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Lecture 10: The Hypothalamic-Pituitary Axis Part 2
Terms in this set (24)
How does the anterior pituitary receive innervation from the hypothalamus?
the anterior pituitary receives innervation from the hypothalamus by way of the hypophesal portal system which is a bed of capillaries that connect the hypothalamus to the AP, hormones are released directly from the hypothalamus called (releasing hormones) which will bind and activate the release of trophins from the AP
How does the posterior pituitary receive innervation from the hypothalamus?
the posterior pituitary receives direct innervation from the hypothalamus by way of neuronal synapses; the hypothalmic neurons will directly synapse onto the posterior pituitary neurons and innitiate the release of particular hormones
What are hormones released by the posterior pituitary?
ADH and Oxytocin are the two major hormone varieties that are released by the posterior pituitary
What are hormones released by the hypothalamus onto the anterior pituitary?
the hormones released by the hypothalamus are the trophin releasing hormones such as GnRH, GHRH, TRH, CRH, STT and Dopamine and will go and bind to their receptors located in the anterior pituitary
What hormones so the 6 releasing hormones initiate to release? 6
TRH --> TSH
GnRH --> FSH & LH
CRH --> ACTH
GHRH --> GH
STT --> inhibits the release of hormones
Dopamine --> inhibits the release of prolactin
What cell variety in the anteiror pituitary do the TRH, GnRH, CRH, and GHRH impact?
TRH --> thyrotrophic cell effector
GnRH --> gonadotrophic cell effector
CRH --> corticotropie cell effector
GHRH --> somatotropic cell effector
What cell variety in the anterior pituitary do STT impact? Dopamie?
STT will act on somatotrophs and decrease the release of GHRH and decrease over active growth, while dopamine released from the hypothalamus will effect lactotrophic cells and decrease the release of prolactin
Structurally, what do all of the hormones of the anterior pituitary have in common?
we see that structurally, the hormones of the anterior pituitary are all peptide hormones that will be hydrophillic and lipophobic
Structurally, describe how the signaling hormones of the anterior pituitary have to be cleaved?
these hormones will have to be cleaved often at either their c-termini or their N-termini to be fully activated
Describe the signal of growth hormone
Growth hormone releasing hormone is released from the hypothalamus and will initiate the release of growth hormone from the somatotrophic cells of the anterior pituitary, this Growth Hormone will go and act on the liver cells and cause the release of IGF-1 which will carry out most of the activities involving GH in the tissue
What are some of the functional and physical changes we see in individuals with IFG-1?
decreased fat levels, increase in muscle mass and increase bone density
How does ghrelin impact the release of GH from the anterior pituitary?
ghrelin will have a positive effect on GH such that it will induce more GH to be released and promote growth and increase in height
How does the circadian rhythm impact the levels of Growth Hormone?
we see that growth hormone will actively be released by the body when the individual falls asleep early on, and then over a period of time in the night, the GH levels will decrease to almost none in the day time
What does growth hormone do at the site of the growth plate? 3
we see that GH will go and increase the density of IGF-1 receptors and increase IGF-2 secretion in addition to increasing the density of bones
How does estradiol impact chondrocyte growth? How does testosterone impact chondrocyte growth?
we see that both estradiol and testosterone will actively promote chondrocyte growth however, after promotion of chondrocyte growth in estradiol treated cells, they will go through senesce where the chondrocytes will after growing for a period of time, stop growing while the cells with testosterone will not
What are some general actions of Growth Hormone?
it is going to promote anabolic processes such as incorporation of amino acids into muscles and also promote bone formation and growth and development
How does GH function through JAK/STAT signaling pathway?
GH activates a cytosolic tyrosine kinase in the JAK-STAT family which will translocate to the nucleus and active as transcriptional regulators that activate specific genes and protein transcription and translation which will vary from tissue to tissue
What are the 2 general effects of taking excess growth hormone? Pre-pubusently vs. post-pubuscently
pre-pubuscently, taking excess GH will cause gigantism while taking GH post-pubuscently will cause
Describe what happens in individuals with gigantism
they essentially have excess GH production during their pubescent years where they are actively growing, these individuals can grow very large and thus unfortunately will be unable to live as it is simply too much strain on the heart
What happens when individuals take excess growth hormone or their body produces excess growth hormone post puberty?
those individuals will typically get acromegaly, a condition in which the bones are going to become thicker and denser in the body and the finer bones like in the fase and fingers as well
Describe hypopituitary dwarfism
it is the condition in which an individual has growth hormone deficiency and or hypo-secretion of GH causing an individual to be born with small and disportioncate parts
What are some possible treatments of pituitary dwarfism? When is it effective and when is it not?
some treatments for pituitary dwarfism is to simply provide the GH that their body is not producing sufficient amounts of; it is highly effective when given to individuals either before or during puberty to allow their stature to improve
Describe Laron Syndrome. Where did it dome from, what causes this disease, and what are some of the potential benefits of having it?
laron syndrome emerged from Jewish individuals who were fleeing Spain during the time of the persecutions, they settled in Ecuador and founders effect occurred --> became a prevalent trait
- it occurs because these individuals are unable to produce GH due to a mutation of the GH gene OR the GH binding protein gene has a mutation
-some benefits for these individuals is that they are immune to diabetes and cancer
What are some physical differences in individuals with Laron Syndrome?
these individuals are going to be physically smaller and have child-like faces; while their intelligence is usually not a factor that is effected
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