Homeostasis
This involves mechanisms which detect the state of the internal environment. There is a time lag between restoring equilibrium and measuring effect.
For a hunger mechanism to be adaptive, it must anticipate and prevent energy deficits.
Dual-Process Model
Decline in glucose
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Activates lateral hypothalamus
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Hunger
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Search and consume food
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Glucose rises
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Activates ventromedial hypothalamus
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Feeling of satiation
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Stops further eating
Lateral Hypothalamus
- Functions as the feeding centre, stimulating feeding in response to signals from the body.
- Damage to LH can cause aphagia. Stimulation elicits feeding behaviour.
- The view that LH serves as an 'on switch' for eating has problems - damage to LH had other behaviour deficits (thirst and sex).
Research: Sakuri (1998)
Ventromedial Hypothalamus
- Part of the hypothalamus that functions as a satiety centre to inhibit feeding.
- Damage to the VMH caused rats to overeat - hyperphagia.
- Usually overeating only occurred when there was also damage to the paraventricular nucleus.
Research: Gold (1973)
Neuropeptide Y
- Important in turning on eating. When injected into hypothalamus of rats, it caused them to begin eating despite having eaten before.
- Obese people may have an over-production of NPY.
Research: Marie et al (2005)
Neural Control of Cognitive Factors
- The Amygdala - Thought to be primarily in the selection of foods on the basis of previous experience.
- Rolls and Rolls (1973)
- Inferior Frontal Cortex - Thought to be linked with odours and food response. Diminished odour response decreased eating.
Research: Zald and Pardo (1997)
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