Neuroendocrinology Flashcards
What is a hormone?
A hormone has to enter the blood.
It is secreted from an endocrine cell in a regulated way.
Describe the development of the pituitary during embryonic development?
The pituitary develops from the base of the wall of the third ventricle and from the upper surface of the oral pharynx.
Up-growth of the oral pharynx is pinched off to generate Rathke’s pouch.
There is down-growth of the third ventricle generating the infundibulum.
Rathke’s pouch wraps around the infundibulum forming the anterior pitiuitary and it then grwons down to form the posterior pituitary.
What kind of tissue is the posterior pituitary made of?
Neural tissue.
What are the 3 regions of the pituitary?
Anterior pituitary
Posterior pituitary
Intermediate lobe
Describe the blood supply of posterior pituitary
The posterior pituitary recieves blood supply from the inferior hypophyseal artery and leaves via the hypophseal vein.
Define rostral and caudal
Rostral = front of the brain. Caudal = back of the brain.
What are the two hormones released by the posterior pituitary?
Vasopressin
Oxytocin
Where to the neurones producing TRH project?
From the paraventricular nucleus to the median eminence.
What % of cells of the anterior pituitary are thyrotrophs?
5%
What are the two factors positively driving release of ACTH?
CRH and AVP neurones.
What are the first cell types of the anterior pituitary to appear?
Corticotrophs
The appearance of corticotrophs is under the control of what?
NeuroD1/Tpit
Expression of what transciption factors drives cells of the anterior pituitary down a lineage other than corticotrophs?
Linx3
Expression of what is crucial for development and expansion of the corticotroph lineage?
Tpit.
What are the two rhythms underying the secretion in cortisol/corticosterone?
Circadian rhythm.
Ultradian rhythm.
Which rhythm underlying corticosterone secretion is more exaggerated in females?
Ultradian.
What is responsible for generating circadian rhythmicity of corticosterone release?
There is a rhythmic gene expression within suprachiasmatic nucleus in the hypothalamus creating a 24-hour output.
The suprachiasmatic nucleus recieves triggering signals like light which reset the clock.
The output of the suprachiasmatic nucleus feed into the paraventricular nucleus altering the vasopressin neurones.
What is driving the rhythmicity in cortisol release?
The rhythmicity in ACTH release.
How does the timing of the stresser effect the stress actviation of the HPA aixs?
You can give the same stresser at different times and that generates a different response.
If you give a stresser on a rising phase of the underlying puslatility you get an exaggerated response, it increases facilitated HPA response.
If you give a stresser on a falling phase of the underlying pulsatility you get a poor response.
What is driving the periodicity of the ultradian rhythm?
Hormones in biosynthetic pahtways are feeding back to alter production, steroids in the blood are products of production not secretion because we don’t store steroids.
The periodicity is kicked by ACTH to produce timing.
Response to glucocorticoids is also involved.
What is the effect of anaesthetic on the HPA axis?
There is a stress response to anaesthetic and surgical stress, there is a large release in ACTH mirrored by a larger release in cortisol.
Current theory is that anaesthetic excites expression of somatostatin but there is evidence to say anaesthetic inhibits ACTH.
