Neuroendocrinology

Question 1

What is a hormone?

Answer 1

A hormone has to enter the blood.

It is secreted from an endocrine cell in a regulated way.

Question 2

Describe the development of the pituitary during embryonic development?

Answer 2

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.

Question 3

What kind of tissue is the posterior pituitary made of?

Answer 3

Neural tissue.

Question 4

What are the 3 regions of the pituitary?

Answer 4

Anterior pituitary
Posterior pituitary
Intermediate lobe

Question 5

Describe the blood supply of posterior pituitary

Answer 5

The posterior pituitary recieves blood supply from the inferior hypophyseal artery and leaves via the hypophseal vein.

Question 6

Define rostral and caudal

Answer 6

Rostral = front of the brain.
Caudal = back of the brain.

Question 7

What are the two hormones released by the posterior pituitary?

Answer 7

Vasopressin

Oxytocin

Question 8

Where to the neurones producing TRH project?

Answer 8

From the paraventricular nucleus to the median eminence.

Question 9

What % of cells of the anterior pituitary are thyrotrophs?

Answer 9

5%

Question 10

What are the two factors positively driving release of ACTH?

Answer 10

CRH and AVP neurones.

Question 11

What are the first cell types of the anterior pituitary to appear?

Answer 11

Corticotrophs

Question 12

The appearance of corticotrophs is under the control of what?

Answer 12

NeuroD1/Tpit

Question 13

Expression of what transciption factors drives cells of the anterior pituitary down a lineage other than corticotrophs?

Answer 13

Linx3

Question 14

Expression of what is crucial for development and expansion of the corticotroph lineage?

Answer 14

Tpit.

Question 15

What are the two rhythms underying the secretion in cortisol/corticosterone?

Answer 15

Circadian rhythm.

Ultradian rhythm.

Question 16

Which rhythm underlying corticosterone secretion is more exaggerated in females?

Answer 16

Ultradian.

Question 17

What is responsible for generating circadian rhythmicity of corticosterone release?

Answer 17

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.

Question 18

What is driving the rhythmicity in cortisol release?

Answer 18

The rhythmicity in ACTH release.

Question 19

How does the timing of the stresser effect the stress actviation of the HPA aixs?

Answer 19

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.

Question 20

What is driving the periodicity of the ultradian rhythm?

Answer 20

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.

Question 21

What is the effect of anaesthetic on the HPA axis?

Answer 21

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.