Chapter 16 Endocrine System Flashcards
hormone
steroidal or amino acid-based molecules released to the blood that act as chemical messengers to regulate specific body functions
target cell
tissue cells that have a specific receptor for a hormone
endocrine cell
ductless glands that secrete their hormones into the surrounding tissues
endocrine system
body system that includes internal organs that secrete hormones
neuroendocrine cells
have a neural function and release hormones (hypothalamus)
norepinephrine
A catecholamine neurotransmitter and adrenal medullary hormone, associated with sympathetic nervous system activation
exocrine gland
glands that have ducts through which their secretions are carried to a particular site
amino acid based hormone
most hormones are composed of amino acids; hydrophilic
steroids
synthesized from cholesterol (only gonadal and adrenocortical); hydrophobic
eicosnaoids
leukotrienes: inflammation and allergic reactions
prostaglandins: multiple targets and effects (blood pressure, contractions, pain, etc.)
hydrophilic hormones
all amino acid-based hormones (except thyroid); do not need a carrier protein and act on receptor in the plasma membrane
transport protein
required by steroids and thyroid hormone to move through the blood
free (unbound) hormone
does not have a transport protein; can leave capillary to reach target cell
bound hormone
hormone attached to a transport protein
secondary messenger system
A system of plasma membrane receptors for hormone action (Cyclic AMP & PIP2-Calcium signaling mechanisms)
cyclic AMP signaling mechanism
- Hormone binds receptor
- Receptor activates G protein
- G protein activates adenylate cyclase
- Adenylate cyclase converts ATP to cyclic AMP
- Cyclic AMP activates protein kinases
cAMP
Cyclic AMP; activates protein kinases during cAMP mechanisms
hormone receptor
Acts as the first messenger; hormone causes receptor to change shape
G protein
Activated by receptor; activates an enzyme (such as adenylate cyclase)
effector enzymes
Activated by a G protein; may be stimulated or inhibited depending on the enzyme
amplification effect
when one hormone molecule leads to millions of final product molecules
phosphodiesterase
Intracellular enzyme that degrades cAMP
PIP2-calcium signaling mechanism
- Receptor activates G protein
- G protein activates phospholipase C
- Phospholipase C splits PIP2 into 2 second messengers: diacylglycerol (DAG) and inosital triphosphate (IP3)
- DAG activates protein kinase enzyme; IP3 releases Ca2+
- Ca2+ takes on second-messenger role
phospholipase C
splits a plasma membrane phospholipid called PIP2 into 2 second messengers: diacylglycerol (DAG) & inositol triphosphate (IP3)
cGMP
acts as a second messenger for selected hormones
up-regulation
when low levels of a hormone cause its target cells to form additional receptors
down-regulation
when prolonged exposure to high hormone levels causes a decrease in the number of receptors
affinity of hormone
the strength of the bond between the hormone and receptor
permissiveness
when one hormone cannot exert its full effects without the presence of another hormone
synergism
when more than one hormone produces the same affect at the target cell and their combined effects are amplified
antagonism
when one hormone opposes the effects of another hormone
negative feedback system
when release of a hormone inhibits the production of itself
humoral stimuli
when a change in blood levels of certain critical ions and nutrients stimulates hormone release
neural stimuli
when nerve fibers stimulate hormone release
hormonal stimuli
when hormones produced by other endocrine glands simulate the release of other hormones
hypothalamus
controls the release of hormones from the pituitary gland; connected by infundibulum
pituitary gland
seated in the sella turcica of the sphenoid bone; contains two lobes, the anterior pituitary and the posterior pituitary
hypophysis
another name for the pituitary gland; means “to grow under”
adenohypophysis
another name for the anterior pituitary; secretes growth hormone (GH), thyroid-stimulating hormone (TSH), adrenocorticotrophic hormone (ACTH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL)
hypophyseal portal system
An unusual arrangement of blood vessels that carries releasing and inhibiting hormones to the anterior pituitary to regulate hormone secretion
neurohypophysis
another name for the posterior pituitary plus the infundibulum; hormone storage area that secretes neurohormones (oxytocin and ADH) made by the hypothalamus
gonadotropins
hormones that regulate the function of the gonads; FSH and LH
FSH
stimulates production of gametes (sperm and eggs)
LH
promotes production of gonadal hormones
TSH
stimulates normal development and secretory activity of the thyroid gland
ACTH
stimulates the adrenal cortex to release corticosteroid hormones
PRL
stimulates milk production by the breasts
GH
an anabolic (tissue building) hormone that has both metabolic and growth-promoting actions
hypopituitarism
-pituitary dwarfism
hyperpituitarism
- gigantism
- acromegaly
thyroid follicles
make up the thyroid gland; follicular cells produce thyroglobulin
colloid
an amber colored, sticky material in the central cavity of the follicle consisting of thyroglobulin molecules with attached iodine atoms
parafollicular cells
a population of endocrine glands in the thyroid that produce calcitonin
thyroid hormones
composed of two iodine containing amine hormones, thyroxine (T4) and triiodothyronine (T3)
parathyroid gland
located in the posterior aspect of the thyroid gland
chief cells
cells of the parathyroid gland that produce parathyroid hormone (PTH)
oxyphil cells
make up the parathyroid gland
PTH
controls calcium balance in the blood
corticosteroids
steroid hormones produced by the adrenal cortex
mineralocorticoids
produced by the zona glomerulosa layer of the adrenal cortex; regulate electrolyte levels of the extracellular fluid
gluocorticoids
produced by the zona fasciculata; influence the energy metabolism of most body cells and help us resist stressors
sex steroids
(gonadocorticoids) produced by the zona reticularis; secretes weak androgens, or male sex hormones
Cushing syndrome
Caused by hypersecretion of ACTH;
Pheochromocytoma
Caused by hypersecretion of catecholamines
adrenogenital syndrome
Caused by hypersecretion of gonadocorticoids
Addison disease
Major hyposecretory disorder of the adrenal cortex
chromaffin cells
Modified ganglionic neurons that produce catecholamines
catecholamines
epinephrine and norepinephrine; reinforce and prolong the fight-or-flight response
gonads
ovaries and testes; produce steroid sex hormones
estrogen
maturation of reproductive organs and promotes secondary sexual characteristics at puberty
progesterone
works with estrogen for breast development and uterine cycle
testes
male gonads that produce testosterone
testosterone
maturation and maintenance of male reproductive organs; responsible for sex drive and normal sperm production
