Lecture: Physiology of the Pituitary and Adrenal Glands

Question 1

Where does the glandular tissue of the anterior pituitary arise from?

Answer 1

invagination of pharangeal epithelial tissue

Question 2

Where does the posterior pituitary arise from?

Answer 2

Out growth/extension of the hypothalamus

Question 3

Where are the hormones that are released from the posterior pituitary synthesised?

Answer 3

Magnocellular neurons from the Supraoptic Nucleus and Paraventricular Nucleus.

Question 4

What hormones are released from the PP?

Answer 4

ADH (SON)

Oxytocin (PVN)

Question 5

What stimulates glandular tissue in AP to release hormones?

Answer 5

Neurohormones from hypothalamus carried by capillaries - hypophysal portal vein to stimulate glandular tissue

Question 6

What cell types is the PP primarily comprised of?

Answer 6

The posterior pituitary is comprised primarily of glial-like
cells called pituicytes – these cells do not secrete hormones. Hormones of the posterior pituitary are secreted by magnocellular neurons - cell bodies in the PVN and SON of the hypothalamus. The hormones are synthesized in the cell bodies and transported down the nerve axons into the posterior pituitary

Question 7

What stimulates oxytocin release?

Answer 7

Positive feedback loop. Suckling, sensory stimulation areola,

Question 8

Function of oxytoxin?

Answer 8

1. Milk ejection – contracts myoepithelial cells that surround
   the mammary alveoli
2. Hastens delivery, promotes delivery of the placenta, reduces
   bleeding – contracts uterine smooth muscle
   (NOT THE PHYSIOLOGICAL TRIGGER FOR PARTURITION)

Question 9

MOA of oxytocin?

Answer 9

via G-Protein coupled receptor; 2nd
messengers: IP3, DAG
IP3 is the chemical mediator that causes the release of calcium.

Question 10

MOA of ADH?

Answer 10

1. Reabsorption of water in connecting/collecting tubules via V2 rec. -> cAMP -> insertion of aquaporin-2 into the luminal membrane.
2. Vasoconstriction via V1 rec. -> IP3, DAG -> ↑[Ca2+]i
3. Increases thirst (via actions on the CNS)
4. ↑ACTH from anterior pituitary - ↑aldosterone - ↑
   conservation of Na+ and H2O (Note: plasma K+ and angiotensin II are the main regulators of aldosterone secretion)

Question 11

What stimulates hormone secretion from the anterior pituitary?

Answer 11

Hypothalamic releasing/inhibitory hormones enter a portal system and are conducted to the anterior pituitary

Question 12

Proportion of AP cells made up of thyrotropes?

Answer 12

Thyrotropes (3-5%)
Thyroid-stimulating hormone (TSH) (aka thyrotropin)
Target: thyroid
stimulates T3 & T4 secretion

Question 13

Proportion of AP cells made up of corticotropes?

Answer 13

Corticotropes (15-20%)
Adrenocorticotropic hormone (ACTH) (aka corticotropin)
Target: adrenal cortex
stimulates cortisol secretion

Question 14

Proportion of AP cells made up of somatotropes?

Answer 14

Somatotropes (40-50%)
Growth hormone (GH) (aka somatotropin)
Target: bone, tissues, liver
Growth; influences metabolism

Question 15

Proportion of AP cells made up of gonadotropes?

Answer 15

Gonadotropes (10-15%)
Follicle-stimulating hormone (FSH) & Luteinizing hormone (LH)
Target: ovaries & testes sex hormone secretion;
gamete production

Question 16

Proportion of AP cells made up of lactotropes?

Answer 16

Lactotropes (10-15%)
Prolactin (PRL)
Target: mammary glands
Breast growth; milk secretion

Question 17

What do chromaffin cells in adrenal medulla produce?

Answer 17

Adrenalin