Appetite Flashcards
(58 cards)
What are the three stimulus for the control of thirst?
Body fluid osmolality
Blood volume reduction
Blood pressure reduction
What is the most potent stimulus for the control of thirst?
Body fluid osmolality, change by 2-3% in comparison to 10-15%
When plasma ADH is high what is the effect on the volume of urine excreted?
A small volume of urine is excreted
When plasma ADH is low what is the effect on the volume of urine that is excreted?
A large volume of urine is excreted
How does ADH act to regulate osmolality?
Acts on kidneys to regulate the volume and osmolality of urine by upregulation/down regulation of Aquaporin2 channels in the collection duct
Where is ADH stored?
Posterior pituitary
What type of receptors are osmoreceptors, what is their function and where are they found?
They are sensory receptors, involved in osmoregulation and found in the hypothalamus
Cell shrinkage due to a high plasma concentration causes fluid retention and invokes drinking, how?
The cells shrink meaning the proportion of cation channels increases causing the membrane to depolarise, this sends signals to the ADH producing cells to increase ADH secretion
How is the sensation of thirst satisfied?
Receptors in mouth, pharynx and oesophagus are involved before water has been absorbed by the GI tract and relief of the thirst sensation via these receptors is short lived.
Thirst is only completely satisfied once plasma osmolality is decreased or blood volume/ arterial pressure is corrected
How does a decreased blood pressure result in H20 retention? (RAAS )
A low blood pressure is detected by the juxtaglomerular cells of the renal afferent arteriole
Juxtaglomerular cells secrete renin
Renin acts on angiotensin -> angiotensin 1
ACE from the vascular endothelium of lungs and kidneys act on angiotensin1 -> angiotensin2
Angiotensin2 acts to increase Na+/H exchange, increasing sodium reabsorption, increasing osmolarity of the blood
Angiotensin2 acts on zona glomerulosa cells of the adrenal cortex to stimulate aldosterone release which causes H2O retention
How does aldosterone secretion result in H2O retention?
Via Na+ Cl- absorption and K+ excretion
Where is ACE found?
In the vascular endothelium of the kidneys and lungs
Where is angiotensin produced?
The liver
The conversion of angiotensin1 to angiotensin2 is catalysed by which enzyme?
Angiotensin converting enzyme (ACE)
How does angiotensin2 exert its affects?
By binding to angiotensin 2 type 1 and angiotensin2 type 2 receptors in the brain, kidney, adrenal cortex, and arterioles
How does aldosterone work?
By stimulating the insertion of luminal Na channels and basolateral Na-K ATPase proteins
What mechanisms are there to manage excessive fluid intake?
Receptors in mouth, pharynx and oesophagus relieve thirst sensation initially to avoid overload
Weight homeostasis favours ________ weight
Stable weight
If weights reduces:
> ↓ sympathetic activity
↓ energy expenditure
↓ thyroid activity
↑ hunger/foot intake
If weight increases?
> ↑ sympathetic activity
↑ energy expenditure
↓ hunger/food intake
How does the central circuit defend against reduction in body fat?
Via leptin
The regulation of appetite occurs in _____, peripheral input for appetite reaches the brain via ______
The hypothalamus
The vagus nerve
What are the key gut hormones in appetite regulation?
Ghrelin and PYY
How does the hypothalamus regulate appetite through the arcuate nucleus?
Arcuate nucleus produces orexigenic and anorectic peptides
