BIOL 319 Lecture: GH-IGF1 Axis

What regulates the growth of the skeletal system?

endocrine system and nervous system

What things does the endocrine system mainly regulate?

growth

metabolism

reproduction 

What produces and secretes oxytocin?

oxytocin is produced in the brain and the pituitary gland releases it

How are the pituitary gland and the brain connected?

system of small blood vessels

What part of the brain specifically releases hormones?

hypothalamus

Which hormones regulate the release of somatotropin?

GHIH and GHRH

What is GHRH's role in the pituitary gland?

it is the accelerator of the release of growth hormone

stimulates pituitary gland to release GH into the circulation 

What is GHIH's role in the pituitary gland?

it is the brake: inhibits release of GH

How is GH released?

short big pulse in the morning hours when sleeping

What rhythm does GH follow?

circadian: a rhythm that occurs every 24 hours

How is GH an indirect growth hormone?

it is used to stimulate another hormone: on it's own it is not enough to grow bone

Where does GH interact?

the hepatocytes of the liver: to make IGF-1

What is IGF-1 and what does it target?

insulin growth factor: targets the chondrocytes to increase rate of mitosis in zone of hyperplasia

What is an exocrine gland and how is it different from an endocrine gland?

gland that makes secretion through a duct: endocrine makes a hormone that goes through the bloodstream

What is a paracrine gland?

gland secretes into the interstitial fluid but not the bloodstream

How is IGF-1 functioning as a paracrine gland?

binds to chondrocytes and moves through interstitial fluid affecting cells around it

What kind of feedback loop is IGF-1 similar to?

almost positive feedback loop: can be stimulated for a very long time

What are some other hormones that affect the GH-IGF-1 Axis?

thyroid hormone

cortisol and adrenaline

What makes thyroid hormone and what does it do?

thyroid

regulates basal metabolic rate: allows you to burn ATP and make heat 

What is hyper/hypothyroidism?

hyperthyroidism: body makes too much thyroid hormone

hypothyroidism: body makes too little thyroid hormone