Lecture 5 Flashcards
In order to regulate nutritional intake, animals needs to be able to assess the nutritional quality of the food item, assess it’s own nutritional stage and compare the two. This is akin to an animal asking what 3 questions?
What is the nutritional composition of the food?
What nutrients do I need?
How much of this food do I eat to balance my diet?
What is taste used for?
Simplest way to detect nutrients
All organisms have specialised receptors to detect amino acids, sugars, salts.
External- Tarsi, palms, barbels
Internal- tongue, gut lining
Provide info to CNS about nutrients in food
Strength of signal increases with concentration in food (positive =responding to nutrients. Negative = potentially toxic compounds)
What is phagostimulatory power?
Tastes the best
What is 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
What is a taste model?
Model shows how taste could regulate to an intake target
Foods vary in PS power according to concentration of nutrient
Optimal concentration is the most PS
How would you assess nutritional state in an animal?
Concentration of Amino acids, glucose, fatty acids, mineral ion in the blood provides instant measure of nutritional state
Are there issues with assessing an animals nutritional state through blood?
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 overestimation of nutritional state
How would you assess nutritional state through cells?
2 main protein kinase pathways that sense nutrients - AMPK and TOR
What is AMPK?
A protein kinase pathway that responds to declining levels of nutrients (AA, fatty acids), it triggers catabolic processes, releasing stored nutrients and inhibiting growth and reproduction
What is TOR?
A protein kinase pathway. TOR works antagonistically, it is stimulated by high levels of energy (ATB) and nutrients. It triggers anabolic processes, stimulating growth and reproduction
How is nutrition regulated in mammals
Brain- major site of integration between food composition and nutritional state
Taste receptors on tongue stimulated by food, activate neurons, send signals to brain
GI releases hormones that act on gut motility, digestive enzyme secretion, vagus nerve and brain
How would you know if a mammal hasn’t eaten?
Low blood conc of AAs, glucose, fatty acids
Secretion of ghrelin by gut
Release of NPY/AgRP proteins
How would you know if a mammal has eaten?
High blood conc of AAs, glucose, fatty acids, Low AMP:ATP
Stretch receptors in gut send ‘full’ messages to brain
Release of a-melanocyte stimulating hormone, inhibits feeding
Positive food associations
Animals learn to associate characteristics of food (colour, taste, location etc) with nutritional reward
What is an active hunter?
Actively hunts for prey
-compensates for a previously unbalanced diet by choosing alternative prey
