Control Flashcards
Hormonal control and water and hypothalamus
Leptin, what is it?
hormone that provides long term appetite regulation
Where is the arcuate nucleus found?
Base of brai
What is ghrelin?
peptide hormone that regulates short-term appetite control by promoting eating behaviours.
‘hunger hormone’ and is secreted from cells in the stomach in increasingly higher quantities in the build up to a meal
What is peptide YY
Peptide hormone that regulates short-term appetite control by suppressing eating behaviours.
What do NPY/Agrp neurons do? Where are they located
Stimuate food intake and are located medially
What do POMC neurones do?
Inhibit food intake and are located more laterally
What is POMC
Long peptide that can be cleaved in many ways for many different purposes
What is the key site for axons of neurones what’s cell bodies lie in arcuate nucleus for appetite
Paraventricular nucleus
What does Agrp; POMC form?
Alpha melanocyte stimulating hormone - alpha MSH
What does alpha MSH do?
Bind to receptors in paraventricular nucleus eg melanocortin 4 receptor MC4R which is involved in regulation of food intake, and receptor when activated decreases food intake behaviours
What are the actions of alpha MSH and Agrp to MC4R
alpha-MSH binds to MC4R, which responds by reducing food intake behaviours
Agrp binds to MC4R and competitively blocks the satieting signal (i.e. I’m full and I don’t need to eat) from α-MSH. This causes an increase in food intake behaviours
What does POMC deficiency and MC4R mutation cause
Morbid obesity
Where is leptin secreted?
Cells in white adipose tissue
What does leptin do? What does it bind to?
Receptors in the hypothalamic circuits and stimulates anorexigenic behaviours (i.e. suppresses appetite).
What is leptin resistance associated with
Obesity
What does ghrelin do and what does it bind to?
binds to hypothalamic receptors and increases the perception of hunger and the urge to eat.
Where is peptide YY secreted?
from cells in the ileum and colon in response to a meal.
What does peptide YY bind to? What does it do?
PYY3-36 binds to hypothalamic receptors and reduces the perception of hunger and the urge to eat.
What are the sensing organs for solute concentration?
Osmoreceptors
Found in brain adjacent to structures with incomplete blood brain barrier - principally hypothalamus, within the OVLT and SFO regions
What does vasopressin do
To insert aquaporin-2 channels into the collecting duct of renal nephrons to increase water reabsorption
To stimulate vasoconstriction
which conserves blood volume and increase BP
Stimulate thirst
Where is vasopressin produced and released?
Produced in the hypothalamus and released from the posterior pituitary gland.
What do osmoreceptive cells do in response to changes in osmolarity?
affect the firing rate of these cells, which will adjust the basal level of ADH being secreted. Increased ADH secretion will lead to water retention (and a decreased osmolality).
How can thirst be satisfied?
Presence of water in the GI tract can quench thirst, for a short period of time at least - receptors in the upper GI tract (mouth to oesophagus) - short term feedback
Once the original stimulus (osmolality or blood pressure) has been corrected, then the perception of thirst is no longer felt - long term feedback
What are the 5 primary effects of angiotensin II
It binds to receptors on vascular smooth muscle cells to stimulate VASOCONSTRICTION
It upregulates activity of the sympathetic nervous system - VASOCONSTRICTION
It stimulates ALDOSTERONE SECRETION, which increases NA+ REABSORPTION in nephron - osmotic gradient for water reabsorption
It directly influences sodium reabsorption, causing water reabsorption
It stimulates ADH RELEASE and stimulates thirst
Where is angiotensinogen produced?
Liver
Where is angiotensinogen converted to angiotensin I
Kidney
- renin secreted in response to low BP
How is Angiotensin I converted to angiotensin II? What cells express the enzyme
Angiotensin converting enzyme ACE
Expressed on vascular endothelial cells of pulmonary and renal microvessels
