Recitation Week 8 Review Part 1

Question 1

What is the pathway and steps in the HPG axis from the 1st neural signal in the brain to the pituitary gland?

Answer 1

1) a neural signal happens in the brain
2) the parvocellular neurons (pre-optic area of the hypothalamus) gets stimulated
3) which sends the signal down to the median eminence (also part of the hypothalamus)
4) which sends the signal to the primary plexus in the ME
5) which sends the signal to the portal vein (pituitary stalk of the pituitary gland)
6) which sends the signal to the secondary plexus in the anterior pituitary gland

Question 2

of the areas listed above, which are a part of the portal blood system?

Answer 2

the primary plexus of the ME
the portal stalk of the pituitary vein
and the secondary plexus of the anterior pituitary gland

Question 3

In the hormonal pathways of the HPG axis, what does the pituitary cells release?

Answer 3

the endocrine cells of the pituitary release tropic, releasing or effector hormones

Question 3

In the hormonal pathways of the HPG axis, what does the hypothalamus neurons release?

Answer 3

they release neurohormones

Question 4

In the hormonal pathways of the HPG axis, what does the gonadal cells release?

Answer 4

the gonadal cells release effector hormones

Question 5

In the hormonal pathways of the HPG axis, what do the target cells do?

Answer 5

target cells respond to effector hormones

Question 6

please describe the main components of the HPG axis

Answer 6

1) the hypothalamus releases neurohormones
2) the anterior pituitary receives the signal from the hypothalamus and releases tropic hormones
3) the endocrine cells receive the signal from the tropic hormones and send effector hormones to their target cells
4) the target cells create a biological response

Question 7

please describe the difference between the two main types of neurons in the hypothalamus

Answer 7

1) the parvocellular neurons are smaller and synapse onto the ME (which flows to the anterior pituitary) and release GnRH
2) the magnocellular neurons are larger and synapse onto the blood vessels in the posterior pituitary releasing OXY and vasopressin

Question 8

Besides the above, what differentiates the anterior and posterior pituitary?

Answer 8

1) the anterior pituitary is part of the HPG axis and releases tropic and releasing hormones, examples being LH and FSH
2) the posterior pituitary is not part of the HPG axis, releasing OXY and vasopressin (which are effector hormones)

Question 9

When talking about the gonads, there are different parts and cell types. What are they for the males and females?

Answer 9

1) for the females, the organ is the ovaries and the main gonadal cells are the follicle and corpus luteum which release estrogen and progesterone
2) for the males, the organ is the testes and the main cells are the Leydig cells and the Sertoli cells which release testosterone

Question 10

Where is GnRH produced?

Answer 10

In the hypothalamus

Question 10

And when GnRH stimulates the anterior pituitary gland, what does the latter release?

Answer 10

FSH and LH

Question 11

Do both the follicles in the ovaries and the corpus luteum produce estrogen?

Answer 11

Yes, both of them produce estrogen while the corpus luteum also produces progesterone

Question 11

What does release of GnRH stimulate?

Answer 11

the anterior pituitary gland

Question 12

FSH and LH stimulate specific cells within the male/female gonads. What are those?

Answer 12

1)FSH stimulates the follicle in the ovaries and the Sertoli cells in the testes
2) LH stimulates the Corpus Luteum in the ovaries and the Leydig cells in the testes

Question 12

Once the main hormones are produced (estrogen, testosterone and progesterone), what is the path they take from there?

Answer 12

From there, they go into general circulation, and then pass onto their target cells (particularly the intracellular receptors) and then pass onto the HRE (hormone response element) where they activate transcription factors

Question 13

Do both the Leydig cells and Sertoli cells produce testosterone?

Answer 13

No, only the Leydig cells, the Sertoli cells are more important for spermatogenesis

Question 14

If you lesion the pre-optic area/parvocellular neurons) (of the hypothalamus), what happens to GnRH, LH, FSH and Testosterone?

Answer 14

All of them go down since GnRH would go down which would affect all the other hormones downstream and since GnRH is produced and released (pulsatile manner) from the pre-optic area and then sent to the anterior pituitary via the hypophyseal portal system.

Question 15

If you lesion the anterior pituitary gland, what would happen to GnRH, LH, FSH and testosterone?

Answer 15

-well GnRH would go up since its being produced in the pre-optic area and would have reduced negative feedback
-but LH would go down since its not being produced since its produced in the anterior pituitary, which has been lesioned
-FSH would also go down for the same reason as above
-testosterone would go down since its dependent upon the production of LH

Question 15

If you lesion or remove the testes, what would happen to GnRH, LH, FSH and testosterone?

Answer 15

-GnRH would go up due to the lack of negative feedback from testosterone and inhibin
-LH would also go up due to above
-FSH would also go up due to above
-testosterone would go down since the testes are the primary site of testosterone production