Hypothalamus-Pituitary Relationship

Question 1

What are the nuclei of the hypothalamus?

Answer 1

PVN (Paraventricular Nucleus)
POA (Preoptic Nucleus)
ARC (Arcuate Nucleus)
SCN/SC (Suprachiasmatic Nucleus)
SON (Supraoptic Nucleus)

Question 2

What is the median eminence?

Answer 2

The floor of the hypothalamus and the convergence point for axons

Question 3

What are some general hypothalamic functions and the associated nuclei?

Answer 3

Sleep - SCN
Feeding behavior/Satiety - ARC
Thirst - PVN
Reproduction - POA
Circadian Rhythms - SCN
Mood/Emotions/Stress - PVN/ARC
Body Temp - POA
Blood Pressure - PVN

Question 4

What are some important hypothalamic releasing hormones?

Answer 4

GnRH (inhibited by GnIH)
CRH
TRH
GHRH
Somatostatin
Dopamine

Question 5

What do the hypothalamic releasing factors target?

Answer 5

the anterior pituitary

Question 6

Discuss the type, origin, target, second messengers, and function GnRH

Answer 6

Peptide hormone (10AA)
The brain nuclei are scattered, but the POA has majority
Gonadotropes - FSH and LH
IP3/DAG/PKC (via GPCR)
Reproduction

Question 7

Discuss the type, origin, target, second messengers, and function of CRH

Answer 7

Peptide (41AA)
PVN
Corticotrope - ACTH
cAMP
Glucocorticoids - Pleiotropic effects

Question 8

Discuss the type, origin, target, second messengers, and function of TRH

Answer 8

peptide (3AA)
PVN
Thyrotrope - TSH
IP3/DAG/PKC
Thyroid Hormone - pleiotropic effects

Question 9

Discuss the type, origin, target, second messengers, and function of GHRH

Answer 9

peptide (44AA)
ARC
Somatotrope - GH
cAMP
Growth and development

Question 10

Discuss the type, origin, target, second messengers, and function of somatostatin

Answer 10

peptide (14AA)
periventricular (PeVN)
Somatotrope
cAMP
Inhibits GH

Question 11

Discuss the type, origin, target, and function of dopamine

Answer 11

amine
ARC
Lactotrope - prolactin
Milk production

Question 12

Discuss Kallman’s syndrome

Answer 12

genetic disease where neurons fail to enter the CNS
characterized by sterility and anosmia
X-linked: Kal1
autosomal: Kal2

Question 13

Describe the hypophyseal portal system

Answer 13

vascular connections between the hypothalamus and pituitary gland

Question 14

Describe the connections of the hypophyseal portal system

Answer 14

the anterior pituitary axons release hormones into the superior hypophyseal artery which carries them to the anterior pituitary

Question 15

What is the importance of hormone pulsatility?

Answer 15

Can help in the sensitization problem

TSH, FSH, LH, hCG all require the common subunit alpha-glycoprotein subunit (alpha-GSU): Pulse frequency can determine which subunit & subsequent hormone is released

Question 16

What are the two major pathways of the hypothalamic-pituitary connection?

Answer 16

Tuberoinfundibular system

Neurohypophyseal tract

Question 17

Discuss the tuberoinfundibular system

Answer 17

Comprises all neurons that send projections to the median eminence - they have a portal system

Hormones target the anterior pituitary via the capillary system (endocrine)

Question 18

Discuss the Neurohypophyseal tract

Answer 18

comprises neurons whose axons terminate in the posterior pituitary - does NOT have a portal system

Question 19

What are the different anatomical landmarks of the anterior pituitary?

Answer 19

Pars distalis (90%)
Pars intermedia
Pars tuberalis

Question 20

What are the different anatomical landmarks of the posterior pituitary?

Answer 20

Pars nervosa

Infundibulum (stalk)

Question 21

What is another name of the anterior pituitary and what kind of tissue is it made up of?

Answer 21

Adenohypophysis

made up of glandular tissue: cords of epithelial cells

Question 22

What is another name for the posterior pituitary and what kind of tissue is it made up of?

Answer 22

Neurohypophysis

made up of neural tissue: terminal axons and glial cells

Question 23

What is the blood supply of the posterior pituitary?

Answer 23

via inferior hypophyseal artery - has it’s own capillary bed, does not use a portal system

Question 24

From where do the axons that terminate in the neurohypophysis originate?

Answer 24

Magnocellular axons

Question 25

What are the major hormones of the neurohypophysis?

Answer 25

Arginine vasopressin (AVN) and oxytocin (OXY)

Question 26

How do the hormones synthesized in magnocellular axons reach the neurohypophysis to be released?

Answer 26

Axonal transport

Question 27

What are Herring bodies?

Answer 27

Dilations of unmyelinated axons near their terminals (terminal end of axons where hormones are temporarily stored) Contain vesicles of either AVP or Oxytocin plus a binding protein, neurophysin

Question 28

What is the significance of the median eminence (ME)?

Answer 28

the interface for all hypophysiotrophic hormones

Question 29

Discuss some anatomical features of the median eminence

Answer 29

Lies outside the BBB (signals don't have to cross BBB to reach the ME) and forms the floor of the third ventricle

Question 30

What are the 5 major cell types in the anterior pituitary?

Answer 30

Acidophils (40%): somatotrophs and lactotrophes Basophils (10%): corticotrophs, gonadotrophs, thyrotrophs Chromophobes (50%)

Question 31

What do somatotrophs secrete?

Answer 31

Growth hormone (GH)

Question 32

What do lactotrophs secrete?

Answer 32

Prolactin (lactation)

Question 33

What do corticotrophs secrete?

Answer 33

ACTH (stress)

Question 34

What do gonadotrophs secrete?

Answer 34

LH/FSH (reproduction)

Question 35

What do thyrotrophs secrete?

Answer 35

TSH

Question 36

What do chromophobes do?

Answer 36

paracrine actions

Question 37

Where is ACTH generally secreted?

Answer 37

centrally

Question 38

Where is GH/PRL generally secreted?

Answer 38

in the periphery

Question 39

Where is TSH generally secreted?

Answer 39

Anteriorly

Question 40

Do hormones have a circadian rhythm?

Answer 40

Yep!