Motivation Flashcards
What is motivation?
Driving force, physical need and wanting or liking something
What is motivation controlled by?
Hypothalamus
What is the prandial state?
Full/ eating state when anabolism happens
What is anabolism?
Food breakdown
What is catabolism?
Breakdown of food stores
What is the postabsorbtive state?
Fasting state when catabolism happens
What is parabiosis?
Sharing of blood circulation between animals
What is the effect of parabiosis on body weight in ob/ob mice?
Blood bourne signals are shared about the hypothalamus (so a genetically obese mouse would loose weight)
What happens following a fat-rich meal?
Adipose tissues produce leptin which signals to the Arcuate nucleus to tell you to stop eating
What do mice show if they’ve got a lesion in the ventromedial hypothalamus?
Increase in food intake and body weight
What does lateral hypothalamic syndrome cause?
Diminished appetite for food = anorexia
What does ventromedial hypothalamic syndrome cause?
Overeating and obesity
What are lateral and ventromedial hypothalamic syndromes both associated with?
Related to leptin signalling
What is the anorexic response?
Elevated leptin levels sensed by specialised cell bodies in the Arcuate nucleus that release alpha MSH and CART
What does CART stand for?
Cocaine and amphetamine regulated transcript
What does alpha MSH and CART project to?
Lateral hypothalamus, paraventricular nucleus, spinal cord and preganglionic neurons of sympathetic autonomic NS
What do alpha MSH and CART do in the lateral hypothalamus?
Inhibit feeding behaviour
What do alpha MSH and CART do in the paraventricular nucleus?
Induce CRH and TRH
What is an orexigenic response?
Response to decreased leptin levels
What happens when decreased leptin levels are sensed?
Arcuate nucleus releases NPY and AgRP
What do NPY and AgRP project to?
Lateral hypothalamic area and paraventricular nucleus
What do NPY and AgRP do in the lateral hypothalamic area?
Stimulates feeding behaviour
What do NPY and AgRP do in the paraventricular nucleus?
Inhibits secretion of hypophysiotropic hormones controlling ACTH and TSH
What do the LH neurons stimulating feeding behaviour contain?
Melanin-concentrating hormone (MCH) and orexin
What does MCH do?
Prolongs consumption
What does orexin do?
Promotes meal initiation and related to narcolepsy and addiction behaviour
What are the three phases in the satiety cascade?
Cephalic, gastric and substrate (intestinal)
What happens in the cephalic phase?
Ghrelin released when the stomach is empty
Activated NPY/AgRP containing neurons in the Arcuate nucleus
What can doctors do to cause a loss of appetite?
Removal of the ghrelin-secreting cells of the stomach
What happens in the substrate (intestinal) phase?
Gastric distension signals to the brain via the vagus nerve
Works with CCK released in the intestines in response to foods
Why do we eat?
Hedonic (liking food) Drive reduction (Wanting food)
Which facet of eating are the dopaminergic systems involved in?
Wanting/craving
What is the reward system?
Dopaminergic projections from the ventral tegmental area to the nucleus accumbens where dopamine gets released
How do drugs of abuse hijack the reward system?
Causing extensive and disproportionate release of dopamine
What are the stages of the addiction cycle?
Acute reinforcement/social drug taking Escalating/compulsive use Dependence Withdrawal Protracted withdrawal Recovery
What is dependant drug use driven by?
Need to stop withdrawal symptoms
What happens in obese people that binge eat?
Downregulation of D2 receptors so they get less reward
What are the key neural circuits of reinforcement?
Hippocampus involved in the memory of reward and the amygdalas involved in the emotional connection
What is microdialysis?
Measuring neurotransmitter release in vivo
What is dopamine release in the nucleus accumbens correlated with?
Motivation and the anticipation of reward
How are mood and food connected?
Serotonin in hypothalamus rises in anticipation of food and spike during a meal
