Hypothalamic-Pituitary Relationships and Biofeedback Pt. I Flashcards
what is another name for the pituitary gland?
hypophysis
what is another name for the anterior pituitary gland?
adenohypophysis
what is the anterior pituitary made up of?
epithelium
what is the posterior pituitary made up of?
neural tissue
what is the connection between the hypothalamus and the pituitary gland?
the hypophyseal stalk
Due to the anatomical location, tumors in the pituitary expand and put pressure on what?
the optic nerves
the connection between the hypothalamus and the posterior pituitary is what type of signal?
neural signal
what are the two areas in the hypothalamus that house the cell bodies that will extend their axons down to the posterior pituitary?
supraoptic nucleus and the paraventricular nucleus
what do the axons in the supraoptic nucleus and the paraventricular nucleus secrete?
ADH and oxytocin
the connections between the hypothalamus and the anterior pituitary are what type of signal?
both neuronal and hormonal
Hypothalamic neurons produce what type of hormones that target the anterior pituitary?
releasing or release-inhibiting hormones
how do the releasing or release-inhibiting hormones get to the anterior pituitary?
via the hypothalamic-hypophyseal portal blood vessels
what do corticotrophs secrete?
ACTH
what do thyrotrophs secrete?
TSH
what do gonadotrophs secrete?
FSH and LH
what do somatotrophs secrete?
GH
what do lactotrophs secrete?
PRL (prolactin)
What positively targets thyrotrophs in the anterior pituitary?
TRH
what positively targets corticotrophs in the anterior pituitary?
CRF (corticotropin releasing factor)
What positively targets the gonadotrophs in the anterior pituitary?
GnRH
What positively targets the somatotrophs in the anterior pituitary?
GHRH (growth hormone releasing hormone)
What negatively targets the somatotrophs in the anterior pituitary?
somatostatin (GHIH)
what negatively targets the lactotrophs in the anterior pituitary?
PIF (prolactin inhibiting factor) (dopamine)
what positively targets the lactotrophs in the anterior pituitary?
TRH (elevated levels)
primary disorders are classified how?
defects in the peripheral gland (e.g. the thyroid)
secondary disorders are classified how?
they are associated with altered hormone levels due to a defect in the pituitary gland
tertiary disorders are classified how?
they are associated with altered hormone levels due to a defect in the hypothalamus
what is the HPG axis?
hypothalamic-pituitary-gonado axis
what is the hypothalamic hormone that is released in the HPG axis?
GnRH
what could affect the pulsatile release of GnRH from the hypothalamus?
anorexia/starvation, extremem exercise/ very low body fat, or depression
in males what does LH target?
Leydig cells in the testes
in males, what does FSH target?
Sertoli cells in the testes
when LH acts on the leydig cells in the testes what happens?
it stimulates the production of testosterone
when FSH acts on the sertoli cells in the tests what happens?
it stimulates them to be responsive to androgens–> aids in the process of spermatogenesis
what do the sertoli cells produce that act as a negative feedback?
inhibin, which acts on the anterior pituitary to limit FSH production
in females, what does LH target?
theca cells in the ovaries
in females, what does FSH target?
granulosa cells in the ovaries
what happens when LH acts on theca cells in the ovaries?
there will be a production of androgen, which is then converted by granulosa cells to estrogens and progestins
what happens when FSH targets granulosa cells?
synthesis of estrogens–> allows for follicle development during the reproductive cycle
what occurs at the mid-cycle of a female?
a positve feedback pathway
what is the purpose of the positive feedback pathway?
it allows the oocyte to mature- produces an LH surge right around the time of ovulation
what is acromegaly?
the overgrowth of soft tissues, cartilages, and bone in the face, hands, and feet
what causes acromegaly?
excessive growth hormone
what could excessive growth hormone also cause besides acromegaly?
increase in blood glucose and hyperinsulemia
what are the direct targets of growth hormone (somatotropin) released by the anterior pituitary?
bone and liver
how will the bone and liver cells that respond to growth hormone (somatotropin) respond? (mechanism)
tyrosine-kinase associated pathway called JAK STAT pathway
what happens when the JAK STAT pathway is activated?
there will be a production and secretion of a protein known as insulin-like growth factor 1
what affect does IGF-1 have?
negative feedback on the anterior pituitary and hypothalamus; growth stimulating effects on tissues including bone, muscle, and adipose tissue
when is GH secretion the highest?
during sleep and it peaks with exercise
what causes stimulation of GH?
fasting/hunger/starvation, hypoglycemia, puberty, exercise, sleep, stress
excess growth hormone before the closure of the bone epiphyses due to IGF-1 stimulated long bone growth causes what?
gigantism
excess growth hormone after closure of bone epiphyses due to promotion of growth of deep organs and cartilaginous tissue causes what?
acromegaly
increased GH has a negative feedback where?
to the hypothalamus that causes decreased GHRH
increased levels of IGF-1 has a feedback loop where?
negative feedback loop to the anterior pituitary (so less GH secretion). but a positive feedback loop to the hypothalamus that causes an increase in GHIH from the hypothalamus
an increase in the amount of GH levels would cause suspicion of what?
primary endocrine disorder/ growth hormone insensitivity
if GH and IGF-1 were absent what type of disorder would it be?
secondary deficiency
if GHRH, GH, and IGF-1 were all missing, what type of disorder would it be?
tertiary deficiency
what happens if you have a high carb diet but a low protein diet?
GH is inhibited and the liver will not produce IGF-1 (weight gain)
what happens if you have a decreased carb diet and an increased protein diet?
increased GH levels and increased IGF-1 (ketogenic metabolism)
what is the main regulation of prolactin?
through inhibition using dopamine
what does increased levels of prolactin cause?
a negative feedback on GnRH from the hypothalamus
