Hypothalmic Pituarity Gondal Axis

Question 1

What are some of the characteristics of hypthalmic realeasing hormones?

Answer 1

Secretion in pulses to a biological clock
Act on specific membrane receptors
Transduce signals via second messengers
Stimulate realease of stored pituarity hormones
Stimuate sythensis of pituraty hormones
Stimulates hyperpalais and hypertrophy of target cells

Question 2

Where would you find the pituarity gland?

Answer 2

Lies immeadatly below the hypthalmus, in a depression in the skull knwon as the pitaurity fossa, and also called the turkish saddle (sella turica)

Question 3

What are the two lobes of the pituarity gland called?

Answer 3

The anterior lobe/adenohyposis/pars distalis

The posterior lobe/neurohyposis/pars nervosa

Question 4

What are the emboroynic orgins of the two lobes of the pituarity gland?

Answer 4

Anterior lobe is derivied embroylogically from ectoderm lining the distal pharynx
The posterior portion is derived embryologically from neuroectoderm

Question 5

What connects the anterior pituarity and the hypothalmus?

Answer 5

The superior hypopheseal atery,

Question 6

What are the hormones produced by the anterior pituarity?

Answer 6

Produces 6 peptide horomes
Prolactin, growth hormone, thyroid stimulating hromone, adrenocrotiopic hormone, follicle stimulating hormone, and letuinising hormone

Question 7

Where is GnRH sythesised?

Answer 7

The acurate nucleus of the medial base of the hypothalmus and the peptic areas

Question 8

What are the two hormones that the pituarity realeases because of GnRH?

Answer 8

Leutisining hormone (LH) and Follicle stimulating hormone (FSH)

Question 9

How does GnRH reach the pitaruity?

Answer 9

The hypophaseal portal system

Question 10

In males, what receptors to the pituarity hormones act upon?

Answer 10

Gas PCR and adenylate cylase

Question 11

What cells does LH have an action on in males and what does this produce?

Answer 11

The leydig cells and they produce testerone

Question 12

What are the negative feedback properties of testosterone?

Answer 12

Testerone reduces the realease of LH from the anterior Pituarity, and reduced GnRH secretion from the hypothalmus

Question 13

What are the actions of FSH in the male?

Answer 13

Acts on the sertoli cells of the seminiferous tubules, causing them to grow and secrete spermatogenic substances (which also needs some testosterone) and also produces inhibin

Question 14

What is the aciton of inhibin in males?

Answer 14

Reduces FSH secretion selectively, if spermatogensis is increased then inhbin is realeased, and if spermatogenesis slows down than inhibin will not be realeased

Question 15

How do we keep testosterone in the seminiferous tubules?

Answer 15

Protein antigen binding compoun, which binds to the testosterone and therefore keeps some within the tubules

Question 16

Does the HPG axis in males vary at all?

Answer 16

In the medium to long term the levels are constant but there is a circadian rythum, that is highest in the early morning and there are some effects on environmental stimuli that are driven by the brain

Question 17

What are the target cells of the hormones in women?

Answer 17

Target cells include the ovarian granulosa cells and then the theca interna

Question 18

What cells does FSH act upon on in women and what does this cause?

Answer 18

The granulosa cells, and then porjects the oestrogens and progestins

Question 19

What are the actions of oestrogen and progesterone on GnRH?

Answer 19

Moderate titres of osetrogen reduce GnRH secretion, whereas high tires of oestrogen in the ABSENCE of progesterone promote GnRH secretion and help to create the LH surge

Question 20

What are the actions of progesterone of the GnRH axis?

Answer 20

Progesterone increases the inhbitroy affects of moderate titres of oestrogen, and prevents the postive feedback of high oestrogen, oestrogen reduces the GnRH per pulse whereas progesterone reduces the frequency of pulses