Endocrine - Hormone Axis Physiology Flashcards
What is released from the anterior pituitary gland?
TSH
ACTH
GH
FSH and LH
PRL
What does the posterior pituitary gland release?
Oxytocin
ADH
Outline the thyroid axis
Hypothalamus
TRH release
Anterior pituitary
TSH release
Thyroid gland
T3 (Triiodothyronine)
T4 (Thyroxine)
Blood stream
Relay back to anterior pituitary and hypothalamus for feedback loop
What do T3 and T4 stand for?
T3- Triiodothyronine
T4- Thyroxine
Outline the adrenal axis
Hypothalamus
CRH (corticotropin-releasing hormone) release
Anterior pituitary
ACTH (adrenocorticotropic hormone) release
Adrenal glands
Cortisol release
Blood stream
Feedback loop dependent on cortisol levels
Why does cortisol have diurnal variation?
High in the morning to wake up
Low at night to sleep
What are the functions of cortisol?
Inhibits
- Immune system
- Bone formation
Increases
- Alertness
- Metabolism
- Blood glucose
Outline the growth hormone axis
Hypothalamus
GHRH production
Anterior pituitary
GH release
Liver
Insulin-like growth factor 1 (IGF-1) release stimulated by GH
What are the main functions of growth hormone?
- Stimulate muscle growth
- Increases bone density and strength
- Stimulate cell regeneration and reproduction
- Stimulate internal organ growth
Outline the parathyroid axis
Parathyroid glands
- PTH released in response to low serum calcium, magnesium or phosphate
Bone
-PTH increases activity and number of osteoclasts, reabsorption of calcium from bone to blood
Kidneys
- PTH Stimulates calcium absorption
- Stimulates conversion of Vitamin D3 into calcitriol (active Vitamin D)
Intestines
- Vitamin D promotes calcium absorption from food
Blood
- High calcium supresses PTH
- Low calcium promotes PTH
What is the role of PTH?
Increase serum calcium
Outline RAAS
Juxtaglomerular apparatus cells
Renin secreted in response to low BP
Liver
Renin converts angiotensinogen to angiotensin I
Lungs
Angiotensin I converted to Angiotensin II with ACE
Angiotensin II
- Causes vasoconstriction of blood vessels
- Stimulates aldosterone release from adrenal glands
- Cardiac remodelling by promoting hypertrophy of myocytes
How does aldosterone act on the nephrons?
- Increases ENaC channels in distal tubule
- Increases RomK channels to secrete potassium from distal tubule
- Increases hydrogen secretion from collecting ducts
