Control of regulation Flashcards
An individual perceives thirst when:
What is the more potent stimulus
Body fluid osmolality is increased.
Blood volume is reduced.
Blood pressure is reduced.
Plasma osmolality increased is the more potent stimulus – change of 2-3% induces strong desire to drink.
Decrease of 10-15% in blood volume or arterial pressure required to produce the same response.
When plasma ADH is low how much volume of urine?
large volume of urine is excreted (water diuresis)
When plasma ADH is high how much volume of urine?
a small volume of urine is excreted (anti diuresis).
Osmoreceptors for ADH release found where? Adaptation of brain where they're found? Physiological change? Action? Also regulate?
Found in the hypothalamus, OVLT (Organum vasculosum laminae terminalis) , and SFO (Subfornical organ).
Blood brain barrier selectively allows some things through the brain, so these areas aren’t completely protected by blood brain barrier
Sense changes in body fluid osmolality
Cells shrink or swell in response (expand when plasma more dilute, and vice versa).
Send signals to the ADH producing cells in the hypothalamus to alter ADH release.
Same regions seem to regulate thirst.
Maintaining water balance:
Increased plasma osmolality
Decreased plasma osmolality
Increased plasma osmolality
Invokes drinking and ADH release.
Increased ADH stimulates kidney to conserve water.
Decreased plasma osmolality
Thirst is suppressed and ADH release decreased
Absence of ADH the kidney excretes more water.
Sensation of thirst
What’s involved?
Thirst is decreased by drinking even before sufficient water has been absorbed by the GI tract to correct plasma osmolality.
Receptors in mouth, pharynx, oesophagus seem to be involved.
Relief of thirst sensation via these receptors is short lived.
Thirst is only completely satisfied once plasma osmolality is decreased or blood volume or arterial pressure corrected.
Circuits involved? (don’t know about them much except renin angiotensin system)
Renin-Angiotensin-Aldosterone system related to thirst diagram (slide 11, lecture 12)
Ang II also stimulates thirst
Body weight homeostasis summary diagram
slide 15, lecture 12
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Hypothalamus diagram depicting anatomy
slide 18, lecture 12
Arcuate nucleus= important
Arcuate Nucleus
Key brain area involved in the regulation of food intake.
Incomplete blood brain barrier, allows access to peripheral hormones.
Integrates peripheral and central feeding signals.
Two neuronal populations:
1) Stimulatory (NPY/Agrp neuron)
2) Inhibitory (POMC (Proopiomelanocortin) neuron)
Neuronal populations are separate populations, no overlap at all
Arcuate Nucleus mechanism diagram
slide 21, lecture 12
Things that you want to respond to to regulate appetite cross blood brain barrier
Bind to receptors on neurons, downstream effect= stimulate/ suppress food intake
Cell bodies and receptors of neurons are in arcuate nucleus but axons extend all the way in the brain/ also into paraventricular nucleus which causes other downstream effects (food intake change/ metabolic changes too)
Arcuate Nucleus mechanism diagram
slide 21, lecture 12
Things that you want to respond to to regulate appetite cross blood brain barrier
Bind to receptors on neurons, downstream effect= stimulate/ suppress food intake
Cell bodies and receptors of neurons are in arcuate nucleus but axons extend all the way in the brain/ also into paraventricular nucleus which causes other downstream effects (food intake change/ metabolic changes too)
Melanocortin system summary diagram
slide 22, lecture 12
Agrp= Agouti-related peptide
Alpha MSH= alpha melanocyte stimulating hormone
MC4R=Melanocortin 4 receptor
Stimulation of MC4R= inhibition of food intake
Agrp is released from a different neuronal population but goes to same neurones
Agrp= endogenous antagonist on that receptor, Hungry= increased by increased Agrp which blocks inhibitory signal
Absence of POMC= eat a lot
Human CNS mutations affecting appetite
Symptoms?
No NPY or Agrp mutations associated with appetite discovered in humans.
POMC deficiency and MC4-R mutations cause morbid obesity.
POMC deficiency= lose all the molecules that it makes (ACTH= no corticosteroid regulation so need glucocorticoid replacement immediately after birth), get ginger hair because MC4-R mutation makes ginger hair, no alpha-MSH= obese because food intake not regulated
Signals from other brain regions that regulate appetite
Higher centres.
Amygdala- emotion, memory.
Other parts of the hypothalamus, e.g. lateral hypothalamus
Vagus to brain stem to hypothalamus.
