Appetite (Complete) Flashcards
Give 3 examples of factors that can stimulate thirst
Body fluid osmolality
Body volume reduced
Blood pressure reduced
Out of the three main factors that can stimulate thirst, which factor has the most potent effect?
Plasma osmolality increase is the more potent stimulus – change of 2-3% induces strong desire to drink
N.B. Decrease of 10-15% in blood volume or arterial pressure is required to produce the same response
When is the sensation of thirst decreased?
Immediately after drinking (even before GI tract absorbs water to correct osmolality)
Explain why sensation of thirst is decreased immediately after drinking despite water yet being reabsorbed in the GI tract to correct osmolality.
Receptors in mouth, pharynx, oesophagus are involved
N.B. Relief of thirst sensation via these receptors is short lived.
Despite receptors in the mouth and pharynx decreasing thirst, it is only short lived and is completely relieved once?
Thirst is only completely satisfied once plasma osmolality is decreased or blood volume or arterial pressure corrected.
What effect does reduction in fat mass have on food intake and energy expenditure?
Increases food intake
Reduces energy expenditure
What effect does adipose tissue expansion have on food intake and energy expenditure
Food intake decreases
Energy expenditure increases
Explain body weight homeostasis
Body weight is relatively stable for adults
This is due to effects of adipose tissue expansion and fat reduction.
Adipose tissue expansion decreases food intake and increases energy expenditure
Reduction in body fat increases food intake and decreases energy expenditure
Collectively this creates a homeostatic effect in maintaining body weight
In a weight-reduced underfed state, list 5 ways the body tries to re-achieve body weight homeostasis
Reduces sympathetic activity
Reduces thyroid activity
Reduces energy expenditure
Increases appetite
(Ultimately increases body weight)
In a weight-increased overfed state, list 3 ways the body tries to re-achieve body weight homeostasis
Increased sympathetic nervous activity
Increased energy expenditure
Decreased appetite
Which brain region is important in regulation of appetite?
Hypothalamus
List 4 factors which have an input effect on hypothalamic activity in regulating appetite.
Grehilin (Gut hormone)
PYY (gut hormone)
Leptin (fat hormone)
Neural input from the periphery and other brain regions
What 2 things does the hypothalmus play a role in regulating in terms of appetite?
Regulates food intake
Regulates energy expenditure
The hypothalamus releses peptides which can regulate appetite. Name the peptide which is appetite stimulant.
Orexigenic peptides
The hypothalamus releses peptides which can regulate appetite. Name the peptide which is appetite suppresive
Anorectic peptides
Onorexigenic and anorectic peptides are released from which region of the hypothalamus?
Arcuate nucleus
Which regions of the hypothalamus produces orexigenic peptides?
Lateral hypothalamus (ONLY orexigenic)
Arcuate nucleus (produces both orexigenic and anorectic peptides)
Which region of the hypothalamus is associated with satiety (fullness)?
Ventromedial hypothalamus
Lesion in the ventromedial hypothalamus could theoretically lead to?
Severe obesity due to lack of satiety
Which brain area is involved mainly in the regulation of food intake?
Arcuate nucleus
What structural differences does the arcuate nucleus have that enables it to adequately perform its function?
Has an incomplete blood-brain barrier to enable detection of peripheral hormones
What role does the arcuate nucleus have in regulating food intake?
Integrates peripheral and central feeding signals
What are the two neuronal populations in the arcuate nucleus that plays a role in regulating food intake? Which has a stimulatory function and which has an inhibitory function?
Stimulatory population of neurones (Neuropeptide Y (NPY) neurones and Agouti-Related Peptide (AgRP) neurones.
Inhibitory population of neurones (Pro-opiomelanocortin [POMC] neurones)
What hormone plays a role inhibition/stimulation of arcuate nucleus nuerones. And what role does it play?
Leptin
Inhibitis NPY and AGRP neurones
Stimulates POMC neurones