Endocrine System Flashcards
What is paracrine communication?
the use of chemical messengers (paracrine factors) to transfer information from cell to cell within a single tissue
What is a hormone?
chemical messengers that are released in one tissue and transported in the bloodstream to reach specific cells in other tissues (target cells)
What is endocrine communication?
The use of hormones to coordinate cellular activities in tissues in distant portions of the body
What is in the endocrine system?
includes all the endocrine cells and tissues of the body which release hormones
What are endocrine glands?
- are ductless glands
- many are made of glandular epithelium whose cells manufacture and secrete hormones
- a few are made of neurosecretory tissue
Where are endocrine glands?
widely scattered throughout the body
Where are some of the locations of endocrine glands?
hypothalamus, pineal gland, heart, kidney, digestive tract, pancreatic islets, gonads, adrenal glands, thymus, thyroid gland
What are the three groups of hormones?
- amino acid derivatives
- peptide hormones
- lipid derivatives
Describe amino acid derivatives (amine)
- small molecules structurally related to amino acids
- synthesized from the amino acids tyrosine and tryptophan
What the tyrosine derivatives?
thyroid hormones, catecholamines, epinephrine (E), norepinephrine (NE), dopamine
What is the tryptophan derivative?
melatonin, serotonin
Describe peptide/protein hormones
- chains of amino acids
- all hormones secreted by hypothalamus, heart, thymus, digestive tract, pancrease and some by pituitary gland
What are the two types of peptide/protein hormones?
glycoproteins: > 200aa and short polypeptides <200 aa
What are the three main glycoproteins?
- thyroid-stimulating hormone (TSH)
- luteinizing hormones (LH)
- follicle-stimulating hormone (FSH)
What are the two classes of lipid derivatives?
eicosanoids and steroid hormones
What are the characteristics of eicosanoids?
- derived from arachidonic acid
- include prostaglandins
What are the characteristics of steroid hormones?
- derived from cholesterol
- released by: reproductive organs (androgens by testes, estrogens, and progestins by ovaries), adrenal glands (corticosteroids), kidneys (calcitriol)
How are hormones distributed and transported?
within the blood, hormones may circulate freely or bound to transport proteins. The bloodstream contains substantial reserve of bound hormones. There is an equilibrium, free <–> bound
How do steroid and thyroid hormones react with water?
they are hydrophobic
How long are fre hormones active for?
< 1 hr, theu diffuse out of bloodstream and bind to receptors in raget tissues. enzymes?
Which hormone transport protein is not selective?
albumin
Which transport hormones are selective?
- sex hormone binding globulin (SHBG)
- corticosteroid binding globulin (CBG)
- thyroid binding globulin (TBG) and transthyretin (TTR)
What do the disrupting compounds do?
prevent hormones from reaching its target cels
What determines hormonal sensitivity?
the presence or absence of specific receptors for target cells, there is a lock and key mechanism
What are the actions of hormones on target cells?
- receptor activation
- conversion
- response of the cell
What do some of the response of the cells include?
- synthesis
- transport
- secretion
- contraction
- breakdown
What is synergism and who is involved?
epinephrine and norepinephrine. Hormones act in concert
What is permissiveness and who is involved?
estrogen and progesterone. Estrogen stimulates initial thickening of endometrium, progesterone further increases thickness. Without estrogen, progesterone’s effect would not be as effective
What is antagonism and who is involved?
insulin and glucagon? Insulin decreases blood glucose levels, glucagon increases it
Where are the hormone receptors for catecholamines and peptide hormones?
- are water soluble (hydrophilic)
- unable to penetrate cell membrane
- receptors in cell surface membrane
What are eicosanoids and steroid hormones?
are lipid soluble (hydrophobic)
Where are thyroid hormones receptors?
enter cell by diffusion or transport proteins and receptors are in organelles, hydrophobic
What are the mechanisms of membrane receptors?
- binds to receptors
- G-protein activation (2nd messenger)
- amplification
- cAMP, cGMP, calcium ions
What are the mechanisms of intracellular receptors?
- steroid and thyroid
- binds to cytoplasm or nucleus (DNA)
- metabolic activity
How are endocrine organs controlled?
hormonal regulation (hypothalamus, pituitary gland), neural regulation, humoral regulation, negative feedback
Describe the control the hypothalamus has in hormone secretion
- the highest level of endocrine control
- controls more-complex endocrine reflexes
- integrates activities in three ways
What are the three characterstics of the hypothalamus?
- secrete regulatory hormones (control endocrine cells in pituitary gland which in turn controls activities of other endocrine organs)
- acts as an endocrine organ (release of ADH and oxytocin)
- conrains autonomic centers (exert direct enural control over endocrine cells of adrenal medullae)
What is the structure of the pituitary gland (hypophysis)?
small, oval gland located on the ventral surface of the brain, under the hypothalamus.
What does the infundibulum do?
connects pituitary to the hypothalamus
What are the two seperate glands of the pituitary glands?
anterior pituitary glands (adenohypophysis) and the posterior pituitary gland (neurohypophysis)
What are the 7 hormones of the anterior pituitary?
- thyroid stimulating hormone (TSH)
- adrenocorticotropic hormone (ACTH)
- gonadotropin
- luteinizing hormone (LH)
- prolactin (PRL)
- growth hormone (GH)
- melanocyte-stimulating hormone (MSH)
What does thyroid stimulating hormone (TSH) do?
also called thyrotropin, triggers the release of thyroid hormones
What does adrenocorticotropic hormone (ACTH) do?
stimulates release of glucocorticoids by adrenal cortex