Adrenal Glands and the Stress Response

Question 1

Answer 1

Question 2

Why are the 3 categories of steroids are produced in distinct sections of the adrenal cortex?

Answer 2

Due to the different distribution of catalytic enzymes!

Question 3

What type of hormones are the adernal steroid hormones?

Answer 3

Lipophilic hormones → diffuse into blood after synthesis (∴must regulate this synthesis)

Question 4

How are the adernal steroid hormones transported?

Answer 4

Transported bound to plasma proteins

• Aldosterone and DHEA bound to albumin (nonspecific)
• Cortisol bound to corticosteroid-­‐binding globulin (transcortin)

Question 5

What happens once the adrenal steriod hormone binds to its specific steriod R (in cytoplasm or nucleus)?

Answer 5

Once the steriod has bound to a specific R, the hormone-­‐R complex moves to the nucleus and binds to complementary hormone-­‐response element in DNA.

This initiates specific gene transcription leading to synthesis of new proteins!

–Recent research has revealed steroid plasma membrane R’s (e.g. for aldosterone, testosterone and estrogen)

Question 6

What is the main function of Aldosterone?

Answer 6

INCREASES REABSORPTION OF Na+

WHILST INCREASING THE EXCRETION OF K+

Question 7

Answer 7

Question 8

Where is the main site for the production of sex hormones?

Answer 8

THE GONADS!

–Testes for ANDROGENS

–Ovaries for ESTROGENS

DHEA is the only adrenal sex hormone of importance!

–males; overpowered by testoserone (x100 stronger)

–females; pubic & axillary hair, enhances pubertal growth spurt, maintains sex drive

[[NOTE: DHEA inhibits GnRH, NOT CRH!]]

Question 9

What may occur as a result of the acute stress response?

Answer 9

• ↑ Heart rate
• ↑ Blood P
• ↑ Glycogenolysis
• Dilation of bronchioles

• Δ blood
flow pattern

(alertness, ↓ digestion & urinary output)

• ↑ metabolic rate

Question 10

What affect does a longer term stress response have on mineralcorticoids?

Answer 10

↑ retention of Na & H₂O

↑ blood vol & P

Question 11

What affect does a longer term stress response have on glucocorticoids?

Answer 11

↑ blood sugar

↑ proteolysis

↑ gluconeogenesis

↑ lipolysis

Decrease immune system

Question 12

What is the main function of ACTH?

Answer 12

Acts I^o on the z. fasciculata & z. reticularis to STIMULATE THE RELEASE OF CORTISOL & ANDROGENS

Question 13

Which hormone stimulates the secretion of ACTH?

Answer 13

CRH

Question 14

How is cortisol regulated?

Answer 14

By a NEG (-) F.B LOOP involving both CRH & ACTH!

Question 15

Answer 15

Question 16

What is the main function of Cortisol?

Answer 16

– I^o role is to INCREASE BLOOD GLUCOSE @ thge expense of fats & proteins!

–Stimulates hepatic gluconeogenesis (a.a’s → carbs)

–Inhibits glucose uptake in tissues (except for brain)

–Inhibits protein synth. and stimulates protein degradation in many tissues (especially muscle),

THUS increasing blood a.a’s

–Facilitates lipolysis (in adipose tissue) providing free fatty acids as an alternative fuel

Question 17

T or F:

Cortisol is antagonistic to ACTIONS of insulin?

” “ induces insulin resistence?

Answer 17

T

Question 18

Cortisol also effects…

Answer 18

–inhibits bone formation, stim. bone resorption

–alters modd & behaviour

–effects learning & memory

–stim. RBC production

–stim. gastric acid secretion

Question 19

Answer 19

Question 20

What may happen if there is adrenocorticol insufficiency?

Answer 20

[If one adrenal gland is damaged, the other can take over (hypertrophy & hyperplasia)]

–

PRIMARY (Addison’s Disease): all layers under-secrete (most commonly caused by autoimmune problems)

SECONDARY: e.g. problem with insufficient ACTH.

NOTE that aldosterone doesn’t depend on ACTH stim., so lvls are normal.