Biology Stack Exchange is a question and answer site for biology researchers, academics, and students. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

When food is scarce, the body slows its metabolic rate to conserve energy. Are there any other systems or processes that prioritize which organs receive nutrients?

share|improve this question
up vote 2 down vote accepted

Glucose is prioritized for the brain and erythrocytes over the muscle and adipose tissue, for example, by hormonal control.

The hormones insulin and glucagon respond to strarvation, insulin secretion falling and that of glucagon increasing. The glucose transporter, GLUT4, in muscle and adipose tissue is dependent on insulin, so that in starvation less-essential uptake of glucose to these tissues declines. The glucose transporters of erythrocytes and brain (e.g. GLUT1) do not depend on insulin, so the supply of glucose to these tissues, which absolutely require it, is not cut off.

References

Hormones and Starvation: http://www.ncbi.nlm.nih.gov/books/NBK22414/

Insulin and the GLUT4 Glucose Transporter: https://en.wikipedia.org/wiki/GLUT4

GLUT1, insulin-independent Glucose Transporter: https://en.wikipedia.org/wiki/GLUT1

share|improve this answer
    
Could you add some references and good sources for additional further/reading? – rg255 Mar 13 at 13:02
    
Done. Let me know if you think any further clarification is needed. – David Mar 13 at 13:59

The glycogen in the liver begins providing blood glucose. Muscle glycogen is used as fuel by the muscles, fat cells (adipose tissue) release fatty acids to manufacture ketone bodies in the liver and to be used by the brain as fuel, and body proteins are converted to glucose.

In short, the body's metabolism shifts to catabolic reactions.

If this continues for too long, you begin to see effects of starvation:

  • Inadequate tear production
  • Enlarged/tender liver
  • Muscle atrophy
  • Rashes, sores, or peeling skin

In short, deficiencies of energy, protein, iron, and zinc can really mess you up in the long term.

share|improve this answer
    
Are you sure this is right: "ketone bodies in the liver and to be used by the brain as fuel". If I recall correctly the human brain uses glucose as fuel. – Gabriel Fair Feb 27 '15 at 15:16
    
Could you add some references and good sources for additional further/reading? – rg255 Mar 13 at 13:02
    
@GabrielFair yes, brain is dependent on glucose and requires some amount of it, but it can get some portion of energy from metabolism of ketone bodies as well, you can see: ncbi.nlm.nih.gov/pmc/articles/PMC2874681 or en.wikipedia.org/wiki/… – Matej Pribis Mar 13 at 17:34

The switch from glucose to ketone bodies as the principal blood metabolite accompanies starvation. This prioritizes the heart, which preferentially uses ketone bodies as a fuel (update; actually it's fatty acids, but they're metabolically similar.) This de-prioritizes the brain, which preferentially uses glucose.

[edit] I was asked for a source. This is definitely in Voet, Voet & Pratt's Fundamentals of Biochemistry, but I vouch for Wikipedia's description.

share|improve this answer
1  
Welcome to Biology SE! This is a great answer, but perhaps you could include a reference? (I learned this also in undergrad, but citations are always helpful.) – dd3 Apr 4 '13 at 1:11

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.