Hypothalamus and Pituitary

Question 1

What connects the hypothalamus to the pituitary gland?

Answer 1

Infundibulum

Question 2

How is the hypothalamus connected to the pituitary gland?

Answer 2

Hypothalamic communication with the pituitary gland is both neural (to the posterior pituitary) and endocrine (to the anterior pituitary), hence it’s neuroendocrine function.

Question 3

What is the name of section of bone the pituitary gland is found?

Answer 3

Located in a pocket in the sphenoid bone (hypophyseal fossa), directly below the hypothalamus

Question 4

What types of hormones are released from the hypothalamus?

Answer 4

Neurohormones

Question 5

What types of hormones are released from the anterior pituitary?

Answer 5

Classic endocrine hormones

Question 6

What types of hormones are released from the posterior pituitary?

Answer 6

Neurohormones (extension of hypothalamus)

Question 7

What are the two forms of hypothalamic neurohormones?

Answer 7

Tropic – neurohormones secreted into capillaries travelling to anterior pituitary. Govern release of anterior pituitary hormones (can be stimulatory or inhibitory)

Non-tropic – neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into blood.

Question 8

Define tropic hormones

Answer 8

Tropic – neurohormones secreted from hypothalamus into capillaries travelling to anterior pituitary. Govern release of anterior pituitary hormones (can be stimulatory or inhibitory)

Question 9

Define non-tropic hormones

Answer 9

Non-tropic – neurohormones produced in the hypothalamus and travel to posterior pituitary (via axons of hypothalamic neurons) where they are released into blood.

Question 10

What is the action of hypothalamic tropic hormones?

Answer 10

All hypothalamic tropic hormones bind to receptors on anterior pituitary and stimulate/inhibit release of anterior pituitary hormones

Question 11

What 7 tropic hormones are produced by the hypothalamus?

Answer 11

5 hypothalamic “releasing hormones”:
– Thyrotrophin Releasing Hormone (TRH)
– Corticotropin Releasing Hormone (CRH)
– Growth Hormone Releasing Hormone (GHRH)
– Gonadotrophin Releasing Hormone (GnRH)
– Prolactin Releasing Hormone (PRH)
2 hypothalamic “inhibiting hormones”
– Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin
– Dopamine aka Prolactin Inhibiting Hormone (PIH)

Question 12

What are the releasing hormones released by the hypothalamus?

Answer 12

–	Thyrotrophin Releasing Hormone (TRH)
–	Corticotropin Releasing Hormone (CRH)
–	Growth Hormone Releasing Hormone (GHRH)
–	Gonadotrophin Releasing Hormone (GnRH)
–	Prolactin Releasing Hormone (PRH)

Question 13

What are the inhibiting hormones released by the hypothalamus?

Answer 13

– Growth Hormone Inhibiting Hormone (GHIH) aka somatostatin

– Dopamine aka Prolactin Inhibiting Hormone (PIH)

Question 14

What kind of hormones are the 7 hormones released by the hypothalamus?

Answer 14

All are peptides, except dopamine, which is an amine hormone

Question 15

What is the Hypothalamo-hypophyseal portal system?

Answer 15

Network of tiny vessels which transfer trophic hormones from hypothalamus to anterior pituitary

Question 16

What is responsible for the delivery of tropic hormones from the hypothalamus to the anterior pituitary?

Answer 16

Hypothalamo-hypophyseal portal system

Question 17

What are the major differences between the anterior and posterior pituitary?

Answer 17

Anterior
o	True endocrine tissue
o	Epithelial origin
o	Connected to hypothalamus via capillary portal system 
o	Also called adenohypophysis
o	Makes up 2/3rds of the gland

Posterior
o	Neuroendocrine tissue
o	Neural tissue origin
o	Neural connection to hypothalamus 
o	Secretes neurohormones made in hypothalamus
o	Also called neurohypophysis
o	Makes up 1/3rd of the gland

Question 18

What is the other name for the anterior pituitary?

Answer 18

Adenohypophysis

Question 19

What is the other name for the posterior pituitary?

Answer 19

neurohypophysis

Question 20

What type of hormones are produced by the anterior pituitary?

Answer 20

Classic endocrine hormones, all peptide hormones

Question 21

What 6 hormones are released from the anterior pituitary?

Answer 21

1. Thyroid Stimulating Hormone (TSH) aka thyrotrophin
2. Adrenocorticotrophic Hormone (ACTH) aka corticotrophin
3. Follicle Stimulating Hormone (FSH)
4. Luteinising Hormone (LH)
5. Growth Hormone (GH)
6. Prolactin

Question 22

Which hormone released from the anterior pituitary is non-tropic?

Answer 22

Prolactin

Question 23

What anterior pituitary hormones make up the gonadotrophins?

Answer 23

FSH and LH both make up the gonadotrophins

Question 24

Describe the production, target and action of prolactin

Answer 24

Prolactin – produced by AP, directly targets breast for lactation (only non-trophic)

Question 25

Describe the production, target and action of TSH

Answer 25

Thyroid-stimulating hormone – produced by AP, stimulates thyroid hormone release from thyroid

Question 26

Describe the production, target and action of Adrenocorticotropic hormone (ACH)

Answer 26

Adrenocorticotropic hormone – produced by AP, targets adrenal cortex for cortisol release (trophic)

Question 27

Describe the production, target and action of GH

Answer 27

Growth hormone – produced by AP, targets liver for IGF-1 release (trophic) and tissue metabolism (direct)

Question 28

Describe the production, target and action of FSH and LH

Answer 28

Follicle-stimulating hormone and luteinising hormone – both produced by AP, act on gonads for regulation of reproductive function (direct) and sex hormone release (trophic)

Question 29

Describe feedback control of AP hormone production

Answer 29

Hormones themselves act as negative feedback signal Each hormone feeds back to inhibit hormone secretion by integrating centres earlier in the reflex Feedback from endocrine target = long-loop feedback Feedback from anterior pituitary to hypothalamus = short-loop feedback

Question 30

What is short loop feedback?

Answer 30

Feedback from anterior pituitary to hypothalamus = short-loop feedback

Question 31

What is long loop feedback?

Answer 31

Feedback from endocrine target = long-loop feedback

Question 32

What hormones are produced by the posterior pituitary ?

Answer 32

Stores and releases 2 peptide neurohormones: o Vasopressin (aka anti-diuretic hormone; ADH) o Oxytocin

Question 33

What types of hormone are produced and stored in the posterior pituitary?

Answer 33

Peptide neurohormones

Question 34

What neurons in the posterior pituitary produce its hormones and links it to the hypothalamus?

Answer 34

Magnocellular neurons

Question 35

What is the main function of vasopressin, what triggers its release and where are its sites of action?

Answer 35

Regulates water balance Triggered by increased plasma osmolarity and decreased blood volume/BP Increases water resorption at kindey collecting ducts and increases tone of vascular smooth muscle to increase BP

Question 36

What is the main function of oxytocin, what triggers its release and where are its sites of action?

Answer 36

Milk ejection (not production) and uterine contractions Triggered by labour (baby head on cervix) and suckling Contracts milk duct smooth muscle to eject milk and contraction of uterine smooth muscle for child birth

Question 37

What are primary, secondary and tertiary endocrine disorders?

Answer 37

1° disorders are those in which the defect is in the cells that secrete the hormone e.g. primary thyroid dysfunction 2° disorders are those in which there is too little or too much trophic hormone from pituitary e.g. decreased TSH for the thyroid gland to produce TH 3° disorders relate to hypothalamic defects e.g. affected TRH, leading to altered TSH and therefore TH as well