Metabolism 4

8/3/2019 Metabolism 4

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R e g u l a t i o n o f f o o d i n t a k e

Lecture 3


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Hunger

Appetite

Satiety

It is craving for food and is associated withobjective sensations as hunger contractions ofthe stomach.

It is a desire for specific types of food insteadof food in general.

It is the opposite of hunger and means a feelingof fulfillment in the quest for food

Definitions


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Hypothalamic centers

1- The feeding (hunger) center

It lies in the lateral hypothalamus.


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1- The feeding (hunger) center

It lies in the lateral hypothalamus.

When it is stimulated in experimental animals, itcauses hyperphagia( eating behavior) .

Destruction of this center causes lack of the desire

for food, progressive weight loss, muscleweakness and fatal anorexia

The feeding center is chronically active . It istransiently inhibited by the satiety center after food

ingestion.


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2- The satiety center

It lies in the ventromedial nuclei of the hypothalamus.


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2- The satiety center

Destruction of this center causes hyperphagia andextreme obesity (hypothalamic obesitysyndrome).

Its stimulation causes aphagia (complete satiety

and cessation of eating)

It lies in the ventromedial nuclei of the

hypothalamus.


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Hypothalamic obesity syndrome

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Fifth level


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Other centers

1- The amygdala and the prefrontal cortex


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Other centers

1- The amygdala and the prefrontal cortex

They are closely coupled with the hypothalamus.

Their destruction causes omniphagia; a type ofmoderate hyperphagia where the mechanism

controlling the type and quality of food eaten islost, leading to attempting to eat all sort of objects.


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Other centers

2- Brain stem centers


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Other centers

2- Brain stem centers

They control the actual mechanisms of feeding as

salivation, chewing and swallowing.

They are excited by signals from the hypothalamus.


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Factors regulating

food intake

II) Short termregulation

1-Alimentary factors

2-Psychological factors

) Long termegulation

1-Nutritional regulation

-Effect of body temperature

-Feedback signals fromadipose tissue


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Long term regulation

Nutritional regulation

qWhen the nutrient stores fall below normal, thefeeding center becomes highly active and the

person exhibits increased hunger.qOn the other hand, when the nutrient stores areabundant, the person loses hunger and develops astate ofsatiety.


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Nutritional regulation

The glucostatictheory

The lipostaticand

aminostatictheories


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Effect of body temperature


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Feedback signals from adipose tissue

Leptin


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Feedback signals from adipose tissue

Leptin

Decreased production of appetitestimulators in the hypothalamusas neuropeptide Y

Increased production of appetitesuppressants in the hypothalamusas corticotrophin releasinghormone.

Increased sympathetic nerveactivity which increases themetabolic rate and energyexpenditure.

Decreased insulin secretionwhich decreases energystorage.


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Factors regulating

food intake

II) Short termregulation

Alimentary factors

Psychological factors

) Long termegulation

utritional regulation

ffect of body temperature

eedback signals fromdipose tissue


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Short term regulation

Alimentary factors

Gastrointestinalfilling.

Hormones.

Oral factors


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Short term regulation

Psychological factors


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Metabolism 4

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