Physiology of HPA axis

Question 1

HPA axis function

Answer 1

stimulate corticosteroid synthesis (stress)

Question 2

HPA axis target organ

Answer 2

adrenal cortex

Question 3

What does the anterior pituitary produce in the HPA axis?

Answer 3

adrenocorticotropic hormone (ACTH)

Question 4

What does the hypothalamus produce in the HPA axis?

Answer 4

corticotrophin releasing hormone (CRH)

Question 5

How does the hypothalamus communicate with the posterior pituitary?

Answer 5

through nerves
(posterior pituitary is an extension of the hypothalamus which is neural tissue)

Question 6

How does the anterior pituitary communicate with the hypothalamus?

Answer 6

via hypophyseal portal system (blood stream)

Question 7

What hormones does the anterior pituitary produce?

Answer 7

TSH
prolactin
FSH/LH
ACTH
GH

Question 8

Describe cortisol synthesis

Answer 8

when faced with stress the cerebral cortex stimulates the hypothalamus to release a neuropeptide called corticotropin-releasing hormone
CRH is carried by the pituitary portal system and then stimulates the anterior pituitary to release ACTH
systemic ACTH stimulates the adrenal cortical cells of the adrenal gland to synthesis cortisol

Question 9

What type of steroid is cortisol?

Answer 9

glucocorticoid

Question 10

What is the metabolic action of cortisol?

Answer 10

decreases muscle glucose uptake
decreases muscle amino acid uptake
decreases adipose tissue fat uptake

net effect = increases plasma glucose, free fatty acids and amino acids