Adrenal Control Flashcards
What are the two things that influence corticotrophin releasing hormone and what does this act on to influence release of cortisol?
Circadian rhythm (low blood glucose in morning) and long term stress (physical or psychological). Release ACTH, release cortisol.
What is gluconeogenesis?
Occurs in liver - blood glucose low so liver produces enzymes to break down glycogen into glucose to be released.
How does the liver get the factors is needs for enzyme synthesis to perform gluconeogenesis?
From protein breakdown in the muscle. Cortisol acts directly in the muscle cells for protein catabolism.
What are the pathways by which physiological stress can be resisted in the body?
Metabolic stress - maintain bg levels
Cardiovascular stress - maintain blood pressure and flow
Electrolyte stress - maintain blood Na, K, Ca etc.
What is the clinical use of glucocorticoids?
Suppress immune system and inflammatory response - used for chronic inflammatory diseases e.g. rheumatoid arthritis and asthma.
What is Cushing’s syndrome, Addison’s disease and Conn’s syndrome?
Cush - cortisol excess - decreased muscle mass
Add - cortisol and aldosterone deficiency - hypoglycemia, inhibits actions of adrenal gland.
Conns - aldosterone excess. Excess Na and water retention
What are the four mechanisms of aldosterone secretion?
From adrenal cortex (glomerulosa).
Decreased sodium or increased potassium - goes to kidneys to do add sodium/remove K. Water follow sodium and salt return normal.
Decreased blood volume or pressure - renin and angiotensin systems act to increase secretion.
Stress - into portal system and release CRH into anterior pituitary to release ACTH.
Increased blood pressure or volume - too much fluid or salt - heart releases atrial natriuretic peptide to inhibit aldosterone.
How does aldosterone act to help kidneys manage water, K and Na?
Travels through blood to kidneys into interstitial fluid. Crosses membrane and binds to intracellular receptors. Binds to DNA to cause transcription of mRNA and will increase production of certain proteins. ATPase driven pumps on interstitial fluid side and make new channels on lumen side. Pump pull K into interstitial fluid and Na back out.
How does the body deal with short term stress?
Neuroendocrine activity - hypothalamus will stimulate preganglionic sympathetic fibers in the spinal cord - to adrenal medulla - adrenaline/noradrenaline released.
How does the body deal with prolonged stress?
Stimulates hypothalamic pituitary adrenal axis - CRH from hypothalamus to anterior pituitary get ACTH to blood. Adrenal cortex cells have receptor for ACTH- get release of aldosterone, cortisol.
