Lecture 10 - The Adrenals and their Hormones

Question 1

Where are the adrenal glands found?

Answer 1

On the superior pole of each of the 2 kidneys

Question 2

What are the sections of the adrenal gland - from outside to inside?

Answer 2

Capsule Cortex: 1) Zona Glomerulosa 2) Zona Fasciculata 3) Zona Reticularis

Adrenal Medulla

Tributary of central vein

Question 3

How is the Zona Fasciculata arranged?

Answer 3

Cells line up as strings

Question 4

How does the blood flow into adrenal cortex and to the zones?

Answer 4

To adrenal cortex via arteries that feed the outside of the gland 2 ways for the zones: Most passes through the cells and there are some vessels which go through the cortex to get to adrenal medulla

Question 5

What is the medulla made up of?

Answer 5

Chromaffin cells - post-ganglionic nerve fibres in a specialised form

Question 6

What type of hormones does the medulla secrete?

Answer 6

CATECHOLAMINES from Chromaffin cells

Question 7

What type of hormones does the cortex secrete?

Answer 7

Corticosteroids

Question 8

What specific hormones are released by the medulla?

Answer 8

Adrenaline - 80% Noradrenaline - 20% Dopamine - very small amounts

Question 9

What specific hormones are released by the cortex?

Answer 9

Mineralocorticoids - aldosterone Glucocorticoids - cortisol Sex steroids - Androgens and Oestrogens

Question 10

In which zone is aldosterone produced?

Answer 10

Zona Glomerulosa

Question 11

In which zone are cortisol/androgens/oestrogens produced?

Answer 11

Zona Fasciculata and Reticularis

Question 12

What is the nucleus of cholesterol?

Answer 12

Cyclopentanoperhydrophenanthrene

Question 13

Which steroids are produced in the adrenals?

Answer 13

Mineralocorticoids Glucocorticoids

Question 14

Which steroids produced in the gonads?

Answer 14

Progestogens Androgens Oestrogens

Question 15

Where androgens produced and then moved to become stronger?

Answer 15

Produced in the adrenals (weak) and become stronger in the gonads (testes)

Question 16

What is androstenedione useful for?

Answer 16

Its a less weak androgen and can be converted into testosterone and DHT

Question 17

What is the precursor for aldosterone?

Answer 17

Progesterone

Question 18

What is the precursor for Oestrogen?

Answer 18

Androgens

Question 19

How is cortisol transported around the blood?

Answer 19

75% bound to corticosteroid binding globulin (Transcortin) 15% bound to albumin 10% free - BIOACTIVE

Question 20

How is Aldosterone transported around the blood?

Answer 20

60% bound to corticosteroid binding globulin 40% free - BIOACTIVE

Question 21

What happens to cortisol levels?

Answer 21

Levels change during day Released in pulses In morning higher than evening MORE cortisol than aldosterone

Question 22

What happens to aldosterone levels?

Answer 22

They remain the same during the day Controlled by position - involved in control of fluid and balance

Question 23

What are the main actions of aldosterone?

Answer 23

Stimulate Na+ reabsorption and K+ and H+ secretion in DISTAL CONVOLUTED TUBULE and cortical collecting duct

Question 24

When does the adrenal gland form during pregnancy?

Answer 24

Week 6 when the adrenal glands form but only one zone- fetal zone One week after birth is when the 3 zones develop

Question 25

What is the main target tissue for aldosterone?

Answer 25

Kidneys

Question 26

What is the mechanism of action of aldosterone?

Answer 26

Aldosterone enters cell and binds to receptors in cytoplasm HR complex enter the nucleus and attach to genes Causes increase in ion channel and enzyme production Na/K channel causes Na to move in and K to move out Na is also pumped out into the blood as Na reabsorption is increased

Question 27

What are the key features of the juxtaglomerular apparatus (JGA)?

Answer 27

Efferent and afferent arterioles Glomerulus Macula densa Distal tubule Juxtaglomerular cells

Question 28

What does the macula densa react to?

Answer 28

To Na concentration in tubule fluid

Question 29

What are stressors?

Answer 29

Variety of things perceived by an organism as a threat e.g. Hypoglycaemia, trauma (NOT chronic)

Question 30

What are the causes of renin release?

Answer 30

Decreased renal perfusion pressure Increased renal sympathetic activity Decreased Na load to top of loop of Henle - macula densa

Question 31

Describe the renin-angiotensin-aldosterone system

Answer 31

Question 32

Where is Renin produced?

Answer 32

In the juxta-glomerular cells

Question 33

Where is ACE produced?

Answer 33

Lungs and kidneys

Question 34

What are the metabolic actions of cortisol?

Answer 34

Peripheral protein catabolism Hepatic gluconeogenesis ^ BGL Fat metabolism - lipolysis in adipose cells Enhanced effects of glucagon and catecholamines

Question 35

What are the other effects of cortisol?

Answer 35

Some mineralocorticoid effects Cardiovascular and renal effects - excretion of water load, ^ vascular permeability Other effects - on bone (^ breakdown), growth, CNS (^ = associated with depression)

Question 36

What are the effects of large pharmacological amounts of cortisol?

Answer 36

Anti-inflammatory action Immunosuppressive action Anti-allergic action Associated with decrease production of prosteoglandins, histamine and interleukins and movement and function of leukocytes

Question 37

What does cortisol bind to?

Answer 37

Glucocorticoid receptors Turns into Cortisone (inactive) via T2 Aldosterone receptors (also aldosterone)

Question 38

What is the full name for enzyme T2?

Answer 38

11beta-hydroxysteroid dehydrogenase

Question 39

What are the problems that are caused by binding to aldosterone receptors?

Answer 39

It inhibits greatly as there is 1000x higher concentration of cortisol c.f. aldosterone

Question 40

What is the mechanism of action of cortisol?

Answer 40

Cortisol enters and forms a hormone-receptor complex which acts as a transcription factor New proteins - Annexin: controls prostaglandin synthesis - synthesis AUTOCRINE - acts on Annexin receptor Release of Arachidonic acid which inhibits prostglandin synthesis

Question 41

What does POMC turn into?

Answer 41

POMC \> Pro-ACTH and beta-LPH \> Pro-gamma-MSH, ACTH, gamma-LPH, b-endorphin

Question 42

What is hypothalamic enzymes are secreted to release ACTH?

Answer 42

CRH and VP

Question 43

How is ACTH released?

Answer 43

In a cicadian rhythm - BIOLOGICAL CLOCK otherwise it inhibits CRH

Question 44

Where does ACTH act on in adrenal?

Answer 44

Adrenal cortex - zona fasciculata and reticularis

Question 45

What does the adrenal cortex do when stimulated by ACTH?

Answer 45

Releases CORTISOL and small amounts of androgens

Question 46

What does DHEA stand for?

Answer 46

Dehydroepiandrosterone

Question 47

What is DHEA?

Answer 47

Precursor for androgens and oestrogens Converted to active form when in target cells

Question 48

When is the peak serum level for DHEA?

Answer 48

20-30 years with a particularly important effect

Question 49

What does DHEA do?

Answer 49

Important in postmenopausal women as precursor for oestrogen synthesis by target tissues in absence of ovarian steroids

Question 50

How is cortisol production regulated?

Answer 50