The Hypothalamus and Pituitary Gland

Question 1

To which part of the pituitary does the hypothalamus communicate neurally and which part endocrine?

Answer 1

Communication to posterior pituitary is neural

Communication to anterior pituitary is endocrine

Question 2

What kinds of hormone are released by the hypothalamus, the anterior pituitary and the posterior pituitary?

Answer 2

Hypothalamus- all neurohormones
Posterior pituitary- all neurohormones
Anterior pituitary- all endocrine

Question 3

What is the function of tropic and non-tropic hypothalamic neurohormones?

Answer 3

Tropic- secreted into capillaries travelling to anterior pituitary, govern release of AP hormones
Non-tropic- travels to posterior pituitary via axons of hypothalamic neurons, where they are released into the blood

Question 4

What are the five main hypothalamic tropic “releasing hormones”?

Answer 4

Thyrotropin Releasing Hormone (TRH)
Corticotropin Releasing Hormone (CRH)
Growth Hormone Releasing Hormone (GHRH)
Gonadotropin Releasing Hormone (GnRH)
Prolactin Releasing Hormone (PRH)

Question 5

What are the two main hypothalamic tropic “inhibiting hormones”?

Answer 5

Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin

Dopamine aka Prolactin Inhibiting Hormone (PIH)

Question 6

What kind of hormone are each of the hypothalamic tropic hormones?

Answer 6

All are peptides, except dopamine which is an amine

Question 7

What are the six main anterior pituitary hormones and what is the target organ of each?

Answer 7

Prolactin- breast
Thyrotropin(TSH)- thyroid gland
Corticotropin(ACTH)- adrenal cortex
Growth hormone(GH)- liver
Follicle stimulating hormone (FSH) and luteinizing hormone (LH)- gonads

Question 8

Which of the hypothalamic tropic hormones trigger release of which AP hormones?

Answer 8

Prolactin releasing/inhibiting hormone- prolactin
Growth hormone releasing/inhibiting hormones- growth hormone
Thyrotropin releasing hormone- thyrotropin
Corticotropin releasing hormone- cotricoptropin
Gonadotropin releasing hormone- follicle stimulating and luteinizing hormones

Question 9

Through what system are trophic hormones transported from the hypothalamus to the anterior pituitary?

Answer 9

Through the hypothalamo-hypophyseal portal system

Question 10

Which of the anterior pituitary hormones are tropic?

Answer 10

All except prolactin

Question 11

What is the difference between long and short loop feedback systems with regards to the anterior pituitary?

Answer 11

Long-loop feedback refers to feedback from the endocrine target to the hypothalamus and/or AP, short-loop is feedback from the anterior pituitary to the hypothalamus

Question 12

What are the two neurohormones stored and released by the posterior pituitary, and what kind of hormone are they?

Answer 12

Vasopressin and oxytocin

Both peptide hormones

Question 13

Where are vasopressin and oxytocin synthesised?

Answer 13

In the magnocellular neurons that have their cell bodies in specific areas of the hypothalamus

Question 14

How are vasopressin and oxytocin excreted into the blood?

Answer 14

The hormones are made and packaged in the cell body of the neuron. These vesicles are then transported down the cell and stored in the posterior pituitary. The hormones are then released into the blood as needed.

Question 15

What are the main functions and site of action of vasopressin?

Answer 15

Function- regulates water balance

Site of action- kidney collecting ducts and vascular smooth muscle

Question 16

What are the main functions and site of action of oxytocin?

Answer 16

Function- milk ejection and uterine contraction

Site of action- smooth muscle of milk duct and uterus

Question 17

What differentiates primary, secondary and tertiary endocrine disorders?

Answer 17

Primary- the defect is in the hormone secreting cells
Secondary-there is too much or too little trophic hormone from the pituitary
Tertiary- relate to hypothalamic defects (rare)