Motivation Flashcards
What is motivation?
→ A physical need
→ Wanting/liking something
What does the hypothalamus do?
→ Maintain homeostasis by regulating three interrelated functions
What are the 3 things that the hypothalamus controls?
→ Endocrine secretion
→ Autonomic nervous system
→ Emotions and drive
Describe anabolism?
→ glucose goes to the liver
→ Skeletal muscle stores glucose as glycogen
Describe catabolism?
→ Glycogen gets broken down to glucose
What is parabiosis?
→ Sharing of blood circulation between animals
What do obese mice not produce?
→ leptin
What happens if you connect an ob/ob mouse and a normal mouse via parabiosis?
→ the ob/ob mouse will decrease in size
Where does leptin bind?
→ Leptin receptors on the arcuate nucleus
When is leptin released and why?
→ When you finished eating
→ to stop feeding
Where is the hypothalamus?
→ At the base of the brain
What happens when you lesion the VMH?
→ weight gain
What happens during lateral hypothalamic syndrome?
→ Diminished appetite for food
→ Anorexia
What happens during ventromedial hypothalamic syndrome?
→ Overeating
→ Obesity
What are the anorectic peptides?
→ Alpha MSH
→ CART
Describe the anorexic response?
→ Leptin increases in circulation
→ Leptin binds to receptors on the arcuate nucleus
→ Alpha MSH and CART neurons in arcuate nucleus are activated which project to the lateral hypothalamus
→ These neurons release alpha MSH and CART peptides
→ Peptides inhibit feeding
Describe how the basal metabolic rate is increased during the anorexic response?
→ Leptin stimulates the Alpha MSH and CART neurons of the Arcuate Nucleus.
→ These neurons extend from the Arcuate Nucleus to the Paraventricular Nucleus.
→ The Paraventricular Nucleus is stimulated and stimulates the release of ACTH and TSH from the Anterior Pituitary.
→ ACTH and TSH increases the basal metabolic rate.
Describe the orexigenic response?
→ Leptin levels are low.
→ CART and alpha MSH neurons of the Arcuate Nucleus are inhibited.
→ NPY and AgRP neurons in Arcuate Nucleus are activated which project to the lateral hypothalamus.
→ These neurons release NPY and AgRP peptides.
→ Peptides stimulate feeding.
Describe how the basal metabolic rate is decreased during the orexigenic response?
→ Low Leptin levels inhibits the Alpha MSH and CART neurons of the Arcuate Nucleus whilst activating the AgRP and NPY neurons.
→ These neurons extend from the Arcuate Nucleus to the Paraventricular Nucleus.
→ AgRP and NPY inhibit the Paraventricular Nucleus thus it cannot stimulate the release of ACTH and TSH from the Anterior Pituitary.
→ A lack of ACTH and TSH means a decreased basal metabolic rate.
What do alpha MSH and AgRP bind to?
→ MC4 receptor
What does alpha MSH do to the MC4 receptor?
→ It activates the receptor
→inhibits feeding
What does AgRP do to the MC4 receptor?
→ Inhibits the receptor
→ Increases feeding
What are the 2 lateral hypothalamic peptides?
→ Melanin concentrating hormone (MCH)
→ Orexin
What are the 3 functions of orexins?
→ Promotes meal initiation
→ Decreases sleep and increases arousal
→ Promotes drug addition
What is the function of MCH?
→ Prolongs consumption
What does disruption of the hypothalamus cause?
→ Hyperphagia
→ Anorexia
→ bulimia
What happens during the cephalic phase?
→ Secretion of saliva
→ Gastric juices secreted in the stomach in preparation for food
→ Activated NPY/AgRP
What happens during the gastric phase?
→ More secretion of saliva
→ More secretion of gastric juice
→ Distension signals via the vagus nerve
What two other substances are released during the gastric phase?
→ CCK
→ Insulin
What is the connection between serotonin and food?
→ 5-HT rises in anticipation of food
→ Spikes during a meal
What are the natural rewards?
→ Sex
→ Food
→ Water
→ nurturing
What is the reward pathway in the brain?
→ Dopaminergic neurons that project from the VTA to the nucleus accumbens
What do nicotine, cocaine and heroin cause?
→ Activation of the mesolimbic pathway
How does cocaine work?
→ Blocks dopamine transporters in the nucleus accumbens
How does heroin work?
→ Activates new opioid receptors in the VTA
How does nicotine work?
→ Activates nicotinic receptors in the VTA
What is positive reinforcement?
→ Anything added that follows a behaviour and makes it more likely that the behaviour will occur again in the future
What is negative reinforcement?
→ A response or a behaviour that is strengthened by stopping, removing or avoiding a negative outcome
What classifies someone as being an addict?
→ They suffer from physical and emotional withdrawal symptoms when the drug is taken away
What do people who suffer from addiction have?
→ Suppressed reward systems
What is wanting something driven by?
→ Dopamine
What is liking something driven by?
→ Opioid system
What is the prefrontal cortex involved in?
→ Willpower
Why don’t leptin injections work in humans?
→ Addiction is driven by many factors
