Flashcards in Physiology of the Pituitary Gland Deck (122):
Where is the supraoptic nucleus located? What is its function?
Anterolaterally above the optic tract
Secretes ADH and Oxytocin
Where is the paraventricular nucleus located? What is its function?
Dorsal anterior periventricular area
Regulates appetite and SNS, and
What is the role of the magnocellular PVN?
Secretes ADH and oxytocin
Where is the suprachiasmatic nucleus located? What is its function?
Above the optic chiasm, anteroventral periventricular zone
What part of the brain secretes ADH? Function?
Supraoptic nucleus and PVN
What part of the brain secretes TRH? Function?
regulates thyroid function
What part of the brain secretes CRH? Function?
Regulates adrenocortical function
Besides secreting various hormones, what does the paraventricular nucleus play a role in?
regulates the SNS and appetite
What part of the brain secretes VIP? Function?
What part of the brain secretes GHRH? Function?
Arcuate nucleus and ventromedial nucleus
Stimulates growth hormone
What part of the brain secretes GnRH? Function?
Regulation of pituitary gonadotropins
What is the function of dopamine secretion in the arcuate nucleus?
Functions as PIH
What part of the brain secretes SRIF? Function?
Periventricular and arcuate nuclei
Inhibits GHRH release
What is the "satiety" center of the brain?
Where is the arcuate nucleus located? What is its function (4)?
medial basal hypothalamus; close to the third ventricle
Where is the periventricular nucleus located? What is its function?
Secretes SRIF which inhibits the secretion of growth hormone
What is the function of the ventromedial nucleus of the hypothalamus?
Functions as a satiety center, and secretes:
What is the function of the dorsomedial nucleus of the hypothalamus?
focal point of information processing
-receives input from the VMN and lateral hypothalamus and projects to the PVN
What part of the hypothalamus functions as a hunger center? satiety center?
hunger = lateral hypothalamus
Satiety = Ventromedial
What is the function of the lateral hypothalamus?
What is the function of the preoptic area?
What part of the hypothalamus is the "cooling center"?
What part of the hypothalamus serves as the thirst regulator?
What are the two functions of the anterior hypothalamus?
thermoregulation and thirst regulation
What part of the hypothalamus serves as the regulator of the circadian rhythm?
What is the"heating center" of the brain?
What is the function of the posterior hypothalamus?
What are the four major ways in which cells communicate with one another?
Specificity of gap junctions depends on what? Synapses? Paracrine? Endocrine?
-Gap junctions = anatomic location
-Synaptic = anatomic location and receptors
-Paracrine = receptors
-Endocrine = receptors
What is intracrine signalling?
When cells make signals that do not exit the cell
What determines the specificity of hormones, generally?
Water soluble hormones act where? Lipid soluble?
Water soluble = cell membrane
Lipid soluble = intracellularly
GTP is bound to which protein subunit in the G-protein coupled receptor? What happens to this, as compared to the others?
Moves to activate adenylyl cyclase, whereas the gamma and beta subunit stay put
What are the three types of feedback loops that can occur with the endocrine system?
Where is the hypothalamus located in the brain?
Floor and lateral walls of the third ventricle
Suprachiasmatic nucleus receives fibers from what part of the brain to regulate body rhythms?
What, generally, describes the ultrashort feedback loop in the HPA axis? Short? Long?
Ultrashort = Hypothalamus acting on itself
Short = anterior pituitary feedback onto the hypothalamus
Long = target organ feeding back on the hypothalamus
The area of the hypothalamus where the portal vessels arise is what?
The median eminence
What are the two nuclei of the hypothalamus that send their axons down into the posterior pituitary?
What are the specialized glial cells found in the posterior pituitary?
The posterior pituitary is connected to hypothalamus via what tract?
What is SRIF?
Somatotropin release-inhibiting factor
What is PIH?
Prolactin inhibiting hormone
What is the hypothalamic nucleus that controls the circadian rhythm? What are the two places this receives input from?
-Lateral geniculate nucleus
The anterior pituitary secretes 6 hormones. 4 of them a tropic hormones. What are these?
What are tropic hormones?
Hormones that have effects on the morphology and secretory activity of other endocrine glands
What subunit of the tropic hormones determines its specificity? Which subunit do they have in common?
-Beta determines specificity
-Alpha they all have in common
Adrenocorticotropic hormone is made where?
The corticotroph cells in the anterior pituitary
Corticotrophs first synthesize a large precursor protein known as what? What does this turn into?
Hydrolyzed to ACTH and beta-lipotropin
ACTH is released in what sort of pattern? What does this translate to with cortisol release?
Means that cortisol is released in a pulsatile fashion
What is the function of ACTH?
Stimulates the synthesis of Cortisol, androgens, and aldosterone
What is the function of effect of ACTH on melanocytes?
Binds to melanotropin-1 receptors to accelerate melanin synthesis
Do androgens feedback on ACTH synthesis?
How can primary adrenal insufficiency cause hyperpigmentation?
The anterior pituitary makes too much ACTH since feedback inhibition does not occur
What releasing factor from the hypothalamus causes the release of ACTH?
CRH (corticotropin releasing hormone)
What is the function of thyrotropin (TSH)?
Simulates the thyroid to produce T4 and T3
Why can Iodine deficiency cause the growth of a goiter?
TSH will be upregulated when it does not sense T3 or T4, which are not produced if there is insufficient Iodine
What is the releasing factors for TSH? What else does this stimulate the release of?
Thyroid releasing hormone
What causes the release of FSH?
What is the function of FSH in females? Males?
Females = Growth of ovaries
Males = Sperm maturation
What causes the release of LH?
What is the function of LH in males and females?
Males = stimulation of testosterone synthesis
Females = Stimulation of ovulation, formation of corpus luteum
What are the cells that make GH? What is/are the releasing factor(s)?
