Lecture #25 Flashcards
What role does adipose tissue play in energy balance?
Adipose tissue plays a crucial role in energy balance by serving as an endocrine organ that releases hormones.
Stable adipose tissue signifies energy balance.
In a positive energy balance, more energy is consumed than expended, leading to adipose tissue growth.
In negative energy balance, less energy is consumed than expended, causing adipose tissue to shrink.
How does leptin regulate energy?
Leptin is a hormone produced by adipose tissue as it grows. It travels to the hypothalamus in the brain, signaling energy abundance, which activates the catabolic pathway, promoting satiety and stimulating energy expenditure through the sympathetic nervous system (SNS), which in turn releases catecholamines to speed up metabolism.
Increased leptin = abundance of energy = catabolic pathway = increase satiety & energy expenditure
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What happens when there is a decrease in circulating leptin?
A decrease in circulating leptin due to shrinking adipose tissue signals the hypothalamus to activate the anabolic center. This is mediated by Neuropeptide Y (NPY), which increases hunger and reduces energy expenditure, consequently decreasing metabolism.
Decrease Leptin = decrease of energy = anabolic pathway = increases hunger and reduced energy expenditure
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Negative energy balance is associated with increase or decrease in leptin?
decrease leptin
Positive energy balance is associated with increase or decrease in leptin?
Increase leptin
How does adipose tissue influence the central nervous system (CNS) in energy regulation?
Adipose tissue sends signals to the CNS about the energy available in the body, which interprets these signals to activate brain centers that control mechanisms promoting either weight loss or weight gain, thus regulating energy expenditure.
Besides hormones, what other factors influence hunger and satiety?
Higher brain centers and external cues also affect hunger and satiety.
These factors interact with long-term mechanisms of body weight regulation, influencing the gradual expansion or shrinkage of fat cells.
What are short-term signals in energy homeostasis and what hormones are involved?
Short-term signals are situational or meal-related, arising from the gut to regulate food intake on a meal-to-meal basis.
They act quickly to regulate appetite between meals.
Two hormones:
Ghrelin, released during fasting, promotes hunger,
while Cholecystokinin (CCK), released during meals, promotes satiety through the vagus nerve.
Hedonic Eating
eating triggered by external cues that can override short-term physiological signals of satiety from the gut.
For example, after eating a large meal and feeling full, one might still be tempted to eat a delicious dessert.
The Importance of Glycemic Control for Energy Homeostasis
Glycemic control is crucial for maintaining blood glucose within a narrow range (~5 mmol/L).
Abnormal levels can lead to hypoglycemia (<3 mmol/L) or hyperglycemia (>11 mmol/L).
Postprandial period:
time immediately after the ingestion of a meal when blood glucose levels rise
Post-absorptive period:
Blood glucose stabilizes after food absorption
Serious consequences occur if glycemia falls below _________
Serious consequences occur if glycemia falls below 3 mmol/L (hypoglycemia) or if it climbs above 11 mmol/L (hyperglycemia) such as in diabetic patients
where and how is glucose stored
Glucose is stored as glycogen in the liver and skeletal muscle or as fat in adipose tissue. Storage capacity for glycogen is limited due to the associated water retention (1g glycogen: 3g water).
why is storage capacity for glycogen limited
Storage capacity for glycogen is limited due to the associated water retention (1g glycogen: 3g water).
There is only a limited amount of glucose that can be stored in liver and muscle because for every 1 gram of glycogen stored, 3 grams of water are stored
