Hormonal Axis Flashcards
Briefly describe the Adrenal Axis Physiology
Cortisol is secreted by the Adrenal Glands
This release is controlled by the hypothalamus which secretes Corticotrophin Releasing Hormone (CRH)
CRH acts on the ANTERIOR pituitary to secrete Adrenocorticotrophic hormone (ACTH)
ACTH in turn stimulates the adrenal glands to secrete Cortisol
Cortisol has a negative feedback on the anterior pituitary and the hypothalamus
When is cortisol released?
Cortisol is secreted in a pulsatile manner (peaks in early morning, lowest at night)
and in response to stress stimulus
What actions does cortisol have on the body? 5
- increases alertness
- increase metabolism
- raises blood glucose
- inhibits immune response
- inhibits bone formation
Describe the physiology of the Renin-Angiotensin System
Renin is a hormone+enzyme secreted by the juxtaglomerular cells of the kidneys, sit in the afferent arterioles
Renin is secreted in response to low blood pressure
Renin converts Angiotensinogen released by the liver into Angiotensin I
Angiotensin I is converted to Angiotensin II use ACE (angiotensin converting enzyme) in the lungs
Angiotensin II has two roles: 1 - cause vasoconstriction, 2- cause Aldosterone release from adrenal glands
What is aldosterone?
What is the action of Aldosterone in the kidneys?
Aldosterone is a mineralocortcoid steroid hormone
Acts on the nephrons of the kidneys
- Na+ reabsorption in the distal tubule
- K+ secretion in the distal tubule
- H+ secretion in the collecting duct
When Na+ is reabsorbed, water follows by osmosis which leads to increase intravascular pressure –> increased blood pressure
what is the action of the hypothalamus ?
stimulates the anterior and posterior pituitary gland
What does the anterior pituitary gland secrete?
Thyroid stimulating hormone TSH Adrenocorticotropic hormone ACTH Follicle stimulating hormone (FSH) Growth hormone (GH) Prolactin
What does the posterior pituitary secrete?
Oxytocin Antidiuretic hormone (ADH)
