The hypothalamus-adenohypophysial axis

Question 1

What is the bony dip the pituitary gland lies in called?

Answer 1

Sella Turcica

Question 2

Rough size of pituitary gland

Answer 2

Thumbnail size

Question 3

How many lobes make up the pituitary gland?

Answer 3

2

Anterior and Posterior

Question 4

What is the anterior lobe in the pituitary gland called?

Answer 4

Adenohypophysis

Question 5

What is the posterior lobe in the pituitary gland called?

Answer 5

Neurohypophysis

Question 6

Embryological origin of adenohypophysis

Answer 6

Upward growth derived from part of Buccal cavity- Rathke’s pouch

Question 7

Embryological origin of neurohypophysis

Answer 7

Downward growth from base of brain

Question 8

Which is the secretory lobe of the pituitary gland?

Answer 8

Adenohypophysis

Question 9

Which is the neural lobe of the pituitary gland, made up of nerve axons derived from base of brain?

Answer 9

Neurohypophysis

Question 10

What is a collection of neural cell bodies?

Answer 10

Nuclei

Question 11

Where do hypothalamic nuclei send axons to in pituitary gland?

Answer 11

LONG: Down pituitary stalk to neurohypophysis
SHORT: To median eminence

Question 12

What can median eminence communicate with?

Answer 12

Systemic circulation

Question 13

What is the Pars Distalis?

Answer 13

Body of anterior pituitary

Question 14

What is the Pars Tuberalis?

Answer 14

Part of anterior pituitary which wraps around pituitary stalk

Question 15

How is the anterior pituitary gland regulated?

Answer 15

Via the bloodstream- a special circulation

= Hypothalamic- hypophyseal portal circulation

Question 16

Where is the median eminence?

Answer 16

Between the pituitary stalk and the hypothalamus.

Question 17

What are the 2 areas of the brain that are useful anatomical markers for distinguishing the posterior pituitary from the anterior?

Answer 17

Anterior - Optic chiasma

Posterior - Mammilary body

Question 18

Describe the hypothalamic– hypophyseal portal circulation

Answer 18

Blood supplied by superior hypophyseal artery
Enters 1st plexus in median eminence
Travels down long portal vein
Enters 2nd plexus in anterior pituitary

Question 19

Plexus

Answer 19

Cluster of capillaries

Question 20

How does the hypothalamic-hypophyseal portal circulation allow communication with anterior pituitary

Answer 20

Capillary walls are fenestrated (leaky)
Hormone from hypothalamic neurone can enter at 1st plexus
Hormone leaks out at 2nd plexus and acts on anterior pituitary target cells

Question 21

What do short hypothalamic neurones which terminate in the median eminence lie on?

Answer 21

The surface of the primary capillary plexus

Question 22

Name 5 adenohypophysial cells

Answer 22

Somatotrophs
Lactotrophs
Thyrothrophs
Gonadotrophs
Corticotrophs

Question 23

What do somatotrophs produce?

Answer 23

Somatotrophin

Growth hormone

Question 24

What do lactotrophs produce?

Answer 24

Prolactin

Question 25

What do thyrotrophs produce?

Answer 25

Thyroid stimulating hormone | =TSH/ Thyrotrophin

Question 26

What do gonadotrophs produce?

Answer 26

``` Luteinising Hormone (LH) Follicle Stimulating Hormone (FSH) ```

Question 27

What do corticotrophs produce?

Answer 27

Adrenocorticotropic Hormone | =ACTH/ Corticotrophin

Question 28

Most hormones are made from longer precursors called

Answer 28

Pro-hormones

Question 29

Enzymatic cleavage of pro-hormone yields

Answer 29

Bioactive hormone

Question 30

What are adenohypophysial hormones stored in?

Answer 30

Secretory granules

Question 31

What are the longest adenohypophysial hormones?

Answer 31

Protein hormones: Somatotrophin Prolactin

Question 32

What are adenohypophysial glycoprotein hormones

Answer 32

TSH LH FSH

Question 33

What are the shortest adenohypophysial hormones?

Answer 33

Polypeptide hormones: | ACTH

Question 34

Which hypothalamic hormones regulate production of somatotrophin?

Answer 34

Growth hormone releasing hormone (GHRH) | Somatostatin (SS)

Question 35

Which hypothalamic hormones regulate production of Prolactin?

Answer 35

Dopamine | Thyrotrophin releasing hormone (TRH)

Question 36

Which hypothalamic hormones regulate production of TSH?

Answer 36

Thyrotrophin releasing hormone (TRH)

Question 37

Which hypothalamic hormones regulate production of LH and FSH?

Answer 37

Gonadotrophin releasing hormone (GnRH)

Question 38

Which hypothalamic hormones regulate production of ACTH?

Answer 38

Corticotrophin releasing hormone (CRH) | Vasopressin (VP)

Question 39

Which hypothalamic hormones are inhibitory?

Answer 39

Somatostatin | Dopamine

Question 40

How are hypothalamic hormones (and hence anterior pituitary hormones) released?

Answer 40

In a pulsatile fashion

Question 41

Which is the dominant hypothalamic hormone in regulation of somatotrophin?

Answer 41

GHRH | As SS is a short polypeptide (minor in comparison)

Question 42

Which is the dominant hypothalamic hormone in regulation of prolactin?

Answer 42

Dopamine

Question 43

What are the main targets of growth hormone?

Answer 43

``` General body tissue Particularly liver (causes secretion of IGF 1 and 2) ```

Question 44

What are the main targets of Prolactin?

Answer 44

Breasts in lactating women

Question 45

What is the main target of thyrotrophin?

Answer 45

Thyroid

Question 46

What are the main targets of gonadotrophins?

Answer 46

Testes (men) | Ovaries (women)

Question 47

What is the main target of corticotrophin?

Answer 47

Adrenal cortex

Question 48

Why does growth hormone stimulate liver to make IGF 1 and 2?

Answer 48

They are somatomedins (mediate growth) | IGF 1 also has indirect effect on growth (has anabolic and metabolic effects)

Question 49

What are the indirect effects on growth caused by IGF 1?

Answer 49

Stimulation of aa transport into cells and protein synthesis Increased gluconeogenesis Stimulation of lipolysis leading to increased fatty acid production Increased cartilaginous and somatic cell growth

Question 50

What is the "on" switch for growth hormone?

Answer 50

GHRH

Question 51

What is the "off" switch for growth hormone?

Answer 51

Somatostatin

Question 52

What does dopamine constantly inhibit?

Answer 52

Production of prolactin by lactotrophs in anterior pituitary

Question 53

What do you need to increase prolactin?

Answer 53

Reduction in dopamine

Question 54

What is prolactin essential for?

Answer 54

Milk production

Question 55

How is prolactin regulated?

Answer 55

By neuro-endocrine reflex arc

Question 56

What is the neuro-endocrine reflex arc in a breast feeding woman?

Answer 56

- Neural part- suckling stimulates neuronal tactile receptors - Feedback to hypothalamic dopamineuric neurones - Suppresses dopamine - Less inhibition of prolactin - More prolactin released - Formation of milk in breast