The pituitary gland

Question 1

What is a hormone?

Answer 1

A molecule/molecules that act as messengers throughout the body

Question 2

What 2 types of hormone are there?

Answer 2

Peptide and steroid

Question 3

How are peptide hormones synthesised, stored and what receptors detect them?

Answer 3

Synthesis - Prohormones initially which require further processing to activate
Storage - In vesicles
Receptors - Bind to receptors on cell membrane and activate secondary messenger

Question 4

How are steroid hormones synthesised, stored and what receptors detect them?

Answer 4

Synthesis - Series of reactions from cholesterol
Storage - Released immediately
Receptors - Bind to intracellular receptors to change gene expression directly

Question 5

Where is the pituitary gland located & how is attached?

Answer 5

Inferior to the hypothalamus & posterior to the optic chiasm
Attached to the hypothalamus via the infundibulum
Sits superiorly to the sella turcica of the sphenoid bone

Question 6

How is the anterior pituitary gland regulated?

Answer 6

Parvocellular neurons in the hypothalamus send factors (excitatory or inhibitory) to the median eminence which secrete into the portal circulation (by fenustrations) to the anterior pituitary

Question 7

What type of cells is the anterior pituitary made up of and what hormones do the cells produce?

Answer 7

Endocrine cells (glandular tissue):

• Somatotrophs (growth hormones)
• Lactotrophs (prolactin)
• Corticotrophs (Adrenocorticotrophic hormone, corticotrophin)
• Thyrotrophs (ThyroidStimulaitngHormone)
• Gonadotrophs (gonad stimulating hormones)

Question 8

What stimulate/inhibit the production of the different hormones in the pituitary gland?

Answer 8

Growth Hormones - Inhibited by Somatostatin
Promoted by Growth hormone releasing hormone
Prolactin - Inhibited by Dopamine
Thyroid stimulating hormone (thyrotrophin) - Promoted by Thyrotrophin releasing hormone
Gonadotrophins - Promoted by Gonadotrophin releasing hormone
ACTH - Promoted by Corticotrophin releasing hormone

Question 9

What would occur if there was a pituitary tumour and why?

Answer 9

Bitemporal hemianopia (reduced field of view) - as the tumour would press against the optic chiasm, as fibres from nasal retinae cross at the optic chiasm, they would get ‘squishes’ and make the patient lose there temporal view

Question 10

What are the mechanisms of action of growth hormones?

Answer 10

1. Growth hormone directly binds to the receptors of tissue
2. Growth hormone goes to the liver and causes the secretion on IGF-1 which can also be detected by tissues to stimulate growth

Question 11

What two hormones are produced by the posterior pituitary gland?

Answer 11

Arginine vasopressin (ADH) & oxytocin

Question 12

What type of tissue is the posterior pituitary gland made up of?

Answer 12

Neural tissue

Question 13

What nerves go from the hypothalamus to the posterior pituitary?

Answer 13

Magnocellular neurons

Question 14

Which receptors responds to vasopressin?

Answer 14

V2 receptors in the kidney - to concentrate the urine

V1 receptors - causes vasoconstriction

Question 15

How does vasopressing concentrate urine?

Answer 15

1. The AVP binds to V2 receptors (a g-protein coupled receptor)
2. This activates a G protein which activates cAMP
3. This then causes the acitvation of protein kinase A
4. Protein kinase A then unclusters aquaporin-2 from one another
5. Aquaporin-2 binds the membrane and allows water to travel out of the urine