Exam 2: Endocrine Pt.1 Flashcards
the endocrine system works with the nervous system to…
regulate homeostasis
handle stressors
both the nervous system and endocrine system
release chemical signals and hormones to affect target cells
difference between signals released in nervous system and endocrine system
nervous system: releases signal in close proximity to its target simply crossing a synapse
endocrine system: signals released into bloodstream and can affect multiple targets, some distant to the gland
responses in nervous system vs endocrine system
nervous system: quick and reversible
endocrine system: slower, not reversible at times
how are hormones classified
chemical structure (AA derivatives, peptides, lipids) mechanisms (2nd messengers, direct)
derivatives of tyrosine and tryptophan
AA derivatives
ranges from small peptide to large glycoproteins
most are produced as inactive prohormones
peptide derivative
consists of both steroids and eicosanoids
lipid derivatives
hormones bind membrane bound receptors
ex: peptide, tryptophan derivatives, eicosanoids
second messengers
hormones bind intracellular receptors, receptor/hormone complex acts as transcription factor
ex: tyrosine derivatives and steroids
direct mechanism
what is the hypophysis (pituitary gland) controlled by
hypothalamus
where is the hypophysis located
under the hypothalamus
sits in the sella turcica of the ethmoid bone
infundibular stalk
connects hypothalamus to the pituitary
2 types of development of the hypophysis
adenohypophysis (anterior pituitary)
neurohypophysis (posterior pituitary)
part of pituitary made of glandular epithelium that receives releasing hormones and inhibiting hormones from the hypothalamus to direct secretion
anterior pituitary (adenohypophysis)
parts of the adenohypophysis
pars distalis
pars tuberalis
pars intermedia
pars diatalis
largest part
produces all anterior hormones in adults
pars tuberalis
surrounds infundibulum
pars intermedia
area immediately anterior to the neurohypophysis
normally not active in adults
composed of neuron extensions from cell bodes in the hypothalamus
stores and releass hormones produced in hypothalamus
posterior pituitary
neurohypophysis
2 capillary beds connected by veins
portal system
where is the hypophyseal portal system found
adenohypophysis
RH and IH are released by ____ into a capillary network supplied by the _____
hypothalamus
superior hypophyseal artery
what delivers the signals to the capillary bed in the adenohypophysis
hypophyseal portal veins
hormone leave the hypophysis through the
hypophyseal veins
what is the neurohypophysis supplied by
inferior hypophyseal artery
- it does NOT use a portal system
hormones from the adenohypophysis are…
tropic hormones - release regulated by hypothalamus
tropic hormones
necessary for the function, stimulation, and metabolic support of other endocrine glands or organs
regulation of thyroid stimulating hormone (TSH)
negative feedback loop based on circulating thyroid hormone levels
what do low thyroid hormone levels result in
TSH RH from the hypothalamus
action of thyroid stimulating hormone
upregulates iodide pumps in thyroid membrane
stimulates hormone production
protects thyroid cells from apoptosis
what are variations in TSH efficacy linked to?
modifications in carbohydrate moiety of glycoprotein
- dec in carb inc binding but dec efficacy
regulation of adrenocorticotropic hormone (ACTH)
negative feedback loop based on circulating glucocorticoids (cortisol)
low hormone level results in CRH
action of ACTH
upregulates cholesterol by increasing LDL receptors in the adrenal cortex
stimulates hormone production
stimulates initial hydrolysis of pregnenolone
aids in general cortical maintenance
what is ACTH produced from and wat about the waste products?
produced through POMC
can get MSH as a product
high levels of breakdown products can target melanocytes in skin
if abnormally high ACTH…
high MSH like products - get darkening of skin and mucous membranes
regulation of growth hormone
varied, released in response to developmental signals
fluctuates with circadian rhythms
stimulated by ghrelin
inhibited by negative feedback of IGF-1
GHRH inc transcription and secretion
GHIH: inhibits release, no effect on production
action of growth hormone on liver
diabetogenic effect
stimulates glucogenolysis
stimulates production and release of IGF-1 which targets muscle, bone, cartilage to increase AA uptake and growth
action of growth hormone on adipose
stimulates lipolysis
glucose sparing effect - use fats for energy to save glucose for those that can only use glucose
2 gonadotropins and function
FSH, LH
regulate reproductive activity
regulation of gonadotropin (FSH)
negative feedback loop
low levels of circulating sex hormones stimulates GnRH from hypothalamus
GnRH is inhibited by inhibin
action of gonadotropin FSH
depends on sex
females: promotes follicle development and production of estradiols
male: stimulates sertoli cells and promotes sperm maturation
what is production of FSH like in females vs males
females it is cyclical while in males it is relatively constant
regulation of gonadotropin LH females
combined negative feedback of progesterone levels and high levels of estrogen
regulation of gonadotropin LH in males
negative feedback loop of testosterone levels
action of gonadotropin LH females
triggers ovulation
increases estrogen and progesterone secretion
action of gonadotropin LH males
promotes testosterone production in interstitial cells of Leydig
what do the interstitial cells of Leydig secrete
testosterone
regulation of prolactin
varied, involves developmental signals
unlike other pituitary hormones PRL is secreted unless inhibited - secretion is blocked by dopamine
what can stimulate PRL release
high estrogen levels and the reflex arc involved in nursing
action of prolactin both sexes
stimulate thymus activity and immune response
action of prolactin females vs males
females: stimulates mammary development and lactation
males: increases LH sensitivity in Leydig cells
what cells in the body can produce PRL (prolactin)
pituitary and many others!!
regulation of MSH - Pars intermedia
developmental signals in fetus and newborns
action of MSH
stimulates pigment production in skin
is MSH active in adults?
NO
MSH produced in response to UV radiation
what is MSH produced by
placenta
can cause characteristic pigment changes in pregnant woman
- linea nigra on abdomen
-increased pigment in areola
- melasma (darker blotchy patches on face)
the neurohypophysis contains extensions of?
supraoptic and paraventricular nuclei of the hypothalamus
what do the supraoptic nuclei secrete?
antidiuretic hormone
what do the paraventricular nuclei secrete?
oxytocin
- responds to stretch receptors
regulation of antidiuretic hormone
reflex arc stimulated by osmoreceptors for solute concentration and baroreceptors for blood volume
action of antidiuretic hormone
V1: vasoconstriction
V2: inc aquaporins/water permeability in kidney collecting tubules
the releas of what hormone is inhibited by alcohol
ADH - antidiuretic hormone
regulation of oxytocin
reflex arc stimulated by stretch receptors in smooth muscle
action of oxytocin in both sexes
targets receptors in brain that promote pair bonding/maternal behavior
action of oxytocin in females
stimulates smooth muscle contractions in uterus during labor
in mammary ducts during nursing
in uterus and vagina in sexual intercourse
action of oxytocin in males
stimulates smooth muscle contractions in ductus deferens and prostate during ejaculation
