Hypothalamus, Homeostasis and Motivated Behaviour Flashcards
Does leptin therapy help those who are able to produce leptin and are obese?
No, as one becomes obese, they develop resistance to leptin. Leptin only helps with obesity for those who are unable to produce leptin.
What is the role of the lateral hypothalamus in terms of feeding behaviour and what is the result of lesions to this area?
It is the ‘feeding centre’ that is responsible for stimulating feeding behaviours, increasing bodily weight. The animal becomes underweight if there isa lesion.
What is the role of the ventromedial hypothalamus in terms of feeding and what is the result of lesions in this area?
Responsible for satiety. The animal becomes obese if there is a lesion.
What does the lipostatic theory state?
The brain monitors the amount of body fat through the amount of leptin to prevent changes in body fat stores.
What is leptin?
Product of the ob gene that is produced by adipocytes in proportion to body fat content and signals to the brain about the amount of body fat.
What is the results of joining an obese leptin-deficient rat with a normal rat?
The obese rat becomes of normal weight as it receives leptin from the normal rat.
What peptides do orexigenic neurons in the medial hypothalamus contain?
What neurons do they activate?
Neuropeptide Y (NPY) and Agouti Related Peptide (AgRP). Activate neurons in the lateral hypothalamus to increase food intake.
What peptides to anorexigenic neurons in the medial hypothalamus contain?
What hormone are they excited by?
What is their effect?
Proopiomelanocortin (POMC) and Cocaine Amphetamine Regulated Transcript (CART).
They are excited by leptin.
They are responsible for satiety.
What humoral, visceromotor abd somatic effects do decreased levels of leptin have?
Inhibit secretion of hypophysiotropic hormones controlling ACTH and TSH (to reduce metabolism).
Alter sympathetic outflow to alter energy expenditure.
Stimulate feeding behaviours in the lateral hypothalamic area.
What effect do increased levels on leptin have on the paraventricular nucleus and on the lateral hypothalamic area?
Stimulate secretion of hypophysiotropic hormones controlling ACTH and TSH (to increase metabolism).
Activate brain stem neurons and preganglionic neurons of sympathetic ANS.
Inhibit feeding behaviours int he lateral hypothalamic area.
What does the set point theory suggest?
There is a a set body weight that the brain will always try to achieve.
According to the set point theory, what is metabolic adaptation?
The metabolic rate alters with body fat. As the amount of body fat decreases, so does the metabolic rate (aims to increase fat again). The metabolic rate decreases by more than predicted.
What is Ghrelin?
A hormone produced in the stomach that builds up prior to a meals and acts on NPY and AgRP neurons to stimulate feeding behaviours. Levels of ghrelin decrease following a meal.
What is responsible for satiety signals?
Leptin- adipose tissue PYY3-63- small intestine CKK Amylin- pancreas Stretch receptors detecting stretching of stomach during food intake.
How does the level of hormones alter with weight loss and make it difficult to maintain weight loss?
Ghrelin remains elevated, increasing hunger.
Amylin, CKK and PYY remain low reducing satiety.
Leptin alters with body fat.
