Ingestive Behaviour unit Flashcards
(29 cards)
What is the process responsibile for regulating food and water?
The homeostatic process: a process that keeps body varibales, such as water and nutrient contents, within a certain range.
How does the homeostatic process mechanisam operate?
Homeostasis works through negative feedback: once a correctional mechanism restores balance, it shuts off to prevent overcorrection.
What is the satiety mechanism?
A mechanism that controls the behaviour of injesting food and warter for replenishment. It monitors eating and drinking behaviours and stop them in anticipation of the replenishment whtat will occur later.
Two-thirds of the body’s water is… and the rest is…?
Intracellular fluid: the fluid portion of the cytoplasm in cells. Extracellular fluid: Includes intravascular fluid, cerebrospinal fluid (blood plasma), and interstitial fluid (fluid surroundingcells). They are kept at a certain level.
Keeping intracellular fluid and extracellular (intravascular) fluid at a level prevents what?
Too much of intracellular fluid causes cells to burst and too little stops cells from functioning. Too little intravascular fluid stops the heart being able to pump blood around the body: this is hypovolemia.
What monitors intravasular and intrecellular volumes; and what are the mechanisms that cause us to be thirsty?
Two different receptors one of them is osmoreceptor.
* Volumetric thirst is caused by low intraVASCULAR water volumes Happens when the volume of blood drops (e.g., bleeding, sweating).
* Osmometric thirst is cause by low intraCELLULAR water values. Happens when there’s too much salt and not enough water in the body
How does osmometric thirst happen?
Osmoreceptors detect an increased concentration of solutes in the interstitial fluid. When the blood plasma has a high salt concentration, water moves by osmosis from the interstitial fluid into the plasma, raising the solute concentration in the interstitial fluid. As a result, water from the intracellular fluid (inside cells) moves into the interstitial fluid, also by osmosis. Osmoreceptors, which are a type of mechanoreceptor, respond to these changes in water balance.
Where are Osmoreceptors located?
They are located in the lamina terminalis, next to the third ventricle.
The lamina terminalis does not produce the feeling of satiety after drinking; instead, this sensation is generated by the anterior cingulate cortex (ACC).
What happens when water is reabsorved into the osmoreceptors?
they stop firing.
What is volumetric thirst the result of?
Low intravascular (blood plasma) volume, these decreases are caused by evaporation of water (as is the case in osmometric thirst), as well as blood loss, vomiting, and diarrhoea. Loss of intravascular fluid leads to the loss of both water and sodium, which are normally contained in that fluid. This thurst produces a salt appetitie, as the sodium must also be replenished.
Cells in the kidneys detect low blood flow (as a results of low intravascular vol.) and induce the secretion of what hormone?
Angiotensin, it initiates drinking and produces a salt appetite, causes the kindeys to conserve water and salt and increases blood pressure. Stretch-receptor cells in the heart detect when blood vol. in the heart decreases, initiating drinking.
Where is the hormone for volumetric thirst detected?
It is processes in the lamina terminalis, outside the blood-brain barrier, meaning that angiotensin can interact with the lamina terminalis to prooduce the sensation of thirst.
Damage to the lamina terminalis can produce what disorder?
Adipsia. An abnormal lack of drinking due to inability to detect low water levels. Patients must deliberatly drink water at regular intervals.
There are two main types of hunger signals, what are they?
- The short-term satiety signals: are produced by two hormones (intestines) CCK and (pancreas) insulin. These are like messages that are sent from the liver to the brain via the vagus nerve.
- Long-term satiety singals: are produced by fat cells in the body. They are sent by the digestive system and the other is produced by the liver and the medulla.
What is the main hunger singlas produced by the digestive systems involves the release of what hormone?
Ghrelin is a hormone secreted by the stomach and the duodenum (the first part of the small intestine).
It binds to receptors in the hypothalamus, stimulating hunger.
