Neural mechanisms involved in controlling eating Flashcards
What happens to hunger levels as glucose levels decrease?
Hunger levels increase as blood glucose levels decrease.
Why does a decrease in glucose levels result in an increase in hunger levels?
A decline in blood glucose causes the liver to send a message to the Lateral Hypothalamus (the ‘hunger centre’ in the brain), which triggers the hunger drive, resulting in a mdesire to consume food.
Which part of the hypothalamus receives a message from the liver that blood glucose levels are low, resulting in feelings of hunger?
The Lateral Hypothalamus.
Which part of the hypothalamus receives a message from the liver that blood glucose levels are high, resulting in feelings of satiety?
The Ventromedial Hypothalamus.
What is the ‘dual centre model of eating’?
A theory of eating control which suggests there are two separate but related structures in the brain - one that produces feelings of hunger (the Lateral Hypothalamus) and another that produces feelings of satiety (the Ventromedial Hypothalamus).
From where is the dual process model of eating derived?
The dual process model is derived from studies in which the VMH and LH in rats were surgically damaged. For example, Hetherington & Ranson (1942) found that if the VMH is damaged, rats will overeat and become hyperphagic whereas if the VMH is electrically stimulated, rats will stop eating. Similarly, Anand & Brobeck (1951) found that damaging a rat’s LH led to it under-eating and becoming hypophagic, whilst electrically stimulating the LH caused rats to start eating even if they had just finished eating.
What is the relationship between neuropeptide Y (NPY) and the Lateral Hypothalamus?
Neuropeptide Y (NPY) is a neurotransmitter; among other things, it is an orexigen (an appetite stimulant). NPY stimulates the LH, resulting in feelings of hunger.
What is the evidence that NPY stimulates the LH?
When NPY is injected into the LH of rats, they immediately begin eating, even if they are satiated. Furthermore, repeated injections of NPY produce obesity in rats in just a few days.
What is the relationship between the VMH and cholecystokinin (CCK).
A feeling of fullness is signalled by stretch receptors in the stomach which stimulates a hormone called cholecystokinin (CCK) whose effects is causing the VMH to activate anorexigens (such as peptide YY, which is a hormone that causes a loss of appetite).
What evidence is there that the hormone CCK is involved in the neural mechanisms controlling eating behaviour.
When CCK is injected into rats, there is a reduction in appetite and weight gain is suppressed.
What is ‘set point’?
Set point refers to an ‘ideal’ body weight around which our weight fluctuates within a narrow range. Our set point seems to be determined by fat levels in the adipocytes of the body. Adipocytes are fat cells (sometimes referred to as lipocytes). Set point theory explains why when we diet and lose weight, we usually return to the starting point when we give up; it’s the point at which our physical body feels ‘comfortable’.
What is the relationship between ‘set point’, ‘adipocytes’ and the VMH?
Cells in the VMH detect when fat levels in the adipocytes fall - which is a sign that the body has moved away from its set point (comfort zone) resulting in feelings of hunger.
What is homeostasis and what has it got to do with neural mecnahisms involved in controlling eating behaviour?
It is the body’s system for maintaining a constant optimum state. It is this system which ultimately results in us feeling hungry (or satiated) - because hunger and satiety are the two extremes on a continuum whose mid-point is the optimum state. To maintain homeostasis, the LH and the VMH work together with the digestive system and a number of different neurotransmitters and hormones to control eating behaviour in order that we never feel too hungry or too full - in other words to ensure we are always in, or near to, an optimal state.
What role do the feelings of hunger and satiety play in homeostasis?
Feelings of hunger signal a need for nutrients in order to restore the optimum bodily state. Satiety signals that this need has been satisfied.
Identify four neural mechanisms involved in controlling eating behaviour.
- The LH ‘switches on’ feelings of hunger as a response to falling blood glucose levels. 2. The VMH ‘switches off’ hunger as a response to rising blood glucose levels. 3. The amygdala is involved in the control of cognitive factors relating to the selection of foods - specifically, decisions about whether to eat familiar or novel food is within the control of the amygdala. 4. The inferior frontal cortex is also involved in the cognitive factors associated with choice of certain foods - specifically decisions about whether to eat a food based on its taste are within the control of the inferior frontal cortex (because it receives messages from the olfactory bulb which is responsible for detecting smell).
