecting ducts of the kidneys; secreted in response to increased plasma osmolarity