Back to AI Flashcard MakerBiology /Biology IB HL - 6.6 Homeostasis Part 2
What do periods of starvation cause in relation to leptin?
Conversely, periods of starvation lead to a reduction in adipose tissue and hence less leptin is released, triggering hunger
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Term
Definition
What do periods of starvation cause in relation to leptin?
Conversely, periods of starvation lead to a reduction in adipose tissue and hence less leptin is released, triggering hunger
When may a person become desensitised to leptin?
As obese people are constantly producing higher levels of leptin, their body becomes progressively desensitised to the hormone
What may leptin resistance in obese people lead to?
This means they are more likely to feel hungry, less likely to recognise when they are full and are hence more likely to overeat
What may leptin resistance increase with, other than weight?
Leptin resistance also develops with age, increasing the potential for weight gain later in life (e.g. the ‘middle-age spread’)
What was leptin thought to be a treatment for?
Because leptin suppresses appetite, it was considered as a form of treatment for individuals with clinical obesity
Theoretically, how should leptin treat obesity?
Theoretically, leptin injections would reduce hunger and limit food intake in obese individuals, leading to weight loss
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| Term | Definition |
|---|---|
What do periods of starvation cause in relation to leptin? | Conversely, periods of starvation lead to a reduction in adipose tissue and hence less leptin is released, triggering hunger |
When may a person become desensitised to leptin? | As obese people are constantly producing higher levels of leptin, their body becomes progressively desensitised to the hormone |
What may leptin resistance in obese people lead to? | This means they are more likely to feel hungry, less likely to recognise when they are full and are hence more likely to overeat |
What may leptin resistance increase with, other than weight? | Leptin resistance also develops with age, increasing the potential for weight gain later in life (e.g. the ‘middle-age spread’) |
What was leptin thought to be a treatment for? | Because leptin suppresses appetite, it was considered as a form of treatment for individuals with clinical obesity |
Theoretically, how should leptin treat obesity? | Theoretically, leptin injections would reduce hunger and limit food intake in obese individuals, leading to weight loss |
How were leptin trials initially conducted? | Leptin trials were initially conducted by surgically fusing the blood circulation of obese and healthy mice (parabiosis) |
What mice were used for experiments on leptin? | This experiment was conducted using mice that were either obese due to a leptin gene mutation or a defective leptin receptor |
What were the two findings when the leptin-deficient mouse and healthy mouse were parabiotically fused? | Leptin in the blood of the healthy mouse was transferred to the obese mouse |
What were the two findings when the no leptin mouse and healthy mouse were parabiotically fused? | Leptin in the blood of the healthy mouse was transferred to the obese mouse The obese mouse responded to the leptin and began to lose weight, demonstrating the potential viability of leptin treatment |
What were the two findings when the mouse with defective leptin receptors and healthy mouse were parabiotically fused? | Leptin was transferred to the healthy mouse (the obese mouse overproduced leptin to compensate for low receptor sensitivity) The obese mouse remained obese as its body could not respond to leptin |
What happened to the healthy mouse when the mouse with defective leptin receptors and healthy mouse were parabiotically fused? | The healthy mouse became emaciated due to the abnormally high levels of leptin transferred into its bloodstream |
Do humans naturally have high/low levels of leptin? | Most humans have naturally high levels of leptin in the bloodstream |
Are most cases of obesity caused by an unresponsiveness to leptin or a leptin deficiency? | When linked to leptin activity, most cases of obesity are caused by an unresponsiveness to leptin and not a leptin deficiency |
Were clinical trials with leptin efficient? | Hence, in clinical trials, very few participants experienced significant weight loss in response to leptin injections |
What did patients experience in the clinical trial for leptin? | However, many patients did experience adverse side effects from leptin injections, including skin irritations |
Therefore, can leptin be considered an effective way of controlling obesity? | NO!!! For these reasons, leptin treatments are not considered to be an effective way of controlling obesity |
Where is melatonin produced? | Melatonin is a hormone produced by the pineal gland within the brain in response to changes in light |
When is melatonin secreted? | Melatonin is therefore secreted in response to periods of darkness, resulting in higher concentrations at night |
What is the mechanism of melatonin inhibition? | Light exposure to the retina is relayed via the suprachiasmatic nucleus (in the hypothalamus) and inhibits melatonin secretion |
What does melatonin secretion play a pivotal role in? | Melatonin secretion by the pineal gland of the brain plays a pivotal role in the control of circadian rhythms |
What are circadian rhythms? | Circadian rhythms are the body’s physiological responses to the 24 hour day-night cycle |
What are circadian rhythms controlled by? | Circadian rhythms are driven by an internal (endogenous) circadian clock, although they can be modulated by external factors |
What is melatonin's role in relation to circadian rhythms? | Melatonin is the hormone responsible for synchronising circadian rhythms and regulates the body's sleep schedule |
What is melatonin secretion suppressed by? | Melatonin secretion is suppressed by bright light (principally blue wavelengths) and hence levels increase during the night |
Over a prolonged period of time, what does melatonin secretion become entrained to? | Over a prolonged period, melatonin secretion becomes entrained to anticipate the onset of darkness and the approach of day |