- Created by: John
- Created on: 04-05-13 17:06
There is a complex web of Neurological Mechanisms that play a role in controlling eating and hunger.
One of these mechanisms involves the HYPOTHALAMUS...
- Hypothalamus has TWO PARTS that work in opposition to each other.
- This is called the DUAL PROCESS MODEL.
- The VENTROMEDIAL HYPOTHALAMUS (VMH) is called the 'satiety centre' and stops eating when we are full by monitoring stomach content levels and contractions through the vegus nerve.
- The LATERAL HYPOTHALAMUS (LH) is called the 'feeding centre' and makes us eat when blood sugar levels drop.
- The HYPOTHALAMUS works to maintain homeostasis in the body, so if a person has too many nutrients VMH is activated, and if too few nutrients LH is activated.
However the LH can be linked to two further parts of the Hypothalamus...
- ARCUATE NUCLEUS (ARC)
- PARAVENTRICULAR NUCLEUS (PVN)
The ARC consists of Hunger Neurones and Satiety Neurones
In Hunger Neurones...
- GHRELIN is a hunger hormone produced in the stomach (thought to cause the contraction feelings we experience during hunger)
- This stimulates the vegus nerve
- Which then stimulates hunger neurones in ARC
- TASTE cells send neural signals to hunger neurones in ARC when tasty food is detected.
- The Hunger Neurones in ARC send a chemical message (NPY and AgRP) to the PVN
- This stimulates PVN to send nerve impulses to the LH
- LH to releases Orexin which stimulates food seeking behaviour.
In Satiety Neurones...
- CHOLECYSTOKININ (CKK) is released during distension of the intestines, and stimulates satiety neurones in ARC. (Short Term)
- GLUCOSE levels in the blood are monitored by nerve cells, which then stimulate satiety neurones in the ARC
- LEPTIN is released by body fat which stimulates the satiety neurones in ARC. (Long Term)
- The Satiety Neurones in ARC release Melanocortin
- This inhibits the action of NPY and AgRP
- So hunger is not experienced
Another neural mechanism involves NEUROTRANSMITTERS...
- Neurotransmitters (chemicals in the brain) may be linked to the PARAVENTRICULAR NUCLEUS (PVH…