Endocrine System Flashcards
What are the major differences between the endocrine and nervous system?
the endocrine system;
- transmits ligands
- exhibits longer reaction times
- has longer lasting effects
What are the types of circulating hormones?
- steroids
- biogenic amines
- proteins
What are local hormones?
signaling molecules that don’t circulate in blood
what are Eicosanoids?
a type of local hormone formed from fatty acids within phospholipid bilayer of membrane
What are the effects of eicosanoids?
- autocrine stimulation: effects on the same cell where messenger was formed
- paracrine stimulation:
effects on neighboring cells
What are the advantages of lipid soluble hormones using carrier molecules?
- do not dissolve readily in blood
- carriers are water soluble proteins made by liver
- carriers protect hormones from early destruction
True or false, only lipid soluble hormones use carrier molecules
false, some water soluble hormones use carrier proteins to prolong their life
What two factors determine the concentration of a hormone?
how fast it is synthesized and eliminated
How does hormone elimination occur?
occurs in multiple ways:
- enzymatic degradation in liver cells
- removal from blood via kidney excretion or target cell uptake
What is a hormone’s half life?
time necessary to reduce a hormone’s concentration to half of its original level
How does the half life of water soluble hormones compare to that of steroid hormones?
- water soluble hormones generally have a short half life
- steroid hormones generally have a long half life
What allows for lipid soluble hormones to diffuse across target cell membrane
they are small, nonpolar, and lipophillic
what happens once a lipid soluble hormone enters its target cell
- binds to receptor and forms hormone-receptor complex
- complex binds to a hormone response element of DNA
Why can’t water soluble hormones diffuse through membrane?
they are polar
where are water soluble hormone receptors
on cell membrane
Describe the signal transduction pathway of a water soluble hormone
- hormone is first messenger and binds to receptor
- binding actives a G protein
- G protein activation causes activation of a membrane enzyme
- activated enzyme catalyzes the formation of a second messenger
What are the actions of water soluble hormones?
- enzymes can be activated or inhibited
- growth can be stimulated
- cellular secretions can be released
- membrane permeability can be changed
- muscles can be contracted or relaxed
what are the advantages of a signal transduction pathway?
- signal is amplified at each enzymatic step
- there are many places to regulate pathway activities
What determines the target cells response to a particular hormone?
- number of hormone receptors
- interactions among other hormone actions
What structure is the pituitary gland attached to and how so?
connected to hypothalamus by infundibulum
How do the size and tissue of each part of the pituitary compare?
- posterior pituitary is smaller, neural part
- anterior pituitary is large, glandular part
What are the components of the posterior pituitary?
composed of pars nervosa(lobe) and infundibulum
What are the three sections of the anterior pituitary?
- pars distalis: large anterior rounded portion
- pars tuberalis: thin wrapping around infundibulum
- pars intermedia: scant region between other two
the posterior pituitary is the storage and release site for which hormones?
oxytocin and antidiuretic hormone (both are made in hypothalamus)
What is the relationship between the hypothalamus and the anterior pituitary?
the hypothalamus stimulates anterior pituitary to release its hormones by secreting regulatory hormones
what are the two types of regulatory proteins secreted by the hypothalamus
- releasing hormones: increase secretion of anterior p hormones
- inhibiting hormones: decrease secretion of anterior p hormones
What are the hormones released by the anterior pituitary gland?
- thyroid stimulating hormone (TSH)
- prolactin
- adrenocorticotropic hormone (ACTH)
- follicle-stimulating hormone and leutenizing hormone (FSH and LH)
- growth hormone (GH)
What are the functions of growth hormone?
- stimulation of linear growth at epiphyseal plate
- hypertrophy of muscle
- release of nutrients from storage into blood
what hormone stimulates the releases of GH?
growth hormone releasing hormone (GHRH)
What cells does GH target?
hepatocytes which release insulin like growth factors (IGFs)
What cells have GH receptor cells
all body cells have receptors for GH, IGF, or both
How do GH and IGFs work?
cause adipose cells to release nutrients
- increases levels of glycerol and fatty acids in blood
What is the thyroid gland composed of?
composed of microscopic follicles
- follicular and parafollicular cells
What hormones do follicular cells produce?
thyroid hormone
what hormone do parafollicular cells produce
calcitonin
What is the difference between T3 and T4?
- thyroid gland produces more T4 but T3 is more active form
- most target cells convert T4 to T3
What does thyroid hormone do?
increases metabolic rate and protein synthesis in targets, also fosters energy production
describe the negative feedback loop for TH
- Increases in TH cause decreases in its release
o TH inhibits release of TRH from hypothalamus
o TH inhibits release of TSH from anterior pituitary
o TH causes release of growth hormone inhibiting hormone further inhibiting TSH release
describe the anatomy of the adrenal medulla
- forms inner core of each adrenal gland
- red-brown color due to extensive blood vessels
- releases epinephrine and norepinephrine with sympathetic stimulation
describe the anatomy of the adrenal cortex
- synthesizes over 25 corticosteroids
- yellow color due to lipids within cells
- 3 regions producing different steroid hormones
From superficial to deep, list the three regions of the adrenal cortex
- zona glomerulosa
- zona fasciculata
- zone reticularis
What are the hormones of the adrenal cortex
- mineralocorticoids: hormones that regulate electrolyte levels
- glucocorticoids: hormones that regulate blood sugar
- gonadocorticoids: sex hormones
What is the function of cortisol
increase nutrient levels in blood
what regulates the release of cortisol?
the hypothalamic-pituitary-adrenal axis
Describe the process of how cortisol is released
- stress, late stages of sleep, low cortisol levels stimulate hypothalamus to release CRH
- CRH stimulates ant. pituitary to release ACTH ACTH stimulates adrenal cortex to release cortisol
- cortisol travels through blood attached to carrier proteins
- cortisol diffuses through target cell’s membrane & binds to intracellular receptor
- cortisol causes target cell to increase blood nutrient levels
what is corticosterone used a treatment for?
inflammation
how does corticosterone treat inflammation?
it inhibits inflammatory agents and supresses immune system
What causes Cushing syndrome?
excessive glucocorticoid
what causes Addison disease?
form of adrenal insuffiency when adrenal glands fail
What are the three stages of a stress response?
- alarm reaction
- stage of resistance
- stage of exhaustion
What endocrine organ also has exocrine functions
the pancreas
What is the function of acini cells in the pancreas?
generate exocrine secretions for digestion
What are pancreatic islets?
clusters of endocrine cells in pancreas
what do alpha cells secrete?
glucagon
what do beta cells secrete?
insulin
What is the main function of the pancreatic hormones?
help maintain blood glucose
What is the function of insulin
lowers blood glucose
How does insulin lower blood glucose?
- hepatocytes remove glucose from blood; store it as glycogen
- adipose cell decrease fatty acid levels in blood
- most body cells increase nutrient uptake in response to insulin
What causes type 1 diabetes?
absent or diminished release of insulin by pancreas; requires daily insulin injections
What causes type 2 diabetes?
decreased insulin release or insulin effectiveness usually due to obesity
What is the effect of glucagon?
raises blood glucose
How does glucagon raise blood glucose?
acts through membrane receptors and 2nd messenger causing body cells to release stored nutrients into blood
What hormone does the pineal gland secrete?
melatonin
What does the parathyroid gland do?
helps regulate blood calcium
