Week 1: Ingestive behaviour Flashcards
What are the two basic physiological reasons why we need to eat?
Feul - energy supply
Nutrition - essential chemicals, such as amino acids that can not be manufactured in the body
Give examples of biological factors contributing to indigestive behaviour
Genetics
Neonatal complication
History of dieting
Metabolism
Co-morbidities
Give some exampls of psychological factors contributing to indigestive behaviours.
Perfectionism
Difficulty regulating emotions
Body dissatisfaction
health knowledge
Actitivty and eating habits
Give some examples of social factors that contribute to indigestive behaviour
Pressure to be thin/Muscular
Bullying and teasing
Lack of social support
School and government education around healthy eating
Socioeconomic status
Food policy
Describe how food can become a form of self-medication in stressful situations.
Eating triggers the release of dopamine within the mesolimbic pathway in the brain.
This leads to reduced stress and increased feeling of pressure.
By associative learning food can become associated with reduced stress and pleasure
Hence a habit forms where by food is used as a form of self medication in stressful times
What methods physiological methods control indigestive behaviours?
Satiety mechanisms
Detectors that monitor system variables
Define satiety mechanisms?
Brain based mechanisms that reduce hunger or thirst after behaviours resulting in adequate intake of nutrients or water.
What do satiety mechanisms measure? How does this relate to how indigestive patterns are controlled?
Satiety mechanisms monitor correctional behaviour mechanisms (stretch on stomach) rather that the system variables them selves (low bp).
This means the body system replenishment can be delayed after the need of consumption/ decreased consumption occurs and the appropriate behaviour occurs.
Low BP detected - feel thirst - drink more - signal to stop drinking - blood pressure increases and returns to normal
What type of correction system monitors our indigestive behaviour?
Negative feedback triggering correctional mechanisms
What is plasma osmolarity?
What receptors detect changes in osmolarity?
The level of different solutes (na+, Cl-) in plasma
Osmoreceptrs detect the changes in osmolarity
Give a basic summary mechanism of how the sensation of thirst is activated in the brain.
Plasma osmolarity increases and is detected by osmoreceptors.
Results in circulating angiotensin 11.
Additionally low blood pressure may be detected by baroreceptors and GI hormones can indicate a need to drink.
During pregnancy relaxin may also be circulating.
This stimulates subfornical organ (SFO) and organum vasculosum of the lamina terminaslis (OVLT)
Results in stimulation of the meidan preoptic nucleus (MnPO) which relays signals to the insula and congulate cortex to increase thirst.
What is role of the Insula in thirst regulation?
Interoception - interprets and detects afferent signals from the body that tell the brain of the body state.
What is the role of the cingulate cortex in regulation of thirst?
Motivation/emotional processing
Pleasure you feel after drinking when you are thirsty.
What regions of the CNS influence hunger?
The hypothalamus
Particularly the lateral hypothalamus and the ventromedial hypothalamus
What is the role of the lateral hypothalamus in regulating eating behaviours?
Later hypothalamus - initiates hunger signals
If damaged leads to reduced hunger signals, weight loss and potentially anorexic behaviour
What role does the stomach have in the feedback mechanism of food intake?
Stretch receptors in the stomach
Action potential generated when the stomach is full and stretched
Activated sensory afferent pathways in the vagus nerve to inhibit food intake
What GI hormones can decrease hunger signals?
Peptide YY (PYY)
Cholecystokinin CCK
Insulin
What role does leptin have in regualting appetite?
Leptin is a hormone produces by fat cells as they increase in size
It inhibits food intake and regulates metabolism
What is the role of ghrelin in regulating appetite?
Released by the stomach during fasting (reduced after a meal)
Binds to the hypothalamus
Increases hunger signals and increases the appetite.
Leads to decreased metabolism of fats
What is the role of peptide YY in regualting appetite?
Released by the small intestine and colon after a meal.
Release is proportional to the calories that were just ingested.
Decreases hunger signals
What is the role of CCK in regulating appetite?
Amount released is proportional to the amount of nutrients (particularly fats) that the duodenum recives from the stomach.
CCK could potentially provide a satiety signal to the brain
However, it does not act on the brain directly.
Acts on receptors located in the junction between the stomach and the duodenum
How does blood glucose levels relate to regulating appetite?
Low blood glucose - low insulin - reduced inhibitory effect on appetite
High blood glucose - high insulin - brain detects insulin present in the blood - indicates the body is absorbing nutrients and inhibits hunger signals.
What role does the liver have in regulating appetite?
Nutrient receptors in the liver send neural signal to the brain indicating that ingested food is being broken down and decreasing hunger signals.
What is the difference between short term satiety and long term satiety?
Short term - stops after a sing meal
Long term satiety - arises in the adipose tissue, controls long-term nutrient behaviour
