Midterm 2 - Hypothalamus - Pituitary Axis (Integration of Hormone Axis) Flashcards
what is the hypothalamus
the major integration center
what does the hypothalamus regulate
autonomic nervous system
most of endocrine system
processes most sensory info
what is the pituitary
a small gland attached to the hypothalamus
what are the 3 parts of the pituitary
posterior
intermediate
anterior
what consists of the posterior lobe of the pituitary
neurons from hypothalamus
what consists of the anterior lobe of the pituitary
major endocrine part (glandular tissue)
what does the intermediate lobe of the pituitary do
major function in amphibians and fish (MSH)
what are the anterior lobe and intermediate often considered
anterior pituitary
what is the hypothalamus composed of
neuroendocrine cells
what do some neuroendocrine cells in the hypothalamus do
some project axons down the posterior pituitary lobe
some release factors into the pituitary stalk portal venous system to feed anterior pituitary
where do endocrine cells from the anterior and intermediate pituitary release their hormones
in a second capillary network to enter systemic circulation
what system is very important
the portal vascular system because not a lot of neurons in hypothalamus
what is the role of the intermediate pituitary in mammals
it is unclear, possibly a source of B-endorphins
what does the intermediate pituitary produce
MSH
B-LPH
what is MSH
melanocyte stimulating hormone
what does MSH do
increases skin pigment
what is B-LPH
B-lipotropin
what happensn to B-lipotropin
it is degraded to B-endorphin
what is B-endorphin
an analgesia during stress (fight or flight)
what are all hormone in intermediate pituitary derived from
the common gene POMC
what is the most important regulator of extracellular fluid
the antidiuretic hormone
what does anti-diuretic hormone do
regulates the density of aquaporins in the distal tubule and connecting duct
where does anti-diuretic hormone act
in kidneys
what does ADH increase
reabsorption of water
how is ADH regulated
primarily by hypothalamic osmoreceptors and stretch receptors in blood vessels
where does oxytocin primarily act on
uterus smooth muscle
mammary gland
what happens when oxytocin acts on uterus smooth muscle
contraction during parturition
what happens when oxytocin acts on mammary gland
contraction increases pressure to drive milk towards excretory ducts and the teats
what is the milk ejection reflex
the increase in pressure to drive milk towards ducts due to oxytocin action
what is the receptor for oxytocin
G-coupled receptor with activation of PLC (Ca pathway)
what is the secretion of oxytocin regulated by
several reflexes
when might oxytocin be supplemented in dairy cattle
in first lactation - stimulates milk section or uterus cell contraction
what is the master gland
anterior pituitary
what does the endocrine part of the anterior pituitary contain
5 different cell types producing 6 different hormones
what are proteins/glycoproteins with longer half-lives than their releasing hormones
thyrotrope
gonadotrope
corticotrope
somatotrope
mammotrope
what is the releasing hormone of thyrotrope
TSH (thyroid stimulating hormone)
what is the releasing hormone for gonadotrope
LH and FSH (gonadotropins)
what is the releasing hormone for corticotrope
ACTH (adrenocorticotropin)
what is the releasing hormone for somatotrope
GH (growth hormone)(somatotropin)
what is the releasing hormone for mammotrope (lactotrope)
PRL (prolactin)
what are the tropic effects of anterior pituitary
regulate other endocrine glands
what is the anterior pituitary under the control of
under direct control (positive and/or negative) from hypothalamus
what is the receptor for GH
cytokine receptor types
what are the direct effects of GH (catabolic - break)
stimulates lipolysis
reduces lipogenesis in adipose tissue
what are the direct effects of GH (anabolic - build)
promotes synthesis of protein
what do the direct effects of GH mainly focus on
metabolic control - happens regardless of age
what are the indirect effects of GH
stimulates chondrocyte (cartilage cells) proliferation to increase bone growth
stimulates satellite cells in muscle (muscle fibre growth)
stimulate aa uptake protein synthesis
how do the indirect effects of GH occur
by stimulating synthesis of IGF1 (somatomedin) and its binding proteins in the liver
where does TSH bind
to its G-coupled receptor on membrane of follicular cells in thyroid gland
what does TSH stimulate
cAMP which in turn stimulates the synthesis of thyroid hormones
what is the ACTH receptor
a G-coupled receptor stimulating the cAMP pathway
what does ACTH target
adrenal cortex
what does ACTH stimulate
the mobilization of cholesterol in adrenal cortex = more substrate for cytochrome P-450 which increases the release of corticosteroids
what is are the 2 G-protein coupled receptor of the cAMP pathway
LH and FSH
what does LH stimulate in males
testosterone production by Leydig cells in the testis
what does LH control in females
sex steroid production by the ovary and is responsible for ovulation (surge)
what does FSH stimulate in males
secretion of inhibition by Sertoli cells
what does FSH stimulate in females
development of follicles and secretion of sex steroid
what type of receptor is PRL
cytokine receptor tupe
what does PRL stimulate
the synthesis of milk proteins (casein, lactalbumin)
what is PRL responsible for in poultry
the initiation and maintenance of incubation behaviour (brooding)
how are neurohormones released from hypothalamus
in small amounts - bypass general circulation
what do hypothalamic neurons receive info from
higher brain center (emotions)
exterior (environmental and social stimuli)
internal rhythms
metabolic state (temp, energy level, osmolarity)
endogenous hormones by feedback
what hormones are needed early in life
hormones needed under tonic inhibition (GH, MSH, PRL)
what happens to hormones needed under tonic inhibition as the hypothalamus matures
secretion decreases
in mammals, where is PRL mainly
under dopaminergic tonic inhibition
in birds, where is PRL mainly
under VIP stimulation
what does each anterior pituitary hormone have
a corresponding hypothalamic releasing hormone and/or a corresponding hypothalamic inhibitory factor
what are hypothalamic factors
relatively small peptides - generally fragments from pro protein of larger size
where are releasing hormone precursors made
in cell bodies
where are releasing hormone precursors transported
down axons to nerve endings for storage
what is a characteristic that many hormones from the hypothalamus and pituitary have
they are pulsatile or episodic
what are pulsatile hormones regulated by
the biological clock of hypothalamic suprachiasmatic nucleus
what might pulsatile hormones prevent
may prevent the down regulation of receptors from continuous level of hormone secretion
what can pulsatile hormones trigger
specific action depending on pulse frequency
what does feedback control monitor
amount of hormones that have been released after stimulation
what do circulating hormones from endocrine glands provide
negative feedback both to the hypothalamus and pituitary
what does feedback serve the regulate
the secretion of hormones
what are the 2 major feedback loops
short
long
what is the short feedback loop
pituitary hormones feed back to hypothalamus
what is the long feedback loop
hormones from target glands feed back to the pituitary and hypothalamus
what does negative feedback prevent
overstimulation
