Hormonal physiology Flashcards
Where is the hypothalamus and what is its role
Above the pituitary gland, stimulates it with various hormones
What hormones are produced in the anterior pituitary gland
TSH- thyroid stimulating hormone
ACTH- adrenocorticotropic hormone
FSH+LSH- follicle stimulating hormone + luteinising hormone ( gonadal hormones)
GH- growth hormone
Prolactin- stimulates mammary glands to produce milk in alveoli, travels in ducts
What occurs when the hypothalamus releases thyrotropin releasing hormone?
Stimulates ant. pituitary to release TSH, leading to triiodothyronine and thyroxine (t3 and t4) release from thyroid
What is role of t3 and t4?
T3 more abundant- metabolic rate, heart and digestive functions, muscle control, brain development and function, and the maintenance of bones
t3/4 sensed by HT + AP, suppress release of TRH/ TSH- levels of t3/4 drop > less suppression> increased levels
NEGATIVE FEEDBACK
where is cortisol secreted and what type of hormone is it
secreted by 2 zona fasciculata of adrenal glands, released controlled by hypothalamus
a glucocorticoid responding to stress stimuli- higher in mornings (wake up), lowest in evenings (sleep)
What occurs when hypothalamus releases corticotropin releasing hormone (CRH)
stimulates ant. pituitary to release ACTH> adrenal gland to release cortisol- increased levels leads to suppression of CRH/ACTH, reduced levels cortisol
NEGATIVE FEEDBACK
What actions does cortisol have in the body?
Inhibits immune system Inhibits bone formation Raise blood glucose Increase metabolism Increase alertness
What happens when growth hormone releasing hormone is released from the hypothalamus
Stimulates GH release from ant. pituitary
GH stimulates release of insulin-like growth factor 1 (igf-1) from LIVER
What action does GH exhibit in body?
Stimulates muscle growth
Increases bone density/ strength
Stimulates cell regeneration/ reproduction
Stimulates growth of internal organs
Why would parathyroid hormone be released from the PT glands
In response to reduced serum calcium, magnesium or increased serum phosphate
Role- increase serum calcium concentration
How does PTH bring about an increase in serum calcium concentration
PTH increases activity and number of osteoclasts- reabsorption of bone into blood (inc calcium conc)
Stimulates calcium reabsoprtion in kidney, less excreted in urine
Conversion of vit d3 to calcitriol in kidney- calcium absoprtion from food in S. intestine
NEGATIVE FEEDBACK WHEN HIGH
Where is renin secreted and in response to what
Juxtaglomerular cells in afferent (and some) efferent arterioles in kidney
In response to low blood pressure
What is the RAAS pathway
Angiotensinogen in liver (renin) —> angiotensin I in lungs (ACE) —-> Angiotensin II
Angiotensin II > vasoconstriction (increased blood pressure) and aldosterone release from adrenal glands
What are the functions of aldosterone
Produced in ZG (capsule)- mineralocorticoid steroid hormone acts on nephron to:
1. increase sodium reasborption from distal tubule
2. increase potassium secretion from distal tubule
3. increase hydrogen secretion from collecting ducts
when sodium reabsorbed, water follows by osmosis > increased IV volume and increased BP
Adrenal regions and hormones released
ZG (cortex)- mineralocorticoids e.g aldosterone
ZF (cortex)- glucocorticoids e.g cortisol, corticosterone, cortisone
ZR (cortex)- androgens e.g dehydroepiandrosterone: > Test/ DHT
Adrenal medulla - stress hormones: epinephrine/ norepinephrine