GHRH increases release, somatostatin inhibits
What is the other name for growth hormone inhibiting hormone?
What are the other names for Growth hormone?
Somatotropic hormone or Somatotropin
What are the two forms of growth hormone that are released?
nGH and a splice variant that lacks several amino acids
What is the effect of Ghrelin?
a GH secretagogue from the stomach and other places that acts on a difference receptor than GHRH, to stimulate GH secretion
What is the basic function of GH?
Stimulates protein synthesis and overall growth of most cells and tissues
Stimulates production of IGF
How is GH secreted?
When is GH secretion highest?
Highest = night during deep sleep
Higher in adolescence
What cells produce prolactin?
What is Sheehan syndrome?
postpartum hypopituitarism that results from ischemic necrosis of the pituitary
True or false: Nipple stimulation in nonpregnant women also increases PRL.
How is prolactin regulated?
• Release is predominantly under tonic inhibition by the hypothalamic hormone, prolactin-inhibiting hormone (PIH). PIH is the catecholamine dopamine.
What is the effect of TSH on prolactin?
Induces its release
Which has a stronger effect: the inhibition of prolactin secretion by dopamine (PIH), or increased release of prolactin by TSH
Inhibition by dopamine
What happens to prolactin levels if damage occurs to the portal blood circulation which dopamine and TRH use to travel to the anterior pituitary?
increased prolactin levels
• If dopamine reaching anterior pituitary decreases then prolactin release (increases/decreases)
Is prolactin related to sleep? Circadian rhythm?
Increased release 60 minutes after sleeping, but is not related to the circadian rhythm
What is the effect of prolactin on • If dopamine reaching anterior pituitary decreases then prolactin release increases in females? Male spermatogenesis?
What is the most predominant cell type of the anterior pituitary gland?
What are the two breakdown products of POMC?
ACTH and beta-LPH
What is aldosterone regulated by?
Angiotensin II and [K]
What are the short and long feedback mechanisms for cortisol?
ACTH feedback on hypothalamus = short
Cortisol feedback on hypothalamus = long
true or false: the cholesterol based hormones do not really feedback onto the corticotropin releasing pathway
What is the active hormone: T3 or T4? Which is released in larger amounts?
T3 is active, T4 released in larger amounts
What is T3 and T4 bound to in the serum?
Thyroid binding globulin
Thyroxin = (T3 or T4)?
What happens in the ovarian cycle just prior to the FSH/LH spike?
Spike in estradiol
Where does GH go to? What does this cause?
Liver to cause the release of somatomedins (IGFs)
Can IGF feedback to the pituitary?
What are the effects of growth hormone on adipose tissue?
Decreased glucose uptake
What are the effects of GH on muscle cells?
Increased protein synthesis
Decreased glucose uptake
What is the effect of IGF-1 on somatostatin neurons?
Increases somatostatin release
What happens to GH release with aging in adults?
What is the general effect of prolactin?
Increased breast tissue differentiation to produce milk
Where in the hypothalamus are vasopressin and oxytocin synthesized?
Magnocellular neurons in the supraoptic and paraventricular nuclei of the hypothalamus
Where does the processing of the prepro-hormones of ADH and oxytocin take place?
Hormone processing occurs as the neurosecretory vesicles are transported down the hypothalamic-hypophysial tract.
Where are ADH and oxytocin stored?
At the end of the neuronal neurons (Herring bodies)
What is the cause of neurogenic diabetes insipidus?
Some lesion in the hypothalamus, pituitary, or the connection between
What is the cause of nephrogenic diabetes insipidus?
Mutation that affects the production and insertion of the aquaporins
What is psychogenic diabetes insipidus?
Increased intake of water causes polyuria
What is SIADH?
Producing concentrated urine when not needed or wanted
Is the hyponatremia in SIADH true or pseudohyponatremia? Why or why note?
This is not pseudohyponatremia since plasma sodium concentration is low and plasma osmolarity is also low.
What is the main stimulus for the secretion of ADH?
Increased osmotic pressure
Where does Li act to cause diabetes insipidus (kidney or the brain)?
The release of oxytocin is stimulated when?
During breastfeeding and childbirth.
What causes the milk-let down reflex?
Afferent signals from the nipples of the mother’s breast when an infant suckles result in the release of oxytocin which then causes the milk let-down reflex
What role does oxytocin play in the birthing process?
By term of pregnancy the mother’s uterus has experienced an up- regulation in the number of oxytocin receptors. Distension of the cervix and contraction of the uterus stimulate the release of oxytocin which results in positive feedback and the release of more oxytocin which further increases the contractility of the uterus. This aids in the delivery of the baby and the involution of the uterus after childbirth.
What is the role of oxytocin in the hypothalamus?
oxytocin is released in the hypothalamus (in the supraoptic and paraventricular nuclei) where it acts in an autocrine fashion. Oxytocin in the hypothalamus acts via positive feedback to increase the release of oxytocin from the posterior pituitary.
Which does milk production and which does milk ejection?
Production = Prolactin
Expulsion = oxytocin
What is the effect of GH on the breakdown of protein?
What is the effect of GH on the release of fat?
What is the effect of GH on the glucose uptake?
What is the effect of GH on the glucose synthesis by the liver?
What is the effect of GH on the insulin secretion?
What is the effect of GH on long bones?
Stimulates osteoblasts to increase bone length and density
What are the hormones that GH induces the liver to release?
How is GH secreted? How is this modified?
Strenuous exercise increases, and starvation
What is panhypopituitarism?
Congenital defect (or tumor destroying) leading to a loss of all of the pituitary hormones
What are the causes of dwarfism?
Inability to form somatomedin C (IGF-1) or too little GH