corticotrophs

Question 1

factors that influence the release of CRH

Answer 1

• circadian rhythm
• stress (both physical and psychological)

Question 2

outline the HPA pathway of CRH release (name of factor, hormones, target cells, receptors, effect)

Answer 2

• hypothal release CRH/CRF into portal circulation: target corticotrophs in ant pit > release of ACTH from ant pit: target adrenal cortical cells BINDS MC2R > release glucocorticoids, mineralocorticoids, androgenic steroids (all cholesterol derivatives)

Question 3

how is ACTH made

Answer 3

peptide fragment cleaved from POMC

Question 4

what is the main glucocorticoids, mineralocorticoids, androgenic steroids (effects?)

Answer 4

Cortisol (stress): stimulates gluconeogenesis, lipolysis, and exerts strong anti-inflammatory effects
Aldosterone (water balance): maintain blood volume and blood pressure, promoting sodium reabsorption
DHEA development of secondary sexual characteristics

Question 5

describe the timing of SNS activation and HPA activation in response to stress

Answer 5

both system activated at the same time
- however, effects of glucorticoids will be delayed (WHY) (glucocorticoids activate transcription factor > expression of genes takes time)
- glucocort have effects that aid in recovery from fight or flight

Question 6

where are glucocorticoids R expressed?

Answer 6

almost every cell type

Question 7

what are the 2 types of glucocort R

Answer 7

mineralocorticoids (MR, Type 1 R) - high affinity for glucocorticoids (limited expression in tissues that involves water balance)
glucocortioid (GR, type 2 R) - low affinity (widely expressed + involved in termination and recovery from stress)

Question 8

how is selectivity of glucocorticoids response mediated?

Answer 8

by expression of 11B-HSDs: which convert cortisol between active/inactive form
11B-HSD1 convert inactive (cortisone > cortisol) to active in metabolic cell types (GR rich cells)
11B-HSD2 convert active > inactive in kidneys and colon (MR rich cells)
HSDs prevents unwanted activation of sensitive MR in kidneys

Question 9

describe adrenal insufficiency (addison’s disease)

Answer 9

two major types
Primary: decreased release of hormones from adrenal glands
Secondary: decreased release of ACTH > decrease in glucocorticoids
Addison’s Disease: primary adrenal insufficiency in which patients lack cortisol production and no negative feedback to ACTH release (pigmentation from MSH; masculinization of female fetus)

Question 10

describe cushing’s syndrome

Answer 10

high level of cortisol
Endogenous caused by tumors
Exogenous caused by prescription corticosteroids (prednisone)