* Increased ghrelin levels promote food intake
* Blocking ghrelin reduces eating behavior
In Prader-Willi Syndrome, individuals exhibit chronically elevated ghrelin levels, which contributes to hyperphagia (excessive eating) and obesity.
What are the key metabolic and intestinal signals involved in hunger and satiety regulation?
🔹 Metabolic signals of hunger
- Hunger is triggered when glucose and fatty acid levels drop, as detected by brain and liver cells.
- The brain depends solely on glucose, whereas other tissues can use both glucose and fatty acids.
- Liver receptors detect low energy availability and transmit hunger signals to the brain via the vagus nerve.
- Additionally, glucose-sensitive neurons in the medulla respond directly to drops in blood glucose.
🔹 Intestinal signals of satiety
- Short-term satiety signals arise from the gastrointestinal tract during a meal, limiting intake before nutrient absorption occurs.
- When food enters the duodenum, the release of the hunger-promoting hormone ghrelin is suppressed, contributing to the feeling of fullness.
- Other hormones, like CCK, are also released to reinforce satiety by activating vagal afferents to the brain.
What are the key sources and mechanisms of satiety signals in the body?
- Gastrointestinal and liver signals
* When food enters the duodenum, it triggers the release of cholecystokinin (CCK).
* CCK helps digestion and sends satiety signals to the brain via the vagus nerve.
* After nutrient absorption, the liver detects increased nutrient levels and reinforces satiety by signaling the brain (also via the vagus nerve). - Insulin signals
* Eating stimulates the pancreas to release insulin, which promotes glucose uptake and fat storage.
* Insulin crosses the blood-brain barrier and activates neurons in the hypothalamus, contributing to the feeling of fullness.
What are other satiety signals?
Memory (STS): a patient with short term memory deficit because of damage to the hippocampus and amygdala would eat up to 3 meals after short breaks due to memory loss.
Environmnetal factors: larger portions and eating in company causes people to eat more.
Sensory factors: contribute to satiety
What role does leptin play in long-term satiety regulation?
Leptin is a hormone secreted by fat cells that signals long-term satiety.
It reduces eating, increases metabolism, and boosts activity levels.
Mice without the OB gene (ob mice) lack leptin, leading to overeating and obesity.
Injecting leptin into ob mice normalizes their weight.
In humans, leptin-based treatments for obesity have shown little or no success.
How does the brain stem contribute to hunger and satiety control?
The caudal medulla, including the nucleus of the solitary tract (NST), receives signals from:
Taste receptors,
The stomach, duodenum, and liver,
And detects blood glucose levels.
These signals are relayed to higher brain areas like the hypothalamus, which control eating and metabolism.
What roles do different parts of the hypothalamus play in regulating eating?
- The arcuate nucleus controls appetite.
- It detects signals like ghrelin, leptin, insulin, nicotine, and CCK.
- The lateral hypothalamus makes you want to eat.
- It increases hunger and food reward.
- The ventromedial hypothalamus tells you to stop eating.
- If it’s damaged, you may overeat.
What are the hypothalamic connections involved in eating, and what are the health risks of obesity?
The lateral hypothalamus connects to:
The NST (enhancing taste perception when hungry),
The nucleus accumbens (facilitating ingestion),
The spinal cord (controlling digestive secretions).
Obesity increases risk for heart disease, diabetes, stroke, arthritis, and some cancers.
Its causes are complex and include environmental, physical activity, and genetic factors.
How does the modern environment contribute to obesity?
High-calorie, inexpensive, and convenient foods with large portions promote weight gain.
Many processed foods contain fructose, which doesn’t trigger insulin secretion, weakening satiety signals.
These environmental factors increase the risk of overeating and obesity.
What is the role of physical activity in obesity?
Modern jobs involve less vigorous activity, so less food is needed than in the past.
Non-exercise activity thermogenesis (NEAT)—like fidgeting, posture shifts—is higher in lean people.
Workplaces promoting standing or treadmill use can reduce obesity risk.
