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Regulating Nutrient Intake Part 1
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Covers the regulation of nutrient intake in different organisms.
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Comparative Anatomy and Physiology of AnimalsLecture 17 Regulation of nutrient intake 1 15/12/20
How do animals regulate nutrient intake?
When and how much?
- Over- and under- consumption of nutrients is bad for health.
- For all organisms that have been tested, there is an ideal region in nutritional space, where
consumption in that region maximises fitness. This means that when organisms feed within
that region, they produce the most viable offspring over their lifetime.
- To regulate nutrient intake, animals need to be able to assess the nutritional quality of the
food item, assess its own nutritional state, and compare the two. This is essentially asking:
What is the nutritional composition of the food?, What nutrients do I need?, And how much
of this food do I need to eat to balance my diet?
Taste
- The simplest way of detecting nutrients.
- All organisms have ways to detect amino acids, sugars, salts, and other nutrients.
- External receptors: tarsi, palps, barbels.
- Internal receptors: tongue, gut lining.
- Provides info to CNS about nutrients in food before, during, and after digestion.
- Strength of signal increases with an increase in concentration in the food, up until an
excessively high concentration where it may cause a reduced response.
- Taste is composed of phagostimulatory and phagodeterrent inputs detected by the CNS.
- Positive: receptors responding to nutrients.
- Negative: receptors stimulated by potentially toxic compounds.
- Net: phagostimulatory power of food- its capacity to stimulate and maintain feeding
behaviour.
Nutritionally “wise” behaviour
- Eat predominantly from optimal food.
- Distribute feeding amongst 2 or more complementary foods to mix optimal diet.
- If restricted to suboptimal/non complementary diets – eat most of food (or mix of foods)
closest to optimal.
Assessing nutritional state
- Animals require nutrient and energy sensors in body.
- All cells can assess nutritional/energy status.
- Coordination at level of animal carried out by brain in conjunction with liver, gut and
pancreas (verts) and fat body (inverts)
- [AAs], [glucose], [fatty acids], [mineral ions] in blood provides instant measure of nutritional
state.
- Reflect net result of nutrients arriving from gut and those removed to meet energy/growth
needs of tissues.
- Info from blood could be inaccurate during nutrient deprivation.
- Body fat, liver glycogen and protein from muscles released into blood during deprivation.
- Could lead to overestimate of nutritional state
- Need second measure – size or rate of reduction of reserves.
- Chemical signals released from tissues – e.g., leptin or adiponectin released by fatty tissue,
and insulin and glucagon, released from pancreas to signal C status.
- FGF21 released by muscle for P status (low P:C)
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