Lecture 1 + 2 - 2018

Question 1

What does the hypothalamus do?

Answer 1

It secretes hormones involved in: fluid balance, smooth muscle contraction, and the control of hormone secretion by the anterior pituitary gland.

Question 2

What does the pituitary gland do?

Answer 2

It secretes multiple hormones that regulate: endocrine activities of the adrenal cortex, thyroid gland, reproductive organs and a hormone that stimulates melanin production.

Question 3

Describe the embryonic development of the hypothalamus?

Answer 3

The hypothalamus came from the diencephalon which came from the forebrain.

Question 4

Describe the embryonic development of the anterior pituitary gland?

Answer 4

It is derived from the ectoderm of the primitive mouth cavity, it develops into two parts:

1. Pars distalis.
2. Pars tuberalis.

Question 5

Describe the embryonic development of the posterior pituitary gland?

Answer 5

It is a downward externsion of the floor of the brain (hypothalamus). It becomes the pars nervosa.

Question 6

Describe the hormonal feedback control of the hypothalamus and anterior pituitary?

Answer 6

There is a stimulus which affects the hypothalamus, it causes the hypothalamus to release hormones which act on the anterior pituitary which release hormones that act on the gonads which can release hormones to act on target tissues.

Question 7

What is the purpose of feedback loops?

Answer 7

They are to amplify or inhibit the final hormone that acts on the target tissue.
e.g. Oestrogen acts back on the hypothalamus to stop the release of FSH and LH (negative feedback).

Question 8

What is the posterior boundary of the hypothalamus?

Answer 8

Mamillary bodies and midbrain.

Question 9

What is the anterior boundary of the hypothalamus?

Answer 9

Anterior commissure and lamina terminalis.

Question 10

What is superior boundary of the hypothalamus?

Answer 10

Thalamus.

Question 11

What is the inferior boundary of the hypothalamus?

Answer 11

Pituitary gland.

Question 12

What is the neurohypophysis?

Answer 12

It is what forms the posterior pituitary. It is made up of the: median eminence, hypothalamo-hyophyseal tract, stalk and posterior lobe.

Question 13

What does the posterior pituitary release?

Answer 13

1. Oxytocin.

2. ADH (antidiuretic hormone).

Question 14

Describe the blood supply to the hypothalamus and anterior pituitary gland?

Answer 14

Blood foes from the top of the stalk to the pituitary (flow of blood is not all one way). The superior and inferior hypophyseal artery come off the internal carotid artery.

Question 15

Describe the blood supply from the superior hypophyseal artery? (for ant.pit)

Answer 15

The superior hypophyseal artery comes in at the top of the pituitary and feeds the capillary bed and upper infundibulum. It then runs to the pars distalis (portal vessels). The trabecular artery comes from the superior hypophyseal artery and goes into the lower capillary bed.

Question 16

Describe the blood supply from the inferior hypophyseal artery?

Answer 16

The inferior hypophyseal artery comes in through the posterior pituitary and feeds vessels into the lower capillary bed.

Question 17

Where do short axons go to? (for ant.pit)

Answer 17

Upper capillary bed.

Question 18

Where do long axons go to? (for ant.pit)

Answer 18

Lower capillary bed.

Question 19

What hormones does the anterior pituitary release?

Answer 19

1. LH (lutenising hormone).
2. FSH (follicle stimulating hormone).
3. TSH (thyroid stimulating hormone).
4. GH (growth hormone).
5. Prolactin.
6. ACTH (adrenocortioctrophic hormone).

Question 20

What hormones does the hypothalamus release?

Answer 20

1. GnRH (gonadotropin releasing hormone).
2. Dopamine (inhibits prolactin).
3. Somatostatin (inhibits GH).
4. GHRH (growth hormone releasing hormone).
5. CRF (Corticotropin releasing hormone).
6. TRH (thyrotropin releasing hormone).
7. PRF (prolactin releasing factor).

Question 21

What can cells of the pars distalis (ant pit) be classified as?

Answer 21

Chromotrophs (don’t stain) and chromophils (stain):

1. Acidophils.
2. Basophils.

Question 22

Describe the staining of acidophils?

Answer 22

Acidophils are stained orange, because they are negatively charged and indicate proteins. Acidophils are made up of

1. Somatotrophs (secrete GH).
2. Lactotrophs (secrete prolactin).

Question 23

Describe the staining of basophils?

Answer 23

Basophils are stained purple because they are positively charged and indicate glycoproteins. They are made up of:

1. Gonadotrophs (secrete LH, FSH).
2. Thyrotrophs (secrete TSH).
3. Corticotrophs (secrete ACTH).

Question 24

What happens in pregnancy?

Answer 24

There is marked proliferation of acidophils (prolactin).

Question 25

What happens in acromegaly (in terms of staining)?

Answer 25

There is excess GH, so there is marked orange staining (lots of acidophils).

Question 26

What happens in cushings syndrome (in terms of staining)?

Answer 26

There is excess ACTH, so there is marked purple staining (lots of basophils).

Question 27

Describe the secretion of growth hormone and the feedback control of it?

Answer 27

The hypothalamus releases GHRH which acts on the ant pit, the ant pit then releases GH. GH acts on epithelia, adipose tissue and the liver. The liver produces somatomedins (IGF-1 - insulin growth factor 1) which stimulate growth of skeletal muscle, cartilage and other tissues. Somatomedins also inhibit GHRH (in the hypothalamus), thus it can't act on the ant pit. The somatomedins also stimulate somatostatin (GHIH) which inhibits the ant pit and stops GH from being released.

Question 28

What does prolactin do?

Answer 28

Regulates milk production.

Question 29

What does oxytocin?

Answer 29

Regulates milk lactation.

Question 30

Describe the feedback loop for prolactin?

Answer 30

Prolactin has a positive feedback loop, where the more that is made the more it is produced (prolactin acts back on the hypothalamus - PRF). Dopamine is secreted in the median eminence and acts on the ant pit to inhibit prolactin production.

Question 31

Describe the hormonal control of the male HPO axis?

Answer 31

1. Hypothalamaus secretes GnRH. 2. GnRH acts on the ant pit which causes it to secrete FSH and LH. 3. FSH acts on the sertoli cells (testes), which causes them to stimulate spermatogenesis and inhibin to be released. 4. LH acts on leydig cells (testes) to release testosterone which acts on sertoli cells. 5. Inhibin inhibits the ant pit from releasing FSH. 6. Testosterone

Question 32

Describe the hormonal control of the female HPO axis?

Answer 32

1. Hypothalamus secretes GnRH. 2. GnRH acts on the ant pit which causes it to secrete FSH and LH. 3. FSH and LH act on the ovaries which cause the release of oestrogen and progesterone. 4. Progesterone inhibits FSH and LH (at pit level) and GnRH (at hypothalamus level). 5. Estrogen has both negative and positive feedback loops on FSh and LH.